[time-nuts] question for expert time guys

Chris Albertson albertson.chris at gmail.com
Tue Feb 5 12:32:22 EST 2013


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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