[time-nuts] PN sequence generation using GPS

Bob Camp lists at rtty.us
Fri Feb 25 18:28:14 UTC 2011


Hi

If you are putting out > 20 watts and I'm close enough to see your mailbox, I'll detect you with some pretty simple stuff.

Bob


On Feb 25, 2011, at 1:16 PM, Chuck Harris wrote:

> I guess that is why I mentioned something about doing it competently.
> 
> The FCC so seriously winged the methods usable by hams as to render them
> effectively useless.
> 
> A nice direct sequence spread spectrum system with a couple of MHz
> spread would be well below the background noise of any narrow band
> receiver.  Sure, you could find it with a wide band detector if you were
> close by, but how would you know that you weren't looking at some other
> anomaly, like a bad insulator, or trash coming off of fluorescent lamps?
> 
> Done correctly, you could run spread spectrum just about anywhere you wanted
> to, and remain undetected.  Using direct sequence, you would be so low in
> power density that it could easily be argued that you were operating within
> the constraints of a part 15 device's leakage.
> 
> -Chuck Harris
> 
> Bob Camp wrote:
>> Hi
>> 
>> Remember that this started out running a sequence that was 127 hops long.
>> With something that short, it's pretty likely you will be rude to somebody.
>> 
>> Even if you are running a massive hop rate, I can likely walk around and
>> track you down within the average neighborhood. A diode detector behind a
>> bandpass filter and a small-ish directional antenna is about all I'd try to
>> use.
>> 
>> I suspect it would also work with one of the power detector chips. Range
>> wise, a lot would depend on just how good your local cable company is at
>> keeping their stuff running right. I'm not really sure the chip would add a
>> lot of range in a normal setting.
>> 
>> Bob
> 
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