Hi Hans,
If you have a plenty of RG213 and suitable connectors, you could try making a Coax stub filter. You need a cable length that is an odd multiple of a quarter wave length long at the FM Tx frequency and an even multiple of a quarter wave at the frequency that you want (2M /70CMs). A single RG213 stub would have about 25dB of rejection and would pass 100 Watts OK. You just need a coax T connector and some matching connectors. To trim the stub, use a set of garden secateurs. If you have a Bao feng or similar radio you could use that on the FM band attached to your T and trim the stub for minimum signal on the unwanted Tx frequency.
I haven't run the calculations for how long the stub should be but if it's useful I could do so.
73, Terry Osborne ZL2BAC
-----Original Message----- From: Hans BX2ABT Sent: Thursday, March 14, 2019 12:33 AM To: amsat-bb@amsat.org Subject: [amsat-bb] Shoppinglist
My sis-in-law will be visiting from the States soon and I usually make her bring some stuff for me so I can save on freight costs. She will definitely bring an Arrow Antenna so I can start some portable operations. A Sony voice recorder is also on my list, as well as some coax cable (RG-400 is what I'm thinking of. Really expensive here). Don't have a budget for much more, but since I have a clear line-of-sight to some 10 kW FM transmitters from my QTH I thought I should at least get a good FM-band notch filter.
Any recommendations on where to buy this in the US? I haven't found anything when I googled, not even a lot of 2/70 band pass filters, or low pass filters to prevent desensing on 70 cm. My own creations have a too high insertion loss, so this time I really want something a bit more professional and something that can handle at least 100 Watts of power. Any recommendations are welcome. Cheers. --Hans BX2ABT
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