[OZAPRS] We need a standard HF APRS Audio frequency pair

[Noel Rowe]

Mike, VK2BMM, recently posted here a detailed synopsis of the tone and
frequency issues relating to APRS on the HF bands.  He suggested that we
should refer to the "virtual carrier frequency"  rather than the dial
setting frequency that is the root of much confusion.

At a meeting held in Hamilton (central for ZL hams from Auckland, Rotorua,
and Tauranga) last Sunday to discuss APRS related issues, the HF bands and
the associated problems were debated.  It was suggested that to overcome
the
"what frequency to quote" issue, that we should do what was apparently the
norm, at least arround here, back in the good old RTTY days, and that was
to
quote the centre frequency of the tones.  This lines up nicely with Mike's
thoughts.

All that is needed is for the operator to add together the frequencies of
the two tones to be used, divide by two, then use the result to add to
(for
LSB) or subtract from (for USB) the desired operating frequency (stated as
the tone centre, or virtual carrier as Mike expressed it) and the result
is
the dial frequency.

The fact that it forces the operator to know (or to find out by looking it
up in the TNC manual or a help file) what the tones being used actually
are,
can be seen to be educational and therefore a good thing.

As far as the LSB v USB debate for 30 metres goes, well I believe that
when
the choice is to set a dial frequency in or out of the allotted band edge,
the "in band" setting must win every time.

Now, the tone centre is 10.149.300, my tones are 1600 and 1800, thats
3400/2
= 1700, dial set to 10.147.600 USB, ready and waiting!

Noel, ZL3GR.

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