[time-nuts] GPS interference and history...

Magnus Danielson magnus at rubidium.dyndns.org
Fri Jun 10 21:17:01 UTC 2011

On 06/10/2011 06:42 PM, Bob Camp wrote:
> Hi
> The FCC (like most US agencies) has a mission to promote as well as
> regulate. The promotion side is what drives them to allocate frequencies in
> a way that you can reasonably produce gear. They have always come back years
> later and tried to change things around. Every time, the same issues get
> hashed over. Sometimes a change actually gets made, sometimes not.
> What's surprising with the GPS impact here is that the usual conversations
> are taking place a bit late in the process. The impact on legacy timing gear
> is one part of a much larger issue here. Hopefully it does not get lost in
> the back and forth. There's an enormous amount of gear out there that gets
> timing off of GPS.

Blinding the receivers like that hurts both because antennas and 
front-end isn't prepared for quite that interference, and simple 1-bit 
receivers will be caught... so more dynamics will be needed for the 30 
dB correlation gain to be of any use.

Correlation gain could be increased... with a massive replacement of 
receivers as signal would change... oh and sats. Still the front-end 
would require much more interference tolerance... and to some degree 
this is against the military aspect, as they rely on being able to noise 
out un-keyed receivers when needed. So the counter-measure becomes less 
usefull when counter-counter measures is needed on a wide scale just to 
do normal civilian business.

Raising the signal level in a band by, what was it? 70 dB suddenly might 
be a little too steep a change. Also, it would rule out many hardware 
approaches which have made GPS useful in so many places.


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