[time-nuts] PN sequence generation using GPS

[Bob Camp]

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



-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of jimlux
Sent: Friday, February 25, 2011 10:57 AM
To: time-nuts at febo.com
Subject: Re: [time-nuts] PN sequence generation using GPS

On 2/25/11 7:13 AM, scmcgrath at gmail.com wrote:
> Speaking as a ham,  if this is tried you will have hams complaining and
DF'ing the offending signal.
>
Speaking as a ham, and as someone who used to build (and attempt to 
detect and jam) systems like this for a living..

The odds that a OO would see and recognize the signal is vanishingly 
small.  As for DFing?  It would be very difficult, considering that you 
need a wideband receiver to see the signal, and there are usually plenty 
of other signals in the band.

Yes.. if I were radiating a few watts, and you were my next door 
neighbor, so my signal was really strong, and I used a slow hop rate, 
and you had a fast sweep spectrum analyzer.. you "might" be able to see 
it.  IF you knew what to look for.

More likely, you'd be talking about it to your friends and various 
mailing lists (like this one), and someone who knows someone who knows 
someone who is "interested" in such things would find out, and THEY 
would get out the fancy gear and they would track you down.

That's what leads to the guy in the government car sitting outside your 
house one morning with "just a few questions".

Basically, it all comes down to the "rude rule"  - if you're rude to 
others, bad things happen.  If you're fooling with a 10-20 hop/second 
hopper on, say, 2 meters, and you happen to put the local repeater input 
frequencies in your hop list, and you don't hop over the entire 4 MHz 
band, so you're hammering the repeater every few seconds.. and you run 
your link 24/7, yep.. you deserve the abuse you'll get.

But for most people.. the hopper's interference would barely be 
noticeable.  (4 MHz, 5 kHz channel spacing is 800 hop channels.. so at 
10 hops/sec, you'd hit the same channel every 80 seconds.. And if you 
use a hop sequence that is longer than 800 (no reason not to...), it's 
not even like a repetitive interference.

Maybe a weak signal guy running JT65 or something might notice something 
on their waterfall, but maybe not.


>   Chuck, you are correct in that no one but the hams care but the reason
behind this is that policing the ham bands has been delegated to the hams
and specifically certified 'Official Observers'.  Once a infraction and
especially a.unlicensed infraction is noted penalties are pretty severe and
swift.
>
> If you want to do this get a 'experimental license'

Well.. that *would* be a better solution, and the way to really go.

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