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[aprssig] APRS and UHF voice

Robert Bruninga bruninga at usna.edu
Tue Jul 28 14:18:19 UTC 2009


Old Dog - New Tricks... 
VHF =>> UHF

For some reason, for my 40 years of VHF mobile operation, I seem
to only use 2m repeaters, just I guess out of habit.. And as an
APRS mobile operator with a D700, I put up with the occasional
blocked voice and blocked packets while I drive around only
using the 2m band.  But this weekend Appalachian Trail event was
an obvious eye opener for me.

With all the coordination we were doing on 445, it was just an
all new experience to be TALKING on the radio, and seeing
packets coming in at the same time.  And never be blocked when
packets went out.  And with Murphy and his entire family hanging
around all the mountaintops, we were using the voice
coordination channel orders of magnitude more than expected.

In my mobile, I have 117 VHF channels in memory and only ONE
(446.0 national simplex) in a UHF channel.  Yet, in my area, we
have scores of UHF repeaters...  And really good ones too
(though silent 99.9% of the time)... That I have never bothered
to use... Thanks... This gives me a new bunch of people to talk
to...(and better reliability on APRS at the same time)...

In fact, for the Golden Packet attempt next year I hope we can
eliminate all 2m contact freqs, the reason being that every
second we might be talking on 2m, is totally blocking our reason
for being there, weak-long-haul packets.  Also, every time a
packet goes out, we lose a second of audio on the voice channel
and have to ask for repeats..

I agree, that the UHF is several dB worse than the 2m links for
omni-omni links, but I hope that is just something we plan for,
because once we are operational and lots of packets are flowing,
we cannot afford to lose even one packet (that may have taken 13
hops to get to us and only have one  hop to go to its
destination) because we were talking on 2m.

So thanks for raising this issue.  In fact, I'm going to
re-program my mobile and see who is out there on UHF!

Bob, WB4APR




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