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Searching for Noise (i.e., Samples Thereof)

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wayne burdick

Searching for Noise (i.e., Samples Thereof)

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As time permits, we're trying to better characterize the RF noise that plagues stations at various locations.

So far, data collected during this informal survey has taken the form of verbal descriptions. Scope traces or digitized samples would be much more helpful, since they'd show the actual waveforms. We could then look at how to better suppress the noise profiles, pulse widths, and rep rates encountered by stations surrounded by modern appliances, vehicles, peripherals, lighting, etc. Many of these didn't exist decades ago when the first noise blankers were designed.

On a K3 or K3S, the best place to capture noise signals would be at the output of the first MC1350 in the KNB3's amplifier chain. In the presence of strong noise, the signal at this point is likely to produce a visible scope trace, or a good sample using an RF digitizer. The latter would have to do a good job at the IF, 8.215 MHz.

On a KX3, the RX IQ outputs should work, assuming the noise signal is quite strong. As the RX IQ signal occurs at base band, a much lower-bandwidth scope or an audio-class A-to-D converter would suffice.

Spectral data would also be of use in both cases.

I don't have any specific recommendations for equipment or software. But if you have the means in hand, as well as a noise problem worth capturing, feel free to contact me directly. Please include photos or screen captures as well as details on what remediation techniques work -- and don't.

73,
Wayne
N6KR

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Jim Brown-10

Re: Searching for Noise (i.e., Samples Thereof)

On 2/16/2019 2:56 PM, Wayne Burdick wrote:
> As time permits, we're trying to better characterize the RF noise that plagues stations at various locations.

NK7Z is doing that on his excellent site. https://www.nk7z.net/

73, Jim K9YC

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Dave New, N8SBE

Re: Searching for Noise (i.e., Samples Thereof)

In reply to this post by wayne burdick

Dave New, N8SBE

Re: Searching for Noise (i.e., Samples Thereof)

In reply to this post by wayne burdick

I've always wanted to better understand the tweaks/handles that we have
in the noise blanker/noise reduction algorithms in the K3/K3S. I can
'frob the knobs', until I see some reduction in noise, but I felt it
would be much better to not be flying blind, and be able to know just
what the various modes do and their parameters do, and be able to
actually see some better noise signature to get an idea of whether or
not a particular tweak is doing what I thought it was doing.

I have the Fred Cady book, and it goes into some detail, but I'd like to
see a much better description from the source as to just what all those
parameters actually do, and a means to see it actually happen, on the
P3, or a scope, hooked to the IF out or similar.

I'm plagued with all sorts of noise at my QTH, and I haven't spent much
time trying to hunt it all down. I feel I need better insight than to
just go around pulling circuit breakers. Some of the stuff is quite
likely to be off-premise, as well, which brings me back to likely having
to deal with it as best I can at the receiver end of it.

Thanks and 73,

-- Dave, N8SBE
-------- Original Message --------
Subject: [Elecraft] Searching for Noise (i.e., Samples Thereof)
From: Wayne Burdick <[hidden email]>
Date: Sat, February 16, 2019 5:56 pm
To: Elecraft Reflector <[hidden email]>

As time permits, we're trying to better characterize the RF noise that
plagues stations at various locations.
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John Simmons

Re: Searching for Noise (i.e., Samples Thereof)

Dave,

Yeah I'd like to see that too. I'm lucky that my nearest neighbor is 300
feet away and we have underground power. EVERY noise I've heard on
either HF, VHF or UHF has originated on my premises.

73,
-John NI0K

Dave New, N8SBE wrote on 2/18/2019 12:23 PM:

> I've always wanted to better understand the tweaks/handles that we have
> in the noise blanker/noise reduction algorithms in the K3/K3S. I can
> 'frob the knobs', until I see some reduction in noise, but I felt it
> would be much better to not be flying blind, and be able to know just
> what the various modes do and their parameters do, and be able to
> actually see some better noise signature to get an idea of whether or
> not a particular tweak is doing what I thought it was doing.
>
>
> I have the Fred Cady book, and it goes into some detail, but I'd like to
> see a much better description from the source as to just what all those
> parameters actually do, and a means to see it actually happen, on the
> P3, or a scope, hooked to the IF out or similar.
>
>
> I'm plagued with all sorts of noise at my QTH, and I haven't spent much
> time trying to hunt it all down. I feel I need better insight than to
> just go around pulling circuit breakers. Some of the stuff is quite
> likely to be off-premise, as well, which brings me back to likely having
> to deal with it as best I can at the receiver end of it.
>
>
> Thanks and 73,
>
>
> -- Dave, N8SBE
> -------- Original Message --------
> Subject: [Elecraft] Searching for Noise (i.e., Samples Thereof)
> From: Wayne Burdick <[hidden email]>
> Date: Sat, February 16, 2019 5:56 pm
> To: Elecraft Reflector <[hidden email]>
>
> As time permits, we're trying to better characterize the RF noise that
> plagues stations at various locations.
> ______________________________________________________________
> 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]

Bob McGraw - K4TAX

Re: Searching for Noise (i.e., Samples Thereof)

One of the first things to do is isolate the noise to two sources in
general. (a) inside the house, (b) outside the house.

My approach is to use the 12V battery off of the lawn tractor to power
the transceiver. Use the antenna and band which provides the worst
noise. Then pull the main breaker for the house. What's the noise
difference? If there is little to no difference, the noise is outside
of the house. If the noise drops a noticeable amount, that part of the
noise is inside the house. The MFJ 805 works well for finding noise
inside the house.

To further look for (a), turn all breakers off and the main back on.
Noise should be about the same. Then add one breaker at a time and
observe the noise. Yes, I know this takes many trips between the
breaker panel and the radio. When you flip a breaker ON and the noise
increases, that tells one what circuit and area of the house the noise
is originating. Find it and eliminate it. Then move on to other
breakers in the panel doing the same thing. This is simply the process
of logically identifying the noise and then applying means to reduce or
eliminate the noise. If it is outside of the house than an item such as
the MFJ 852 works well.

The NB and NR functions work well in the K3S but they are no substitute
for finding and eliminating the noise source.

73

Bob, K4TAX

On 2/18/2019 12:41 PM, John Simmons wrote:

> Dave,
>
> Yeah I'd like to see that too. I'm lucky that my nearest neighbor is
> 300 feet away and we have underground power. EVERY noise I've heard on
> either HF, VHF or UHF has originated on my premises.
>
> 73,
> -John NI0K
>
>

Jim Brown-10

Re: Searching for Noise (i.e., Samples Thereof)

On 2/18/2019 12:36 PM, Bob McGraw K4TAX wrote:
> One of the first things to do is isolate the noise to two sources in
> general. (a) inside the house, (b) outside the house.
>
> My approach is to use the 12V battery off of the lawn tractor to power
> the transceiver. Use the antenna and band which provides the worst
> noise.

Great advice. BUT -- when doing this, make sure that all UPS units are
powered off, both because they are noise sources themselves, and because
they keep some equipment running that's also likely to be a noise source.

Lots more detailed advice in http://k9yc.com/KillingReceiveNoise.pdf

Another important delineation of noise type is between 1) electronic
noise, generated by electronic equipment, solar power systems, variable
speed motor controllers, and switch mode power supplies; and 2) impulse
noise, mostly generated by arcing on power lines, electric fences, and
neon signs.

73, Jim K9YC

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donovanf

Re: Searching for Noise (i.e., Samples Thereof)

In reply to this post by Bob McGraw - K4TAX

Don't forget to turn off all uninterruptable power supplies too...

73
Frank
W3LPL

----- Original Message -----

From: "Bob McGraw K4TAX" <[hidden email]>
To: [hidden email]
Sent: Monday, February 18, 2019 8:36:13 PM
Subject: Re: [Elecraft] Searching for Noise (i.e., Samples Thereof)

One of the first things to do is isolate the noise to two sources in
general. (a) inside the house, (b) outside the house.

My approach is to use the 12V battery off of the lawn tractor to power
the transceiver. Use the antenna and band which provides the worst
noise. Then pull the main breaker for the house. What's the noise
difference? If there is little to no difference, the noise is outside
of the house. If the noise drops a noticeable amount, that part of the
noise is inside the house. The MFJ 805 works well for finding noise
inside the house.

To further look for (a), turn all breakers off and the main back on.
Noise should be about the same. Then add one breaker at a time and
observe the noise. Yes, I know this takes many trips between the
breaker panel and the radio. When you flip a breaker ON and the noise
increases, that tells one what circuit and area of the house the noise
is originating. Find it and eliminate it. Then move on to other
breakers in the panel doing the same thing. This is simply the process
of logically identifying the noise and then applying means to reduce or
eliminate the noise. If it is outside of the house than an item such as
the MFJ 852 works well.

The NB and NR functions work well in the K3S but they are no substitute
for finding and eliminating the noise source.

73

Bob, K4TAX

On 2/18/2019 12:41 PM, John Simmons wrote:

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Dave New, N8SBE

Re: Searching for Noise (i.e., Samples Thereof)

In reply to this post by wayne burdick

Thanks for all the tips, guys, especially the MFJ meter references. I
have their ultrasonic sniffer, which helped me point out to the local
power company some dangling insulators.

I have tracked down some on-premise noise sources in the past (in no
particular order):

1) The clock on a Mr. Coffee coffee maker. It put out a buzz-saw that
could be picked up directly for some distance, plus it coupled to the
power line, for an extra boost of signal goodness.

2) A porch light day/night sensor that screwed into the bulb socket.
This was amazingly noisy, and only came on at night (natch).

3) A laser printer switcher power supply. 'Nuff said.

4) A doorbell transformer, likely as old as the house (built in 1954).
It was mounted on the side of a junction box in the basement, and was
exceedingly difficult to track down, as none of the breakers, except the
main, would turn it off. Found out later that the previous owner had
paralleled two breakers in the panel, likely because he kept tripping
one of the circuits in the kitchen or bath -- the effect was that
turning off one or the other breaker had no effect on either of those
circuits. Thus they were 'mystery' breakers until I pulled the panel
cover and discovered what had transpired.

I've since had an electrician put an extra panel put in, and some
circuits split, because the original panel was completely full with
duplex breakers. Making plans now to put in a whole-house generator.
Got the go-ahead from the XYL. She is tired of all the power outages
we've had in our neighborhood over the last 2-3 years.

73,

-- Dave, N8SBE
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