[aprssig] APRS UHF freq? (9600 baud)

Robert Bruninga bruninga at usna.edu
Tue Jan 24 16:09:19 CST 2017

Re 9600 and UHF,

I have slowly begun to start using local UHF repeaters (and meeting newer
voices) for just the reason you mention (VHF desense).  We have DOZENS of
UHF repeaters in our area (Maryland/DC)).

Just a note.  9600 baud APRS gains only about a factor of 2, not the
expected factor of 8, because of the fixed overhead of TXD and other T/R
delays.  Combined with the significantly less range of UHF for the same
class antennas, there is almost no incentive to operate APRS style bursts
on UHF at 9600 baud.  That is why it has never taken off.

But actually moving TRAFFIC through a fixed long linear 9600 baud
conventional packet links is something we should have been doing since 1998
when every APRS radio by Kenwood put dual band 1200/9600 baud TNCs in the
hands of almost every operator.  But no one uses this powerful 9600 baud we
have had for 19 years.

I want to build a 9600 baud East coast packet network.

See:  http://aprs.org/ec9600net.html


*From:* aprssig [mailto:aprssig-bounces at tapr.org] *On Behalf Of *Bob Mueller
*Sent:* Tuesday, January 24, 2017 2:26 PM
*To:* TAPR APRS Mailing List
*Subject:* Re: [aprssig] APRS UHF freq?

I wish a national UHF channel would get established for APRS.  I think it
would be great to run 9600 baud on UHF.  I would really like to build a
digi that cross band digis from 1200 VHF to 9600 UHF.  Both directions.  It
seems that everyone is drawn to 2m FM for phone.  Whether it's club nets,
ARES nets, or Public Service nets.  They seem to always land on 2m.  I
think it'd be great to have a 70cm APRS option.  That way FM phone on 2m
does not de-sense APRS operations.  Or full duplex dual banders such as the
TM-D710G can continue to receive packets on the other band, while
transmitting FM phone.  Or transmit packets while listening to a net on FM

I'm not calling for every digi to get replaced with a cross band digi.  But
it would be nice to have a national 70cm frequency established.  So a 70cm
option can potentially be added to some of the digi's that are out there.
I think it would be very useful in certain cases.

--... ...--
Bob Mueller
bob at funautical.com

On Tue, Jan 24, 2017 at 1:08 PM, Robert Bruninga <bruninga at usna.edu> wrote:

The UHF freq for APRS comes up every now and then.  Here is what I know.

1)      We  use 445.925 on UHF for both APRS voice channel and APRS UHF for

2)      Using operator-to-operator voice here avoids interference with 2m

3)      Also for some events, operating APRS combined with Voice Alert has

4)      I don’t think we want any dedicated permanent UHF links on 445.925

5)      445.925 is NOT an APRS frequency in southern California due to
other uses

6)      There is no national UHF or 9600 channel that I know of.

7)      The only permanent APRS UHF net I know of is in the Pacific
Northwest on 440.800 (or 440.875?) at 9600 baud.


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