[OZAPRS] What's Happened to HF APRS in VK?

[Chris Hill]

Hi All,

I've been thinking about this a bit more, and I reckon that we need to use
a
single, common frequency for 10MHz APRS worldwide, not just an "Australian
frequency".

The arguments for and against a worldwide 10MHz APRS frequency are the
same
as the arguments relating to using a single VHF frequency for VHF APRS in
Australia.

As for frequencies...  HF packet is really quite messy compared to VHF
(FM)
packet, isn't it?  As I've outlined at http://vk6.aprs.net.au/hf.htm:
"The exact two frequencies that you will transmit on are a function of
your
suppressed carrier frequency, whether you are running USB or LSB, and the
audio tones generated by your TNC or modem.

Bell 103 based HF modems (such as the AM7910 used on VK6ZTN's Flash TNC)
use
two different sets of tones, depending on whether the modem is configured
for "Originate" or "Answer" mode. The PK-232, and the Tigertronics TM-1,
use
different audio tones.

o   Bell 103 Originate uses TX tones of 1070Hz and 1270Hz.
o   Bell 103 Answer uses TX tones of 2025Hz and 2225Hz.
o   The PK-232 uses TX tones of 2110Hz and 2310Hz.
o   The TM-1 uses TX tones of 1100Hz and 1300Hz".


I am in partial agreement with Bob's suggestion that we should refer to
the
global APRS HF frequency as "10.149.2 MARK and let the user do his own
math".  However, this still leaves some ambiguity;  is the SPACE tone on
10.1490, or 10.1494 MHz?  (I believe the correct answer is 10.1494 MHz)

I personally recommend that we explicitly state what "Tone_1" and "Tone_2"
are, and leave it to the operator to work out what suppressed carrier
frequency they need to operate on, based on what modem tones they have,
and
whether they are running USB or LSB.  (Most operators will probably feel
happier using USB and therefore having a display frequency which is safely
inside the amateur band.  The Australian "digital modes" assignment for
10MHz is 10.140 to 10.150 inclusive;  see
http://www.wia.org.au/bandplans/Australian_Amateur_Band_Plans.pdf ).


I have now updated the HF APRS webpage to show Tone_1 = 10.1492MHz and
Tone_2 = 10.1494MHz, and have shown the nominal frequency as "10148.13kHz
USB".


What does everyone think about this?
Are we (in VK) happy to operate on the Global 30m APRS frequency?
Bob, are non-VK hams going to be happy to see the occasional APRS packet
flying around on 30m from VK-land?
Can anyone confirm that the two FSK frequencies are indeed 10.1492MHz and
10.1494MHz ?  Exactly?

(... and once we've got the frequencies settled, what's the correct PATH
to
use? )


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 Bob Bruninga
Sent: Sunday, 12 October 2003 11:05 PM
To: Richard Hoskin; ozaprs at marconi.ics.mq.edu.au
Cc: bbeamish at bigpond.net.au
Subject: Re: [OZAPRS] What's Happened to HF APRS in VK?


On Sun, 12 Oct 2003, Richard Hoskin wrote:

> BBS in NSW. We used 10.149Mhz as it appeard not to be used localy and
did
> not feel comftable using 10.151Mhz as it was too close to the band edge
and
> this became confusing for most operators.

1) "too close" to the band edge is groundless concern for the last 20
years since we have digital synthesized rigs.

2) If people are "confused" THen simply don't call it 10.151 LSB, but call
   it 10.147.6  USB.  Its the SAME frequency (assuming someone is using
   an 1600/1800 Hz shift.  But the BEST way to refer to the global APRS
   HF freuqnecy is 10.149.2 MARK and let the user do his own math based
   on what TONES his TNC uses.

They are all the same freq.

>  I beleive it would be great to have a Nationally agreed APRS frequancy
for
> both 30mts and 40 mtrs.

Bob


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