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Re: AO40 dish



Hi Fred,

I have been testing with JT44 during exactly the periods you mention.
Typically when the squint is between 35 and 45. I have been transmitting on
the L-band uplink, and receiving on a second rx with separate
computer/soundcard.

So far, I have noticed that signals just at the edge of audibility, -18
to -20 db, seem to decode quite quickly, typically within 2 or 3 sequences.
When I reduce uplink power so that the rx level drops to -23 db or so, the
decodes start to take quite a bit longer. On the order of 10 sequences or
more.

I have done tests at squint of about 40, uplinking L-mode at .5 watt, (
that's about 100w eirp here ), and was still able to see most sequences
syncing, but averaging was taking a very long time..sigs were on the order
of - 28 db.

Also, doppler shift is not really much of an issue, because you can see the
DF ( difference frequency ) clearly on the display, so it's easy to adjust
for it. In fact, it's probably easier than terrestially, since you can hear
your own signals.

I found that doing this testing also helped me considerably in getting
throught the JT44 learning curve. It's much easier to figure out what
everything does when you can hear and see the adjustments immediately.

regards,

Roy VE7BPB
Vancouver



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