[amsat-bb] Re: Surplus cavity bandpass filters from the AO-10 era?
domenico.i8cvs at tin.it
Thu Apr 28 12:20:05 PDT 2011
----- Original Message -----
From: "Bill Dzurilla" <billdz.geo at yahoo.com>
To: <amsat-bb at amsat.org>
Sent: Wednesday, April 27, 2011 7:00 PM
Subject: [amsat-bb] Surplus cavity bandpass filters from the AO-10 era?
> In attempting to make a list of ham equipment I have owned in the past, I
> recalled with fondness a surplus cavity bandpass filter I used with OSCAR
> 10. At the time, in the 1980s, these were cheap and quite popular with
> satellite users. I was living in downtown New Orleans, and the filter,
> which was mounted at the antenna next to the mast-mounted preamp, totally
> eliminated my problems with birdies and local cross-mod.
> Does anyone recall this filter and perhaps have a photo or info?
> 73, Bill NZ5N
Hi Bill, NZ5N
I suspect that it was a surplus Filter Band Pass F-204/U built for the U.S.
Army by Budd Lewyt Electronics. It is a double cavity filter about 10" long.
The cavities are two in series and the diameter of each gold plated cavity
is 2" while the front panel is blue color 6" wide and 2.5" high with two
tuning black knobs with calibrated dials in channel numbars.
In the bach panel there are two N connectors for input and output.
Originally a set of six or eight cavities was placed into a rack to cover
from about 100 MHz to about 450 MHz.
I have two of them with the original frequency range 374 to 404 MHz and it
was necessary for me to short it by a few millimeters on a milling machine
to get them resonate to 436 MHz for the uplink on OSCAR-10 and OSCAR-13
By the way I was never able to find in the surplus market the model that
resonates to 145 MHz because they were very popular and were used for FM
repeaters but they are cheap and all of them have the same 10" lenght so
that it is easy to mount it at the antenna next to the mast-mounted
If I am correct please let me know.
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