>From the hand drawing of the noises, it looks as if there may be two different
>noises.
Most of the time, noise sources spaced 10 to 100 kHz apart are switching power
supplies or similar devices. They exhibit the following characteristics:
1. The noise appears at intervals across a band, typically 10 to 100 kHz apart.
2. The noise can be very carrier like, but usually is not, having a strong 6o-
or 120-Hz component to it. This is usually best determined by listening to the
noise in the AM mode.
3. There is no "digital" sound to the noise, with nothing that sounds like
data being transmitted.
4. Switching devices are usually a little drifty, so the frequency one
occupies tends to drift up and down as the temperature of the device varies.
5. Switchers are also sensitive to line voltages, so glitches such as power
surges or dips will usually cause a brief frequency change from time to time.
Ed, W1RFI/0
________________________________________
From: RFI [rfi-bounces@contesting.com] on behalf of Cortland Richmond
[ka5s@earthlink.net]
Sent: Sunday, October 28, 2018 4:34 PM
To: rfi@contesting.com
Subject: Re: [RFI] Signals on 160
Ed will remember the AT&T modems on 80 meters.
I had good luck tracking them down in Petaluma and locating each one to
specific rooms in a development of single-story duplexes.
It was Super Bowl Sunday and when people sharing cable co. services saw
someone with antennas on his car and a "sniffer" (AOR 8000 with an
untuned loop) they were running behind their houses to remove the
illegal taps.
A 3-6 inch loop of rigid or even fairly stiff coax can be directive
enough to find these harmonics and then at lower frequencies march right
up to the source. H-field coupling drops off VERY fast away from a
radiating conductor.
Cortland
KA5S
On 10/28/18 3:54 PM, Hare, Ed W1RFI wrote:
> "What is it?" is the wrong question. If someone said that it is a model Z-123
> Netstuff modem, that really wouldn't help much. The real question is: "Where
> is it?" Finding the house or location where the noise is originating is what
> you will get to eventually, so start with that question.
>
> Many noisy devices can sound similar, so if someone tells you that it is a
> Z-123, and it is really a lighting ballast instead, you will be on a
> wild-goose chase.
>
> Ed, W1RFI
>
>
> ________________________________________
> From: RFI [rfi-bounces@contesting.com] on behalf of donovanf@starpower.net
> [donovanf@starpower.net]
> Sent: Sunday, October 28, 2018 3:04 PM
> To: rfi@contesting.com
> Subject: Re: [RFI] Signals on 160
>
> Hi Gary,
>
>
> Of course, the first thing you should do is turn off all of the AC
> power -- including UPSs -- in your own home to determine if any
> of the RFI disappears.
>
>
>
> I don't think anyone will be doing you a favor by helping you guess
> what these signals might be. By far the best way to determine what
> they are is to build -- or if necessary buy -- a simple small loop antenna.
> A loop antenna has a deep, narrow azimuth null off of each side of
> the antenna that allows to quickly identify the RFI source.
>
>
> Good luck!
>
>
> 73
> Frank
> W3LPL
>
> ----- Original Message -----
>
> From: "Gary Smith" <Gary@ka1j.com>
> To: rfi@contesting.com
> Sent: Sunday, October 28, 2018 5:31:51 PM
> Subject: [RFI] Signals on 160
>
> I've been encountering some strong signals
> on 160 recently. I made some approximate
> guesses at the frequency using the P3
> markers to measure them. Here's the
> signals at 1:20PM local time with a center
> frequency of 1.848.67
>
> The main signals are about 42 KHz apart.
> The lesser spikes in-between appear at
> somewhat regular intervals.
>
> http://doctorgary.net/spikes-on-p3.jpg
>
> Here's the measured values of the main
> signals
>
> http://doctorgary.net/frequencies.jpg
>
>
> Any idea what might be the source of
> signals spaced like this?
>
> 73,
>
> Gary
> KA1J
> _______________________________________________
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>
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