[time-nuts] question for expert time guys

Scott McGrath scmcgrath at gmail.com
Tue Feb 5 14:43:50 EST 2013


Think OP has the Choice of 3 bands

Sent from my iPhone

On Feb 5, 2013, at 12:32 PM, Chris Albertson <albertson.chris at gmail.com> wrote:

> On Mon, Feb 4, 2013 at 9:17 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
>> Can you re-transmit on a nearby frequency without blasting the receiver off
>> the air?
> 
> No not if it is in the same band, filters are never that good.  I
> thought the OP had several bands available.
> 
> So if this all needs to happen at one RF frequency the transmitter
> needs to act like a radar and send out modulated pulses.  The
> oscilator that does the modulation (sawtooth?) needs to run
> continuously. so that the phase of the returned signal can be
> compared.    If you don't know the range you need a conservative
> pulse repetition frequency (PRF in Radar speak) then once you find the
> range you can use a faster one to collect better data if you need to.
> The fester PRF transmits on average more energy so you get better data
> 
> The advantage is that all the "smarts" is in just one place, all the
> other units are simply a "mirror with gain" or "bent pipe".
> 
> The next level of sophistication is to scan the antenna and note the
> azimuth position when the signal is maximum.  Then you have both range
> and diction.   No need to triangulate.
> 
> Radars sound expensive but go to any small boat marina and you see
> that even small boats have them.  The newels units integate with GPS
> and the boats auto pilot and still prices at retail level are under
> $2K for entry level systems.
> 
> All that said, why not simply use GPS?   Your mobile unit can have a
> GPS receiver and transmit is location.  This works ten times better
> and cost a lot less.   The cell phone industry gave up on
> triangulation when GPS because cheap and easy
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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