DSP -- Is It All That?
MIKE POSNER (WA2JJH)
on
April 6, 2005
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DSP: IS IT ALL THAT?
Seems to me every NEW rig must have some type of DSP.
One might get the impression that the all mighty DSP will do the following enhancements:
1) Take that signal in the noise and make it arm chair copy.
2) All kinds of fancy digital filters that will allow only the signal you want to here in a pile up.
3) A perfect automatic notch circuit that will zero in on all signals that dare to heterodyne with your rare DX contact.
4) A speech proc, that after you adjust the freq. response,
To your voice and make it punch through everybody else.
You will sound like you kicked in the linear!
Fact of the matter is...do not believe the hype or the sequel.
I have yet to see a single DSP rig that will beat my TS-850's dual IF filters, twin VBT, and manual notch.
As far as I am concerned if there is not a real Xtal after the first mixer, everything else is window dressing.
I have yet to see an auto notch that beats manual notch.
I have yet seen a DSP speech processor that will beat 9db of true RF speech processing.
Am I missing the boat? You tell me.
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DSP -- Is It All That?
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by KB9YUR on April 6, 2005
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My Icom 275H without DSP still hears better then my Icom 746 on 2m.
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RE: DSP -- Is It All That?
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by SP5QIP on April 6, 2005
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746 is simply deaf on 2m. My Alinco DR130 is better performer.
Mike
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DSP -- Is It All That?
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by VK2GWK on April 6, 2005
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Yes, I think you are missing the boat. True, DSP is not the ideal solution for all QRM and does not lift weak signals really out of the noise. And I am sure you know how to manipulate the controls on your trusted older model rig.
However. As soon as you get familiar - and that takes time - with the new controls on your modern DSP rig I am sure you'll experience the same as I did after a while.
With DSP I can change the noise and signal pitch just that bit that the weak signal gets just a tad better to copy. Or blot out the adjacent sideband just a bit more effectively - together with the band pass filter.
The automatic notch zero's in much faster than I can by hand and follows interference that slightly changes in frequency. And.. it is narrower and takes out less of the speech audio I want to preserve.
The $5 K-mart headset mike can be "manipulated" with DSP so that it sounds like a $100 Heil.
DSP is not earth shaking, but an addition that can make the difference between "just not able to copy" and "just able to copy"
Ingnoring DSP is ignoring progress. Progress is slow but gradual and if you do not catch up you are left out in the cold.
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DSP -- Is It All That?
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by NI0C on April 6, 2005
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Mike,
I share your enthusiasm for the TS-850S. I used one for over 7 years, and I had it loaded with super narrow INRAD crystal filters. Yet, I always supplemented it with the MFJ784B audio DSP unit. I still use the MFJ with my current radio, an Omni 6/option 1, which has a very effective DSP noise reduction feature built into the radio.
Digital signal processing is wonderful technology, but as you point out, one needs to know its limitations. The Achille's Heel of DSP is in the pre-filtering and the analog to digital conversion. These are what determine the noise floor and dynamic range, respectively.
However, DSP can achieve filter characteristics that are virtually ideal-- brick wall narrow filtering with linear phase, for instance.
So, I wouldn't make any blanket statements about analog crystal (or mechanical) filtering being superior to DSP. Both have their place.
When I purchased the Omni recently, I was looking for a very quiet receiver that I could afford. I think Ten Tec makes the best use of both worlds-- analog pre-filtering, followed by DSP filtering-- and I would have purchased the Orion if my budget would have allowed it.
I designed DSP filters used for aircraft acoustic and vibration measurement in the late 70's before we had good hardware to do the filtering in real time.
73,
Chuck NI0C
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RE: DSP -- Is It All That?
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by KA4KOE on April 6, 2005
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My IC-756PRO has IF DSP that does work. However the intermodulation products the rig has on 17m and above are maddening. What good is DSP if you are hearing 49m SW BC on the upper bands?
---No roofing filter and its as broad as a barn door as a result of that.
PHILIP
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DSP -- Is It All That?
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by VK5CC on April 6, 2005
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Yes you are correct DSP is not the be all and end all and if you read the design notes from the engineer who designed the TT Orion(Doug Fox) he happily states that at present good front end mechanical/XTAL filtering is still better than DSP down at the fourth IF of say 11 to 50khz. Even certain DSP filter rigs have a cheap and nasty xtal filter before any DSP so all the rubbish that gets through is only masked by DSP. A true DSP filter would need to be running up at least 455khz and the price of the Chip to do this would put ham rigs way out of any price for 99% of hams. I have compared rigs like ICOM PRO 2, TS 870S,FT1000MP/AND MK-5 Against both Collins valve rigs including 75S3A and KWM-2A and also TT OMNI 6 and let me tell you i'll take the KWM-2A and Omni 6 anyday over any DSP filtered Rig. Also DSP Speech processing is ordinary at best and yes a true RF Processor is far superior.The bottom line is rigs like the Elecraft K2, TT Omni 6, and Orion are far superior to any DSP filter only Rigs out there on the market! And thanks to Inrad a narrow roofing filter in most older rigs including OMNI 6, IC765,ts850/950 will slaughter a modern so called all DSP filtered rig in close in Dynamic range and 3RD Order Intecept point.(EXCLUDING ic7800,ftdx 9000,TT Orion series rigs obviously ).And they will sound better on Tx as well.
Best73 From Chris.
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by W2NSF on April 6, 2005
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Any claims by manufacturers should be take with a grain of salt. All DSP is is a digital version of your analog dual IF filters, twin VBT, and manual notch. Nothing more, nothing less. I believe digital copies of analog filters have the potential to work better than their analog originals, but a lot depends on how powerful an algorithm was used as a basis of the software and how good the operator is in adjusting all the parameters. The running discussion on analog vs. digital signal processing sounds like the discussions that used to arise (still do, actually) over the purity of sound from transistor versus tube audio amplifiers. There are some things the human ear can respond to that defy analysis. Bottom line is if you like the sound and performance of a certain signal processing system, then go with that one, but make sure you have thoroughly evaluated both analog and digital systems before making your final decisions. I believe there are great differences among all the various DSP systems as well as analog filters; anyone who's lucky enough to have spent a couple of days operating each one will tell you. Anyway, we're all lucky to have so many choices with plenty of both yesterday's and today's rigs out there for the picking.
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RE: DSP -- Is It All That?
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by KD4AC on April 6, 2005
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I use the DSP on my 746 with some success. As it was pointed out, you have to know the limitations.
One thing that I always wondered about, however, is why my Uniden HR-2510 could wipe out all the noise my Ford Ranger made without noticably affecting the received signal and my FT-100 couldn't do a damn thing to reduce the noise. Why is it that a $200 10M radio has a better noise blanker than an $800 HF radio? Hell, for that matter, a Cobra 29LTD CB radio has a better noise limiter than any HF rig out there.
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DSP -- Is It All That?
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by N0AH on April 6, 2005
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I was on your band wagon until I bought my Icom Pro III. They finally got it right. On the other hand, going from my Icom 756 to my 756 Pro, it was a big step in the wrong direction.
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RE: DSP -- Is It All That?
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by AA4PB on April 6, 2005
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First off, the 756PRO does have a roofing filter (and so does any DSP receiver I've ever seen). Granted the PRO roofing filter is 15KHz wide and if you have strong signals within that passband that overload IF stages before it gets to the DSP filter then it causes problems. The better solution is a selection of narrower roofing filters but that translates to cost and additional complexity.
The wide roofing filter problem however is not directly related to the use of DSP. Mfgs make that filter choice based primarily on cost. DSP does not force them to use a wide roofing filter.
DSP is just another tool and it can be of considerable help if used correctly. Yes, I think you are missing the boat if you reject DSP as totally useless. While listening to a net with the automatic notch filter on, all I hear when someone throws a carrier on frequency is a small "tick". With a manual notch filter I get "blasted" out of my chair and then have to reach for the notch tune control after I pick myself up. Then I get to do it all over again for the next guy who tunes up on a slightly different frequency.
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RE: DSP -- Is It All That?
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by AA4PB on April 6, 2005
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On the other hand, going from my Icom 756 to my 756 Pro, it was a big step in the wrong direction.
---------------------------------------------------
That was because of other front end design issues rather than the fact that they used DSP. DSP gets a bumb wrap because we tend to blame all of a rigs design faults on the DSP. The fact that you have DSP running in the 4th IF doesn't mean that you can ignore filtering in all the stages ahead of it.
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RE: DSP -- Is It All That?
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by K5DVW on April 6, 2005
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I dunno, I think you're missing at least one boat. I have an IC756PII and I use the DSP function frequently in CW mode. On SSB I've used the auto notch and it works perfectly. It works so well that if I try to tune a CW signal and forget to turn it off, I dont hear the CW! I find that the noise reduction (which is DSP) helps my ears not get over strained and tired while listening to CW in a noisy band. Also, the variable filter bandwidths (another DSP function) are excellent on this rig!
Of course the radio marketing department wants you to believe that DSP will remove all manner of noise and make a crappy signal perfect copy. No, it wont do that! Then again, they want to to believe a super sensitive HF receiver is more better too! Don't listen to the hype!
K5DVW
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756 pro issues
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by KA4KOE on April 6, 2005
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So why does it have 3rd Order intermodulation distortion? Other people have noted this on this rig.
Yes, the front end has issues and besmirches an otherwise very fine rig.
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RE: 756 pro issues
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by KE4MOB on April 6, 2005
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All DSP rigs sound muffled to me...it seems like that once the DSP makes a difference, it makes *too much* of a difference.
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RE: 756 pro issues
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by K0BG on April 6, 2005
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Whether you like or dislike DSP, I'll make a prediction. Within 2 years, you will not be able to purchase a new transceiver without it. In other words, it will become as ubiquitous as a digital VFO. How many of you remember the negative comments about them?
Alan, KØBG
www.k0bg.com
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by W0LC on April 6, 2005
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Mike
I had the TS-850 for quite a while and there was nothing it couldn't hear that my IC-775DSP could hear. I too question the hype around DSP. It may make the audio (receive) more "pleasant" to listen to, but to actually tell me that it made the weak signal "jump" out of the noise is ludicrous. I have yet to see DSP (whether in the IF stage or in the AF stage) actually make weak signals into something they are not, arm chair copy.
The TS-850 to me is one of the best receivers on the market and to be sure, the best CW rig I have ever owned.
With all the CRT/TFT/LCD displays out there, DSP and equalizers, none still can make nothing into something when the signal just isn't there!
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DSP -- Is It All That?
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by W0LC on April 6, 2005
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One more comment.
The real issue in all honesty is selectivity. If you can make a receiver front end reject adjacent channel interference, and I don't mean spec-ing something with a spacing of 20 khz, then you have something. To honestly state you can make a less them .5 uV signal jump out of the noise is stupid. DSP can't do it and as stated earlier, if we had 455 khz DSP, you couldn't afford the radio to start wtih.
I have already heard many stations on the air with the new IC-7800 state it really isn't worth the cost they paid for it and frankly, the older radios work as good or better. The IC-7800 just has more eye candy for the op. Be a long time before I fork out $10K on a radio that is for a hobby! Hi.
Antennas seem to be left out of the equation.
I met a fellow the other day with an IC-7800 on a G5RV (all that he had in the way of antennas) and he had a hard time copying signals I could hear easily on my older IC-765.
Just goes to show that it isn't just the radio that makes the difference. If the signal isn't there, you basically have little to nothing to work with!
Ever wonder why Racal receivers, Collins commerical gear is so expensive? Look at some of thier specs sometimes.
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RE: DSP -- Is It All That?
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by W0LC on April 6, 2005
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That is all correct also. I noted that many manufacturers came out touting "DSP" and later, revised it to audio DSP or AF DSP such as in the case of the FT-920 and TS-870. The 870 is good, but not that great. The 920 to me was ergonomically great, but the DSP was a farce.
I had the TT Jupiter for a short period and sent it back. It couldn't hear anything. As to the TT ORion, don't know. Do know there have been a number of them returned also mainly for QC problems which I also encountered on the Jupiter.
To me, some of the nicer receivers out there and this is subjective (of the main manufactuers) are: TS-850, TS-940, IC-775DSP, Omni 6. I can't talk to the others, but based upon what I have used, I would say these are reasonably good to very good options to stick with.
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RE: DSP -- Is It All That?
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by NI0C on April 6, 2005
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W2NSF wrote: "All DSP is is a digital version of your analog dual IF filters, twin VBT, and manual notch. Nothing more, nothing less. I believe digital copies of analog filters have the potential to work better than their analog originals, but a lot depends on how powerful an algorithm was used as a basis of the software and how good the operator is in adjusting all the parameters."
If you were thinking of IIR digital filters mapped to the z-plane from analog poles and zeroes in the s-plane, then you are correct. However, most DSP algorithms are not mere copies of analog filters. The FIR linear-phase filters and the noise-reduction algorithms are unique to the digital domain, and can provide outstanding performance-- once the signal is carefully processed first by analog filtering and converted to digital form with adequate dynamic range.
Operator adjustment is no more (or less) crucial with DSP filters than with analog filters.
73,
Chuck NI0C
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DSP -- Is It All That?
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by WA2DYA on April 6, 2005
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My Kenwood TS-570 has audio DSP. For SSB, I find it effective for eliminating a heterodyne but not for much else. I'm not a CW guy, but the DSP also seems effective as a means to improve selectivity in the CW mode.
As an aside, I worked with a radar that tracks artillery projectiles. Its digital signal processor provides 40 dB receiving power gain allowing the 100 watt transmitter to be as effective as a megawatt transmitter! This performance is only possible because the transmitted signal is coded with a pre-known binary code sequence which will identify the returned target signal energy in the random noise.
--- CHAS
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DSP -- Is It All That?
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by K0RGR on April 6, 2005
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I work mostly with digital modes and DSP benefits some and wipes out others. I try turning it on and off to see if it helps or not in different circumstances. Sometimes, the noise reduction makes a dramatic improvement.
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RE: DSP -- Is It All That?
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by K0IZ on April 6, 2005
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My experience with the MFJ784B is that on SSB it works well for heterodynes, but not much good for helping weak signals out of atmospheric noise. Don't work CW.
I can tell you I have compared my KWM2A (well tuned up)to several recent high priced units (with DSP), and I will take my KWM2A.
That being said, I do think IF DSP has much more potential vs audio DSP, and I think software-defined radios (real DSP) are beginning to offer performance that will eventually be even better.
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DSP -- Is It All That? * It's getting closer! *
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by AA9KK on April 6, 2005
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Hardware and DSP algorithms continually evolve and improve. We're not at the gates of RF paradise yet but have a look at this recent article in RF Design magazine: http://rfdesign.com/mag/radio_direct_digitization_using
It'll be an interesting era in amateur radio when a variation of this filters down (no pun intended...well sort of) to affordable equipment.
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RE: DSP -- Is It All That?
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by NI0C on April 6, 2005
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K0IZ wrote: "My experience with the MFJ784B is that on SSB it works well for heterodynes, but not much good for helping weak signals out of atmospheric noise. Don't work CW."
It works great for CW, which I use nearly 100% of the time. On 80 meter CW, DX signals are generally pretty weak (and often buried by noise) here in my Midwest urban location. A narrow audio bandwidth (75 Hz to 200 Hz) centered at my audio pitch frequency of choice quite often makes the difference between no/poor copy and good/solid copy for me. I use this audio selectivity in addition to cascaded CW IF filters (250 Hz to 500 Hz BW).
73,
Chuck NI0C
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RE: DSP -- Is It All That?
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by K0IZ on April 6, 2005
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Chuck - my comment "Don't work CW" might have been phrased better. "I don't work CW". I agree with you that narrowing the audio bandpass with the brick-sided filters should make a big difference on CW, but can't speak from (CW) experience.
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RE: DSP -- Is It All That?
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by K4JSR on April 6, 2005
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DSP works wonders on cell phones. I am not at all impressed with it on any of the ham rigs I have played
with. As far as a brick wall CW filter, I have seen
nothing that compares with the little old 556 PLL
circuit I made up 30 years ago.
Oh, I still like my little and inexpensive Alinco
DX-70TD. Especially since it isn't GREEN! :-P
73, Cal K4JSR
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DSP -- Is It All That?
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by KB1GMX on April 6, 2005
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Are you missing the boat?
Don't ask us, it's your question to yourself.
Some opinion: DSP is a tool for the rf engineer and at present it's still a new tool. Each generation is better and this is one place where newer is better. However, at the current state of the technology the DSP is limited to the detection end and last IF of a reciever. What that means is even the very best DSP attached after a poor front end electronics will yeild a poor radio. So DSP is a tool to enhance the very best to either simplify the sea of knobs or provide functionality that would be a mechanical or electrical nightmare. This doesn't mean that the very best analog RX in the hands of a competent operator cannot do as well, but it does mean you have to know what your doing. This is where the DSP may simplify things some.
Obviously thre will be some tradeoffs in designs to cut costs or provide features.
My experience with DSP is with several radios and my own TT6n2. In all cases I found it effective and sometimes even convenient. The one radio I have literally years of time with the TenTec6n2 is my 6m benchmark and it compares to my very exotic analog direct conversion phasing rig pretty well. Anything I can hear on the phasing rig I can hear on the TT. The phasing rig due to design however can withstand truely large signals nearby due to use of level 17 mixers and
really strong RF amplifer designs. This is the only area where the two are markedly different for SSB. There is a yabut to this. The phasing rig does not do FM or AM and switching in filters is whats requried to change bandwidth as there is no way to make a good analog variable filter that isn't a compromize somewhere. In that respect the knob on the TT can dial me down to near nothing bandwidths or out to 2.8khz with zero fuss.
In the end it's implementation of the _whole_ radio not dsp vs analog. Very little can make up for a loose easily overloaded frontend. In a pile up I've found IF or audio selectivity was not an issue as a S9+30 signal 10khz away making it impossible to hear anything due to front end overload. I know this as I have an OP nearby (less than 1000ft) that runs a KW for everything.
Allison
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RE: DSP -- Is It All That?
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by NI0C on April 6, 2005
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K0IZ:
No, you were clear. I was just attempting to fill in the blanks. You reported on your experience with the filter on SSB; I gave my report for CW.
73,
Chuck NI0C
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RE: DSP -- Is It All That?
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by W9WHE-II on April 6, 2005
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I have a Yaesu MK-V, cascaded 2.0 crystal filters and a Clearspeech, which is essentially advnaced hearing aid technology. Here are my findings:
1) The Clearspeech. Sometimes it helps, sometimes it actually hurts intelligibillity. Depends on the audio challenges it faces. Useful about 25-30% of the time.
2) MK-V's Digital bandwith filter. It works, is fairly tight, and I like it, but it does not solve all problems. Is it better then the 2 analog cascaded 2.0 Khz crystal filters, I'm not sure. But used in conjunction with the DSP, the two are an amazing combonation!
3) MK-V's IF shift and with. Very, Very, very effective for adjacent interference, as when one of those contester types slips in 2 KC away and runs lots of compression. Does little if the offending signal is within the passband. But since you can shift and narrow the passband, lots of QRM goes away. IF shift & Width, in COMBONATION with analog and crystal filters is superb.
4) MK-V's DSP noise reduction. I like the lower levels of noise reduction. Effectively reduces (not eliminates) white band noise and some static crashes. However, it performs similar to the analog audio filters in my SP-8.
BOTTOM LINE:
No single filter is effective on all problems. Some are more effective on some problems then and less on others. But if you have BOTH, you can throw things at the problem until you get an effective solution. And effective station should have BOTH.
W9WHE
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DSP -- Is It All That?
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by G3RZP on April 6, 2005
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The big point here is the dynamic range of everything that precedes the DSP - including the A - D converter. A good HF rx needs the equivalent of at least 18 bits. It also needs at least 100dB of instantaneous phase noise limited dynamic range, which in an SSB bandwidth means about -140dBc/Hz as close in as possible - and spurs that far down, too.
As many have said, the DSP needs to be preceded by good crystal and/or mechanical filters. I find audio DSP is useful on SSB when the going gets tough, especially the auto notch, but tolerably useless on CW.
About 23 years ago, I went to a research lab where they had substituted DSP for the 1.4MHz crystal filters in a professional rx with a 70MHz first IF. When I demo'd to them that strong signals within the roofing filter but outside the DSP filter overloaded, the response was 'yes, but we've gone digital!'
(they hadn't tried it on antenna!)
No wonder us RF engineers refer to digital guys as 'bit freaks'. And what do well brought up digital guys call RF Engineers?
'Sir!'
73
Peter G3RZP
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DSP -- Is It All That?
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by K3EY on April 6, 2005
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My Two Cents: I guess I think differently than some on here. I bought a TS850S brand new when they were still making them only to sell it because I was not all that impressed, it wasn’t any better than the TS830S that I still own. I have the original PRO and IMO it blows away the 850 on every level. I just can’t understand the mentality that says yesterdays technology is king and today’s technology is a junky expensive waste of money. I think it has to do with humans not liking change clinging to the past and old ways. I will take any new DSP radio over any of the older rigs and only keeping my 830 because I happen to like it, it’s nice and does it’s job but is out matched by light years with any of today’s DSP radios.
k3ey
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RE: DSP -- Is It All That?
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by W3JJH on April 6, 2005
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Theodore Strugeon was the science fiction writer who gave us Sturgeon's Law. When he was asked why he "wasted" his time writting science fiction when 90 % of science fiction was crud, he replied: "Sure, 90 % of science fiction is crud. 90 % of everything is crud."
That's true of RF engineering as well. Roughly 90 % of all store-bought radios have some sort of defect that severely compromises performance. DSP is not a magic bullet that kills the results of poor receiver front-end design. It's not the best way to correct for transmitter deficiencies. The best way to get decent perfomance is to optimize each section of the system and to be sure that each section is properly interfaced to its mates.
The TS-850 is probably the best bit of RF engineering to come out of Kenwood. Thus, it's not surprising that it will outperform many other radios. Properly integrated DSP would improve the 850's audio selectivity a bit, but would not have any effect on its RF performance.
The TenTec Orion is an excellent example of a balanced design that is well optimized section-by-section and well integrated section-to-section. Of course, the Orion was as much designed and specified by the TenTec engineering department as their marketing department.
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RE: DSP -- Is It All That?
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by W0LC on April 6, 2005
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I have to agree. However, in regards to the Orion, although I haven't used one, one aspect of TT that concerns me is their frequent problems with QC issues in products that get out the door. If they would clean that up, then I would be serious about looking at their products again.
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RE: DSP -- Is It All That?
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by KB9VWH on April 6, 2005
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Man, this must be a hot topic. it is one that I have been discussing at length with my uncle/elmer. my take is that DSP's potential is yet unrealized. Also there is confusion as to what DSP really is. The manufacturers don't do anything to clear the air. some recreate the function of the mechanical, crystal, band pass, notch etc filters and technically call it DSP. it really is a form of digital signal processing, and it serves to reduce noise. And some put digital circuits in the audio strip that allow you to shift the band pass and alter the upper and lower edges. All could be calle and really are on some level DSP. But they are all a new way to do what has been around since the 50's. What I consider to be DSP is processing of signals that make it to the pass band. some processors work in the pass band after all the rest of the filtering has taken place. This is where sophisticated processing can shine. the ability to decern voice like characteristics or other data from noise of the same or near frequency is the key. then through digital means cancelling the signals deemed noise and passing those considered to be voice/data. there are processors that do this through some processing i believe they reproduce the noise out of phase and effectively cancel it. I have a 10+year old JPS NIR 10. it does a passable job and it works strictly in the audio output. Many improvements are possible since this device was produced. I think conventional wisdom is that the processing really should be done in the IF stages, but i think that clever engineers who always manage to surprise us could produce an effective dsp that works in the audio. having a tight preselected front end and quality double or triple conversion then using DSP in the pass band would, I feel, be the sweet set up.
Regards
Mike Rannow
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DSP -- Is It All That?
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by N0AH on April 6, 2005
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AA4PB....ok, how's this: My 756 Pro sucked on reducing noise. My Pro III has taken my S-9 noise down to S-(1-2)without screwing up anything. I can hear things now almost like I used to in an RF noise free environment in Wyoming vs where I am now in a cluttered RF filled Denver neighborhood near broadcast towers, neon signs and a highway. I've been reborn to the chigrin of many of those who know me. So there, blah, and I will be back on 160M next year so get use to it. Never give in, never surrender to noise. Just go get an Icom 756 Pro III for DSP that does what it was suppose to do 5 years ago. - Since the 756 worked great, but my 756 Pro didn't, I assumed it was over DSP- I also agree with those who refer back to the dark ages of CB NB's.....they really did work well. Back to reality, I've tried 3 HF rigs in the truck and only my FT-900's NB works. Alinco and Kenwood need help- Not that this has anything to do with the subject, but it came up- My NB on my 756 Pro III really does not seem to do much. But that noise is not present. The noise that is, the Pro III swallows up and spits out.
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RE: DSP -- Is It All That?
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by G4AON on April 6, 2005
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Here's another 2 pence worth... I have audio DSP on both a K2 and a TS-570 - both mostly used on CW.
Neither of these DSP units seem to really dig CW signals out of the noise, what seems to happen is similar to the companders used in old tape recorders. When using "noise reduction" signals above a threshold seem to be amplified and below that threshold attenuated. When the CW signals are buried in the noise the DSP doesn't seem to achieve anything. Stronger signals are sometimes improved slightly, often signals sound "strange". I hardly ever use noise reduction.
The most useful function would seem to be using DSP for narrow band filters. Having used ordinary audio filters on older transceivers, I can see the advantage of using DSP as they seem narrower and generally work down to quite narrow bandwidth without sounding too much like you are listening down a tube.
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DSP -- Is It All That?
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by WA7NCL on April 6, 2005
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You probably think vacuum tubes sound better as well. I'm sure the marketing guys hyped xtal filters in their day as well.
I find IF DSP to be a great advance. I have a TS870 and within the limitations of its design, I find it be be a great improvement. I've also used a 756proII and found it even better. Selectivity is better, and the line enhancer works great for really weak CW.
Noise blankers are subject to some fundamental limitations that seem to cover both analog and digital implementations. Hopefully with new ideas, perhaps active noise cancellation techniques, DSP will show progress there as well.
Are DSP radios 20db better than old analog radios? No, we are in the stages of late incremental improvement in SSB and CW radios. So we can't expect the great strides that were made late in the last century.
As an electronic engineer, I would say DSP is a must have in a new radio. But to each his own. The boat anchor crowd loves their AM, you can love you xtal filters and analog radios.
Mean while I'll take all the incremental improvements that manufacturers give us, especially when they keep selling it to us cheaper (in real dollars).
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DSP -- Is It All That?
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by K2WU on April 6, 2005
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I've been using an FT-1000MP with EDSP - "Enhanced" DSP - for almost 10 years (enhanced over what I couldn't tell you). In all those years, with a countless number of different tweakings, I have not found a single instance where the EDSP would allow me to copy a signal that I couldn't copy with it off. Not once. Doesn't make good signals any more pleasant to listen to either. Theory is nice, but from my perspective, it's totally useless.
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RE: DSP -- Is It All That?
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by N6AJR on April 6, 2005
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some problems ( noise) really needs to be taken care of in the if stages, and least we forget, if you put a 500 hz filter inline before a 2.8 khz filter you will only pass 500 hz through both, ya need to take steps to attack different problems where they are best handled.
Audio dsp can work at any level from basic tone control to computer controled systems looking for cyclic ( repetative ) noises, or compare against a local antenna and remove noise, or get rid of any noise that is not between 300 and 3000 cycles and constantly changing. ( I.E. voice) or signals other than what you want to hear.
A good dsp will actuall notch out the CW signal you are listening to if set properly for voice. there is not one "do all" set for everying.
and remember the best "filter" is between our ears. I tried the mfj audio contraption, and it worked for some stuff, and the dsp on my 746, 756 and ts2000 can help, and the clear speech works well but everything has low audio and sounds muddy, and my friends MK V has great and useful DSP function, but they are confusing to me to use, although probably one of the better ones. Some of the older Ten Tec stuff has better DSP than the newer stuff...
So folks its digital signal processing, its not noise removal 101 or speech enhancement,
its digital (0's and 1's),
signal ( all the crap coming in from the antenna),
processing ( having you and a chip decide what not to send through.)
its not a mystery, or a fix all, its one more tool. Hopefully it will get better, remember in the "old days" side band made every one sound like a duck, that has improved and this will too.
Compared to a screwdrive on a shed, a good fan dipole will help the signal more than another device for processing your rf. A good antenna is probably the best DSP around.
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All That Jazz
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by WB2WIK on April 6, 2005
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I don't really care.
But I do care about how the rig actually performs, on the air, when I'm sitting in front of it; and this is a function of a great many things, DSP or not. The Physical User Interface of box to man is highly important and not well done with many rigs.
As wonderful as DSP can be, and there are few electronic products made today that don't use DSP somewhere, implementation is key, as are all the peripherals creating the I-O paths for DSP.
The software defined radios I've used and worked are, for the most part, very lacking in many ways and their DSP implementations aren't nearly fully evolved.
Even worse, my iPod battery pack charge doesn't hold nearly long enough, especially if I use the wireless adapter to broadcast it through my car stereo. Now, this is serious stuff.
WB2WIK/6
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RE: DSP -- Is It All That?
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by WA6BFH on April 6, 2005
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As DSP is able within the 'State of the Art' to move to considerably higher (RF) I.F. frequencies, it will get better and better!
Until then, a radio that has superior analog design, with maybe also DSP at a low I.F., will be tops!
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RE: DSP -- Is It All That?
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by AA4PB on April 6, 2005
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Unless it gets to the point where you can just hook the antenna to the A/D converter there will always be a need for analog circuits (and roofing filters) ahead of the DSP. Even the sofware defined radios are are using analog amps, mixers, and filters ahead of the A/D converter for the DSP. I haven't had any success yet hooking a 40M dipole to my sound card input :-)
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RE: DSP -- Is It All That?
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by KV6O on April 6, 2005
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How about cost? How much does a good mechanical filter run? $150? $200? If I want a 500Hz CW filter and a 2.3kHz SSB, I could be looking at a $300- $400 bill! Even if you doubt the effectiveness of DSP for noise reduction (I like the wet processing between the ears), you can’t ignore the cost factor when it comes to filters.
SteveL
KV6O
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RE: DSP -- Is It All That?
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by NS6Y_ on April 6, 2005
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Software radios like the SDR-100 are going to answer all of your prayers, yeah I know, that silly toy :-D
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RE: DSP -- Is It All That?
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by K2WH on April 6, 2005
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I have lots of rigs with DSP and DSP sucks! My TS-820s with IF shift does a better job.
K2WH
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DSP -- Is It All That?
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by N9TA on April 6, 2005
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Manufacturers added DSP and FORGOT about basic rx performance. I've owned a FT1000 Field, a TS-870, a IC746, a IC756 Pro2, and a TS-2000. The Field was a MAJOR joke, GOD what a peice of junk!! I unloaded it with 2 months!!...the 870 had a frontend open wide as a barn door...the 746 was just ok....the 756Pro2 was a pretty darn good rig (For over 2k$ it outha be!!)...
and the TS2000 was a heck of a mult-purpose rig, but it really stunk on RX performance on HF.
I've went back to a TS-850SAT and a Yaesu FT-990DC both full of filters. These radios are Quality thru and thru. The TS-850 has the best receiver I've EVER seen and that includes my Elecraft K2. If you want bells and whistles go with a DSP rig.....But if you want serious RX performance in a radio that oozes quality go with a TS850/TS950SDX or a FT990/FT1000D.
I WHOLEHEARTEDLY agree with WA2JJH....Amen and pass the crystals!! Any of you fellows want to send me your old 850/950/990/1000D, I'm good on QRZ !!!
73....de.....Fred N9TA
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RE: DSP -- Is It All That?
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by W6TH on April 6, 2005
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DSP? Never need it as what is between my ears fits the bill.
.:
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RE: DSP -- Is It All That?
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by W6TH on April 6, 2005
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DSP? Never need it as what is between my ears fits the bill.
.:
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DSP -- Is It All That?
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by K2ROK on April 6, 2005
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I'm happy with the DSP in my Ten Tec Argo V (IF DSP/variable BW filters). I have used it to successfully pull weak ones out and eliminate (combined with the passband tuning) interfering signals which is certainly was it was designed to do. I like it much better than my Icom 703's DSP for instance. I also hear and read great things about SGC's DSP -- so there must be something to DSP!! Maybe it's not "all that" but I think at least in Ten Tec's case, it is doing what it was designed to do quite successfully. While I did like my Collins CW filter on my '817 -- I had only one "setting" -- the Ten Tec allows dor multiple setting at a price I was willing to pay.
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RE: DSP -- Is It All That?
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by W3ULS on April 6, 2005
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I agree with K2ROK: the Ten-Tec Argonaut V is a wonderful implementation of DSP in a low-priced rig. The audio is excellent, both on CW and on SSB and AM. Ditto for the Kenwood TS-870, which started out as a far more expensive rig and unfortunately has not been updated to reflect the availability of new DSP hardware. Neither rig, of course, will quite survive in a DX contest with multiple strong signals, but for 95% of operating, they provide excellent results.
If you want a DSP primer, look at Adam Farson's ICOM pages, and especially the authoritative essays by the late George Baker, W5YR:
<http://www.qsl.net/ab4oj/icom/icom.html>.
Between Adam and George, there isn't much left to be said about DSP as offered at the ham level.
73,
John, W3ULS
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RE: DSP -- Is It All That?
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by AE6IP on April 6, 2005
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So when is some bright amateur going to stick a very low noise 30mhz bandwidth amp in front of a 66 MSPS ADC and feed the result into a systolic array (or even a beowulf cluster) resulting in a digital audio stream fed into a decent audio amp?
You could maybe even beat the pros to this, and produce the first fully software defined radio.
Last time I did a BOM estimate, it came out to about $75,000, though, unless you wanted to do some custom semiconductors.
Somebody cough up the development money, and I'll do it. ;)
Haven't done the BOM on a transmitter, though.
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RE: DSP -- Is It All That?
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by X-WB1AUW on April 6, 2005
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"Am I missing the boat?"
Don't think you missed the boat; but rather, you got on the wrong boat.
I've never expected DSP to do any of what you cite.
"Course, when I looked for a new rig, I choose a 950S, over a 950SDX.
I still have the 950S; but, I use a C-Line or TR4CW with an external DSP unit that I rarely use.
Bob
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RE: DSP -- Is It All That?
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by K4JSR on April 6, 2005
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K2WH said, "I have lots of rigs with DSP and DSP sucks! My TS-820s with IF shift does a better job.
K2WH"
Bill, that is because it is DIGITAL Signal Processing, *NOT* DUDE Signal Processing!!!
Trust me! ;-D
73, and I do agree with you. DSP ain't getting my $$
just yet, either. DSP will not be a deciding factor
in my selection of a new rig. My old Ten Tec 544 and
my little Alinco do just fine. IF shift and tuneable
pass band is not obsolete nor will they be for quite
a while.
Cal K4JSR
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DSP -- Is It All That?
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by KF3EG on April 6, 2005
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all I know is I have dsp radio's and when I hear like VR2XMT in China, its when i have the old Kenwood Ts 520 se turned on. Seems to me that many DSP radio's do not hear as well as some of the older non DSP radio's
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DSP -- Is It All That?
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by N0FQN on April 7, 2005
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I agree with most that DSP has limitations and you must learn to work within those limits. Strange that someone mentioned a HR-2510. It has a ANL, Automatic Noise limiter. I had a Atlas 350XL that had it. Now there's circuit that can remove the noise. Turn it on and ambient noise is gone. I had much better success with it than DSP for noise removal. Wonder why they never tried putting the circuit in other rigs??
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RE: DSP -- Is It All That?
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by VK4TZL on April 7, 2005
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Buy an Elecraft K2 Kit...even the DSP works better than my 756Pro2...that I now no longer own. The K2 is the First Rig I have owned that the DSP actually improves things.
73
Glenn
VK4TZL
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I have yielded to the masses....
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by KA4KOE on April 7, 2005
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And have therefore written another DED (we're at 18 now). The cries of outrage at my reluctance to write more of these little essays hurt my sensitive hears....so more are just around the bend in order to shut up Cal, Mike, and Charles.
The tears and lamentations of Cal, in particular, were too much to bear from this bear of a man.
DED 17 should be hitting the streets any day now.
Are we happy now?
Flippit
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RE: DSP -- Is It All That?
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by K4TBN on April 7, 2005
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Not only did you miss the boat, you missed the pier and much of the shoreline.
When running mobile, with DSP off, I can't hear anything other than ignition noise (from my truck as well as other vehicles), powerline noise, and lot's of other man made junk. With the DSP on, I can easily (for a mobile) conduct QSO's.
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RE: DSP -- Is It All That?
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by KC9AWS on April 7, 2005
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I've had Yaesus, Kenwoods, and Icoms. You have to spend the money to get something that really works. You can't spend $500 and think it will work like a $3000+ radio. Buy some good filters also. I personally like the Yaesu FT-1000MP MkV, with the filters, external speaker, and MD-200A8X microphone. It's all a matter of what you beleive works best for you!
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DSP -- Is It All That?
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by NA4IT on April 7, 2005
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The idea is to make a signal "intelligible" in bad conditions. We have become to accustomed to wanting the signal we hear to sound "broadcast quality" instead of "communications quality".
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DSP -- Is It All That?
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by K6YE on April 7, 2005
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I do not think that you have missed the boat. Perhaps it would help if you had a bit more time comparing both DSP and non-DSP radios. Armed with that, you might have a better opinion.
I have been a ham for 40+ years and I do not think that anyone has all of the answers. I think that DSP has great possibilities but I am content with my current rig (FT-1000D). It is fully filtered and meets my needs (for now). I have only sampled an IC-775DSP and TS-870 and they are fine radios. I did not get to use them in pile-up or contest situations and this is where I measure a radio's worth beyond casual rag-chewing. Some of my friends have the latest radios and they seem to really like them. I have had very positive feedback.
The majority of hams that are really into the hobby (DXers, Contesters, QRPers) will spend whatever it takes to have an edge be it gain and/or selectivity. This includes rigs, antennas, amplifiers, feedlines, etc. That is probably why the PRO series, Orion, the new 7800, and the FTDX-9000 series with DSP S-E-L-L (or will sell). But it does not mean that this is the only way to go. I have seen tons of threads of contented hams lauding old Collins, Drake, Yaesu, Icom, etc gear sans DSP. It boils down to what you are used to and are willing to tolerate.
It is not a question of "Can I afford it?" From my viewpoint, if the desire is there, money is no object. If money mattered, the newer gear would not sell.
No matter what your choice happens to be, have fun and enjoy the hobby. Diversity is a good thing.
Semper Fi,
Tommy - K6YE
DX IS
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DSP -- Is It All That?
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by WA8HHH on April 7, 2005
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Lots of opinions. I've had very different experiences with AF DSP in two different brands of modern transceivers. One was great and the other was an out-and-out failure. DSP in my current radio is just fine. But I must admit that I used to have more fun on the air when the only control for noise reduction was marked ANL, and the receiver tuned four MHz in 180 degrees of main tuning knob rotation.
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RE: DSP -- Is It All That?
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by KC9AGG on April 7, 2005
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"broad as a barn door because of that"--same problem on the ts2000...the dsp can, in certain situations, make the difference between copy and no copy...but really shines on cw--that's my opinion.
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DSP -- Is It All That?
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by NK7J on April 7, 2005
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Missing the boat? Heck I think you fell off the dock.
;-)
Jack
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RE: DSP -- Is It All That?
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by K4JSR on April 7, 2005
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I must respectfully disagree with those who look at DSP as a cure all for receiver problems such as noise
(Mobile environment) and a lack of selectivity.
The best cure for mobile noise problems is to attack the source of those noises. Those noises do occupy
spectrum and with sufficient amplitude will "block"
weak signals from being heard. The noise is just simply another strong signal that the receiver must
deal with while a weak signal is contending for detection. No amount of DSP will retrieve a signal
that does not make it through the receiver. There is
some point the "good signal" simply disappears and is
gone. This is true for most noise in a receiver regardless of cause. Killing external noise sources at
their source is the superior method of weak signal
receiving--weak being anything of less amplitude than
the desired signal.
The inherent selectivity of an excellent communications receiver as well as superior dynamic range also are preferable to asking DSP to taking up the slack.
All I am saying is do not put all of your eggs in the
DSP basket. If you are a serious contester, then you
will obviously want every possible advantage available. But then you would already be painfully aware of the shortcoming of not taking a "holistic"
approach to solving the problems of contest grade or
even just pleasurable communications.
To answer Mike's question, NO! IT AIN"T ALL THAT!
But then, Mikey knew the answer to the question before he asked. He ain't got all of those initials
behind his name so he would have graffitti ammo in
NYC! Or did he? HMMMMMM! :-P
PS. K4TBN, Do you think DSP would be of any use at the Brevard School of Music? ;-P
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RE: DSP -- Is It All That?
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by KF4VGX on April 7, 2005
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Now this is a great article . Amateurs can learn from a conversation like this.
I use my 746 on two meters and HF with great results.
It seems to hear fairly good on two, of course I use a 20 element cushcraft yagi.
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RE: DSP -- Is It All That?
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by K4JSR on April 7, 2005
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NK7J sed, "Missing the boat? Heck I think you fell off the dock.
;-)
Jack"
Jack, Mikey has a MS in BioMedical Engineering.
I think he knows lots of DOCs! ;-P
Besides, if Mike fell off of the dock in NYC the water is so thick that he would simply bounce around
on the surface! ;-P
In fact, one of his favorite pastimes is to take a
running leap and belly flop into the river and skip
like a stone all the way to Jersey!
Fat Calbert strikes again!
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RE: DSP -- Is It All That?
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by KA4KOE on April 7, 2005
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Cal
You need to get out more...these puns are getting out of hand. If you remove the "n" and "s" you simply have
p u
Remember, Mikee is now a fudge, er I mean manpack owner now...he has a Racal TRA-931x on the way.
PHILIP
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Code is Pure Evil
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by KA4KOE on April 7, 2005
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Mikee has more letters after his name than I do, Cal. Does that mean
A. He is a man of letters?
B. He is smarter than me?
C. It is a listing of the various syndromes he is afflicted with?
D. None of the above.
E. All of the above.
F. Blame the ARRL.
G. Praise the ARRL.
H. Code is good.
I. Code is pure evil.
Tell me quick what it is!!!
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DSP -- Is It All That?
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by KB0GU on April 7, 2005
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I have a very early iteration of the TS870 and have been happy with its receiver performance for what I use it for. However, I have also seen the complaints about the wide front end, and modification posted which replaces the crystal filters to make a "super" radio out of it. Have not had chance to listen to one that has been modified but read many reports about it from those who have and it all sounded good. I have strong desire to do the same to mine and have the factory do the updates on the chip set.
The DSP as it came out of the box made urban DX operations on 80 meters a possibility for me a number of years ago when I had three phased verticals. The couple of rigs I had prior could not hear through the noises.
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DSP -- Is It All That?
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by WA6BFH on April 7, 2005
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<The majority of hams that are really into the hobby (DX’ers, Contesters, QRPers) >
Now above is a comment that made my blood boil!
So, only DX'ers, Contester's, and QRP'ers are REALLY INTO THE HOBBY?
I will try to suppress my baser motivations! There are other pursuits in Ham radio that I think are certainly as laudable (and more-so) than the three mentioned!
In fact simply discussing the technical merits of receivers is better laudable!
So Hrrrrrrrrmph!
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RE: Code is Pure Evil
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by K3UD on April 7, 2005
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First of all I never owned a radio with cascaded crystal filters or mechanical filters, and never had a 75-150 foot tower with a Long John yagi for each band mounted on it.
However, I have used very good radios with good dynamic range and good single crystal filters coupled to my low (40FT) tower, triband beam and wire antennas, and was very happy with the performance.
This past summer I opted for a IC-746PRO which uses DSP for all filtering at the IF. I figured that if it did not work out I would sell it and go back to a radio using traditional crystal filtering.
After I learned how to use and manipulate the DSP functions, I have to say that I was amazed at how versatile the rig is when it comes to selectivity and noise reduction. I do not miss the crystal filter. I have operated both phone and CW contests, DX pileups and weak signal work and have never felt the need for better filtering. I also saved a lot of dollars by not having to add a wide and narrow CW filter and a narrow SSB filter. I figure close to $500.
However, If I was using what the author of this article uses and had the big antenna system it might be a completely different story.
On the other hand, I also have an FT-100 with the CW crystal filter. The Yaesu has what I consider to be very good DSP audio filtering which is adjustable as to bandwidth and noise reduction. Using the very narrow DSP CW audio bandwidths along with the crystal CW filter, I have found that it is a tremendous combination, and is INHO a bit better CW radio then the 746PRO is. Many times the audio DSP CW filter is all I really need when there are no CW contests going on.
I don't think that the crystal filter is going away very soon, but the radios with IF DSP seem to be gaining.
73
George
K3UD
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RE: DSP -- Is It All That?
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by NI0C on April 7, 2005
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WA6BFH wrote:
"In fact simply discussing the technical merits of receivers is better laudable!"
Yapping on eHam does not prove that one is "really into the hobby." I thought the operations mentioned, namely DX'ing, contesting and QRP, were good examples of hamming that are the most demanding in terms of receiver performance. Perhaps you're Hmmmph'ing because your favorite aspects of the hobby were not included.
73,
Chuck NI0C
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RE: DSP -- Is It All That?
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by W4LGH on April 7, 2005
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DSP is what it is...DIGITAL SIGNAL PROCESSING. It is now easier and cheaper to allow a digital device to do the work of older mechanical devices. DSP is NOT for everyone, BUT it does have its place! Every good receiver is still going to have crystal filters, the DSP IS AN ENHANCEMENT to these filters.
My FT-920 has pretty good filtering, and very good DSP. However I kept my external JPS NIR-12 dual DSP, because if will mske 40meter SSB sound like FM, removing all the white noise, along with other noise elements. WONDERFUL BOX! I would recommend everyone to try one.
73 - W4LGH - Alan
www.w4lgh.com
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RE: DSP -- Is It All That?
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by WA6BFH on April 7, 2005
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Maybe so!
Here is one though for an example:
http://www.hb9bbd.ch/
I'm sure I could come up with a bunch but, maybe I will have to write an article to that effect! I won't take up further bandwidth on JJH's piece!
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DSP -- Is It All That?
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by KG6TT on April 7, 2005
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I am about to step into it... I am sure. If you feel inclined to flame go ahead I just ask that you read through everything I write and consider it as one opinion, albeit a reasonably informed one I hope.
The short of it:
I strongly believe DSP is being pushed ahead of its time. However, DSP's potential will improve steadily as technology improves. BUT Today... we are NOT getting any choices from the major manufactures. Is this bad? Well yes if you want maximum performance for your dollar invested. Are today's DSP designs horrible? No, they are actually pretty good considering their still somewhat primitive processing capabilities.
Are DSP designs better than previous designs that did not have DSP? Better than many BUT NOT better than ALL. So is it a natural design progression for manufactures to push DSP on us? Yes!!! There are tremendous 'potentials' in processing signals digitally. Potential performance enhancements, design flexibility, reduced manufacturing costs... creating great opporunities to market new products!
If it is not ready for prime time then why are manufactures pushing DSP now? Those potentials again... And they have to compete with one another or possibly loose market share. And generally DSP designs work pretty well and manufacturers probably feel that they are delivering what buyers want. Whatever DSP design weeknesses there are in the current breed of available rigs provides future opportunity for improvements and new sales.
If DSP isn't always better why do we buy it? Well, we hardly have a choice if we want new equipment. Also there is this growing 'perception' that DSP must be better in the long run... otherwise why would it be everywhere? Let's not forget that amateur operators as a user community are not, in general, as technically savy as in the past.... and consequently as customers we are generally fairly receptive to slick 'marketing claims'... and eventually additionally encouraged by the 'early adopters' user testimonials (the true value of these testimonials is what?).
What are the downsides of buying a DSP designed rig? You won't necessarily be getting the best of today's design art but rather the best of what is being offered today. Frankly, it is hard to buy one that isn't unless you go used (and do the manufactures hate that!). You could, however, stick with your 70s, 80s, or even early 90s vintage rigs... or opt to buy one of the best of those generations... instead.
The technical issues/concerns behind my opinions:
I believe I am a fairly technical ham (just over 40 years), which is good and bad I suppose. Degree in EE including Analog, RF, digital design, computer programming, and some years as a product engineer/designer for 'one' of the amateur equipment manufactures (pre DSP). And although I am secretly a very hopeful individual on the surface I am devote skeptic, especially where advertizing claims and user testimonials are concerned. Can't help it. I also have owned several DSP equipped rigs so I have my own first-hand experience (good and bad).
Technical Stuff:
Where receiver design is concerned the simpler the path from antenna to your ear the better. Mixers, amplifiers, filters, and detectors need to process the widest range of signals cleanly while inserting the least possible circuit noise and distortion. Filters must pass the desired signal width and maintain that amount of bandwidth rejection regardless of the strength of offending signals (theoretically).
While there are arguments to be made for single versus mutilple conversions, filter choices, tubes versus solid state (hear we have to examine the time frame of the designs), tuned front ends versus wide-band types.... Overall, engineer and user experience has proven that some designs work better than others and that users 'requirements' change over time which impacts design choices as well.
Why we can't have our cake and eat it too!
Having said all this there are a number of great operating paradoxes in the ham community. We want the best performance in our equipment BUT we want 'easy-to-use' more. And although we really want best performance in an easy-to-use rig we want 'Swiss Army Knife' designs MORE. We want reliability and easy servicability, BUT we want miniturization MORE! Lastly, we want to believe we know what is best, BUT we trust others MORE.
The Descrete VERSUS DSP Emulated Design Paradox:
Those paradoxes (and others) are seen everywhere in actual equipment design choices. For example, for general amateur HF communications (cs, ssb, fsk, digital) we generally need to improve circuit Q beginning at the antenna stages thus maximizing selectivity before the first amp or mixer (what doesn't get in can't hurt us later) and yet we have abandoned 'preselectors' for the convenience of broad-banded front end designs. We have opted for 'do everything' receiver designs (general coverage, FM, etc.) rather than using more specialized equipment (to reduce cost? to save space? convenience?) while doing so inserts multiple nasty compromises in design and results in performance issues/problems.
Case in point: Emulating Noise Blanker functinality in DSP. Ahhh, well RF designers know that broadbanded pulse noise must be removed as early as possible in the antenna to ear path... in other words incorporate pulse noise reduction circuits BEFORE as much of a receiver's selectivity stages as possible, otherwise the pulses are literally stretched making their removal with out resultant signal artifacts nearly impossible. As the current crop of DSP designs are at the end of a multiple conversion IF chain (DSPs operating at high frequency IF ranges are prohibitively expensive) DSP derived noise blanking simply doesnt' work very well.
The real Paradox:
I will grant you that DSP offers interesting alternate design approaches, but as with all designs actual DSP implementations can vary dramatically in their effectiveness. All DSPs are NOT alike.
I believe some manufactures have delivered products with DSP functionality that actually delivers as generally promised. Unfortunately, except for other non-DSP design improvements I don't believe that their current crop of DSP rigs are that much better (if at all) than their best, pre-DSP designs. But as I mentioned before, from a manufacturing and support standpoint substituting digital circuits for descrete components is cheaper... while at the same time cheap digital functions allow for cheap 'bells and whistles' which sell. And of course, if the competition is doing it you fear loosing market share if you don't.
Do we really need it?
No. Lots of great 'used' rig choices as options. Don't make it too easy for today's amateur product manufactures to get your money. And it is sort of neat to know just how much they hate it when you buy older used (and usually very servicable) products.
The DSP forcast?
I think there are a couple of manufactures that are getting the message and putting back the critical descrete circuits were performance is an issue and using DSP enhancements where they truly enhance, and that the ultimate performance will improve by leaps and bounds in future rig generations. But today, the best melds of tradional and DSP designs are limited to the top-end models... which are really only for those with very deep pockets.
What do I use?
Contesting: Ten-Tec Omni-VI Plus
General rag chewing: Ten-Tec Paragon
Mobile: Ten-Tec Scout (yes, a lowly Scout)
Am I evaluating anything else:
I recently picked up a used Kenwood TS-940SAT, pre DSP rig with wow bells and whistles!
Most disappointing rig that I have owned?
Ten-Tec Jupiter (not terrible, just not good in my noisy environment)
What I would like to own?
Not sure yet.
73,
Jerry, KG6TT
Albany, CA
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RE: DSP -- Is It All That?
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by NI0C on April 7, 2005
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WA6BFH:
Nice link-- thanks for sharing. This lowband op gets nosebleed just thinking about those frequencies, but I'll look forward to learning something from your article, as always.
73,
Chuck NI0C
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RE: DSP -- Is It All That?
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by VE7RF on April 7, 2005
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The TX DSP in my MK-V is horrible. The analog is superb... after I replaced both stock filters with 6 khz INRADS... (the 455 being a CMF).
The TX DSP in ALL the Icom's including the 7800 is bad news.... they ALL have this "digital artifact gunky sound to em". I can pick out a Pro1-2-3 7800 in seconds.
### The auto notch dsp in the mk-V works BUT... when on, and notching nothing... u know it's in line.... it layers a 300-2900 filter on top.... and has this hollow sound to it. The DSP auto notch filters on my Behringer audio gear just blow away any of these dsp auto notch filters inside the xcvr's. You can set the Behringer to permanently notch a freq.
### Sure the DSP RX is in the IF of the Icoms.... but alas it OUTSIDE the agc loop !!
## IE: u auto notch the 40+ over cxr..... but it's STILL 40 over S-9 on the s- meter... and RX is desensitized.
### On the flip side.... IF notches ARE inside the agc loop.... BUT.... even after notching a huge cxr..... you STILL have the same level of audio in the spkr.... simply cuz of AGC action.... anything from S-3 to 60 over.... produces the same level of audio out the spkr.
## To be really effective... you need BOTH DSP auto /manual notch.. AND IF NOTCH.
### On the MK-V... you can use dsp auto notch... manual IF notch or BOTH at the same time.....
On the Pro-1-2-3.. you can only do ONE AT A TIME... which sucks.
### 12 khz wide roofing filters in ALL the IF's in a Icom.... with these cheap DSP filters at last IF is a joke. Anything inside the roofing filter fries the mixers.
### You need narrow roofing filters, narrow IF xtal filters ans narrow xtal/mech filters... THEN the DSP.
### The yaesu 2.0 khz filters are pure junk. The skirts are really bad. Ditto with the stock yaesu 2.6 filters (they are 2.6 not 2.4).
### I replaced ALL the yaesu filters in my 1000-D with PAIRS of INRADS.... 1.8...2.1....2.8....6.0
### The pair of Inrad 2.8's is as good or better than the stock yaesu 2.6's.
### I owned 2 x R4C's yrs ago... modified to the hilt. Replaced 8 khz roof filter with a PAIR of 2.0 xtal filters one for USB... one for LSB.... and a 600hz lsb for cw.
### These current 12 khz roof filters are a joke..... ditto with the narrower 4-6 khz roof filters. Roofing filters gotta be wide enough to pass BOTH sidebands.... OR you have to use SEPARATE roof filter for EACH sideband.... which is a tough order for vhf 1st IF's.
### Switchable roof filters on these new radio's is 28 yrs old. The ultimate is narrow roof filters for each sideband.... narrow xtal filters at lower IF's.... mech/xtal filters at 455... then IF DSP.
later..... Jim VE7RF
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RE: Code is Pure Evil
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by NL7W on April 7, 2005
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All:
I presently have my second TS-850Sat -- won't get rid of it anytime soon. I made a mistake selling my first one in the late 90's. The receiver is still incredible, given the installation of effective International Radio filters in both IF stages. The filters make the slope tuning controls wonderfully sharp. As someone else said, the notch filter really works quite well.
After also owning an early NIR-10, a newer, audio DSP-based FT-920, as well as operating the 756 Pro series on occasion, I can say that the later generation audio and IF DSP filtering has really come far. My FT-920 was a pleasure on HF, with similar experiences with the Pro's. If they only had an 850-class receiver, with dual IF filtering and audio qualities and characteristics, they would be close to perfect.
Speaking of perfect, I believe the Ten-Tec Orion may be the first rig to properly incorporate proper RF and DSP design. The new Yaesu FTDX-9000 series may equal or better the Orion's pure receiver performance, but that remains to be seen.
As far as cheaper radios go, the later FT-1000MP series and Icom's 756 Pro II and III are able performers, and offer good noise reduction (I wouldn't mind op'ing a Pro III for awhile).
Here's some food for thought. Maybe Kenwood could design and market a follow up rig to Kenwood's popular 850 and 870 series, combining the best analog and DSP technical features of both -- at a reasonable "ham radio" price tag? We shall see...
73 de Steve, NL7W
Palmer, Alaska
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RE: DSP -- Is It All That?
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by WA6BFH on April 7, 2005
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As I was reading Jerry KG6TT’s response I found myself agreeing with just about all that he said. In many instances, I thought of certain Tentec equipment as good ‘case in point’ models for what he was saying. When I got down to the bottom of his post, I nearly laughed out loud! Here though may be a couple additional things that he didn’t say, or maybe just another way to look at things!
Those of us who have been around Ham radio longer can appreciate the design differences inherent through different periods of time as they affect the “State of the Art”. Older radios just were not up to anything like what we expect from a radio today.
If an older vacuum tube radio used a 6AK5, or 6AM4 at its front-end, or as a mixer, it would be deaf compared to what can be done today with HempFet’s, N-MOSFET’s, or even J-FETs. Also, these devices need to be appropriately chosen or selected (which is available from the front panel of some radios) for the best noise figure, verses intermodulation etc. Another point, even some older tubes have better gain, sufficient noise figure (for the noise floor of that given frequency band) and ALWAYS better dynamic range (such as 6CW4’s or 6DN4’s). Ya can’t beat a tube for both gain and dynamic range!
I think that Tentec has understood this, and cultivated a sort of design philosophy through the years. I remember when all they produced was QRP power level radios -- because they wanted to be ALL solid state, and you couldn’t get serious power from a transistor in the late 60’s or early 1970’s. Now you can get decent solid state transmitters, and the small signal amplification vs. noise figure makes for very good design possibilities for receivers.
DSP simply still has a ways to go yet up the design curve. A good testimonial to this is the excellent ANALOG filters provided by companies like Inrad, and that such ANALOG filters are very marketable!
I will still take a nice (mostly, or all) analog radio any day. The Yaesu FT-920 is a wonderful radio, as is the even older Drake R4C. I like some Tentec stuff Jerry, they are still just a little slow with 6 Meters and up -- as is in keeping with that slow baby step philosophy of theirs. I think that soon though they too will come out with some really good VHF stuff. I hope so, I would feel awfully stuck in the mud if I only operated MF and HF!
Ya gotta get up there where a person can breathe -- in the world above 50 MHz!
73, and good comments all the way around! de John
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RE: DSP -- Is It All That?
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by WB9YCJ on April 7, 2005
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So far, the best DSP is between the ears. I choose Ham radio and shortwave and accept it for ALL it's characteristics including fading, snap crackle pop, etc. Thats what makes it Radio and FUN. If I want crystal clear - I will use a fiber optic land line.
I think DSP is over rated. The commercial people have made alot of money selling dsp. I'd rather see better basic receivers with higher dynamic range, intercept points, etc.
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RE: DSP -- Is It All That?
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by AA4PB on April 7, 2005
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### Sure the DSP RX is in the IF of the Icoms.... but alas it OUTSIDE the agc loop !!
-------------------------------------------------
That's not correct if you are including the 756PRO series. The DSP IF filters are indeed inside the AGC loop.
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RE: DSP -- Is It All That?
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by AA4PB on April 7, 2005
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Wow! If its the noise and QRM that makes HF fun then maybe we should add noise generators to our repeaters so the 2M guys can have some fun too :-)
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RE: DSP -- Is It All That?
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by WA6BFH on April 7, 2005
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Shoot, most of'em run their cute little VX-5's etc, and can't put a near quieting signal to the receiver anyway!
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RE: DSP -- Is It All That?
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by AA4PB on April 7, 2005
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Now lets see, what would be the easiest way to generate realistic sounding static crashes and QRM for the repeater? Oh yes, a DSP chip of course :-)
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RE: DSP -- Is It All That?
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by NS6Y_ on April 7, 2005
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Trouble with the cute lil' vx5's is the cute lil' antennas - with a decent antenna they could put a good signal into the repeater.
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RE: DSP -- Is It All That?
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by NS6Y_ on April 7, 2005
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DSP = Digital Signal Processor = What the nerds do with your IF output signal
- According to the acronym dictionary at www.microwaves101.com which is a GREAT site!
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RE: DSP -- Is It All That?
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by WA6BFH on April 7, 2005
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VX5, Bah Humbug! Give me a good Motorola radio with 40 dB's or more of limiting, a good squelch circuit, and FM deviation that starts at such a low oscillator frequency and is so symetric it just sounds goooood!
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RE: DSP -- Is It All That?
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by NS6Y_ on April 7, 2005
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Oh come on we all want to be Motosexual, those things cost though!
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RE: DSP -- Is It All That?
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by K4JSR on April 7, 2005
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Chuckster, N1 Orange County sed, "I think it must mean he is a fan of dipoles"
To which the smart alec reply is, "YAGI GO HOME!" ;-D
KA4KOE said too danged much! The correct answer would be, "any possible combination of the above at
any given moment."
And BFH, I must commend Ms. Alex on her astute observation about VX-5s. I liked mine so much that I got KG4RJM one for our anniversary two years ago.
And Alex was correct in asserting that with a real antenna the VX-5 gets out great! I use a Larsen 5/8
for 2 meters. Works great on 6 M as a 1/4 wave,
is a real killer on 2, and is a very acceptable
compromise on 440. Also the broad frequency receive coverage is a neat-o plus. Let's see the boyz from
Schaumburg beat that for the price.
Also do not hold your breath for the good guys in Sevierville to go all ga-ga over VHF. They have made
several forays into 6 and 2 meters and have found that their market share is too small to really be
gonzo for it. I have had the pleasure of meeting and knowing all of the Ten Tec founders for over thirty
years. They were also some of the founders of Electro-Voice Corp. In fact the Ten Tec factory is just down the street from where EV was. Al and Jack were both
and still are, committed CW ops. That is where they
found their niche, in HF CW with SSB as an after thought for their customers. Can't argue with their success, but I also would love to see more 6 meter
and above serious equipment come from up in those
hills! But they have a payroll to meet and giving in
to our instant gratification may not be in the best interest to their stock holders or good, old USA
workforce. Sigh!
I gotta go get some ZZZ. I have a job interview tomorrow and a chance to break out of the world famous
Forget-Me-Not Rest QTH. Cabin fever sux harder than the tornado that pulled Dorothy out of Kansas!
Alex and Caity, pound on John, BFH. It is good for him
and will keep him in a proper frame of mind.
TRUST ME! ;->
73, Cal K4JSR
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RE: DSP -- Is It All That?
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by K4JSR on April 7, 2005
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Actually, Alex, he may have wanted to be "QUASI-MOTO
SEXUAL" but just could not get past the hump!
Does that ring a bell?
I'm outa here! Tempus is fugiting like crazy.
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RE: DSP -- Is It All That?
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by NS6Y_ on April 7, 2005
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Ten-Tec is NOT a good word with me these days, their QC seems to be in the toilet - if I want the ultimate CW rig I'll just build a K2.
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DSP -- Is It All That?
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by N5EAT on April 7, 2005
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Yes. It's all that. I have a ClearSpeech speaker, and DSP in several radios. If you have a horzontal beam and $12,000 receiver, perhaps it wont' improve much. If you've got a bunch of 700.00 dollar radios and run a vertical antenna in a crowded city environment - DSP is the cat's pajamas.
I really like it, and it can only get better.
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RE: DSP -- Is It All That?
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by NS6Y_ on April 7, 2005
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Elecraft actually has a whole raft of products in the pipeline too, and I have no doubt a DPS unit is in there, in fact there's a DSP for the K2, and keep in mind, Elecraft doesn't add stuff to their line unless it's something useful that works.
I like the variable filter on my KX-1, there's like 4 xtals in there and you twiddle a knob, all the way from say 3kHz down to 300Hz, you can tweak it wider or narrower anywhere in the continuum with a knob right on the front of the rig, now that's nice!
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RE: DSP -- Is It All That?
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by NS6Y_ on April 7, 2005
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I mean DSP, DPS lol, digital piece of um, pie yeah that's it, pie hehe.
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RE: DSP -- Is It All That?
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by NS6Y_ on April 7, 2005
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Actually I think the real reason they're putting DSP in all these rigs is it's working out cheaper than putting in real filtering. If Inrad's getting $125 for a CW filter, I'm willing to bet the Collins unit is at least 50% of that price if not 3/4 of the price. Building xtal filters takes matching by hand apparently, and that's expensive too. I think these companies are getting these DSP chips in huge quantities and thus very cheaply and it's a way to save a buck. It all comes down to ham cheapness again, my little 817 didn't cost me much, but the filter to really use CW is another $125 and if I were serious about SSB I'd want one of those too and the board to put both filters in, that makes it about $300 more than the price it took to liberate it from the store.
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DSP -- Is It All That?
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by WA2JJH on April 8, 2005
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Thanks to all. I got an iteresting answer from Elecrft.
They use DSP in the audio stages. I was surprised at first.
As an OM put it..."audio DSP are just a bunch of OP-AMP filters and amps that are CPU controlled with a little program and A/D then D/A conversion.
Many new cheap rigs are that process. The ELEKRAFT
engineer had this take....,"32 bit processors simply lack the power nd programing to emulate a good 1st IF stage DSP. We decided to use our DSP in the audio chain.
The DSP, A/D,D/A, and alorythms, simply are not fast
to make a decent 1st IF DSP. This a good partial answer
from Elekraft.
The IF I judge all others by is the 1st mixer and IF used in theold Drake TR-7. The front end is so good, that no RF amp before the 1st mixer is used.
After the 1st mixer is a simple 2 pole monolithic crytal filter, and an active L/c filter. This is your so called brickwall.
I look to the TS-850 FOR A GREAT 2ND IF. dUAL 8 pole xtal filter witha great dual PBT.
IMHO, we did miss the boat. We should have used DSP to ENHANCE good rigs.
Save all your fancy DSP for the 455khz 2nd IF and audio stages.
IMO, this is why we can choose from a $600DSP cheap rig or go to $3000++ for a good rig!
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RE: DSP -- Is It All That?
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by NL7W on April 8, 2005
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Yes, I would love an 850-class receiver with the addition of a low IF DSP stage (below and after the 455 KHz IF), and/or a well-designed audio DSP stage. This "new" radio should also include an appropriately narrow 1st IF filter (in the up-converted stage), such as those be offered for the 1000MP by International Radio.
What a rig this would be! Heck, this almost sounds like an Orion... but not quite. Speaking of the Orion, I certainly don't need the bandscope or many of the other bells and whistles that rig has. Love the rig's specs anyway.
I want pure analog HF performance -- only enhanced by DSP at the back-end, or in the last "included" IF or audio stage.
Is this too much to ask for these days?
73 de Steve, NL7W
Palmer, AK
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RE: DSP -- Is It All That?
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by W4VR on April 8, 2005
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Yes indeed, I agree with your sentiments. Those old tube receivers with low-distortion front ends and brick-wall filtering are gone for forever. Unfortunately, DSP is here to stay. Don't give up quite yet though, improvements are on the way, at a price. We're beginning to see this in the $10K+ radios. When I compared my 1000D to my PROIII, I found that the benefits offered by the PROIII outweighed what the 1000D had to offer, so I sold the 1000D and am very happy with the PROIII.
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RE: DSP -- Is It All That?
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by WA6BFH on April 8, 2005
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Alex, if you are seriously interested in iCW, make a resonant speaker housing. You can use it with any radio, and it will provide real signal to noise performence!
Also, my comment about Motorola is in reference to real radios, not hand-held toys. A radio like a MoComm or Micor can be had for $20.00 to $40.00 bucks. You will not find better (FM) receiver performance in ANY Japanese radio, and the transmitter also is a joy to use!
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RE: DSP -- Is It All That?
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by NS6Y_ on April 8, 2005
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Haha a resonent speaker housing, that's a mechanical filter all right, that's a good idea.
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RE: DSP -- Is It All That?
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by K4JSR on April 8, 2005
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Micor? MUHUHAHAHAHAHA!
Try permanently repairing "THOSE THINGS" that the big
Blue M (Not the process oven company) used for plated through holes on their circuit cards. Haw! Haw! Haw!
Now get straight, John, or I'll tell Alex that you are
an OF who carbon dates back to when microwavers were
iron and waveguides were wood! HAH! And I'll raise you one toothless cackle!
73 from the world famous Forget-Me-Not Rest QTH.
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RE: DSP -- Is It All That?
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by WA6BFH on April 8, 2005
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Alex, GET REAL! An acousticaly designed housing IS the ultimate MECHANICAL FILTER! You know, or maybe you don't, that that is why crystals (ya know, ROCKS) are used -- they have a NATURAL resonance!
If you only want about 500 Hz of bandpass -- why would that be a bad idea? Tell me, please do????
And JSR, I have never had to repair one of those radios. You simply tune them up, and they work forever! I have some in repeater service you know, and nothing will kill radios like repeater duty cycle!
I don't need absurd comments from a person who should be plugged in! Like I said.... don't!
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My DSP dream.....Lets see your DSP enhanced......
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by WA2JJH on April 9, 2005
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FIRST OFF LETS NOT BICKER! The exchange of opinions was
great. LETS GO FURTHER! no bickering, just free exhange of your ideal design. YOUR CHOICE FROM NO DSP,
DSP ENHANCEMENT OF A GOOD NON DSP RIG, TO FULL BLOWN DSP/SDR.
I would start out with a Hybrid of the TS-850, DRAKE TR-7 AND THE ELEKRAFT K2.
g I like what is done in the K2. The L/C networks are optimised for ham bands only. HOWEVER flick a switch, and the front end is opened up to lets say that of A
DRAKE TR-7A. The first mixer should be the sae as a TR-7. The mixer is so good, no pre-amp is needed.
However we should be able to kick in a pre-amp,is desired. When you use the K2 ham band only mode,a pre-amp may prove handy. The gain will have a bypass position,3db gain, 6db, 10db and 14db.
After the mixer, a 4 pole 12KC wide xtal filter for IF bandwdith. In the K2,they do not upconvert to 60-90mhz. We down convert. We chose an IF frequency, such that the image frequencies will be in a band we have no desire to listen to.
Now use your A/D and DSP. Create all the filters you want. Put in your Auto-notch with a manual over ride.
The next IF,simply duplicate the dual 8 pole filters with twin VBT the TS-850 has. Simplify it a little bit.
Have dual 2.7khz and dual real 8 pole 500hz CW filters.
I would to do it one stage. The TS-850 uses a 2 stage IF. The goal is to have twin VBT variable from
500hz-2.4hz. Also use an auxillary 2nd IF to demod
5 and 15khz AM and FM MODES, DUAL AND WIDE.
This Aux 2nd stage can be used to derive 3 AGC time
constance and noise blanker pulse processor.
The 3erd IF would be at 50KHZ. This ultra low IF will
allow maximum DSP. Put in a set of filters, 2nd auto notch, NB,and ANY OTHER DSP FUNCTION.
Use exact same audio out as the TR-7. It almost sounds like tubes. Use a front mounted speaker too.
One the TX side I would use audio only DSP. Perhaps
use DSP to optimise the ALC voltage for the final.
This would a good IF for 10 band voice EQ
One can also provide for 6 db of audio compression.
After the audio is converted to an SSB signal,use real RF speech clipper before the 8 pole SSB FILTER.
I AM SURE I Made a few design mistakes. Much can be done better.
This Transceiver is Babout 70% ANALOG. THE 30% DSP IS USED TO ENHANCE A TS-850/TR-7 LIKE RIG.
I KNOW DSP AND SDR ARE HERE TO STAY. HOWEVER, LETS NOT TOSS THE BABY WITH THE BATH WATER!
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RE: DSP -- Is It All That?
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by WO0Z on April 9, 2005
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"1) Take that signal in the noise and make it arm chair copy.
2) All kinds of fancy digital filters that will allow only the signal you want to here in a pile up.
3) A perfect automatic notch circuit that will zero in on all signals that dare to heterodyne with your rare DX contact.
4) A speech proc, that after you adjust the freq. response, To your voice and make it punch through everybody else. You will sound like you kicked in the linear!
Fact of the matter is...do not believe the hype or the sequel. "
Well, a while back, I would have agreed with you.
But, my rig, the SDR 1000, really does that kind of thing, and for a lot less money than some rigs out there.
Have you ever heard CW with a 25 Hz (yes, 25 Hz) filter?
It really can make armchair copy out of a noisy signal. Can't do 25 Hz with a mechanical filter. But, turn software loose on it and it's a different story.
And, there really is such a thing as an automatic notch filter. Speaking as someone who likes 40 meters, I can tell you, the feature gets used and it works.
And, if some Ph. D. invents a new noise filter idea, then someone can implement it and we can all try it out. No physical changes to the radio are needed. So, every kind of filter ever designed can be simultated -- on my rig, at least. And, I've seen some of them make a difference. That rat-a-tat-tat sound all over 17 meters lately? I can kill it.
Now, of course, any sort of DSP can't repeal the laws of physics. If that idiot (who seems to be omni-present on the bands) is within 25 Hz of Mr. Rare DX, then no DSP can do anything about it. If he is 50 Hz off, you'll still get a little splatter. But, somewhere between 75 and 100 Hz away, you don't know he's there at all. If I toss on the auto-notch, he's gone on SSB, too, wherever he is.
I can't speak to the DSP on the microphone side of it. I never have done much speech processing -- I like to think the clarity of an ordinary voice gives me a different kind of edge.
But, at the least, you can do everything with the software that you can imagine in terms of compression, equalization, and shaping the signal to your heart's content. I believe time will prove it is the equal, at least, of anything that is out there.
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DSP -- Is It All That?
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by G7TOK on April 9, 2005
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The problem with DSP in ALL current amateur radios is that they use a 15 year old operational model.
For example, noise reduction is generally a fourier based subtraction process, but using a pre-set noise signature.
The problem of course, is that the signature will never match your actual receiving conditions, and will only provide general reduction.
Compare this to even modest software solutions that can record a noise signature which will completely remove the background noise while leaving the wanted audio literally intact.
I have been very critical of modern DSP based transceivers for this very reason.
When manufacturers like Kenwood wheel out old technology(TS2000 springs to mind) dressed up as the bleeding edge and we fall for it time and time again.
The chipset required to perform snapshot based interference reduction is now available for a few dollars, providing in excess of 80dB reduction at 32bit rates, yet I can guarantee we will not see its like for many a year, at least, not as long as we are prepared to shell out thousands on the IC-7800 and the Yaesu 9000 sure in belief that we have our hands on the latest kit.
I can assure you, you haven't.
Gary - G7TOK/M3KPK
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RE: DSP -- Is It All That?
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by AA4PB on April 9, 2005
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audio DSP are just a bunch of OP-AMP filters and amps that are CPU controlled with a little program
-----------------------------------------------------
There are no OP-AMP filters in audio DSP. In DSP an A/D converter converts the analog signal to a digital representation. All the filtering is done with mathematical manipulation of the digital data. Then the modified digital signal is converted back to analog with a D/A converter.
Elecraft is right that currently available inexpensive DSP chips don't have the power to do DSP at a high IF frequency. You can do IF DSP at a lower IF frequency and obtain the benefits of having it operate inside the AGC loop. I think however that Elecraft forgot to mention to you that they already had the K2 radio design and developed their audio DSP as a "drop in" replacement for their old analog audio filter. I'll bet that had more to do with their decision to go with audio DSP than anything else. They would have to develop a whole new radio to do any kind of IF DSP, even at a lower IF frequency.
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RE: DSP -- Is It All That?
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by NG1I on April 9, 2005
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After reading ALL these posts on DSP, I realized I am still happy to have my TS-940S I bought in 1986!
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DSP -- Is It All That?
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by N9DG on April 9, 2005
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After reading ALL these posts on DSP, I realized I am extremely happy to not be clinging to my old radios and bought an SDR-1000 last December instead. I just keep some old technology radios around to remind myself why what I have now is so much better. I suppose though if I want to spend a lot of money to keep on feeling nostalgic I can go out buy a radio like a FT-1000MP, FT-9000, IC-756 Pro III, or IC-7800.
I also concur 100% with what WO0Z has said. A 25 Hz filter (that doesn't ring) is indeed something to behold, you simply can't do that with any crystal or mechanical means. The automatic notch is superb, the best I’ve used in any radio. It also has the cleanest, lowest distortion RX audio of any radio that I’ve ever used. It is the most fun radio that I have worked with in years, I haven’t been this fired up about piece of gear since getting my first Novice rig back when I was poor high school kid years ago and just getting started in ham radio.
And for the being the first model fielded from a startup company that is using an entirely new design paradigm for ham radio such as PC based DSP, and an extremely clever and novel sampling detector design to perform as good as it does is noteworthy. Most of its performance limitations are due to the chosen sound card of the PC coupled to the RF hardware, not the RF hardware itself. The upper limits of its true performance aren’t really known yet.
The open source nature of the SDR-1000 is really starting to accelerate with an increasing amount of software to load and use albeit it is most experimental in nature at this point. It's pretty cool having new software to try every other week or so. Other ideas like "client-server" software architecture to form the basis of Ethernet based radios are also being kicked around over in Flex Radio land. Doubt if we'll see any of that kind of technology out of the big 4 any time soon.
So yes DSP, and more broadly SDR is "all that", and more, and it *when* it is finally freed from the shackles of a "box with knobs" radio designs it will really come into it's own. Until then its true potential will not be realized.
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DSP -- Is It All That?
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by K8WTR on April 9, 2005
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Seems from all I have read and heard, the best would be a quality analog receiver with a quality outboard DSP unit. Add this combo to an operator who can hear the weak ones in the hash and there is a great combo. Mac, K8WTR
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RE: DSP -- Is It All That?
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by AE6IP on April 9, 2005
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The SDR-1000 looks like it would be a fun toy, and I'm sure I'd enjoy it if someone got me one for Christmas, but I didn't buy one because I'm waiting for someone to design a software defined *radio* rather than a radio with a software defined audio section.
For a receiver, that would be the SDR with everything after the quadrature detector replaced by circuitry that turned I/Q pairs into a data stream and fed the data stream to a firewire or usb 2 interface so I could do all the signal processing, without the extra dac/adac required by using the soundcard interface.
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RE: DSP -- Is It All That?
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by AA4PB on April 10, 2005
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It seems to me that the best receiver using currently affordable technology would be a quality front end design with suitable selected roofing filters followed by a DSP last IF (as high a freq as possible). The problem with add-on DSP is that it is at the audio level and therefore outside of the AGC loop. While it can keep you from hearing an interferring signal, it can't keep it from affecting the AGC and overall receiver gain. Its the same effect as PSK31 when the whole waterfall dims and the weaker signals drop off the screen because there is a very strong signal somewhere else in the passband. You can remove the interferring signal at the audio level but its already done its damage to the receiver.
That brings up a question about the SDR-1000. If all the signal processing and filtering is done in the sound card then it must be outside of the AGC loop and I would expect it to have the same problems. Perhaps they have some narrow analog IF filters inside the receiver unit that are remotely selected by the software.
I'm waiting for a real software defined radio (SDR) where there are no analog tuned circuits. Right now mfgs are calling their radios software defined if it has program memory in flash (so it can be changed), if the audio is processed by a sound card, or if the analog circuits can be remotely controlled by software (which has been done for at least 20 years now). SDR has become a sales buzz word in my opinion.
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RE: DSP -- Is It All That?
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by NL7W on April 10, 2005
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AA4PB, WA2JJH, and others (including myself) have it right. DSP does not negate the need for a quality RF front end, and a few stages of selectable IF filtering right after. In the future, advances in DSP and computing power technology will offer amazing achievements in modulation formats, TX and RX receive capabilities, operator convenience and ease, but digital circuitry will not bypass the need for RF components and circuits. Though, digital and analog tech will marry -- through necessity.
Beyond software defined radio (SDR), are the advances of cognitive radio tecnologies (CR), or "smart" radios. From a spectrum management standpoint, the FCC will have their hands full with that technology. Look up cognitive radio on Google, and read up on it.
73.
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DSP -- Is It All That?
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by N4HY on April 10, 2005
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I agree that almost DSP and SDR back ends do not give you the wow that they could. This has next to nothing to do with DSP. It has everything to do with the rig manufacturers doing nothing more than building the same old approaches into software. Having written the DSP code for the AEA DSP-2232 and participated in the writing for FLex Radio (SDR-1000), I can assure everyone that only now are we finally beginning to see DSP show its abilities. It has just been too difficult when one needed to write the entire body of code in DSP special purpose chip assembler. Don't give up on DSP yet. If FLex Radio, Ten-Tec, etc. "make it", expect to begin to see the full benefit of DSP in these radios in the near future.
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RE: DSP -- Is It All That?
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by KA4KOE on April 11, 2005
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Properly implemented, the sophisticated direct conversion scheme works pretty good. The receiver in my PRC-2000 (80's technology) manpack is superior to that in my Icom IC-756PRO (although the PRO is so-so at best).
A big advantage is the excellent AGC design. One can do alot with a properly designed receiver, even if its a direct conversion design. I wouldn't discount the SDR-1000 just yet.
PHILIP
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RE: DSP -- Is It All That?
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by KA4KOE on April 11, 2005
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Properly implemented, the sophisticated direct conversion scheme works pretty good. The receiver in my PRC-2000 (80's technology) manpack is superior to that in my Icom IC-756PRO (although the PRO is so-so at best).
A big advantage is the excellent AGC design. One can do alot with a properly designed receiver, even if its a direct conversion design. I wouldn't discount the SDR-1000 just yet.
PHILIP
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DSP -- Is It All That?
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by W6WO on April 11, 2005
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I agree with you on the need for front end XTAL filtering. The back end DSP adaptive DSP filter in my Tentec Omni VI-Pro does however differentiate between CW signals and noise and improves the SNR both audibly and as viewed on a spectrum display. I also have an external high performance 100 Hz DSP audio filter but this is seldom needed. Dynamic range and impulse response are the most important parameters for DSP filtering.
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DSP -- Is It All That?
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by KE5C on April 12, 2005
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> I have yet to see a single DSP rig that will beat my TS-850's dual IF filters, twin VBT, and manual notch.
you should get out more.
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DSP -- Is It All That?
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by W3DCG on April 13, 2005
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My world only knows the truths and limitations with regard to the TS 850 and just only a Pegasus/Jupiter with RF DSP.
Without a doubt, the 850 is where I turned when conditions were intensely loud and crowded, when full-on raw receiver performance coupled with excellent QSK make this rig in a class all it's own when you consider performance vs. price. But it's getting old and I believe reliability is in question. I've had to repair mine 2x but it's in pristine condition inside and out- visually.
Jupiter has limitations, the skirts are obviously- shallow. However, under non-contest-normal operating conditions, with careful adjustment, I find that the DSP DOES make a big difference in comfort. Auto notch works great, sometimes resulting in my heart skipping a beat when I move back to CW sub-bands and I'm thinking uh oh, I knew the honeymoon couldn't last forever, the rig's finally suffered a stroke of some kind. And then I notice, oh-duh- you have your Auto Notch engaged still, and I breath a huge WHEW and am again very pleased as I move on about my business. For 500-600 bux it's hard to complain about Pegasus- if you do, I suspect your expectations are a bit unrealistic.
It's not like Ten Tec wasn't aware of the limitations, they obviously were listening, because next came the best of both worlds. 3300 dollars base isn't out of line really, it's really more by the time you figure roofing filter options, etc, but it's not far out in the ten thousand dollar range. Likely performs as well. Probably better. Who knows? A few know.
I have always suspected SDR-1000/Flex Radio to be on the cutting edge, and I believe this is the future of RF, that eventually it will be the norm, instead of on the fringes.
I have read every bit of W0OZ's and N9DG's posts carefully, examining every letter of every word, hoping to divine more about the characteristics of what to me is the most intriguing radio currently available. All things considered, I believe N4HY. The potential for DSP remains huge.
Sure would be nice to read some eHam Product Reviews on the SDR-1000.
Most will scoff at the notion of their huge traditional boxes with all those cool knobs, being outperformed by a computer with a peripheral device connected to it. But I think the potential is there, and it will be achieved.
We'll resist it, I know I fear such a future. But the future draws nearer, and I for one, am curious.
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DSP -- Is It All That?
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by XV2PS on April 13, 2005
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DSP should be taken for what they are not more.
Icom 718: notch filter is for me an excellent tool against all QRMers. Noise reducer as well, although it distorts (when set too high), when monitoring the bands, it really makes it more comfortable.
FT-857: notch filter not as good as IC 718. But in CW, I am astonished by its abilities to dig out a signal off the noise.
Wouldn't do without DSP.
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RE: DSP -- Is It All That?
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by KE4SKY on April 13, 2005
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Not all DSP units are created equal, so depending upon which you have, your mileage may vary. I use the Clear Speech external unit connected to a Heil headset on my Kenwood TM255A 2-meter all-mode and it makes ALL the difference in noise reduction and being able to pick weak signals out near the noise floor. I'm able to work stations I cannot even hear without it.
I use the Clear Speech external speaker for HF mobile, mostly on 40 meters during the day and 60 meters at night, where it is very effective in reducing background noise and reducing ear fatigue when the squelch is set open enough LA1V in Norway on 5371.5, I couldn't have heard or worked him without it.
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DSP -- Is It All That?
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by YI9VCQ on April 13, 2005
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Take a CW signal that is just at or near the noise floor. Turn on the DSP NR on the Icom ProIII and 9 times out of 10 it will cause the signal to clear up dramatically. I don't know all the technical facts and figures but my ears hear a welcome difference. It's not "armchair copy" but who the heck can expect that from a weak signal. I'm just realistic in expectation I guess.
Of course, the ProIII's receiver is top-notch to begin with anyway. I have found that I keep the DSP on most of the time just to remove extraneous noise and that really goes a long way towards reducing operating fatigue.
Before the ProIII, I used a 706MkIIg and the DSP on it sucks. I never used it because it usually made reception worse instead of better. The only thing that helped was installing crystal filters. The filters helped a lot during the WPX SSB contest and helped me beat my arch enemy competitor YI9QWO. HI HI!
I say if it works for you then that's great. If it doesn't then don't buy it. Mine works for me!
73,
Korey
YI9VCQ
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DSP -- Is It All That?
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by KD5VHF on April 13, 2005
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"Am I missing the boat? You tell me." Mike, I don't think you have missed the boat. You just happen to have a really nice rig that the DSP rigs can't beat. I've owned several rigs like the FT-990 and TS-570 and have played with the Orion , ProII,1000D etc. and have yet to find anything that can wipe out interference like the TS-850's,TS-940's & TS-950's. I guess if you had never used anything other than a FT-101 then the DSP rigs would seem nice. I feel the folks that praise the DSP rigs are the ones that missed the boat. Now if only Kenwood would trash the TS-2000 shack in a box rig (what a step backwards!)and return to making a real radio like the TS-850 again.
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TS-850/TS-940
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by KA4KOE on April 13, 2005
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Which is better? I think its time for my 756PRO to go on the auction block.
PHILIP
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RE: DSP -- Is It All That?
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by WO0Z on April 13, 2005
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For what it's worth, I worked around 270 countries and 150 zones with a TS 930 with the optional crystal filter and no tower/tribander/amplifier. Modest antennas throughout.
That's my comparison point.
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DSP -- Is It All That?
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by K7VO on April 14, 2005
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"Missing the boat" is kind of strong language. As others have pointed out, AF and IF DSP come in many different implementations, some good, some not so good, and some outstanding. Even a good outboard audio DSP (Timewave 599zx, JPS NIR-12, W9GR DSP III) will help an older radio pull signals out of the noise that would otherwise be impossible to copy. Auto notch works incredibly well if it's implemented right. Reducing background noise may simply make listening less fatiguing.
While I have yet to play with a truly high end IF DSP rig (IC-7800, IC-756ProIII, Yaesu FT-DX9000) on rigs most of us can easily afford there is still no substitute for a crystal filter or three. OTOH, having those filters and DSP in addition can be a powerful combination.
Another good place for an outboard DSP is on a rig that lacks adequate filtering. Sometimes DSP can turn a rig that would otherwise be so-so at best into something decent. A good example of this would be an old Yaesu FT-7. It is very sensitive, has a very low noise floor thanks to an excellent analog design, and has excellent transmitted and received audio. It has no CW filter, no narrow SSB filter, and no allowance for either. Add a good quality AF DSP and it takes what basically was a decent receiver in it's day and makes it quite friendly on today's bands.
I have a fully loaded Kenwood TS-430V (the rare QRP version of the TS-430S). I have all three crystal filters. The rig is OK but not quite up to the standards of today's technology. It is, however, a rig that is very pleasant to operate with lovely audio. The outboard DSP helps it quite a bit.
I suspect if you used a top notch IF DSP rig and used it long enough to be comfortable with the DSP features you would change your opinion.
73,
Caity
K7VO
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RE: TS-850/TS-940
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by NL7W on April 15, 2005
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Philip:
Depends... but the 850 has the better receiver by far (including comparison to the 756pro)! It is one of the best radios of all time.
Boy, do I want Kenwood to come out with an 850-class receiver with properly implemented, last stage, digital signal processing. The receiver should include the FTDX-9000's selectable roofing filters, too.
As far as the transmitter goes, design in a 40 or 50-volt, 150 to 200-watt, low distortion transmitter. DSP action on the transmitter would be nice, as long as it meets or exceeds the specs of the 850's DSP-100 on the transmit.
Obviously, Kenwood must keep their famous Kenwood quality audio throughout the transceiver...
73!
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DSP -- Is It All That?
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by N6CIC on April 16, 2005
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I think that DSP has its place, but that it is not a miracle cure as some manufacturers would have you believe. With my FT-920, I have installed the INRAD 2.1 KHz SSB filter, and that in combination with Yaesu's audio DSP works quite well. However, without the improved IF filter, no amount of DSP can help. Another value of DSP is in older rigs where an outboad DSP can help reduce noise and improve signal readability. With my ICOM IC-735 on 80 meters, I use a Timewave DSP-59+ and it turns a signal buried in noise into a quite readable signal.
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DSP -- Is It All That? TNX OM'S
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by WA2JJH on April 17, 2005
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tNX TO ALL FOR YOUR OPINIONS. I respect them all.
Hey we set a first!!!! A THREAD WITH NO BICKERING!!!
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DSP -- Is It All That? TNX OM'S
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by WA2JJH on April 17, 2005
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tNX TO ALL FOR YOUR OPINIONS. I respect them all.
Hey we set a first!!!! A THREAD WITH NO BICKERING!!!
73 DE MIKE WA2JJH
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RE: TS-850/TS-940
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by WA2JJH on April 18, 2005
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Visa-vi KENWOOD. Many have said that KENWOOD is not really interested in KENWOOD.
I would not hold ones breath waiting for a new flagship rig from Kenwood. Ham radio is a tiny fraction of KENWOODS sales.
I would love a ""TS-890"". A upgraded TS-850 with DSP. Looks like KENWOOD is Missing the boat.
Perhaps a 3erd party has the Moxy to do it.
KENWOOD did make an external DSP. However the last one was spotted at a rain drenched table at Dayton for $500.
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RE: DSP -- Is It All That? TNX OM'S
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by S5M on April 19, 2005
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I did PhD research on CW HF DSP in 1990. DSP RX beat me EU champ, #5 Dayton in simulated CW pileup receiving 80% of callsigns against my 60%. Some 200+ QSO were made by robot in ARRL DX contest Feb. 1991. My only advantage was prior knowledge of USA callsigns at band opening under flutter condx. It made me humble after working KS on 80 m.
Auto carrier notch on SSB is better in DSP, RTTY and other digital modes decode also. It is also cheaper to mass produce and more stable then analog stuff. I am looking forward to all DSP HF RX 0-30 MHz. Better ADC is required under present technology.
73 de Mario, S56A, N1YU
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RE: TS-850/TS-940
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by K4JSR on April 20, 2005
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KOE asked, "Which is better? I think its time for my 756PRO to go on the auction block."
Get an Alinco DX-70TH!!!!
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