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AO-51 Sig Obs

Just a few notes from listening:

435.300 Voice appears to be Right Hand Circular (RHC) most of the time. This
is consistent with the info that appears on the amsat web site

Using an M2 CP-30 in fixed RHC at 14.5 dBc with no preamp and 80' of LMR-400
is producing a peak signal of about S-7 (S-0 noise level), and AO-51 is full
quieting most of the pass, above 10 degrees for me. (I have severe close-in
vegetation attenuation at less than 10 degrees elevation). My az/el system
is only 8' off the ground.

N.B. If you have fully leafed out trees and bushes that you are "shooting
through" on 70cm receive, it would explain why you are not hearing all that
well. Vegetation loss is pretty bad on 70cm...not as bad as AO-40 2.4 gig,
but it is VERY SIGNIFICANT. This was true on Oscar 8 mode J...which is
another reason I love mode B. You can always create more tx power to get
through the vegetation on 70cm, but you can't make the bird create more
downlink power. Vegetation loss is quite a bit less on 2m. In fact, I never
noticed any obvious loss on the 2m side of things, either up or down.

On transmit (2m), I'm using a 4 element quad on a 44" boom, rear mounted,
vertical polarization. I estimate the gain at slightly above 10 dBd.

On receive, I can also use an 8 element quad for 70cm, vertically polarized,
with a mast mounted 0.7 dB NF, 20 dB gain gasfet preamp. Feedline is also
80' of LMR-400. There are times when this receive setup does quite a bit
better than the RHC with no preamp. Overall, it is much more "peaky" than
the RHC antenna. Smoother and more "comfortable" operation is with the M2
CP-30, even though the peak signal levels are less because of no preamp.

Tomorrow, I'm going to route my 2m uplink feedline through a remote antenna
switch and see how an M2 2m EggBeater (RHC) antenna will work on the uplink.
A later experiment may be to put the M2 70cm EggBeater with the gasfet
preamp and see if I can avoid using any az/el at all. This will require
another feedline run, because the remote switch is not rated above 250 mhz.

Anywho, lots of experimenting to do. The audio from AO-51 is very good and
signal levels are surprisingly good for the power being turned down so far.


Two programs that are free and do an excellent job:

Sat_Explorer 2.6 (Google will find it for ya)
Orbitron (Amsat Software download, really an exceptional program,

My main tracking/control program is SatPC32 from Amsat. It does a beautiful
job of doppler correction with the Yaesu FT-847 (and others). It's 50 bucks
as I recall, with the money going to Amsat, thanks to the generosity of the
German author.


p.s. I heard myself through AO-51 three times during the one high elevation
pass earlier today, making two very brief exchanges. Callsigns only on one,
and grid square plus call sign on the other. After I confirmed that things
were working, I stopped tx'ing and just enjoyed tracking the bird and making
antenna comparisons.

...hasan, N0AN
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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