[time-nuts] strange carrier
alexpcs at ieee.org
Sun Nov 16 23:40:33 EST 2014
something like that is not a case for the FCC?
On 11/16/2014 2:26 PM, Max Robinson wrote:
> Don't touch it. If you do you become responsible, in your neighbor's
> eyes, for any and all subsequent failures.
> 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."
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