[amsat-bb] Re: Planning

[Bruce Robertson]

Quoting "Jeff Davis, KE9V" <jl.davis at gmail.com>:

> Sat Friends,
> 
> Have you noticed the confluence of satellites scheduled to be launched
> in 2009? With the recent SSETI-ESEO news it seems that there is a good
> chance that P3E, SSETI and maybe even Eagle will fly in the 2009 time
> frame (plus/minus the normal delays).
> 
> While that seems like a long time to have to wait, it also provides
> the opportunity to begin planning a new groundstation that can take
> advantage of the 2009 "Feast of Satellites."

Jeff:


I, too, am trying slowly to improve my homebrew antenna set-up so that it
will be HEO-ready. 

I don't have a dish up for s-band, but when I do, I plan to test it using
the advice on
http://www.amsat.org/amsat/articles/g3ruh/116.html
(Hey, here's a cool computer programming job: a little application that
takes the sound volume samples and also pulls the sun noise value from the
Internet. Extra points for being able to take multiple samples or graph G/T
ratio over time.)

As for mode U/V, what I really need to test this is a LEO satellite to
launch with a SSB/CW transponder and very low power. Hey, how about that:
Delfi C3!

Using a modified version of the spreadsheet at 
http://www.amsat.org/amsat-new/echo/Echo_Linkbudget.php
to do the link calculations, I've worked out the following, assuming 0 dB
antenna gain, no polarization loss, no atmospheric loss, and 2m signals in
both cases. Fancy things like squint angle aren't calculated in, either.

*Delfi C3*
Max range: 2500km
Power:     0.4W
signal:    -117 dBm

*P3E*
Range:  20,000km (not max, but in the ballpark)
Power:  30W (just a guess, folks)
signal: -117 dBm

At max range of P3E, say worst case of 50,000 km, we have a -125 dBm signal
to contend with.  Perhaps we can bribe the good folks at U. Delfi
temporarily to drop the transmit power to .04W and we'll have a good idea
of what's what at that range, too :-)

The power specified for P3E 2m transmit is loosely based on that of
previous P3 birds. Given its larger size, I expect that P3E will have more
directional, and therefore higher-gain, antennas. I'm also not sure if
doing the test right at the horizon is such a good idea: I find signals
pretty choppy there, presumably due to ground reflections. Perhaps a
~2000km distance at about 8 deg. would be a better point of comparison. In
any case, what I'm trying to demonstrate is that these two power levels are
similar, not that the estimated signal strength is an accurate number.

Now we just need to remember that Delfi C3 won't need HEO-type uplink power :-)

I'm taking this approach because I believe it is quite difficult to
characterize my antenna/preamp/cable/receiver system noise temp. at 2m
without some serious test equipment. Does anyone have some tips on this, or
have some basic figures for common equipment, such as the FT-847 and
TS-2000, and the ARR or SSBUSA preamps?

73, Bruce 
VE9QRP