[OZAPRS] Decoding HF APRS

[Richard Hoskin]

The tuning of HF packet is critical down to about 20Hz or so. Most Amateur
HF radios are not calibrated to this level of accuracy on their frequency
readouts.

Using the same type of TNCs, it's fair to say that your frequency read out
may read 10.147.60 and mine may read 10.147.68 yet our stations are
communicating with each other.

What the read out on your radio says is not that important, it's just a
guide. What is -most- important is that we can communicate to each other.

In VK the Primary Net station is VK3MY-4. If you can communicate with him
or
one of the Secondary Net stations that have tuned to VK3MY-4's signal you
are on the correct frequency to communicate to all other HF APRS station
in
VK/ZL.

Visit http://www.aprs.net.au/hf_aprs_information.htm for details.

(If you find any of the information on the web page incorrect please email
me)

Cheers
Richard
VK3JFK


> -----Original Message-----
> From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
> Behalf Of Tony Hunt
> Sent: Saturday, 8 July 2006 7:12 PM
> To: ozaprs at aprs.net.au
> Subject: Re: [OZAPRS] Decoding HF APRS (Rob)
> 
> Very interesting .. After Robs first posting late last week and his
> comments
> on the lack of decode on HF I put the HF Gate back to air friday
morning..
> Since then ive got plenty of stations and Gated them.. In no particular
> order..
> 
> VK4DMI-4 VK2JN-15 VK2HL-15 VK3MY-4 VK5EX-15 VK2IT VK2SX-9
> VK2TVQ-15 VK5EX-4 VK2KCM-1 ZL1GTB
> 
> I use a PK232 modified for 200Hz operation. I note that the PK232 was
> originally setup and the alignent procedure for them recomends 2295 and
> 2125
> 170Hz operation. I have however changed mine to use 200 Hz 2300 and 2100
> Hz
> tones and it seems to decode just as well if not better. More to the
point
> it probably gets decoded better by others.
> 
> The old 170Hz shift originated with RTTY by these days some RTTY
activity
> seems to even be using 200Hz shift so its all a bit confusing and more
to
> the point all a bit painful.. I say painful because it appears that you
> can
> decode and be decoded by a station running 170Hz shift when you are in
> fact
> yourself using 200Hz shift.. But I ask really how well is it all going
to
> work mixing the standards? I suspect at times this is where we come
> unstuck.
> I am pretty happy with the decode I get here with the PK232.
> 
> Yes Sound card PC based decoders can and are better at times.. The only
> one
> I can say confidently that comes near the Pk232 or betters it is MixW ..
> This one is certainly worth a look..
> 
> Tony Hunt  VK5AH
> 
> 
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