[time-nuts] strange carrier

Alexander Pummer alexpcs at ieee.org
Sun Nov 16 23:40:33 EST 2014


something like that is not a case for the FCC?
73
Alex
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.
>
> 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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