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[aprssig] APRS on UHF?

Bob Bruninga bruninga at usna.edu
Thu Nov 27 02:13:16 UTC 2008


> My input would say that some area networks 
> can utilize UHF for example to stay off the 
> main 2M freq., and use the 70cm band for 
> local stuff.  

Since APRS (to me as a mobile) is to be able to *receive* and see the local situation around me, I see no value in moving any local actiivty off of 144.39 and then making it invisible to the whole intent of 144.39 in the first place to other mobiles.

If the purpose of 144.39 is to be the place where you see everything around you, then the only way I would think of using a UHF freq is as an alternate input freq for a 144.39 digi, which would give priority to local incoming UHF packets that would not have to contend with QRM on 144.39 to get in.

This would bias the 144.39 all-seeing channel towards better reliability for locals to get in (on UHF) without colision. (but by  paying a 6 dB penalty).  Which is half the range.

So that is why I have never used it.  If I want an alternate input freq, then I would use 144.99 (which is 144.39 + 600) so that I dont give up that half range.

ANother good idea for using UHF as an input though is to avoid QRM at an EOC or other event where  you dont want to intrfere with other 2m voice nets.

Just my 2 cents.
bob, wb4apr

Now local can mean different things to different people geographically.
>
>Chris 
>KB8UIH
>
>
>--- On Wed, 11/26/08, Phil - AD6NH <ad6nh_lists at dslextreme.com> wrote:
>
>> From: Phil - AD6NH <ad6nh_lists at dslextreme.com>
>> Subject: Re: [aprssig] APRS on UHF?
>> To: "TAPR APRS Mailing List" <aprssig at tapr.org>
>> Date: Wednesday, November 26, 2008, 12:02 PM
>> This question gets asked every few years.  Some areas do
>> have recognized UHF
>> frequencies for APRS (So. Cal is 438.975 for example).  The
>> problem is, the
>> UHF band plan varies widely in different parts of the
>> country, and efforts
>> to standardize have always run into road blocks because of
>> local band plan
>> incompatibilities.
>> 
>> 73
>> Phil - AD6NH
>> www.aprsca.net
>> 
>> On Wed, Nov 26, 2008 at 8:42 AM, Patrick
>> <winston at winston1.net> wrote:
>> 
>> > A question came to mind today to a couple of us on the
>> way to work...  Why
>> > hasn't aprs
>> > standardized on UHF?  Being on the uhf bands would
>> resolve many of the
>> > issues for mobile
>> > installations (ie de-sense to other 2m radios, car
>> stereos, etc)...  True
>> > the coverage
>> > wouldn't be quite as long distanced, but the uhf
>> bands seem to be a lot
>> > less used, and
>> > commercial uhf hardware is available cheaply and in
>> abundance which could
>> > be easily
>> > modified for this sort of use...
>> >
>> > p
>> >
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>> >
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