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Author Topic: DSP NOISE BLANKERS--THEY SUCK!..  (Read 3721 times)
ZS5WC
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« on: April 09, 2013, 01:48:53 AM »

 Huh
I have several OLDER ANALOGUE rigs from 70's to 90's--the NB works as expected, and does not affect the station you are listening to if there is a close by strong station.
Obviously on VERY strong signals you have to switch the NB out, otherwise it will distort the audio slightly.

Fast Forward to modern day State of the ART DSP rigs--newer is better right?.
EVERYTHING is now handled in the digital domain, so noise is mathematically removed via algorithms WITHIN THE DSP.
I have YET to find a DSP NB in a SUB $2000 rig that actually works on noise, does NOT distort the wanted signal in the passband, and does NOT distort the wanted signal if there is a close by station OUT of the passband.
Irrespective of levels set--(when you ARE ABLE) to set them. Angry

My ancient old Kenwood TS-830s beats them all, actually being able to remove pulse type noise, and some forms of QRM!.
Are the new rigs not supposed to be BETTER at this?..--are we losing attention to the details?..
LIKE TX IMD levels?..

What do you think?.
73!
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W1JKA
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« Reply #1 on: April 09, 2013, 02:35:15 AM »

  If possible try out an IC-7200 and see for yourself.The NB does work and works well.At least read the reviews on it.
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KS2G
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Posts: 440




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« Reply #2 on: April 10, 2013, 04:37:57 PM »

Kenwood TS-590s.

Had an '830s for ten years and LOVED it.

The '590 blows it away.

73,
Mel - KS2G
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N4DOV
Member

Posts: 52




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« Reply #3 on: April 10, 2013, 04:58:34 PM »

Could not resist this reply, but the TenTec eagle has an excellent noise blanker, does not quite cost and arm and a leg ($2000) but does perform rather well in this category. Sorry to be a little "chronic" on this issue !
Please see my video that I made for another thread on this forum.

http://www.youtube.com/watch?v=Si26cABHa9s
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AF5CC
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Posts: 1018




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« Reply #4 on: April 10, 2013, 10:09:22 PM »

Huh
I have several OLDER ANALOGUE rigs from 70's to 90's--the NB works as expected, and does not affect the station you are listening to if there is a close by strong station.
Obviously on VERY strong signals you have to switch the NB out, otherwise it will distort the audio slightly.

Fast Forward to modern day State of the ART DSP rigs--newer is better right?.
EVERYTHING is now handled in the digital domain, so noise is mathematically removed via algorithms WITHIN THE DSP.
I have YET to find a DSP NB in a SUB $2000 rig that actually works on noise, does NOT distort the wanted signal in the passband, and does NOT distort the wanted signal if there is a close by station OUT of the passband.
Irrespective of levels set--(when you ARE ABLE) to set them. Angry

My ancient old Kenwood TS-830s beats them all, actually being able to remove pulse type noise, and some forms of QRM!.
Are the new rigs not supposed to be BETTER at this?..--are we losing attention to the details?..
LIKE TX IMD levels?..

What do you think?.
73!

Other than the 830, which other rigs from this era had great NBs?

John AF5CC
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ZS5WC
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« Reply #5 on: April 11, 2013, 12:18:02 AM »

 Smiley Thanks for the INPUT!.
I also own a TS-590s and don't like its' Noise Blanker--anything above 3 on the level setting distorts the recieve audio.
Good noise blankers--TS-430s (I restored one and to set up the noise blanker I wired a 12v relay coil in series with its' NC contact for a noise source--works like a charm!.. Simply had to "TUNE" the NB for minimum noise.)
MORE GOOD noise blankers: TS-820s, FT-901dm , Cubic Astro 151, Yaesu FT-ONE .

DSP to my ears , even when not using the DSP noise reduction has artifacts in the audio, which gets worse when using the NB.
In fact, my TS-590s is in the market and I am saving towards a FTDX-3000, which I believe has excellent RX audio.
Half the fun of operating is listening to well balanced-non-fatiguing audio in my opinion.
If I wanted telephone quality I would use the mobile phone.

73!.
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TANAKASAN
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Posts: 933




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« Reply #6 on: April 11, 2013, 02:51:32 AM »

Whilst not a true DSP (I believe it's an ASIC) I have had good experiences with the devices made by BHI. Their main purpose is to pull voice signals out of the noise so one of these will not be your solution if you're a CW man.

Tanakasan
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AD6KA
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Posts: 2238




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« Reply #7 on: April 11, 2013, 01:57:20 PM »

I once heard someone say that "DSP"
stands for "Doesn't Sound Pretty".
  Grin

The Noise Blanker on my PROII is almost useless.
For pulse noise, even the NB on my K2 works better!
The Noise Blankers (2 levels buttons, with one adjustable pot)
on my TS-940 works very, very well.

However, the Auto Notch feature on the PROII
is outstanding....great for tuner uppers and CW
sigs near SSB stations.

I also have a Timewave DSP-599zx, which I bought long ago
use with my 940 before I got the PROII. It works
OK, sort of, on overall noise reduction, even though it is
in the audio and not the IF chain. I hardly ever use the
NR on the 599zx, but I DO use the programmed bandwidth
filters on it for CW, PSK, and RTTY with the TS-940. Very handy.
(The 599zx also has what they call a "Tone" filter which
works like the Auto Notch on the PROII, and works very well.)

Interestingly, the 599zx has a lot of "hidden features" not
obvious unless you read the manual. It has user programable
filter widths, dual filters for RTTY,
 line level inputs, line level outputs, and speaker
outputs for two radios. It has an audio millivolt meter and a two
tone test generator. With the correct firmware upgrade it can
be used as a sound card interface for two radios.

But the DSP Noise Reduction on both the PROII and 599zx
are nothing to write home about. Both cause muddy
sounding audio. I've never completed a successful QSO, DX
or otherwise, using DSP Noise Reduction that I couldn't have
done without using it.

I hope someday...... somebody will get it right!
73, Ken  AD6KA
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N7EKU
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Posts: 148




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« Reply #8 on: April 14, 2013, 09:15:32 PM »



Other than the 830, which other rigs from this era had great NBs?

John AF5CC

Hi John,

The one on my Kenwood TS-520 is excellent.  It generally gets lots of good reviews from others too.

Couple notes on noise blankers:

Some rigs have buttons on the front panel for one, but the blanker was actually an option so you need to know whether the board is installed inside before you conclude it's a bad one!

Also, for a while in "old times" the blankers were made to defeat the Russian Woodpecker radar noise.  These designs aren't very effective on the impulse noise we experience nowadays.  So the blanker may actually be great but not on what we want it for!  I don't think the radar noise from Russia is a problem much anymore.

Cheers and 73,

Mark.



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K2GWK
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Posts: 534


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« Reply #9 on: April 18, 2013, 01:11:44 PM »

Whilst not a true DSP (I believe it's an ASIC) I have had good experiences with the devices made by BHI. Their main purpose is to pull voice signals out of the noise so one of these will not be your solution if you're a CW man.

Tanakasan

That device is an audio noise filter and will help with background hash (white noise). Noise blankers will only get rid of impulse noise (car ignition etc.). BHI does not make a noise blanker to my knowlege.
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Guy
Lawn Guyland, New York

K2GWK Website
M0HCN
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Posts: 473




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« Reply #10 on: April 20, 2013, 06:22:05 AM »

Part of this is actually down to changes in fashion among rig designers rather then anything to do with the move to dsp.

Basically, to work well an impulse noise blanker needs to see a really wide bandwidth (much wider then the desired audio).
Modern radios tend to put a roofing filter very early in the chain (often right after the first mixer), this filter does good things for overload performance, but converts fast rise time impulse noise into a slow rise time damped oscillation that is then very hard for anything to tell from a valid signal.
Fixing this really means driving the noise blanker from before the roofing filter, tricky in a rig using an upconverting first IF to provide continuous coverage. I guess that ideally you would wrap the noise blanker around the roofing filter with its level detector at the input side and the gating happening at the output, but with the woodpecker transmitter now glowing in the dark, it is not generally given the consideration it once was.

DSP filtering (Especially when turned up to stun) can sound really nasty, but if you have the controls turned that far up is is probably because you are trying to dig something out of the noise, and you probably could not even hear it without the processing.
 
Now I will grant that there are DSP rigs out there where the AGC design falls to bits in the presence of multiple strong signals, which really comes down to poor design, but there have always been poor quality radios.

73 Dan.
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KE3WD
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Posts: 5689




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« Reply #11 on: April 20, 2013, 06:19:42 PM »

We have to consider that there was once a time when Noise Blankers were all about the famous "Russian Woodpecker" - and many hams judged the effectiveness of the NB as to how well it worked on the woodpecker. 

The rigs so far cited as having the "excellent" NB circuits are from that era, no? 

That pushed the rig designers to follow suit in order to gain sales advantage. 

Today, with the woodpecker not being what it once was, perhaps there is no perceived gain for the mfrs to go to the extra expense.


73
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KA4WJA
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Posts: 704




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« Reply #12 on: April 23, 2013, 12:00:37 PM »

Dan, M0HCN,
While I generally agree with you....
Part of this is actually down to changes in fashion among rig designers rather then anything to do with the move to dsp.

Basically, to work well an impulse noise blanker needs to see a really wide bandwidth (much wider then the desired audio).
Modern radios tend to put a roofing filter very early in the chain (often right after the first mixer), this filter does good things for overload performance, but converts fast rise time impulse noise into a slow rise time damped oscillation that is then very hard for anything to tell from a valid signal.
There actually ARE some older "up-conversion" radios, with medium-width 1st IF filters ("roofing filter"), that have excellent noise blankers....
The Drake TR-7 is one....(I own 2 of 'em, one I bought new in 1977/78!!)
The Drake TR-7 uses "up-conversion" with a 1st IF freq of 48.05mhz, and a 1st IF filter bandwidth of approx. 8khz (with moderate skirts), allowing both USB and LSB, etc. to pass thru...
Albeit, this 8khz 1st IF filter is a 4-pole filter with moderate skirts, with the primary receive selectivity occurring at the 5.645mhz 2nd IF (8-pole 2.3khz "standard" SSB filter, plus 3 optional / accessory filter positions), the TR-7 noise blanker (~$140 optional NB-7), works extremely well on impulse noise (power line noise, engine/ignition noise, even the old "Russian Woodpecker"), and does NOT adversely effect receiver performance...This was a rarity even in the days when the Drake TR-7 was still being made, and today this is rarer than an honest politician!!!

{If you discount the "close-spaced" (2khz) receive 3rd order IMD, which compares to the TS-590 (in "up-conversion") and the 756ProII/ProIII, etc. at 76db (as this does fall inside the 1st IF filter's bandwidth here), and compare the wider spaced receive 3rd order IMD specs (99db), the 35 year old Drake TR-7 still preforms with the very best rigs made today....
And, if looking at Blocking Dynamic Range / overload susceptibility, not even the multi-thousand dollar ($$$$$) Hilberling PT-8000A, can match the TR-7's -146db BDR measurement....
(not to mention that the transmit IMD3 and IMD5 is 10db-15db-20db better than today's transmitters!!)...}
 




In addition to my TR-7's, I also have (and use) a modern commercial/maritime HF radio, with IF DSP, an Icom M-802...which has excellent transmit specs (meets FCC Part 80 certification) and superb audio quality, but lacks a bit in receive DSP noise blanking....
DSP filtering (Especially when turned up to stun) can sound really nasty, but if you have the controls turned that far up is is probably because you are trying to dig something out of the noise, and you probably could not even hear it without the processing.
  The Icom M-802 DSP "noise blanker" does work, but if adjusted enough to actually "blank" / remove the noise completely, it distorts the receive audio some....NOT to the point of "nasty", but certainly "unpleasant" to listen to...
Here again there actually are some modern HF rigs, w/ IF-DSP noise blanking, that do work, to some extent at least....but in my experience there aren't very many!!!



So, in general, I do agree that DSP noise blankers, with a few exceptions, mostly suck....and DSP noise reduction, etc. also suck!!
But, also the fact that most amateur radio noise blankers (DSP or otherwise) are poor at best, and many fall into the "suck" category....it's just what you get when radios are marketed "by numbers/specs" rather than by how/what actually works and is needed by the users....


Just my 2 cents......(and while I haven't posted here on eham in many years, I have been reading along with many discussions!!!!) 

73, 
John, KA4WJA

 
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