[OZAPRS] UHF APRS Channel - 434 or 439

[Chris Hill]

Hi Richard,

A significant advantage to using 434.175MHz is that it allows licensed
amateurs to transmit APRS using inexpensive ($50 to $70) LIPD
transceivers.

The cost of a handheld or mobile isn't too bad when it's an amateur's
"main
rig", but cost rapidly becomes an issue when trying to extend amateur
radio
to a wider audience;  for instance, using APRS to track Boy Scouts / Cubs
during a navigation exercise.

Is there a formal set of selection criteria published anywhere, showing
how
the official UHF APRS frequency will be chosen?  It would be interesting
to
see the weightings assigned to conflicting considerations, such as keeping
away from non-amateurs vs availability of cheap transceivers, etc


73 Chris vk6kch



-----Original Message-----
From: ozaprs-bounces at marconi.ics.mq.edu.au
[mailto:ozaprs-bounces at marconi.ics.mq.edu.au]On Behalf Of Richard Hoskin
Sent: Saturday, 12 July 2003 4:55 PM
To: ozaprs at marconi.ics.mq.edu.au
Subject: Re: [OZAPRS] UHF APRS Channel - 434 or 439


Hi Chris,

I've been in discussions with the WIA and a few others in VK3 on the
subject
of a National UHF APRS channel.
It was suggested to me by John Martin that the most likely frequency for
National UHF APRS  will be 439.100Mhz. But we need to wait for an offical
announcment after the new UHF band plan has been completed. (This is due
to
the imminent loss of the lower half of the UHF band.)

We have set up are testing a UHF digi (VK3MY-2) and IGate on that
frequency
in the eastern suburbs of Melbourne. It's been running for about 12 months
now. There are plans to install a UHF APRS digi at VK3CV-1 in the not to
distant future.

Cheers
Richard.
VK3JFK

----- Original Message -----
From: "Chris Hill" <chris.hill at crhtelnet.com.au>
To: <ozaprs at marconi.ics.mq.edu.au>
Sent: Saturday, July 12, 2003 4:19 PM
Subject: RE: [OZAPRS] UHF APRS Channel - 434 or 439


> Hello All,
>
> I have recently purchased a 70cm LIPD transceiver, which has prompted me
to
> look at the frequency assignments (LIPDs vs Amateur).
>
> This is summarised on the WA VHF Group's site at
> http://vhf.worldsbest.com.au/LIPD.htm
>
> In the above summary, I have shown 434.175MHz as "Packet - APRS".
>
> Personally, I think that 434.175MHz should be denoted as the Australian
UHF
> APRS frequency, on a national basis...  either for simplex use, or as
the
> uplink to a bit-regenerative repeater.
>
> Any comments?
>
> (Also, can anyone provide any additional info on frequency usage in
> Australia on the 433.075MHz to 434.775MHz sub-band?)
>
>
> Regards,
>
>
>
> Chris vk6kch
>
>
>
>
>
> -----Original Message-----
> From: ozaprs-admin at marconi.ics.mq.edu.au
> [mailto:ozaprs-admin at marconi.ics.mq.edu.au]On Behalf Of Grant Willis
> (VK5ZWI)
> Sent: Tuesday, 23 July 2002 9:23 PM
> To: ozaprs at marconi.ics.mq.edu.au
> Subject: [OZAPRS] UHF APRS Channel - 434 or 439
>
>
> Hi Folks,
>
> Only recently subscribed but have read the archived digests.
>
> There is merit in 439 and 434 approaches. However I favour putting
> it somewhere on 434. Here is my reasoning:
>
> (a) Packet transmitters make the channel unatractive to LIPDs - they
will
> go away :-)
> (b) Packet repeaters with DCD-State machine Squelches (ie bit stream
> detecting rather
> than noise or audio detecting) will be immune to lockout by LIPD
> transmitters - ie they will
> transmit over the top of them if they hear them
>
> The only remaining argument with (b) is that then stations accessing
> repeaters etc need to be able
> to get enough signal into the repeater to overcome the LIPD. From what I
> have seen of high-site
> voice repeater LIPD interference, the EIRP reaching the repeater is not
> very high - but it is enough
> to open squelches and keep them open. Most users when they transmitted
over
> the top could
> override the interference. This does limit the range a little that a
single
> high site repeater could
> work over, but with other home stations on channel able to act as relays
-
> the signal level problem
> will go away to some extent in the uplink to a WIDE repeater, and if the
> WIDE high-site APRS
> repeater runs reasonable power (most single regional WIDEs should run
> probably 25-50W at least
> to give APRS-Messaging a chance) then interference into the roaming
mobiles
> will be limited also,
> particularly as they are mobile, and in a mobile environment LIPDs do
only
> reach 200-500m due
> to ground clutter. (This clutter is lost if you go ground to high site -
as
> there are reduced quantities
> of local obstructions).
>
> I can also demonstrate that LIPDs dont seem to be bothering other 434
> packet networks.
> Here in Adelaide, we have a 4800 baud noise-gate squelch based inter BBS
> network sitting
> on 434.050 - and we know that locally we can hear LIPDs on 434-434.1
MHZ.
> The BBS
> network doesnt seem to have blinked and it is still keeping on
forwarding.
>
> So - I would still recommend 434.175 be chosen as the national APRS 70cm
> channel.
>
> Incidently, there is a case for APRS using 70cm in a mobile environment
> more-so than 2m!
>
> 2m is very noise prone - from ignition noise, and other man made noise
> sources - far more
> so than 70cm. Packet is particularly susseptible to noise - as noise
> generates bit-errors on
> receive. So you might actually find that 70cm in urban environments (ie
> cities) is a better
> choice for running APRS mobile and in particular APRS messaging than 2m.
Of
> course,
> the argument is reversed when you get out into regional areas with
reeaters
> many tens or
> even hundreds of km away - where the lower path loss on 2m wins the day
-
> and the environments
> are generally quieter. I have moved most of my mobile voice activity to
> 70cm in part due to
> this reason (and because I got sick of the endless chatter on the main
2m
> repeater here :?)
>
> Something for you all to think about.
>
> Regards,
> Grant VK5ZWI
>
>
>
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