[ARDF] AM A2A Modulation...

[Matthew Robbins]

The ARDF Region 1 Rules for 2m require:  Mode A2A (keyed carrier
modulated by AF tone *or* continuous carrier modulated by keyed AF
tone). {emphasis added}

The second way seems to be similar to an AM radio station (RF out all
the time?).  It should be similar to the FM MCW signal we Americans
tend to use for ARDF, at least in the sense of it being on the whole
minute.

Saturday (October 8th), I was the fox for a local mobile hunt. 
Because 3 of the hunters are planning to go to Raleigh next April, I
proposed attempting to use A2A modulation (the first type listed in
the rules), even though I had no idea how to do it with my radio.

My first thought was to apply an audio tone to the microphone input
and key the PTT.  My first thought is often wrong, so I ran it by some
serious radio guys I know, and they recommended using SSB.  That way,
I could key the PTT, and key an audio tone into the mic input. 
Between the keyed bits of audio, the RF out drops to zero
(supposedly).  Fortunately, a PicCon can do what is needed.

Long story short is---The hunt went well.  Everyone agreed it was much
more difficult than FM.  The ARDFers who have hunted A2A thought it
was representative for ARDF, at least in the difficulty of taking
bearings..

I don't know how bespoke ARDF 2m transmitters achieve A2A, and I don't
know if an SSB circuit makes any sense for ARDF, but I do know it
works with a SSB 2m rig, and it's pretty simple if you can figure out
how to attach a PicCon.

(Another thing---I'm pretty sure no one used an FM radio for the hunt,
so I/we have no idea how difficult it is to hunt using one.)

Matthew
AA9YH
Cincinnati, Ohio