[OZAPRS] QRG drift HF APRS

[Gerard Hill]

Hi Ray,

On 2/07/2011 8:35 AM, Ray Wells VK2TV wrote:
> Mike,
>
> A query re the figures shown at http://aprs.fi/?c=raw&call=vk6uz-4
>
> VK3MY-4 is shown with a figure of +78 which suggests he is higher in
> frequency than a station shown as +50, for example.
>
> How can this be so when VK3MY-4 is clearly displayed in a waterfall
> display as being lower in frequency than almost every other station and
> other contributors to this forum have made the same observation?
>
> I know the figures are relative but that relativity suggests that, given
> the number of stations shown as +50, those stations are on the correct
> frequency and VK6UZ-4 is not.

As someone pointed out, the sign is backwards. VK6UZ is probably using 
LSB. I use LSB myself on 30m so my waterfall comes out "backwards" too. 
This is so the tone for GMSK/QPSK/PSK is offset in the right direction 
from the FSK300 tones. I'm using AGW PacketEngine and the FSK300 tones 
are fixed at 2110 and 2310 Hz. The Pro version doesn't have that 
restriction, and neither does APRS Messenger.

To use USB I would have to use a tone at 2610 Hz for GMSK/QPSK/PSK which 
is getting a bit too close to the edge of the audio passband.

> I think we need to decide on a reference (net) station that is on
> frequency and from that known reference, every station would be able to
> use a waterfall display to net to the reference station. Those simple
> steps would eliminate most of the frequency error related problems. In
> fact, if one station was the standard, every other station could, by
> using a waterfall display, become a pseudo sub-standard - a bit like
> calibrating meters.
>
> How many applications are out there with a waterfall display?
>
> For Windoze I know of Digipan and WinMX and,
> for Linux there is fldigi

APRS Messenger, MixW and AGW PacketEngine all have waterfall displays 
(for Windows). The best one I have found so far is MixW. You can make 
the waterfall width as wide as your display and can add marker lines on 
particular frequencies. It makes it very easy to estimate the 
frequencies of the FSK300 tones. I have lines positioned at 2110 and 
2310 Hz for FSK300 packet and another one at 1810 Hz for GMSK/QPSK/PSK.

I have found very little difference in receive performance between MixW 
and AGW PE or AGW PE Pro. They're all good - just like a DSP TNC, but 
not frequency agile.

> There may be more applications for both operating systems but since I
> haven't used Windoze for most things for some years I wouldn't know and
> in Linux I've found something that does the job so why look any further?
>
> Ray vk2tv

Cheers ... Gerard, VK2IO