----- 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