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RE: LF: Strange signal 500khz

To: <[email protected]>
Subject: RE: LF: Strange signal 500khz
From: "Gary - G4WGT" <[email protected]>
Date: Thu, 5 Oct 2006 11:52:44 +0100
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Hi Markus,
Not so  :-)  the TV was continuously on one channel for 2 programs whilst I monitored, I watched 500KHz last night deliberately around the time my wife switched the set on therefore proving it was my own TV. I believe that the stepping effect is probably due to the "Freeview" digi-box because the TV is an older analogue model & I would expect a steady (ish) interference with no prominent stepping. I will do some tests with & without the digi-box.
I do always see a continuous weaker line near the same point which was also visible in my previous attachment which is not due to the TV being in standby as we always switch the set off by the mains on/off switch, the line could be generated by one of my other electronic items which are always in stanby mode as they do not have a mains power switch.
It seems that Alan's comments about TV interference at that frequency were correct.
Gary - G4WGT.
-----Original Message-----
From: [email protected] [mailto:[email protected]]On Behalf Of [email protected]
Sent: 05 October 2006 10:53
To: [email protected]
Subject: Re: LF: Strange signal 500khz

interesting - one of your family members seems to be switching channels rapidly ;-)
During my LORAN monitoring, I often saw a grid pattern which didn't average out in 5 minutes or longer integration times. It appeared only on certain chains, having group repetition intervals which were multiples of 40 (i.e. 0.8 ms).
The explanation turned out to be a weak carrier at 93.750 kHz (6x line scan) from my neighbour's TV. This became visible only when she was watching either "ZDF" which used to have their line rate sysnchronized to UTC, or "3sat" which showed a small variable slant due to geostationary satellite residual Doppler.
73 de Markus, DF6NM

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