doppler frequency selectivity - FoxHunting Forum at eHam.net

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eHam.net Forum : FoxHunting : doppler frequency selectivity

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doppler frequency selectivity	Reply
by KC0QNB on June 7, 2008	Mail this to a friend!
I have searched around the net but could not find a good answer. I have an interest in doing some RDF. The way I understand it a separate receiver is used in the activity and the Doppler (Roanoke and Montreal type) units work by finding the signal and then indicate the relative direction of that signal on a display. Now the question I have how does the Doppler system "know" that the signal it is indicating is the right one? In my area all the public safety agencies and a lot of businesses use VHF and if the unit is not selective in frequency it could "lock" on any of those signals and lead the user astray. 73 Ryan

RE: doppler frequency selectivity	Reply
by WB6BYU on June 7, 2008	Mail this to a friend!
You use a regular 2m receiver attached to the doppler - it can be the receiver in your mobile rig, HT, scanner, etc. The selectivity is the same as for normal ham 2m use. The doppler will indicate a direction based on the signal it is receiving, whether it is the one you are trying to find or not. So you have to be listening to the audio to know what it is hearing. (I think some dopplers include an audio output with the doppler tone notched out of it.)

RE: doppler frequency selectivity	Reply
by KC0QNB on June 7, 2008	Mail this to a friend!
OK thanks

RE: doppler frequency selectivity	Reply
by WB6BYU on June 7, 2008	Mail this to a friend!
On re-reading my comments I may not have been clear: you set the receiver frequency just as you would for any other 2m signal. The doppler doesn't do a frequency search, it simply responds to whatever signal it hears on the frequncy the receiver is tuned to.

RE: doppler frequency selectivity	Reply
by N6DMR on August 8, 2008	Mail this to a friend!
Here's a good link that shows the connections of a pic based doppler PicoDopp. The link takes you to the hook up diagram and build instruction page. You'll see that the HT audio and the data from the antennas are both ported to the doppler. http://www.silcom.com/~pelican2/PicoDopp/COMPLETION.html Duane N6DMR

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