[OZAPRS] FW: [Fwd: RE: 70 cm APRS frequencies]

Thu Nov 20 09:20:10 EST 2003

It seems really odd that there is so much unused 70 cm band and still we
have drawn out discussions and can't make our minds up.

Why not have a vote ?

Get every one to put in a submition. I am willing to make a vote page on
the
net.

Cheers Andrew vk4tec

PS it think 9600 is a waste of time on uhf ....but 1200 would be ok

Thoughts ?

----- Original Message -----
From: "Geoff Gatward" <geoff.gatward at optusnet.com.au>
To: "'Ozaprs'" <ozaprs at marconi.ics.mq.edu.au>
Sent: Wednesday, November 19, 2003 9:10 PM
Subject: [OZAPRS] FW: [Fwd: RE: 70 cm APRS frequencies]

More fuel onto the fire. . .
(I think we've been down this road before and got nowhere ??)

Geoff VK2XJG

-----Original Message-----
From: Barry White [mailto:bewhite at tpg.com.au]
Sent: Wednesday, November 19, 2003 9:37 AM
To: Geoff Gatward
Subject: [Fwd: RE: 70 cm APRS frequencies]

Here is some further discussion on UHF APRS.
It seems that 434.100 is out because it is used interstate already.
73 Barry FTAC Packet advisor

-------- Original Message --------
Subject: RE: 70 cm APRS frequencies
Date: Tue, 18 Nov 2003 20:20:18 +0800
From: Chris Hill <chris.hill at crhtelnet.com.au>
To: Grant Willis (VK5ZWI) <Grant.Willis at internode.on.net>,   Len Falknau
<lfalk5 at eq.edu.au>, 'John Martin' <jmartin at xcel.net.au>
CC: 'Walter Howse' <wjhowse at bigpond.com>,   'Rex Moncur'
<Rex.Moncur at bigpond.com>,   'Peter Mill (via Vic Div)'
<wiavic at wiavic.org.au>,   'Peter Hallgarten'
<peterhallgarten at optushome.com.au>,   'Peter Cockburn'
<Peter.Cockburn at cck.net.au>,   'Mike Dower' <vk1eng at tpg.com.au>,
'Gilbert Hughes' <ghughes3 at bigpond.com>,   'Eddie Saunders'
<eddie at suncity.com.au>,   'Brian Kelly' <wbk at bigpond.com>, 'Bill
Sebbens' <vk4xz at wia.org.au>,   'Barry White' <bewhite at tpg.com.au>,
'VK1 WIA' <federal at vk1.wia.ampr.org>

Hi All,

Looks like 434.100MHz is already quite busy!

My original thoughts were:

1.  Set aside a "repeater pair" (5Mhz offset) for APRS
2.  Primary National UHF APRS frequency = 434.175MHz
3.  Secondary National UHF APRS frequency = 439.175MHz

These frequencies can be used as we see fit for APRS use, but
possibilities
include:

1.  434.175MHz reserved for local / low-powered devices;  (eg a $70 "LIPD"
transmitter coupled to a TinyTrack, in a Boy Scout's backpack)
2.  439.175MHz used for high-powered wide area "backbone" work (eg 50W
into
14dBi, on a 50m mast at 300m ASL)
3.  A "cross frequency" repeater relaying signals from 434.175 out onto
439.175

The only reason I changed my suggestion from the above frequencies, to
439.100/434.100, was to fit reported existing use in Melbourne...  but it
now looks like the original 439.175/434.175 is better.

Does anyone have a problem with these frequencies?

73 Chris
VK6KCH

p.s  Have a look at http://vhf.worldsbest.com.au/LIPD.htm for the
relationship of LIPD channels to known 70cm Amateur activity.

-----Original Message-----
From: Grant Willis (VK5ZWI) [mailto:Grant.Willis at internode.on.net]
Sent: Tuesday, 18 November 2003 4:38 PM
To: Len Falknau; 'John Martin'
Cc: chris.hill at crhtelnet.com.au; 'Walter Howse'; 'Rex Moncur'; 'Peter
Mill (via Vic Div)'; 'Peter Hallgarten'; 'Peter Cockburn'; 'Mike Dower';
'Gilbert Hughes'; 'Eddie Saunders'; 'Brian Kelly'; 'Bill Sebbens';
'Barry White'; 'VK1 WIA'
Subject: RE: 70 cm APRS frequencies

Folks,

Both 434.100 and 439.100 are free in VK5 & I know there is interest in
trialing
9600bps APRS on 70cm in Adelaide. My first response is that I dont see any
major
issues with 439.100 for APRS here or in general.

However.....

Mobile users of 2m mobile trying to also listen to 439.100 APRS could have
some
issues
with the 3rd hardmonic of their own 2m transmitters bloting their local
APRS
receivers if trying to operate on repeaters using 146.950/146.350 or
146.975/
146.375MHz. (146.350 x 3 = 439.050, 146.375 x 3 = 439.125). We see this
problem
already for 2m voice to 70cm voice repeater allocations in overlaping
coverage
areas. (NOTE that the interference in this circumstance is real - and is
avoidable
with good frequency coordination - and only affects amateurs trying to
transmit
to 2m repeaters and receive on 70cm repeaters at the same time - something
that
happens more often than you think with modern dual band mobile
tranceivers).

The only other solution to this problem is to put the APRS down on 434
somewhere
(how about 434.175) - but being in amongst LIPDs will ultimately have
problems
with C/I and say 9600 data from mobile stations which will be having a
hard
enough
time with mobile fading without having additional LIPD crud to get over
making
the C/I equation even worst than it needs to be.

I would be in favour of allocating two channels - with a preference for
high
speed
APRS (>4800bps) only on 439.100, and 1200baud APRS on say 434.175 (or
wherever
one
can find room amongst existing local activity to allocate a new national
channel).
The allocation of permenant repeaters on 146.975 should be discouraged
(use
it
for
temp systems for WICEN as a primary) so as to give the national APRS
channel
a
fair
go - however this doesnt mean we should go out and retune existing 6975
systems
and
doesnt mean 6975 shouldnt be allocated for fixed systems where there is a
spectrum
availability driven need to do so.

Regards,
Grant VK5ZWI
Packet/Repeater Adviser to FTAC

.

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