[time-nuts] question for expert time guys (Hal Murray)

Bob Camp lists at rtty.us
Fri Feb 1 12:45:37 EST 2013


To complete the thought:

Three base stations on three different transmit frequencies over a 50 MHz
range. Mobile has a local oscillator at say 200 MHz. Filter the incoming
frequency range, stuff it into a mixer, filter the output. What's
transmitted back gets processed at the base station. 

Yes you would have to be running at a high enough frequency to keep
everything in an appropriate band. 


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of johncroos at aol.com
Sent: Friday, February 01, 2013 12:16 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] question for expert time guys (Hal Murray)

Hello Hal -

I spent a lot of my RF engineering career in related areas, including radar,
EW, and spread spectrum timing
systems. Since the distance is short and the cost is an issue you may wish
to consider an analog
system solution.

Specifically your master station transmits a RF signal that is FM modulated
with a high frequency tone.
The remote unit is a transponder. It receives the tone and re-transmits back
on another frequency. Almost no parts required.

At the master station the phases of the outgoing and returning tones are
compared. The distance is directly
proportional to the phase shift between the outgoing and incoming tones. For
instance if the tone is 10 MHz
the 360 degrees of phase  is 100 nS which is about 100 ft round trip.

The phase may be measured either analog and A/D converted or digitally and
in either case is then easily converted to range by your processor.

By adjusting the tone frequency you can set the full scale range. To
increase resolution higher frequency tones may be used. To overcome
ambiguity when the range goes beyond 360 degrees of phase, add a lower
frequency tone to resolve the ambiguity.

This scheme has been used in surveying instruments (the Teleurometer) and
even an ill fated German bombing system in WWI. The latter proved
delightfully easy to jam since the Brits had a spare TV
transmitter in the correct band.


 Look up something like "tone ranging".

-john c roos k6iql

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