[VHFcontesting] APRS on Rovers - Pt 2

[Ev Tupis]

Thanks to a conversation with Mark (N2MH), a few other items came to light that will help to maximize your contest-APRS effectiveness.  These apply only to APRS on 144.39 MHz because it deals with DIGIpeating, not HamIM (which is simplex on 147.585 MHz and has none of these issues).

1. If you are using a TNC, do *not* set it up to be a DIGIpeater to other stations for any reason or on any alias.  The APRS frequency of 144.39 MHz is waaaaaaaaaaaaay too close to the SSB sub-band centered on 144.200 MHz and I'm betting that the self-QRM from your *own* APRS station's ID will cause you fits...let alone the traffic caused by having it DIGIpeat others.

2. When launching on APRS, use the path of "WIDE1-1,WIDE3-3".  This will provide you with 4-hops of DIGIpeating, which will be about what your SSB/CW RF range will be during the contest (yes, this is a generality).  This is *different* than the suggested pathway of "WIDE1-1,WIDE2-2" because there is a tactical need for it to be...but *only* for the VHF contest this weekend.  Do not leave your Rovers APRS configuration in that state, after the contest.

3. Test your APRS ID QRM now, before the contest begins.  Set your TX interval to something that won't make your head explode as you have your volume turned up on 144.200, trying to dig-out a weak one and it kicks-in.  Under no circumstances should your ID be any more frequent than every 5-minutes.  Even when travelling at 60MPH, that is a location error of only 5-miles.  Frankly, every 10 to 15 minutes is probably plenty.  The only risk that you'll assume by longer ID intervals is that you won't show as having moved from your hilltop until it ID's again.

4. Lastly...remember that APRS is supposed to HELP.  If you find that the self-QRM is unbearable to your contest operation, SHUT IT OFF and contest.  Just remember to turn it on while travelling and not operating so at least we know you're out there. :)

Have fun!

Regards,
Ev, W2EV





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