Re: [amsat-bb] Microwave signal generator

["John Stephensen, KD6OZH" <kd6ozh@xxxxxxx>]

If I remember correctly, the 8616 uses a klystron oscillator which isn't
stable enough for SSB. It will be useful for antenna tuning if you have a
directional coupler. The LO for any receiving converter needs to be crystal
controlled.

73,

John
KD6OZH

----- Original Message -----
From: "Bruce Nolte" <brucenol@abs.net>
To: <amsat-bb@AMSAT.Org>
Sent: Thursday, 14 June 2001 01:50 UTC
Subject: [amsat-bb] Microwave signal generator


> Greetings, I am contemplating the path I will need to take to receive
> S-band on AO-40, and on a hunch I picked up a surplus HP 8616B microwave
> signal generator at a recent hamfest for $20. I figure if nothing else,
> it might be useful for testing and alignment purposes of whatever
> downconverter I end up getting to feed my FT-736.
>
> I was discussing my plans for it with the guy I got it from, and he
> suggested that the signal generator could prove useful as a local
> oscillator for my S-band receiver by tuning it the appropriate frequency
> needed to produce a mixing product in the 2 meter band.  I have only a
> vague idea how to do this, I can probably map out a block diagram, but
> am a bit intimidated about the practical aspects of making it work.
>
> A couple of practical concerns about the generator are also on my mind
> as well. First, any receiver would have to be at or near the antenna,
> since line loss over a nominal 75 foot run of coax, or even 7/8 CATV
> hardline would be enormous at 2.4 gig.  Since the generator is a large
> rack mounted piece of 1960's high technology, it is not practical to
> mount it near the feedpoint of the antenna.  I would have to run coax
> from the generator out to the downconverter at the antenna, and expect
> from 20 to 30 dB of loss, even with top quality feedline. The signal
> source is probably strong enough to overcome this, but I really have no
> idea how much signal I need.  The 145 Mhz downlink should be fine with
> 9913, LDF4-50 or whatever decide to use.  Another concern is the
> stability of  the signal source, for even a 0.1 percent drift at those
> frequencies is a couple of Mhz.
>
> It is an intresting concept, but before I invest any serious amount of
> time or cash into a project, I want to see if this proposal passes the
> practicality test.
>
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