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RE: AO-16 Mode S reception



Hello Jens...

I don't think I was explaining myself very well...

I don't believe currently _anyone_ relies on computer predicted doppler
tuning for the whole S-Band pass. Two reasons:

o	Accuracy - that's why I say I get a +/- 2kHz true doppler deviation
between the prediction at one part of the pass and another, say five minutes
later. That's not to say I don't use the computer prediction: I do all the
time, to get me close to start with. Then I let my fingers do the walking,
with regular cross references to the computer prediction during QSB: I guess
it's like trying to drive in fog.

o	The (ir)regularity of updates is such that even once per second may not be
sufficient.

I believe the preferred option (when there's no QSB) is to initially
automatically/manually get on frequency & then let the Mic up/down AFC
buttons do the work. That's how I did it a lot of the time on the V beacon
when that was on, and I still do it on the likes of AO-16. But you need a
signal without QSB to be able to do this on the wild doppler shifts of S
band. You need to be around in case it gets lost in QSB of course.

I do stand to be corrected, though!!

> Unfortunately my AR5K is the original without AFC, so i am trying to let
> the computer tune for the doppler. there seems to be an error when using
> wispdde, not sure why. it tunes ok but 300khz too low. i must investigate
> it. i use a USB-serial adapter, i wonder if this is it?

I don't get this error. 300kHz is way out. I'm barely 2kHz off frequency.
What build of WispDDE are you using (Press the About menu and you'll get a
window with the version 3.0.xx in it)? I've used USB serial ports fine
before.

BTW, to use mic up/down, I take the 10.7MHz IF out of the AR5000 and feed it
into my FT-847 where the mic up/down buttons are. Unfortunately I've never
managed to get a signal strong enough on S-band to take full advantage of
this!

73 Howard G6LVB


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