[RFI] RFI Digest, Vol 251, Issue 3

Sat Dec 23 19:15:04 EST 2023

 It does look like a amp of some sort.  

TV, a blue-tooth speaker bar, etc or like a cellphone BDA.. chased a few in my day.   

When you find it, please let us know what is was.  

KA1FFO 

AL  

    On Saturday, December 23, 2023 at 06:49:16 PM EST, rfi-request at contesting.com <rfi-request at contesting.com> wrote:  

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Today's Topics:

  1. Re: Peculiar Noise (Jim Brown)
  2. Re: Peculiar Noise (k1ttt.dave at gmail.com)
  3. Re: Peculiar Noise (Jim Brown)
  4. Re: Peculiar Noise (David Eckhardt)
  5. Re: Sources of wideband hiss (AA5CT)
  6. Re: Sources of wideband hiss (David Eckhardt)

----------------------------------------------------------------------

Message: 1
Date: Sat, 23 Dec 2023 11:46:47 -0800
From: Jim Brown <jim at audiosystemsgroup.com>
To: rfi at contesting.com
Subject: Re: [RFI] Peculiar Noise
Message-ID:
    <c8294032-b2ba-4396-8ecc-0c49efc24712 at audiosystemsgroup.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

On 12/23/2023 11:34 AM, Steve London wrote:
> It will be on for several hours at a time, then disappear. Nothing else
> like it between 40 and 60 MHz. I would never have noticed it, except it
> sometimes parks itself on 50313, the 6 meter FT8 frequency.

I strongly recommend NK7I's technique, using a wide waterfall from an 
SDR over 24 hours to study the comings and goings of what are often 
multiple sources, and identifying one or more as what you're hearing. 
This gives clues about WHEN to DF it, and on what frequency(ies).

Also, my applications note about using that spectrum/waterfall to 
determine whether the source is electronically generated or arcing, 
usually in the power distribution system.

k9yc.com/publish.htm

73, Jim K9YC

------------------------------

Message: 2
Date: Sat, 23 Dec 2023 16:28:12 -0500
From: <k1ttt.dave at gmail.com>
To: "'Steve London'" <n2icarrl at gmail.com>,    "'Rfi List'"
    <rfi at contesting.com>
Subject: Re: [RFI] Peculiar Noise
Message-ID: <01c401da35e6$ef5d72c0$ce185840$@gmail.com>
Content-Type: text/plain;    charset="us-ascii"

I tracked down a noise like that many years ago to a tv preamp on an
external antenna, would wander up and down the band but occasionally liked
to park on a local repeater input.... first step is to find it, then figure
out what it is!

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: telnet://k1ttt.net:7373

-----Original Message-----
From: RFI <rfi-bounces+k1ttt=arrl.net at contesting.com> On Behalf Of Steve
London
Sent: Saturday, December 23, 2023 14:34
To: Rfi List <rfi at contesting.com>
Subject: [RFI] Peculiar Noise

Anyone care to make a guess at this ?

https://www.kkn.net/~n2ic/n2ic_noise.mp4

I have flipped the main breaker and turned off all UPS's in the house.
Peaks SW, which is towards a neighborhood over a mile away, and a large
copper mine, 2 miles away. There is also a line of 14.4 kV power lines in
that direction.

It will be on for several hours at a time, then disappear. Nothing else like
it between 40 and 60 MHz. I would never have noticed it, except it sometimes
parks itself on 50313, the 6 meter FT8 frequency.

73,
Steve, N2IC
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------------------------------

Message: 3
Date: Sat, 23 Dec 2023 14:05:57 -0800
From: Jim Brown <jim at audiosystemsgroup.com>
To: rfi at contesting.com
Subject: Re: [RFI] Peculiar Noise
Message-ID:
    <d88469f7-a109-413d-8dd3-1179b8b9d7e1 at audiosystemsgroup.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

On 12/23/2023 1:28 PM, k1ttt.dave at gmail.com wrote:
> I tracked down a noise like that many years ago to a tv preamp on an
> external antenna, would wander up and down the band but occasionally liked
> to park on a local repeater input..

This can be either instability in the preamp or from an SMPS PSU. Years 
ago, we traced that sort of issue to instability in the preamp for 
wireless microphone receivers. It helped that the contractor on the 
project was a ham.

73, Jim K9YC

------------------------------

Message: 4
Date: Sat, 23 Dec 2023 22:11:26 +0000
From: David Eckhardt <davearea51a at gmail.com>
To: jim at audiosystemsgroup.com
Cc: rfi at contesting.com
Subject: Re: [RFI] Peculiar Noise
Message-ID:
    <CAODdWWGYfU+jMfbtkf2HUYfMYNj8uGgWYEgYi1MKOZp9UiDFEQ at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

Try FM demodulation.  I have something much like that on 160-meters.  It's
from one of the more-or-less local FM BC stations mixing with an AM
station.

Dave - W?LEV

On Sat, Dec 23, 2023 at 10:06?PM Jim Brown <jim at audiosystemsgroup.com>
wrote:

> On 12/23/2023 1:28 PM, k1ttt.dave at gmail.com wrote:
> > I tracked down a noise like that many years ago to a tv preamp on an
> > external antenna, would wander up and down the band but occasionally
> liked
> > to park on a local repeater input..
>
> This can be either instability in the preamp or from an SMPS PSU. Years
> ago, we traced that sort of issue to instability in the preamp for
> wireless microphone receivers. It helped that the contractor on the
> project was a ham.
>
> 73, Jim K9YC
>
>
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>

-- 

*Dave - W?LEV*

------------------------------

Message: 5
Date: Sat, 23 Dec 2023 22:51:01 +0000 (UTC)
From: AA5CT <jwin95 at yahoo.com>
To: 'Rfi List' <rfi at contesting.com>, "nlsa at nlsa.com" <nlsa at nlsa.com>
Subject: Re: [RFI] Sources of wideband hiss
Message-ID: <926333542.2772505.1703371861726 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8

 Q: What mode are you using to note 'hiss'?
Can I ask whey you hear in AM mode, IOW, 'envelope detection' mode (vs say, SSB)?
de AA5CT Jim

    On Saturday, December 23, 2023, 1:14:01 PM GMT-6, <nlsa at nlsa.com> wrote:  

 Dear friends,

What are some sources of wideband hiss?? I'm talking about an unstructured,
apparently unmodulated many-dB increase in the noise floor across the 2m
band*? No associated birdies or other noticeable signals, just a nasty hiss.
I see it in the direction of high-voltage power lines 2km away and also
toward a couple of houses I just a few hundred meters distant.? The
mechanisms of those sources are not necessarily the same of course.? Ideas
welcome.

Best regards,

Michael

*I don't know whether it affects other HF or VHF bands.

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------------------------------

Message: 6
Date: Sat, 23 Dec 2023 23:48:24 +0000
From: David Eckhardt <davearea51a at gmail.com>
To: Frank W3LPL <donovanf at starpower.net>
Cc: Rfi List <rfi at contesting.com>
Subject: Re: [RFI] Sources of wideband hiss
Message-ID:
    <CAODdWWFA7-UPaeOS-EwOajktPPO5zwvpUQpa3PdmYZfUShkFuA at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

The "hiss" should be demodulated best in AM mode with a wide bandwidth.
Does it contain any component of grid power?  If so, that would be a strong
indication of bad power distribution.  If not, dig deeper, but use AM demod
with a wide BW.

Also, in sleuthing interfering RFI, why try to identify WHAT is it?  That
really doesn't help much in determining WHERE the source might be.  Once
you know the source, you can formulate a fix.  Just determining what it
might be really doesn't lead to a fix other than knowing what service to
point a finger at.  Do the DFing first.

Dave - W?LEV

On Sat, Dec 23, 2023 at 7:20?PM Frank W3LPL <donovanf at starpower.net> wrote:

> Like all other RFI, the first steps are
>
>  1. turn off all AC power in your own home and turn off
> all UPSes.  If the noise disappears, you can use your
> circuit breakers as a next step in isolating the RFI source
>
> 2.  If that fails, use a small directional antenna and hand portable
> radio to determine the location of the source
>
> Guessing the source is rarely useful
>
> 73
> Frank
> W3LPL
>
>
>
>
>
> ----- Original Message -----
> From: nlsa at nlsa.com
> To: "Rfi List" <rfi at contesting.com>
> Sent: Saturday, December 23, 2023 7:09:53 PM
> Subject: [RFI] Sources of wideband hiss
>
> Dear friends,
>
> What are some sources of wideband hiss?  I'm talking about an unstructured,
> apparently unmodulated many-dB increase in the noise floor across the 2m
> band*  No associated birdies or other noticeable signals, just a nasty
> hiss.
> I see it in the direction of high-voltage power lines 2km away and also
> toward a couple of houses I just a few hundred meters distant.  The
> mechanisms of those sources are not necessarily the same of course.  Ideas
> welcome.
>
> Best regards,
>
> Michael
>
>
>
> *I don't know whether it affects other HF or VHF bands.
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>

-- 

*Dave - W?LEV*

------------------------------

Subject: Digest Footer

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------------------------------

End of RFI Digest, Vol 251, Issue 3
***********************************