What is beacon mode?
One side of the radio set up for general use and the other side is an APRS radio. It sends a position periodically from the internal GPS. It's essentially a RTG with a couple of differences - listens for other stations before transmitting, gives a station list of heard stations, does APRS messaging, feeds APRS data as GPS waypoints to the serial port, etc.
I've used my truck to chase balloon launches which requires many stations to report and know other's locations. So having the Nuvi 350 with topo maps and letting the radio deal with voice & data diplexing is handy. My old set-up with a second radio was clumsy and a mess in my cramped cab, plus I was having front end interference with two radios transmitting so close in frequency. With the APRS radio set to anything higher than low power, the beacon would wipe out my voice radio RX, so long term that was going to blow out one or both radios' receivers. A lot of times the balloon drift way out on the plains, so the APRS beacons often need to be at high power for coverage.
I needed some sort of isolation and by far the easiest way to achieve this was using a FTM-350, TM-D710 as they are designed specifically to handle this by internally blanking the voice side during an APRS transmit. Otherwise I would have had to add a notch filter to one radio and a bandpass on the other, a difficult task to achieve when the separation frequency was 1MHz and the attentuation has to be 40dB or more. I would have had to essentially build a repeater cavity duplexer in my truck, which is not simple.
Last edited by DaveInDenver; 05-25-2012 at 01:16 PM.
You don't have to use one side of an FTM-350 or TM-D710 for APRS, but you have the option of it since they both have a TNC built-in the radio. Everyone gets to use their own dual-band radio for whatever two things they want; choice is good and more choices are better.
'80 FJ40, '86 FJ60, '07 FJC
N5MUD Parker County ARES/RACES
TLCA # 16550
I am looking for a good dualbander 2M / 70CM moonraker for back country comms - I have a city antenna just need one for the sticks...
A good 2M stick is a J Pole, for you homebrew types. Mount it on a heavy spring base, you won't bash it off. The instructions are online and can be cut for different freqs. I have used mine for the station on a tower and for mobile use with my Icom 706. Cheap, very efficient over 40db, I also like the 5/8 wave GP.
The J Pole is odd looking and if you make a nice one, people will still wonder "what the heck is that?????"
I was going to put a model airplane propeller on the top so it would spin and tell people it was my Ion Generator....