Sunday, August 26, 2007

APRS Band Opening

It is too bad I didn't have time to pack up the radio gear and head up on the mountain yesterday morning. First I noticed that I was hearing a station out of New York come in on the local Frederick repeater. There is 440 MHz transmitter up there on the same frequency that links the Frederick repeater with the rest of Western Maryland. After hearing that, I thought to check my APRS program. I was delighted to see stations all the way up to Maine. Now this isn't exactly good for the ARPS network, but it is an interesting phenomenon. It is all the more reason to use appropriate APRS paths like WIDE2-2, because you never know when your packets could be retransmitted 100s of miles away and cause network congestion in some other region.

If you notice the yellow circle on the picture, that is known as the ALOHA circle, which is basically the edge of the network for me. Packets I send that are heard outside of that network do more harm than good to the network. My ALOHA circle typically includes the Baltimore and Washington DC metro areas, but it all depends on the number of stations that are active at the time, during commuting hours, the circle gets a little smaller. It all has to do with the number of stations using the same frequency and the limitations of 1200 baud packet radio data signals.

More on APRS:

1 comment:

Earl Voss said...

Hi Joe,
I'm Earl - I used to author the zero2fifty blog. I was looking at getting my first decent rig - thinking of the ICOM 706MKII - so I can use it at home and mobile. With respect to APRS, I've been doing a bit of reading. I have a couple handheld GPS RXs, and I was wondering what APRS software you use (UI-View32?) and the TNC you've been using. Lastly, I don't believe my Garmin handheld GPS units (e-Trex Vista C, e-Trex legend and the older GPS III Plus) supply NEMA output. What do you use? I'm dissatisfied with waht I see on the web re APRS - most of this stuff looks upwards of 10 years old (Dos software, 16 bit, etc) and stale. I guess what I'm asking is some direction and perhaps a more current on-line source for information. Thanks!