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RE: WiSP, AO10 & FM sats



Michael Hart asked (in part):

> Well.  I have quite a lot of things to ask.

Feel free to ask.  That way lots of people learn.

> Do any satellite tracking software tell you the doppler shift on both
> the uplink and downlink freqs.  I know some of the software will
> calculate it and automatically adjust the freqs in a CAT rig - but I
> have an old radio which I have to tune by hand so would liek the
> numbers to be displayed.

The Station Program does.  It will also control a CAT rig (if you have one)
, but it displays the doppler shift on the screen.

> OK.  Item #2.  AO10.  I think I heard AO10's beacon yesterday but
> haven't heard it before or since.  Also I cannot hear myself on the
> downlink.

In the next paragraph you said you are using a 70cm 5/8 wave ground plane
for both 2M and 430.  That is a lousy antenna for the FM satellites and it
would almost qualify as a miracle for you to be able to work AO-10 with
that.  Yes, it's been done with less, but under "normal" circumstances, it
would be very hard.  For example, I'm running 22 elements CP with a tower
mounted GAsFet preamp and I can't hear AO-10 part of the time (even when
it's working).

> FM sats.  I seem to be able to get into these for about one over
> again - particularly when they are going down the eastern coast of
> australia.  I have some mountains to the north and west (and a little
> further away to  the south also) which limit my view until they come
> up to about 25 to 30 degrees on the 70cm downlink.  I belive WiSP
> has facilities for taking into account surrounding high objects.  This
> means I will have to go back up on the roof and actually measure
> the angles to the mountaintops some how in the various directions.

I don't know about WiSP, but as to measuring the blockage, what I did is to
make sure I keep current keps and the computer clock is exactly correct and
then over the course of may passes, record the elevation (as reported by
Nova - what I use for tracking) of LOS and AOS.  I now have a chart that
shows where the blockage actually is for 70 cm RF.  It's quite accurate.

> One of my biggest problems is trying to sort out real (wanted) signals
> from the muck.  I seem to get some "birdies" as I have said before.

Most of us do to some sort or another.

> I also get some intermodulation when I transmit.  This has thrown me
> a number of times. I though I was getting a real return from UO14 for
> over 30 minutes ;).  Then I turned the 70cm preamp off and it went away.

UO-14 passes are not that long so that should have been a clue.  If you have
directional antennas, it's easy to move the antennas away from the satellite
and watch the beacon or downlink go away.  If it doesn't then it's not the
bird.  Since you are running omni antennas, that technique does not work.

> I find that with the 70cm preamp on I get a lot of blanking on the
> receiver when I tune the transmitter across the 2m band.

I gather you are running a multiband antenna with a diplexer.  It would
likely help if you had separate antennas and are able to keep them well
apart.

> Today I thought I hear a carrier from my transmitter on the AO10
> downlink. I was xmitting on 435.125 and rcving on 145.900.  I
> heard the signal only when transmitting and it would change
> freq as I adjusted the VFO.  OK 0-well then I adjusted my output
> power from 100w down to <1W and turned the antenna side on
> to the satellite (90 degrees away from it).  When I keyed up
> the transmitter again it was still there :(((  Must be another intermod
> for my radio.

As someone else suggested, move to near the top or bottom of the passband
for tests as there is seldom anyone there and you won't interfere with
another conversation.
Someone also suggested leaving your transmit alone and dialing around the
receive so your transmit signal does not pass over other conversations.
There are two schools of thought on that one.  One says to dial around the
receive and the other says to dial around the transmit to find yourself.
The argument for moving the TX is that while you likely will sweep across
someone else, it will only be momentarily and not much of a problem, whereas
if you leave the uplink frequency constant and dial around the receive you
may be transmitting right on top of someone else for a somewhat extended
period of time.

73
-------------------------
Jim Walls - K6CCC
k6ccc@amsat.org
http://home.earthlink.net/~k6ccc/
Ofc:  626-302-8515    FAX:  626-302-9999
AMSAT member 32537 / WSWSS member 395

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