[CW] Mystery interference

Sat, 12 Apr 2003 16:28:06 -0400

The Horizontal Scan Frequency for the USA standard NTSC (National Television
Standards Committee) frequency is:  15,734.265734265700000 Hz.  You
"strongest signal" is very close to the  3,579,545.454545450000000 Hz Color
Subcarrier Frequency. (10 Hz off!)

I would strongly suspect a nearby color television receiver.

You could recalibrate your equipment with this signal you're hearing because
it has to be very precise!

See: http://www.edlmax.com/NTSC3.html

73

David J. Ring, Jr., N1EA

-30-
----- Original Message -----
From: "Donald Chester" <[email protected]>
To: <[email protected]>
Sent: Saturday, April 12, 2003 3:02 PM
Subject: [CW] Mystery interference

>
> A few days ago, a new interference appeared on 80m.  It consists of rough,
> 60kHz modulated carriers, spaced at 15.7325 kHz intervals.  At first I
> thought it might be a touch lamp, but the carrier frequencies are
extremely
> stable, despite the rough sounding modulation.  The strongest carrier
> appears to be at 3579.55 kHz.  Carriers are clearly audible from 3406.48
kHz
> to 3736.9 kHz, with vestiges detected above 4 mHz.  The sound of the
> modulation changes every few seconds, and the signal strength varies as
the
> modulation changes.  At its strongest point it is about 10 dB above S9.  I
> get the strongest signal on the 160m. beverage, but it is audible on the
> 10m. ground plane and indoor loop.  The signal is weakest on the
> transmitting dipole.
>
> I measured the frequencies using a DDS vfo with 1 Hz resolution.
Individual
> frequencies may be inaccurate due to the difficulty in finding zero-beat
in
> the presence of the rough 60Hz modulation, but the spacing of the signals
> was determined by averaging the difference in measured frequency between
> adjacent carriers throughout the band.  At the time, the DDS vfo was
> zero-beat with WWV at 10 mHz.
>
> Readings were taken at the following frequencies:
>
> 3500.88
> 3516.662
> 3532.25
> 3548.15
> 3563.69
> 3579.55
> 3595.29
> 3611.02
> 3626.74
> 3642 (approx)
> 3698 (approx)
> 3674 (approx)
> 3690 (approx)
> 3706 (approx)
> 3721 (approx)
> 3736.9
>
>
> I am hoping someone might save me from having to re-invent the wheel in
> chasing down this interference, by identifying a probable source based on
> the above data.
>
> 73 de K4KYV
>
>
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