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Noise Blankers

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K9MA

Noise Blankers

I have never found the K3 noise blanker to be effective. On the other hand, in side-by-side comparisons, the noise blanker in my old FT-1000D can be very effective on my ever present power line noise. However, like all noise blankers of that design, it only works if there are no strong signals within many kHz of the operating frequency, so it's completely useless on a crowded band. The only way around this I know of is to use a second receiver, tuned to a clear spot nearby, to control the noise blanker.

BTW, the K3 noise blanker uses a filter with a bandwidth of about 100 kHz. The idea is that, in such a wide bandwidth, the amplitude of the noise pulses should be large, making them easier to distinguish from signals. (The FT-1000 uses something like 15 kHz.) However, I've never been able to get the K3 NB to work, even on a completely dead band. Under the same conditions, I can often get a 20 dB reduction with the other radio. That I don't understand. I should investigate that sometime.

73,

Scott K9MA

----------

Scott Ellington

--- via iPad

> On Sep 3, 2017, at 10:37 AM, Rick Tavan <[hidden email]> wrote:
>
> Noise blankers are difficult to design and to use. They work by blanking
> out the receiver during noise pulses. The user defines what is a noise
> pulse and how aggressively to blank it by adjusting the NB parameters. If
> you don't blank out enough, you still hear the noise. If the signal is
> below that noise, you won't hear it. If you blank out too much, you lose so
> much real signal that it is no longer possible to copy or to copy
> comfortably. *I have had very good results with the NB in the K3 on some
> kinds of human-made noise.* Other noises seem to have too high a duty cycle
> or signal strength to be effectively blanked. Your noise sources may be in
> that category. I don't think it is fair to say the K3 NB "doesn't work." It
> certainly does work on many kinds of noise. No NB that I have tried or
> heard of can work on all kinds of noise.
>
> 73,
>
> /Rick N6XI
>
>
> Rick Tavan
> Truckee, CA
>
> On Sun, Sep 3, 2017 at 8:12 AM, Gian Luca Cazzola <[hidden email]>
> wrote:
>
>> To Wayne and his Elecraft crew:
>>
>> I am an ultra satisfied cw user of a Elecraft K3S ( that I use with P3 and
>> two SP3).
>>
>> The only things that I dont like are:
>> - the noise blanker - i havent found situations where it help - or I am
>> unable to use it, even if I tried lot of settings…
>>
>> - the NOISE REDUCTOR, that first times I thought it help barely, but after
>> some time I found that it simply need to be reset (simple OFF-ON) at band
>> noise changing time after time and it work well.
>>
>> About the NB I dont ask anything ( I simply accept that it doesn’t work),
>>
>> but about NR - Noise Reductor I ask you that with next firmware
>> modifications you introduce an automatic NR reset ( at least every 5
>> minutes a ciclic OFF-ON, it simply improve a lot its results)
>>
>> Many thanks.
>>
>> 73 es gl,
>> Ian IK4EWX
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Jim Brown-10

Re: Noise Blankers

On 9/3/2017 9:18 AM, K9MA wrote:
> I have never found the K3 noise blanker to be effective.
<SNIP>

> BTW, the K3 noise blanker uses a filter with a bandwidth of about 100 kHz.
<SNIP>

The K3 NB is really TWO blankers, operating in two different IFs. Each
can be tweaked for various kinds of noise from the menu system. Access
the menu by a Long Push of the NB button.

It's important to understand that there are many kinds of noise. Noise
blankers are most effective on IMPULSE NOISE, which is the result of
something arcing, usually in the power system, but also electric fences
and neon signs.

Most of the residential noise we hear today is ELECTRONIC noise,
generated by switch-mode power supplies and microprocessors. Noise
blankers must be very different to suppress this sort of noise. The menu
tweaks provided by the K3, K3S, KX3, and KX2 are very critical to making
the NB effective on the noise you're experiencing. One size does NOT fit
all.

73, Jim K9YC

>> On Sep 3, 2017, at 10:37 AM, Rick Tavan<[hidden email]> wrote:
>>
>> Noise blankers are difficult to design and to use. They work by blanking
>> out the receiver during noise pulses. The user defines what is a noise
>> pulse and how aggressively to blank it by adjusting the NB parameters.
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k6dgw

Re: Noise Blankers

I find the K3 NB to be surprisingly effective. I also find that
adjustment is highly dependent on the characteristics of the signal and
the noise, and the effects of changing those adjustments is subtle. The
effect of a blanker on ignition noise was really astounding ... "was,"
because ignition noise seems to be history these days. I suspect that
many of the "it doesn't work very well" observations may stem from
anticipation of a dramatic disappearance of today's noise from
incidental and unintended radiators with NB on. My local noise comes
from the NV Energy power system and an uncountable number of Part 15
violators in the house and neighborhood. K3 NB is very effective for me
against them.

I am a bit sorry that both the IF and DSP blanker parameters are so
cryptic in the K3. Depth of the blanking pulse and width of the
blanking interval are the two "real" parameters involved. The K3 seems
to camouflage them which, for me at least, makes them a bit harder to
adjust properly, I'm not sure what I'm doing when I change them.
Incidentally, punching holes in the receiver sensitivity to block noise
pulses is itself introducing noise. As with everything else in life,
it's a trade-off.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 9/3/2017 9:40 AM, Jim Brown wrote:

> On 9/3/2017 9:18 AM, K9MA wrote:
>> I have never found the K3 noise blanker to be effective.
> <SNIP>
>
>> BTW, the K3 noise blanker uses a filter with a bandwidth of about 100
>> kHz.
> <SNIP>
>
> The K3 NB is really TWO blankers, operating in two different IFs. Each
> can be tweaked for various kinds of noise from the menu system.
> Access the menu by a Long Push of the NB button.
>
> It's important to understand that there are many kinds of noise. Noise
> blankers are most effective on IMPULSE NOISE, which is the result of
> something arcing, usually in the power system, but also electric
> fences and neon signs.
>
> Most of the residential noise we hear today is ELECTRONIC noise,
> generated by switch-mode power supplies and microprocessors. Noise
> blankers must be very different to suppress this sort of noise. The
> menu tweaks provided by the K3, K3S, KX3, and KX2 are very critical to
> making the NB effective on the noise you're experiencing. One size
> does NOT fit all.
>
> 73, Jim K9YC

Wes Stewart-2

Re: Noise Blankers

In reply to this post by K9MA

I agree. The adjustments are far too many and arcane. I'm currently plagued
with powerline noise that has yet to be fixed, although they are supposed to be
working on it. The K3S blanker is slightly better than useless. When I set it
aggressive enough to be audibly useful, FT8 decodes multiple signals at 120 Hz
intervals, which upsets sequencing.

I'm finding that my SDR-IQ that I normally use only as a bandscope, has better
noise blanking on its demodulated audio than the K3. Too bad I can't use it
with WSJT-X.

I suspect, but do not know for sure, (maybe the designer can enlighten us) that
there is insufficient delay in the (analog) signal path and the noise gets
through before blanking takes place.

Wes N7WS

On 9/3/2017 9:18 AM, K9MA wrote:

> I have never found the K3 noise blanker to be effective. On the other hand, in side-by-side comparisons, the noise blanker in my old FT-1000D can be very effective on my ever present power line noise. However, like all noise blankers of that design, it only works if there are no strong signals within many kHz of the operating frequency, so it's completely useless on a crowded band. The only way around this I know of is to use a second receiver, tuned to a clear spot nearby, to control the noise blanker.
>
> BTW, the K3 noise blanker uses a filter with a bandwidth of about 100 kHz. The idea is that, in such a wide bandwidth, the amplitude of the noise pulses should be large, making them easier to distinguish from signals. (The FT-1000 uses something like 15 kHz.) However, I've never been able to get the K3 NB to work, even on a completely dead band. Under the same conditions, I can often get a 20 dB reduction with the other radio. That I don't understand. I should investigate that sometime.
>
> 73,
>
> Scott K9MA
>
> ----------
>
> Scott Ellington
>
>

jh3sif

Re: Noise Blankers

In my experience, NR is much better than NB against power line noise.
However, NR does not work on DATA mode. I use BHI Compact In-line DSP Noise Eliminating Module, which is inserted between K3 line out and USB audio module.

For effectively eliminating noise, tuning RF gain and AGC level in addition to NB and/or NR would give you better results.

de JH3SIF, Keith

> 2017/09/04 4:38、Wes Stewart <[hidden email]> のメール：
>
> I agree. The adjustments are far too many and arcane. I'm currently plagued with powerline noise that has yet to be fixed, although they are supposed to be working on it. The K3S blanker is slightly better than useless. When I set it aggressive enough to be audibly useful, FT8 decodes multiple signals at 120 Hz intervals, which upsets sequencing.
>
> I'm finding that my SDR-IQ that I normally use only as a bandscope, has better noise blanking on its demodulated audio than the K3. Too bad I can't use it with WSJT-X.
>
> I suspect, but do not know for sure, (maybe the designer can enlighten us) that there is insufficient delay in the (analog) signal path and the noise gets through before blanking takes place.
>
> Wes N7WS
>
>
>
> On 9/3/2017 9:18 AM, K9MA wrote:
>> I have never found the K3 noise blanker to be effective. On the other hand, in side-by-side comparisons, the noise blanker in my old FT-1000D can be very effective on my ever present power line noise. However, like all noise blankers of that design, it only works if there are no strong signals within many kHz of the operating frequency, so it's completely useless on a crowded band. The only way around this I know of is to use a second receiver, tuned to a clear spot nearby, to control the noise blanker.
>>
>> BTW, the K3 noise blanker uses a filter with a bandwidth of about 100 kHz. The idea is that, in such a wide bandwidth, the amplitude of the noise pulses should be large, making them easier to distinguish from signals. (The FT-1000 uses something like 15 kHz.) However, I've never been able to get the K3 NB to work, even on a completely dead band. Under the same conditions, I can often get a 20 dB reduction with the other radio. That I don't understand. I should investigate that sometime.
>>
>> 73,
>>
>> Scott K9MA
>>
>> ----------
>>
>> Scott Ellington
>>
>>
>
> ______________________________________________________________
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Bob McGraw - K4TAX

Re: Noise Blankers

Depending the type of noise, for repetitive pulse type noise only, the
Noise Blanker does it job. Now one must understand that all pulse noise
is not alike. Therefore, different values of NB, both with the IF
values and with DSP values, will require some adjustments.    If the
noise is not repetitive then the NB is not the better choice but the NR
is the better choice. Again, depending on they type of noise, certain
combinations of NR values will be necessary.

Yes, that is correct in that the Noise Reduction function is not
available or can not be activated in the DATA mode. However the Noise
Blanker can be used in the DATA mode.   Again, the Noise Blanker is for
repetitive pulse type noise.

I've spoken with many hams and find their understanding of Noise
Reduction being described as often does not work as expected. Further
discussion seems to indicate they want NE........Noise Elimination.
Well, NR........Noise Reduction does in fact work when the values are
selected based on the type of broad noise spectrum being encountered.
NR has very little effect on pulse type noise.

One fact not clearly understood, is that most hams operate with too much
RF Gain. Thus the correct application of ATTENUATION and RF Gain
reduction will greatly improve receiver performance in the face of noise.

Optimizing receiver gain compared to band noise and the noise floor of
the receiver is explained in a quote from Rob Sherwood, Sherwood
Engineering:

"If receiver noise floor is 10 dB below band noise, the receiver is
contributing less than 0.5 dB of the total noise.
Band noise varies by band over 30 dB, 160-10 meters. It also varies by
direction and time of day, plus what the sun is doing. In an noisy urban
environment it is anybody's guess as to your band noise level.
A simple test is to see how much the noise coming out your speaker
increases when you switch between a dummy load and your antenna, when
tuned to a dead spot on the band.
Example on 10 meters at my rural QTH, IC-756 Pro III: preamp OFF, noise
goes up 3 dB. That means the receiver is contributing half the noise.
Preamp 1 ON, band noise goes up 9.5 dB.   Almost all legacy receivers
are designed for 10 meters, and attenuation is desirable on the low HF
bands."

In Rob's first statement, how do we get the band noise to be 10 dB above
receiver noise? Use Attenuation and RF Gain reduction. As an example,
if receiver noise floor is -130 dBm and the band noise, no signal, is
S-5 or -97 dBm, the difference being 33 dB. This would then indicate one
should employ 15 dB of Attenuation and 8 dB of RF Gain reduction. Or 10
dB of Attenuation and some 13 dB of RF Gain reduction.   Of course the
band noise will be comprised of different noise components, depending on
band and many other factors as he suggests.

73

Bob, K4TAX

On 9/3/2017 3:06 PM, Keith Onishi wrote:

> In my experience, NR is much better than NB against power line noise.
> However, NR does not work on DATA mode. I use BHI Compact In-line DSP Noise Eliminating Module, which is inserted between K3 line out and USB audio module.
>
> For effectively eliminating noise, tuning RF gain and AGC level in addition to NB and/or NR would give you better results.
>
> de JH3SIF, Keith
>
>
>> 2017/09/04 4:38、Wes Stewart <[hidden email]> のメール：
>>
>> I agree. The adjustments are far too many and arcane. I'm currently plagued with powerline noise that has yet to be fixed, although they are supposed to be working on it. The K3S blanker is slightly better than useless. When I set it aggressive enough to be audibly useful, FT8 decodes multiple signals at 120 Hz intervals, which upsets sequencing.
>>
>> I'm finding that my SDR-IQ that I normally use only as a bandscope, has better noise blanking on its demodulated audio than the K3. Too bad I can't use it with WSJT-X.
>>
>> I suspect, but do not know for sure, (maybe the designer can enlighten us) that there is insufficient delay in the (analog) signal path and the noise gets through before blanking takes place.
>>
>> Wes N7WS
>>
>>
>>
>> On 9/3/2017 9:18 AM, K9MA wrote:
>>> I have never found the K3 noise blanker to be effective. On the other hand, in side-by-side comparisons, the noise blanker in my old FT-1000D can be very effective on my ever present power line noise. However, like all noise blankers of that design, it only works if there are no strong signals within many kHz of the operating frequency, so it's completely useless on a crowded band. The only way around this I know of is to use a second receiver, tuned to a clear spot nearby, to control the noise blanker.
>>>
>>> BTW, the K3 noise blanker uses a filter with a bandwidth of about 100 kHz. The idea is that, in such a wide bandwidth, the amplitude of the noise pulses should be large, making them easier to distinguish from signals. (The FT-1000 uses something like 15 kHz.) However, I've never been able to get the K3 NB to work, even on a completely dead band. Under the same conditions, I can often get a 20 dB reduction with the other radio. That I don't understand. I should investigate that sometime.
>>>
>>> 73,
>>>
>>> Scott K9MA
>>>
>>> ----------
>>>
>>> Scott Ellington
>>>
>>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
> ______________________________________________________________
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> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Wes Stewart-2

Re: Noise Blankers

Just a couple of points.

In the K3(S) there is no "RF Gain" control unless by RF gain you mean "It's not
the audio gain gain control."

The "RF" gain control operates on the i-f amplifier, which is after the analog
noise blanker. In this regard, it is little different from AGC, which operates
on exactly the same circuitry. Why some people believe that they are better at
controlling i-f gain than the AGC system does is beyond me, but old wife's tales
die hard. If this is hard to fathom, watch the S meter as you reduce "RF"
gain. The reading increases, no different from letting the AGC do it.

Attenuation is a different matter. It operates at RF and is a viable tool.

About noise blanking, I think I had a little to say about that almost 40 years
ago: http://k6mhe.com/n7ws/Noise_Blanker.pdf

Wes N7WS

On 9/3/2017 1:48 PM, Bob McGraw K4TAX wrote:

> Depending the type of noise, for repetitive pulse type noise only, the Noise
> Blanker does it job. Now one must understand that all pulse noise is not
> alike. Therefore, different values of NB, both with the IF values and with
> DSP values, will require some adjustments.    If the noise is not repetitive
> then the NB is not the better choice but the NR is the better choice. Again,
> depending on they type of noise, certain combinations of NR values will be
> necessary.
>
> Yes, that is correct in that the Noise Reduction function is not available or
> can not be activated in the DATA mode. However the Noise Blanker can be used
> in the DATA mode.   Again, the Noise Blanker is for repetitive pulse type noise.
>
> I've spoken with many hams and find their understanding of Noise Reduction
> being described as often does not work as expected. Further discussion seems
> to indicate they want NE........Noise Elimination.    Well, NR........Noise
> Reduction does in fact work when the values are selected based on the type of
> broad noise spectrum being encountered. NR has very little effect on pulse
> type noise.
>
> One fact not clearly understood, is that most hams operate with too much RF
> Gain. Thus the correct application of ATTENUATION and RF Gain reduction will
> greatly improve receiver performance in the face of noise.
>
> Optimizing receiver gain compared to band noise and the noise floor of the
> receiver is explained in a quote from Rob Sherwood, Sherwood Engineering:
>
> "If receiver noise floor is 10 dB below band noise, the receiver is
> contributing less than 0.5 dB of the total noise.
> Band noise varies by band over 30 dB, 160-10 meters. It also varies by
> direction and time of day, plus what the sun is doing. In an noisy urban
> environment it is anybody's guess as to your band noise level.
> A simple test is to see how much the noise coming out your speaker increases
> when you switch between a dummy load and your antenna, when tuned to a dead
> spot on the band.
> Example on 10 meters at my rural QTH, IC-756 Pro III: preamp OFF, noise goes
> up 3 dB. That means the receiver is contributing half the noise. Preamp 1 ON,
> band noise goes up 9.5 dB.   Almost all legacy receivers are designed for 10
> meters, and attenuation is desirable on the low HF bands."
>
> In Rob's first statement, how do we get the band noise to be 10 dB above
> receiver noise? Use Attenuation and RF Gain reduction. As an example, if
> receiver noise floor is -130 dBm and the band noise, no signal, is S-5 or -97
> dBm, the difference being 33 dB. This would then indicate one should employ 15
> dB of Attenuation and 8 dB of RF Gain reduction. Or 10 dB of Attenuation and
> some 13 dB of RF Gain reduction.   Of course the band noise will be comprised
> of different noise components, depending on band and many other factors as he
> suggests.
>
> 73
>
> Bob, K4TAX
>
>
> On 9/3/2017 3:06 PM, Keith Onishi wrote:
>> In my experience, NR is much better than NB against power line noise.
>> However, NR does not work on DATA mode. I use BHI Compact In-line DSP Noise
>> Eliminating Module, which is inserted between K3 line out and USB audio module.
>>
>> For effectively eliminating noise, tuning RF gain and AGC level in addition
>> to NB and/or NR would give you better results.
>>
>> de JH3SIF, Keith
>>
>>
>>> 2017/09/04 4:38、Wes Stewart <[hidden email]> のメール：
>>>
>>> I agree. The adjustments are far too many and arcane. I'm currently plagued
>>> with powerline noise that has yet to be fixed, although they are supposed to
>>> be working on it. The K3S blanker is slightly better than useless. When I
>>> set it aggressive enough to be audibly useful, FT8 decodes multiple signals
>>> at 120 Hz intervals, which upsets sequencing.
>>>
>>> I'm finding that my SDR-IQ that I normally use only as a bandscope, has
>>> better noise blanking on its demodulated audio than the K3. Too bad I can't
>>> use it with WSJT-X.
>>>
>>> I suspect, but do not know for sure, (maybe the designer can enlighten us)
>>> that there is insufficient delay in the (analog) signal path and the noise
>>> gets through before blanking takes place.
>>>
>>> Wes N7WS
>>>

Richard Lamont

Re: Noise Blankers

In reply to this post by Wes Stewart-2

On 03/09/17 20:38, Wes Stewart wrote:

> The K3S blanker is slightly better than
> useless. When I set it aggressive enough to be audibly useful, FT8
> decodes multiple signals at 120 Hz intervals, which upsets sequencing.

That's an inevitable consequence of how a noise blanker works.

It removes power line noise by muting reception 120 (or 100) times a
second, corresponding to peaks in the power line voltage when the arcing
occurs.

If you chop an audio tone up at 120 Hz, you are amplitude modulating the
tone with a 120 Hz waveform. That produces sidebands either side of the
tone 'carrier'. This is why you should never use a noise blanker with
FT8 and similar modes.

The best way to use a rig with WSJT-X is, generally speaking, to make
the computer do as much as possible and make the rig do as little as
possible. Treat it more or less as a dumb transverter. Don't use the
noise blanker, don't reduce the bandwidth below about 2.5 kHz, don't use
the notch filter. WSJT-X's decoder works best if you just get the level
about right and let it deal with the QRM.

73,
Richard G4DYA
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Fred Moore-2

Re: Noise Blankers

In reply to this post by Wes Stewart-2

Ron, you are 100% on the money.. I was thinking about how I wanted to
explain the same thing.. thanks.. Fred

Fred Moore
email: [hidden email]
[hidden email]
phone: 321-217-8699

On 9/3/17 7:04 PM, Ron D'Eau Claire wrote:

> The advantage of controlling the gain manually is not an "old wife's tale". Rather, it's clearly just a technique that is not for everyone.
>
> AGC will reduce the gain according to the strongest signal inside the I.F. passband. Manually riding the "RF" gain ensures that a very weak signal is not affected by a strong signal that is also inside the I.F. passband. Of course that means your ears could be blasted by that strong signal, which is why Wayne included a hard limiter that can be enabled to chop such a signal down to size, making it no louder than the weak signal we want to copy.
>
> It has become a moot point for many operators today who cannot read CW if they are hearing two or three (or more) signals within the I.F. passband all at the same time. For them, it's essential to have enough I.F. selectivity to isolate one signal and so AGC is just fine.
>
> But some of us have a lifetime of experience sorting out multiple signals with our gray matter between the ears and prefer to continue to do so -- probably until we all become SKs.
>
> 73, Ron AC7AC
>
>
>
> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On Behalf Of Wes Stewart
> Sent: Sunday, September 3, 2017 3:00 PM
> To: [hidden email]
> Subject: Re: [Elecraft] Noise Blankers
>
> Just a couple of points.
>
> In the K3(S) there is no "RF Gain" control unless by RF gain you mean "It's not the audio gain gain control."
>
> The "RF" gain control operates on the i-f amplifier, which is after the analog noise blanker. In this regard, it is little different from AGC, which operates on exactly the same circuitry. Why some people believe that they are better at controlling i-f gain than the AGC system does is beyond me, but old wife's tales die hard. If this is hard to fathom, watch the S meter as you reduce "RF"
> gain. The reading increases, no different from letting the AGC do it.
>
> Attenuation is a different matter. It operates at RF and is a viable tool.
>
> About noise blanking, I think I had a little to say about that almost 40 years
> ago: http://k6mhe.com/n7ws/Noise_Blanker.pdf
>
> Wes N7WS
>
> ______________________________________________________________
> Elecraft mailing list
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Wes Stewart-2

Re: Noise Blankers

In reply to this post by Wes Stewart-2

In addition to the hard limiter Elecraft provided threshold and slope controls
in the AGC system.

On 9/3/2017 4:04 PM, Ron D'Eau Claire wrote:
> The advantage of controlling the gain manually is not an "old wife's tale". Rather, it's clearly just a technique that is not for everyone.
>
> AGC will reduce the gain according to the strongest signal inside the I.F. passband. Manually riding the "RF" gain ensures that a very weak signal is not affected by a strong signal that is also inside the I.F. passband. Of course that means your ears could be blasted by that strong signal, which is why Wayne included a hard limiter that can be enabled to chop such a signal down to size, making it no louder than the weak signal we want to copy.
>

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