[OZAPRS] 10MHz HF Gateway -Re: New to list

Rodney Mitchell rodney at melecom.com.au
Fri Aug 31 16:11:27 EST 2007

Top of email, sorry, couln't quickly find the reference point.

Why would it be a waste to use a top radio for APRS? I have a toggle
switch so one position is APRS, the other normal HF with the curly cord,
too easy!

73 de Rod, VK5KFB.

On Fri, 2007-08-31 at 12:26 +1000, Ray Wells wrote:
> Mike Zwingl oe3mzc wrote:
> >Gday,
> >just one comment on HF-APRS Gateway operation:
> >in practice it is not the signal to noise ratio that decides about
decode or 
> >nodecode of an APRS beacon on 10Mhz.
> >  
> >
> I've only been on HF packet for about 8 years so I guess I've still got 
> a lot to learn about it.
> The two most significant things that affect the ability to decode HF 
> packet are:
> 1. Noise
> 2. Phase distortion. Yes, even with just 200Hz shift it can be a real 
> problem. It's more of a problem than noise at my QTH.
> There is no doubt that a rig that drifts will cause problems, but with 
> any modern synthesised rig the stability is excellent and unliley to be 
> a consideration. Even my 23 years old Kenwood TS430 (which I'm currently

> using for the 30m gate) is more than satisfactory. I know the reference 
> crystal is off by a100Hz or so but that's another issue that I can 
> easily resolve when the need to do so gets to the top of my priority
> >More important is to use a TNC that allows some frequency drift, like
> >DSP-TNC from SCS.
> >The DSP-TNC is currently the only hardware that will simultaneously
> >several APRS signals at same time in a 800Hz wide channel!
> >So the frequency offset of a mobile station can be plus/minus 400Hz and

> >still have successful decode on 10.147,6 USB (10151LSB)
> >See the result at VK6UZ-4 and VK8ZAB-4, Fritz and Alan are using these
> >Most other TNCs/Soundcards require 30Hz accuracy in frequency, which is

> >almost impossible to achive.
> >www.scs-ptc.com/datasheets/scs_datasheet_tracker_english.pdf
> >vy 73 de Mike
> >oe3mzc
> >ex VK3FPF/8
> >  
> >
> And how many are going to spend big money on another TNC when what they 
> use works fine. We all know that Pactor-II is better than 0k3 packet but

> at near $2000 in Australia for the controller it would want to be.
> VK6UZ and VK8ZAB are seeing lots of travellers in outback Australia, 
> that's true, but have a look at where the travellers are, and then 
> back-track to when they  were closer to stations in the eastern states 
> and you'll see that other stations got hit more often. It's a matter of 
> distance and propagation, not frequency drift in a mobile.
> Far from being almost impossible to achieve, modern rigs easily maintain

> 30Hz acuracy, and better.
> I've had my TS430 in Central Australia on some of the most horrenous 
> tracks you can imagine - try the flint country from the vk4/vk5  border 
> up onto the Lamamour Plateau in South Australia, or the potholes and 
> corrugations on the Birdsville Track just prior to it being graded. At 
> no time did I detect the slightest stabilty problems, and I spent a lot 
> of time listening to  both amateur and broadcast signals  (in SSB mode) 
> while mobile.
> On could be forgiven for thinking that you're selling those TNC's??
> Ray vk2tv
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Rodney Mitchell
Senior Technical Officer

73 Fiveash Drive
South Australia     5042



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