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



If'n it were me, I would go over all the changes I did one more time. Or,
maybe even better, give the instructions to a buddy and have them go over
your work to see if they can see anything obvious. Sometimes "fresh eyes"
see better...

Also a possiblity could be the antenna you are using or its feedline to the
Drake. Of course, here I am just guessing. You might try using the simple
signal generator that is on various web sites - the one that uses the 1N4001
diode and 1k resistor. Feed it with 6 or 10 meter energy (low level !! ) and
look for a signal at the proper multiple. This should give you a good stable
signal to work with. Move the feed line, input and/or output connectors to
check for an intermittent.

The above leaps to the conclusion that you have extra radios around to
accomplish generating a signal while listening to your S band receive setup.

I built the DEM (Down East Microwave) WSS (weak signal source) for 2401. It
was a great lesson in SMD construction for me and it worked first time
(Heathkit style!). Having this around has about paid for itself by now.
Makes testing antennas and conversions real easy. It has also proven to be a
sanity check on more than one occaison as well ( did you know that you have
to point your antennas AT the satellite to hear it? I finally figured that
one out).....

----- Original Message -----
From: Timothy S. Zibrat <tzibrat@adelphia.net>
To: John / NS1Z <ns1z@arrl.net>; <amsat-bb@AMSAT.Org>
Sent: Friday, May 18, 2001 11:53 AM
Subject: RE: [amsat-bb] 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!
>
> 73,
> Tim
> K3TZ
>
>
> -----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.........
>
> <snip>
>

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