[amsat-bb] Some Elmering requested for uplinking to ARISSAT-1
burns at fisher.cc
Wed Nov 2 14:12:17 PDT 2011
A few months ago I asked for help receiving the beacon on ARISSAT-1 and got
a lot of helpful suggestions. It turns out that my biggest problem was
trying to listen from inside the house. Moving the antenna outside was the
key. Heaven only knows what my shingles are made of...I never expected a
So now that I got pretty comfortable with receiving, it was time to step up
from my little HT and get a somewhat more flexible and powerful rig. The
only satellite rigs still on the market are the ICOM 9100 and the Kenwood
TS-2000 family. I know about the birdies in the TS-2000, but I could not
really afford the ICOM...maybe should have gone for a used 910 or
something, but I did end up with a TS-2000.
I still have the Eggbeater omni/circularly polarized 2m antenna for the
downlink, and it is working great! I get a nice strong signal from the FM
beacon, and I'm able to hear people on the transponder. I also either
picked up the CW beacon or someone using CW on the transponder. So
anyway, the downlink is working fine.
Now for the uplink: I built myself a 70cm Parasitic Lindenblad per the
plans of Tony, AA2TX. I have it outside about 10 feet up, and an SWR meter
shows something reasonable (1.3ish) so I guess I did not totally mess
it up. I can also hit the local repeater 5 miles away on fairly low power,
etc. The Lindenblad should be circularly polarized with kind of a
donut-shaped pattern (more gain toward the horizon where the bird is
further away, less overhead where it is closer). But so far I have not
been able to hear myself trying to contact ARISSAT.
Here is what I tried: I set the TS2000 to satellite mode, and set it up
so I was transmitting in the middle of the transponder uplink band on USB.
Then I started scanning through the downlink passband while transmitting
("W2BFJ, tuning") using the "RIT" control so that transmit frequency was
not changing. I was listening with LSB. I heard another station weakly,
but not myself.
Can someone comment on my method, both in terms of technical goodness and
good operating practice? A couple specific questions: 1) Xmitting in the
middle of the passband and just scanning, I should be able to at least
briefly find myself without messing with doppler, right? I was planning to
lock the receive and transmit frequencies (constant sum) once I found
myself and follow the doppler by hand, but I never got to that step. 2)
I'm right that the sidebands are inverted from receive to xmit, right? I
think I would hear something even if that was wrong. 3) Finally, what
about power? How much have you required for success on ARRISAT? I was
running around 25W. I could boost up to as high as 50, but I can only
diddle so many knobs in 5 or 10 minutes :-) 3) I know a beam would be
better, but trying to reduce variables, and pointing is one of them.
Besides, I'm inside in my shack! But has anyone successfully uplinked with
an omni/circular? I can always remove the parasitic elements and end up
with a center-fed dipole to remove the circularity. (Not sure how that
would affect the impedance match...)
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