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RE: General AO-40 Observations



Gunther,

My observations are not quite as in-depth as yours, however I have noticed
some similarities.

Last weekend I worked the bird for the second time (though I've tried more
times than that).  Both times that I worked AO-40, I received very weak
reports.

I was using a BBQ dish for the downlink and I thought that was my problem.
In an effort to improve my ears, I am now using a 1M offset dish with a
patch feed and that GREATLY improved things for the downlink and the beacon
was the strongest I've heard yet.  The squint varied from around 15-30
degrees and the bird was approaching perigee (MA 150-220) for the duration
of my operating time.

I am using an M^2 30 element RHCP yagi on the uplink and the only way I
could even hear myself is if I used the 100W brick amplifier.  Even then I
am VERY weak on the downlink and just above the noise.  Pretty much the same
as when I was using the BBQ dish.  The antenna SWR is reasonable and can be
improved (around 1.8:1).  Other stations on the downlink are very strong now
and are easy to copy.  I worked a station that is perhaps 100 miles from me
and he was a lot stronger than I was.

I didn't think much about it because I figured I needed to tweak my antenna
SWR and perhaps shorten the run of 9913UF (100', brand new) to the antenna.
That along with a better squint and I figured I would have better luck.

But since you mentioned it, I'm wondering if that's all I have to do.  Like
you, I'm pretty satisfied with my downlink setup, what to do to improve my
uplink?  I shouldn't need to run 100W to get a barely discernable signal
into the bird.

-K3TZ

> -----Original Message-----
> From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
> Behalf Of Gunther Meisse
> Sent: Monday, November 05, 2001 7:38 PM
> To: amsat-bb@AMSAT.Org
> Subject: [amsat-bb] General AO-40 Observations
>
>
> bb members:
>
> I am going to share some observations on the AO-40 bird. I would like to
> know if you concur on any of these. If you have general thoughts about my
> thoughts, please speak up.
>
> 	1. 70cm up link: I read that the up link is RHCP. I do
> substantially better
> with LHCP, using an m2 30 element crossed yagi and power from 20 to 100
> watts TPO.
>
> 	2. When the bird is east  of my location I do very well
> getting great 5/7
> 5/8 reports, and often need to power down to keep the girl in her cave.
> When the bird is west of my location, even with a full 100 watts TPO the
> signal stinks. I also hear very few if any other operators on
> her. The MB is
> still strong, S-7 above the noise floor thus, the only difference
> (east-to-west) is the Up-link rx antenna position in relation to me.
>
> 	3.  23 cm Up-link: I run up to 80 watts TPO on the 23cm
> uplink always RHCP.
> I use a 60cm dish or a 25 turn RHCP helix, all with wonderful VSWR. I can
> barely make the bird. The result is very much like of the 70cm
> tests when I
> reverse the polarization. The people I have spoken to on the bird
> (L-Band up
> / S Down) have generally been using a liner polarized L-Band antenna. Many
> with good results. None with as much power as I am running. Now,
> I must tell
> you that my helix antennas are made with 3m 1/4" copper tape. Could such a
> design be worthless? Good tune-up, poor radiation? I do know the concept
> works, since I have a 1/4" 3m tape feed for S-band on a 60cm downlink dish
> and it works great.
>
> Your input appreciated.
>
> 73
> Gunther Meisse
> W8GSM
> AMSAT LM: 594
>
> ----
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