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RE: Re: RE:Help with 2880 (was Orbit 250 apogee)

I wish to thank EVERYONE who replied to my dilemma.  All of the replies are
pretty much saying the same thing, Houston, we have a problem....  However,
in one of my previous posts, I did say that I took my 2880 into work and
connected it up to an RF generator and it appeared to work fine.  However
(number 2), the RF generator could only go up to 1.05GHz so I set it to
800MHz and listened for the 3rd harmonic and could hear it fine on my 2
meter radio.  The 3rd harmonic from the generator was verified with a
spectrum analyzer.  I could also pick up the oscillator @ 8.125MHz and at
2???MHz (forgot to write this down) with a sniffer probe on the analyzer.

Using this set up to verify my 2880 is working, what can I do?  How can I
tell if I'm oscillating?  How can I determine conversion gain?  I believe I
had the generator set to -55 dBm @ 800 MHz to begin to hear the 3rd harmonic
which was about -75 dBm or so when connected directly to the spectrum
analyzer.  All I did was set the generator to -150dBm output, and slowly
increased it until I started to receive a signal on my 2 meter transceiver.
Once I could hear it, I let it sit all day and observed no drifting (after
the 30min warm-up period of course).

OK, one last thing.  When I had my 2880 set up on the bench at work, I
wanted to see how temperature sensitive it was.  I took a heat gun and
slowly heated up the case and the 2880 immediately began to drift.  Right
now my Drake is exposed to the elements, I have it attached to my crossboom.
Should I consider some sort of cover?  If so, what kind?

Thanks again for all of the help!


-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of John / NS1Z
Sent: Thursday, May 17, 2001 4:09 PM
To: amsat-bb@AMSAT.Org; Timothy S. Zibrat
Subject: [amsat-bb] Re: RE:Help with 2880 (was Orbit 250 apogee)

I have two Drakes that I modified and I don't see the ambient level
fluctuations that you speak of (NOT steady and jumps from around S5-S9).
This may indicate a poor solder joint or other malady. Both of mine give
steady signals from stable sources (either my Weak Signal Source from DEM or
the satellite). I could easily hear the satellite with either of them using
my 24dB gain BBQ dish..

I added the DEM ULNA pre-amp between the dish and the Drake. This brought
signals up quite a bit. I don't run the radio's pre-amp fo r2 meters now and
the ambient level seems to be aroundd S1-2 on the IC-746.

I would have to agree with the others: the addition of a pre-amp is WELL
worth the expense. I am not sure which is better the DEM or the SSB but I
intend to buy a SSB pre-amp soon to find out. I know it has more gain....

Please, keep us posted on your progress. There are a lot of lurkers out
there who don't say a thing while they are in the development stage - they
just sit back and learn, learn, learn.........


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