"Tim Wescott" wrote in message
...
Mike Andrews wrote:

Allan Butler wrote:

[snip preconditions]


Withoug the previous parts of the thread this may be duplication since I
don't know the original constraints...but

I have always wanted to build a model rocket altitude transponder using this
concept:

On-board the rocket we have a "transponder"... a one transistor superregen
Rx on, say 10 or 6 Meters. I hae a schematic around here somewhere for a
one tranny FM broadcast receiver from Pop Tronics. Have it's demodulated
signal modulate a 2 meter TX. This can be a 9 or 12 Mhz. xtal osc and 2
meter tuned circuit (gets you a few miles on the ground from a tower
receiver).
On the ground you have the "Ground Station" 10 or 6 meter mobile. Since
you can have lots of power, the crummy Rx onboard the rocket is no problem.
From the mobile, transmit a tone. Measure the time delay of a zero crossing
of the transponded tone. A simple freq counter can be made to do this if it
had (I forget the official name--triggered event counter maybe??) the
ability to start counting on the TX tone's edge and stop on the RX tone's
edge. Just a few chips for this.
You pick the frequency that the counter is counting to display feet or
whatever units you like.
What's-it, something like a nano second per foot?
You also need a delay in the proper place to account for the "zero distance"
delay of the receivers & transmitters.
Seems like one other "Ground" receiver is all that's needed to triangulate
the location horizontally...

There was an article in QST within the last year or so where some fellas
measured the delay through a, I think, 2M repeater versus distance...same
concept, 'cept they just used a dual trace scope..

--
Steve N, K,9;d, c. i My email has no u's..