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Author Topic: Multi-receiver board with a single clock  (Read 9388 times)
K2ROC
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« on: February 14, 2016, 12:15:16 PM »

Does anyone know of a company that makes a board that has three (or more) 70cm receivers (FSK), that use a single clock source as their reference?  I'm thinking that if I have three antennas far enough apart (> 30 meters) that I could use time difference of arrival (TDOA) after timestamping periodic announcements from the transmission source to estimate a location.  RSSI seems too unpredictable.  The major problems with TDOA, from my understanding, is that the reference clocks for the receivers either have to be exactly in synch (within a nanosecond of each other) or have just one clock for all receivers.  Maybe this is an old idea to everyone else.  Just trying to get through a long, cold winter with more project ideas than I have time for.  :-)

Larry
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WB6BYU
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« Reply #1 on: February 14, 2016, 12:38:34 PM »

The simplest approach that I know of is to take 3 nominally "identical" receivers,
extract the clock or reference oscillator out of one, amplify it, and wire it into all
three receivers in an identical manner.  (That ensures that the propagation delays
are the same for all receivers.)

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K2ROC
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« Reply #2 on: February 15, 2016, 02:46:44 PM »

The extraction, amplify, and wire part may be a bit out of my "hardwaring" skill set, but I'll look into that approach.  Thanks.
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AG6JU
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« Reply #3 on: November 18, 2016, 11:32:50 PM »

I did exactly that once.

I used 2 receiver boards for 218 MHz.

I used one of receiver's 1st LO, 2nd LO, BFO feed to second receiver.  so they share same 1, 2 LO, and BFO. so phase relation ship are same.  1st LO 230 MHz is conneted with 1 inch of coax, 2nd LO, BFO use several inch of Coax, but they are lower frequency 10.7 MHz, 456 kHz.

I connected Right Antenna to #1 Receiver , Left Antenna to #2 Receiver.

and Audio output of #1 to Left ear, audio from #2 Receiver to Right ear.

I was wondering if I can discern direction of RF signal by phase difference in demodulated audio signal.

it actually worked well.  I can tell where the RF signal is coming from just as if you are hearing Audio signal source, except multipass signal, I could not tell the difference.

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