[time-nuts] strange carrier

[Max Robinson]

Don't touch it.  If you do you become responsible, in your neighbor's eyes, 
for any and all subsequent failures.

Regards.

Max.  K 4 O DS.

----- Original Message ----- 
From: "ed breya" <eb at telight.com>
To: <time-nuts at febo.com>
Sent: Saturday, November 15, 2014 2:30 PM
Subject: Re: [time-nuts] strange carrier


>A signal like that coming from a dish makes some sense to me. I vaguely 
>recall from about ten years ago investigating how the satellite receivers 
>work, that a fairly strong control signal of around 20 kHz was used in some 
>to select the various LNBs and their polarizations in more complicated 
>systems. This was passed via the cables superimposed on the DC power along 
>with the returning IF signals between the set-top box and the dish units.
>
> If the neighbor's setup has a bad connection in a cable end, there could 
> be a pretty strong third harmonic of a 20 kHz-ish signal leaking out, with 
> a good-sized antenna possibly formed by maybe 50-100 feet of partly-opened 
> cable shield, depending on the possible ground loop paths. Another 
> possibility is if the LNB power line from the STB has lots of 20 kHz-ish 
> noise on it from a failure in the local SMPS.
>
> If the possible faults were large, you would think it would be noticed as 
> a reception problem by the neighbor, but maybe a partial problem is enough 
> for you to see interference. If the interference is from the control 
> signal, it would likely be derived from a uP clock, so quite stable, while 
> if it's from SMPS switching, it should not be very stable, and also loaded 
> with line frequency sidebands.
>
> If that is the case, maybe you could inform the neighbor so that they can 
> fix the problem (or you fix it for them), thus improving their reception 
> and reliability, and eliminating the interference.
>
> I could be entirely wrong on this, but your last post rang a bell in my 
> head as soon as I saw "satellite dish."
>
> Ed
>
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