[time-nuts] PN sequence generation using GPS

scmcgrath at gmail.com scmcgrath at gmail.com
Sat Feb 26 12:52:40 UTC 2011


Hi Chuck,

Serious contesters have directional antennas and most of the new contest quality rigs have FFT spectrum displays and the ability to record several Mhz of spectrum directly to disk for later analysis.   

   The old stereotype of unsophsticated home brewed gear is now a subculture of the Ham community.

These are the guys who will hear you and FIND you esp since most of these guys have north of 50k invested in their stations and anything which interferes with getting that last elusive multiplier will be tracked to the end of the earth. 

 and some of them like me are also time-nuts.


Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Chuck Harris <cfharris at erols.com>
Sender: time-nuts-bounces at febo.com
Date: Fri, 25 Feb 2011 13:16:13 
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] PN sequence generation using GPS

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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