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
Just picked up a VX-3R to build a Microsat portable station. Reading the specs, it appears I should have any problems programming it for the birds but have been told that I have to "mod" the radio to get it accept all the sat frequencies. Has anyone used the VX-3R and did you need to do the radio mod and if so, which one ?
Ron KA4KYI
Hi Ron!
Just picked up a VX-3R to build a Microsat portable station. Reading the specs, it appears I should have any problems programming it for the birds but have been told that I have to "mod" the radio to get it accept all the sat frequencies. Has anyone used the VX-3R and did you need to do the radio mod and if so, which one ?
No mods are needed. The VX-3Rs for North America transmit and receive across the 430-450 MHz range, so you are covered for satellites at 435-438 MHz. You will not have full-duplex operation with that radio, but can use a couple of ways to work the FM birds. I programmed groups of memories for each satellite in the VX-3R I previously had, and it worked OK.
73!
Patrick WD9EWK/VA7EWK http://www.wd9ewk.net/
----- Original Message ----- From: "Bill Dzurilla" [email protected] To: [email protected] 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
What you describes is exacly what I did for AO-10 and AO-13 mounting between the 2 meter antenna and the preamplifier input a big passband cavity for FM repeaters tuned on 145.900 MHz satellite center frequency and another similar cavity tuned as a notch filter to 145.200 MHz to suck the strong local signals desensing my receiver due to QRO Hams using high power for local QSO's in FM.
I still use the above setup to receive VO-52 and OSCAR-7 and it works very well. In addition I have homemade Norton circuit 2 meter preamplifiers having high dinamic range and 2 meter convertes using MCL double balanced mixers having very high -1 dB compression point to reduce overload and intermodulation distorsion from very strong nearby signals.
To show local friends how it was nice to work satellites with the above setup I remember I was able to receive OSCAR-13 at 145.950 MHz in SSB and simultaneously retransmit this signal at 145.200 MHz FM using 10 watt over another 2 meters antenna on my roof without to desense OSCAR-13
Actually no way to receive satellites in 2 meters band using a commercial receivers or tranceivers here in the bay of Naples wich is full of powerfull FM users ! !
73" de
i8CVS Domenico
----- Original Message ----- From: "Bill Dzurilla" [email protected] To: [email protected] 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 preamplifier.
If I am correct please let me know.
Tanks
73" de
i8CVS Domenico
participants (4)
-
Bill Dzurilla -
i8cvs -
Patrick STODDARD (WD9EWK/VA7EWK) -
Ronald Nutter