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Author Topic: SDR Hype ..  (Read 3894 times)
ZS5WC
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« on: November 10, 2017, 09:36:47 PM »

 :)SDR Radio-sure future of Ham Radio, but with some SDR characteristics I am still a bit sceptical.

It had to happen, the natural flow of progression had to herald in the new dawn of radio manufacture, namely SDR.
I see , apart from good performance vs. simplicity- COST.
Of COURSE the bean counters will jump at the opportunity to produce rigs like this. There are hardly any inductors or lumpy components inside the rig, the Direct Conversion / FPGA architecture makes for a very simple circuit, and there are no conversion stages as compared to a standard superhet.

So now apparently the strong signal handling characteristic is just out of this world-then why need a digital preselector?.
Preselectors go WAY back to tube rigs!.
Why the OVF (overflow) indication on the screen?.

Looking at the Sherwood table all rigs are classified according to close in strong signal handling characteristic.. Does one Parameter tell the whole story?.
Does it mean the OLD 1000mp is way inferior to an Atlas 350xl?..

Most ICOM rigs and most other DSP rigs have poor 'S' meter readings below 'S' 9 , my view is that these rigs, without the preamps in, lack front end gain, specifically in order to achieve close in RX selectivity.
Even the 7300 shows this "S" meter phenomenon, and QST commented about it.
(Below 'S' 9 'S' meter starts at ZERO with 30dB offset.)

Apart from the Bling-waterfalls etc, I am still a bit sceptical, and since ICOM went the DSP noise blanker route, I am amazed that many, since the PRO series, still suffer from the AGC NB overshoot.
Be interesting to know if this occurs in the IC-7610..
You know the annoying 'POP!' in the audio peaking 40dB over 9 with NB engaged!.

Call me old school, I like superhets, but watching the reviews on The IC-7610 closely to see what  progression has been made regarding actual Performance.

73 de William
ZS4L / ZS5WC
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VK3BL
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Posts: 1355


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« Reply #1 on: November 11, 2017, 01:36:34 AM »

Apart from the Bling-waterfalls etc, I am still a bit sceptical, and since ICOM went the DSP noise blanker route, I am amazed that many, since the PRO series, still suffer from the AGC NB overshoot.
Be interesting to know if this occurs in the IC-7610..
You know the annoying 'POP!' in the audio peaking 40dB over 9 with NB engaged!.

Call me old school, I like superhets, but watching the reviews on The IC-7610 closely to see what  progression has been made regarding actual Performance.

73 de William
ZS4L / ZS5WC


Dear William,

The pops are still there with the IC-7610; although I am sure I could tune it to my taste with the different parameters available such as width etc.

I feel there is a lot of beauty in the classical superhet, especially the down conversion types; they're much more like a work of art especially a high performance one.

I agree there is a lot of hype with SDRs.  A lot of the 'benefits' are actually realized by increased processing power, rather than the signal processing. 

I personally feel Icom isn't going to be offering many updates either, which is a pity.  I can't remember the time my IC-7300 last needed an update, or got a new feature.

BUT all that said, there is something 'clean' about the SDR design.  Its digital and uncomplicated, and its not like the average joe can repair a superhet these days anyhow; so no disadvantage there.

The real question now is what will the revolution actually mean; will new features lead to new operating modes, or new discoveries?

Time will tell!

73,

Jarrad VK3BL
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J.D. Mitchell - VK3BL / XU7AGA - http://vk3bl.wordpress.com
KENNETH
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Posts: 90




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« Reply #2 on: November 11, 2017, 06:57:21 AM »

"I am still a bit sceptical"...."I am still a bit sceptical..."

So said the horse and buggy folks about those new fangled horseless carriages.
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KA4DPO
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Posts: 807




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« Reply #3 on: November 11, 2017, 08:07:50 AM »

:)SDR Radio-sure future of Ham Radio, but with some SDR characteristics I am still a bit sceptical.

It had to happen, the natural flow of progression had to herald in the new dawn of radio manufacture, namely SDR.
I see , apart from good performance vs. simplicity- COST.
Of COURSE the bean counters will jump at the opportunity to produce rigs like this. There are hardly any inductors or lumpy components inside the rig, the Direct Conversion / FPGA architecture makes for a very simple circuit, and there are no conversion stages as compared to a standard superhet.

So now apparently the strong signal handling characteristic is just out of this world-then why need a digital preselector?.
Preselectors go WAY back to tube rigs!.
Why the OVF (overflow) indication on the screen?.

Looking at the Sherwood table all rigs are classified according to close in strong signal handling characteristic.. Does one Parameter tell the whole story?.
Does it mean the OLD 1000mp is way inferior to an Atlas 350xl?..

Most ICOM rigs and most other DSP rigs have poor 'S' meter readings below 'S' 9 , my view is that these rigs, without the preamps in, lack front end gain, specifically in order to achieve close in RX selectivity.
Even the 7300 shows this "S" meter phenomenon, and QST commented about it.
(Below 'S' 9 'S' meter starts at ZERO with 30dB offset.)

Apart from the Bling-waterfalls etc, I am still a bit sceptical, and since ICOM went the DSP noise blanker route, I am amazed that many, since the PRO series, still suffer from the AGC NB overshoot.
Be interesting to know if this occurs in the IC-7610..
You know the annoying 'POP!' in the audio peaking 40dB over 9 with NB engaged!.

Call me old school, I like superhets, but watching the reviews on The IC-7610 closely to see what  progression has been made regarding actual Performance.

73 de William
ZS4L / ZS5WC


I have been a ham for just over 50 years now.  I have seen us go from tubes to transistors and from DSP to all digital.  There is nothing wrong with a well designed superhet receiver.  The latest SDR technology reminds me of when we were making the transition from tubes to solid state, there were skeptics then and rightfully so, the first solid state radios were far from perfect.

 I look at the new IC-7610 as a continuation of the state of the art in amateur radio.  You are correct about the Sherwood list, far too many amateurs only look at the RMDR at 2KHZ spacing and think that is the only spec that matters.  If you are a contester operating in a multi radio environment it matters, otherwise it doesn't mean much, we know that from experience.  I have several well designed superhet radios and I can work weak signal DX with them all day long.

I think the real driving force behind the push toward SDR is the cost to build vs profit ratio.  You already pointed it out, and we all know that an all digital radio is less expensive to build and can be automatically tested and calibrated in less than a minute.  So I guess they are better in some ways but still have issues that need to be resolved.  I am planning to get a 7610 just because I like to stay current but I am keeping my surpehet radios because they still work very well for the kind of hamming that I do.  So I get where you are coming from and I suppose only time will tell just how good SDR really is.  I do know the manufacturers are probably not going back to costly superhet designs for economic reasons.
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K0OD
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« Reply #4 on: November 11, 2017, 10:55:20 AM »

Some hype, no doubt, but in many areas modern SDRs are ludicrously superior to their forefathers.

A  $575 1950s-vintage Collins 75A4 had a rated readout accuracy of about 400 Hz. Using its built-in scope, my Flex-5000 can measure frequency to about 0.2 Hertz. If my Flex drifts, I've been unable to detect it, and I've tried!
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KA4DPO
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« Reply #5 on: November 11, 2017, 11:32:18 AM »

Some hype, no doubt, but in many areas modern SDRs are ludicrously superior to their forefathers.

A  $575 1950s-vintage Collins 75A4 had a rated readout accuracy of about 400 Hz. Using its built-in scope, my Flex-5000 can measure frequency to about 0.2 Hertz. If my Flex drifts, I've been unable to detect it, and I've tried!

If you want to go to that extreme an FT-890 is ludicrously better than a 75A4.  In fact, I once sold a KWM-2 and bought a Drake TR4CW and it was better than the KWM-2 by a mile.  Now to put things into perspective, lets take a modern super heterodyne radio like the Elecraft K3S or the Kenwood TS-590SG.  Are they accurate?  Oh you bet they are, every bit as accurate as your Flex 5000 and they don't drift any more tha your Flex because all of their oscillator frequencies are derived from a master oscillator (digital clock circuit) that is very similar to the one in your Flex radio.

The close spaced dynamic range of the K3S is better than your Flex 5000 and because it is a superhet, it does not suffer from latency or several other pesky SDR issues that Icom seems to have overcome. 

So are modern SDRs better than 1950's radios?  Oh hell yes...  Are they better than contemporary top end super heterodyne radios?  Not necessarily, from a performance standpoint a well designed superhet is still a potent receiving device no matter how you look at it.  And for the record I don't consider a spectrum analyzer display when determining receiver performance.  That software is available for any modern radio and it does not improve the capability of the rig. 

As for multi-slice receivers?  That contributes to latency and reduced performance because of the extra processing required, except in the case of the Icom where the two receivers are truly independent and not derived by chopping up the I/Q bit stream.

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VE3WGO
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Posts: 162




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« Reply #6 on: November 11, 2017, 12:13:01 PM »

Performance specs aside, the runaway popularity of SDRs is due in large part because they offer amazing receive spectrum analyzers (band scopes) and easy wideband tuning for low cost.  The easiest way to do that these days is with a digital sampling receiver.  The earliest versions still used a superhet frontend to get the RF range down to a low enough frequency for the sampling Analog/Digital converters.  But digital samplers can vary from low resolution (8 or 10 bits), limited dynamic range, poor noise figure, lowest cost units, all the way up to high resolution (14 or 16+ bits) high dynamic range, good noise figure, high speed units.  Low cost ones often suffer from various other problems like images, intermod, and poor sensivity. You really do get what you pay for.

SDRs are not really new.  Believe it or not, the cellular base station that your smartphone/cellphone talks to has probably had an SDR in it since about 1992, depending on your cellphone provider and whether they bought their gear from the huge (sadly now defunct) telecoms company that I used to work for.  The SDR is easily tuneable, and can switch modulation/demodulation modes in an instant, and be upgraded in the field,  (hence the software programability advantage). The Military's been using SDRs for even longer than that.  But low cost ones have become available with the advent of digital cable TV which required high speed high resolution D/A converters for a number of years while people still used analog TVs on cable boxes, and direct digital broadcast TV satellite receivers mainly in Europe and Asia.

Are SDRs hype?  Well, band scopes have always had a certain appeal to receiver users, because the scope display shows what's happening on the band at a glance, and allows the user to find where the activity is faster than by using just their ears.  They've also been called Panascopes, Panadaptors, Spectrum Scopes, etc.  Do you remember Heathkit's popular "SB-620 Scanalyzer" bandscope in the late 1960s/early 70s?

I guess SDRs are here to stay.  Ham transceivers are probably going to go the way of the PC at some time in the future, and whoever develops the software will kind of run the show while everybody else fights for scraps of market share with their low profit hardware clones.   A bit of that's already beginning to happen with the low and midrange SDR receiver marketplace now.

The real problem with SDRs is that there are poor performers and there are superb performers, depending on some of the factors I mentioned above.  Some people buy a cheap SDR dongle and don't like the results so they decide that SDRs are bad, but that's not really a fair assessment.  I am convinced that high end SDRs can and do provide the best performance possible in a transceiver.  IF the transmitter takes advantage of some of the processing opportunities it has when your signal is still in digital form before it reaches the power amplifier, then signal cleanliness and accuracy improves, and the radio's behaviour on air can get better very quickly.

And by the way, your radio's frequency accuracy has nothing to do with it being or not being an SDR.  That's all about the internal oscillator, which any SDR or superhet can benefit from if it's stable or temperature controlled, or even GPS disciplined.  Throw a GPS-D synthesizer into an old Drake or Collins or Heathkit and you'll be better than rock stable.

73, Ed VE3WGO
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W6UV
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« Reply #7 on: November 11, 2017, 12:13:59 PM »

SDR performance will continue to improve as ADC, DDS, and software continues to improve. Just look how much progress has been made in the last decade.

The hardware improvements in the form of faster, better ADCs and DDS chips is being driven by the cellular and other commercial communications industries and we hams will benefit from these better parts. The rest is just a matter of software, which can be trivially updated in the field. That really wasn't possible in the past without making circuit modifications to a rig, and that was expensive and difficult to do compared to a simple software download.

The rest of the communications industry has already made the transition to SDR and it's only a matter of time before hams do as well.

I predict than ten years from now all new ham rigs will be SDR, except for a few boutique rigs intended to appeal to the same crowd that thinks vinyl LPs are superior to CDs.
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AC7CW
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« Reply #8 on: November 11, 2017, 01:55:17 PM »

People went wild over "direct sampling" right? Elecraft rigs are down converting and still very muchly in the top of the listings at Sherwood Engineering's website. That points to the idea that we can homebrew SDR rigs that are great. We might see only as little as 384khz of a band [there's a little sarcasm intended there] so there's that...
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Novice 1958, 20WPM Extra now... (and get off my lawn)
W6UV
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« Reply #9 on: November 11, 2017, 03:02:18 PM »

People went wild over "direct sampling" right? Elecraft rigs are down converting and still very muchly in the top of the listings at Sherwood Engineering's website. That points to the idea that we can homebrew SDR rigs that are great. We might see only as little as 384khz of a band [there's a little sarcasm intended there] so there's that...

Superhet rigs have been around for a hundred years and have probably gone as far as they can go, while SDR rigs are just starting to scratch the surface of what's possible.
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VA3VF
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« Reply #10 on: November 11, 2017, 04:32:26 PM »

SDR performance will continue to improve as ADC, DDS, and software continues to improve. Just look how much progress has been made in the last decade.

Even the change from the SoftRock to the RTL dongle shows the progression. New chips, that will certainly be developed, may bring features that are only a dream now.
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VA3VF
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« Reply #11 on: November 11, 2017, 04:36:57 PM »

Some hype, no doubt, but in many areas modern SDRs are ludicrously superior to their forefathers.

Then there is no hype, I would say.  Grin

Some may not like the black box concept, myself included, where one needs a computer to operate it. But SDRs a la IC-7300, only an example, are the way to go.
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NI8R
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« Reply #12 on: November 11, 2017, 06:13:11 PM »

Performance can be obtained from a sdr at a fraction of the price of a superhet design.  My icom 7851 is a better receiver than the flex 6500, but 1/10 of a thin hair better is not worth 3x the price.
The user interface of the ic7610 looks odd because i use menus and buttons. The basic 7610 rig looks like the 7851, but i bet it weighs 30lbs less.


Greg ni8r
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VE3WGO
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« Reply #13 on: November 11, 2017, 07:15:50 PM »

well, when you calculate the price of your 6500, don't forget to add in the cost of a software subscription and the Maestro (or PC, monitor, and Flex control - not realistic to say they're free because you had them already), plus the external 300 Watt DC power supply that the 6500 needs. 

7851 has twice the Transmitter output power of the 6500.  That's got to be worth something too.  But if there's not enough in the 7851 to make it worth the money, how is it that you came to own a 7851 and a 6500?

Even an SDR has many spurious responses and needs serious passive filters ahead of the A/D converter or it will just bellyflop in a sea of aliasing and image signal responses.  Ole Harry Nyqvist was serious when he told us where we could and couldn't sample our signals.  RF DACs are even worse... so while the direct sampling SDR principle sounds like it should be easy, it isn't there yet, and probably won't be for a while.  And so a high performance SDR is going to be emblazoned with lots of filters to make sure the receiver ADC and the transmitter DAC behave themselves.  Zenki thinks it's easy, but those converters are a pain is the a** to keep clean.

Truth is that most SDR pricing has to include some serious cost recovery of the massive software development.  I'll hazard a guess that the workforce at a company like Flex is 75%+ software development.  Therefore, if companies are successful in figuring out to make a true profit from SDR software sales, then they will survive the SDR era.  Otherwise this is going to be a replay of the 1980s where there were dozens of orphan computer designs and we all know how that turned out....  only 2 software companies (Apple & Microsoft) survived by 1990 or so.  Then it replayed again in around 2010 with cellphones and smartphones.  Again only 2 software companies (A & Goog) survived that.  The rest of them make a few crumbs of profit selling smartphone hardware.  Surprisingly, M saved itself by perfecting (maybe?) those ubiquitous Office apps to survive its disastrous mobile collapse, and Sammy has a lock on critical components for everybody.  The serious money's being made in computing software these days.

And so it shall be with ham radios..... and by the looks of it, eventually cars too.

73, Ed VE3WGO
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N2DTS
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« Reply #14 on: November 11, 2017, 08:01:47 PM »

For me there is a lot more to it then strong signal handling.
There is the band scope, lots of useful information on it for me.
There are the filters, any bandwidth you want, very good filters, drag the edge just where you want.
There is the fidelity, AM, sync AM, ssb, all mode, 20Hz to 20 KHz if you want, with low noise and low distortion.
The ability to click between bands with the mouse, I have an all band fan dipole so I can go between 160 and 6 meters with just the click of the mouse.
Transmit fidelity and the ability to set the bandwidth to whatever you want, wide or narrow.
Built in audio tools, with profiles, DX pileup sharp to broadcast station fidelity, EQ, phase rotation, multiband compressors.
The ability to operate remote, some guys work their home station from their car over the cell network and it works great.
Pure signal, which can make a signal VERY clean, even out of a dirty amp.
Diversity reception with its qsb elimination and noise cancellation.

Some good sdr receivers can cover 100 KHz to 2 GHz with no gaps, all mode, for around $150.00.
Show me an all mode receiver with a band scope that will show up to 6 MHz of bandwidth if you want for under $200.00 without it being an sdr.


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