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RE: FO-29 & bandpass filter



Bill,
You can buy rather expensive (and large) bandpass filters, or you could try making the tin can version in the Satellite Handbook (AMSAT-NA), but just using an inexpensive duplexer can be a very effective solution to cross-band interference.  

I too had interference when the antenna elevation was low and I got RF reflection off the roof.  I installed and ran one for 3 years on my 70 cm antennas.  I mounted one of the $29 MFJ units on the input side of the mast-mounted preamp up at the antenna.  I wrapped it in coax-tape to keep the elements out (especially since it had UHF connectors).  If you don't have a preamp, it probably does not matter where you put it in the coax line to the receiver.  I also experimented with putting one on the 2 m side, but saw little or no improvement.
73,
Jerry, VK8OE

--------------------------------------------------------------
Working fo-29 at low antenna elevations my down link sig sounded very
distorted. At higher elevations it was clear. I thought the 2m sig might be
getting into the 70 cm side. so I tried feeding the antenna coax to the mast
mounted preamp, thru the 70 cm side of a duplexer. On the last pass my
downlink was clear as long as i could hear it. I have to try a few more
passes to confirm its fixed.
Question: If this did fix the problem what kind of filter should i be
looking for to use in place of the duplexer,and where in the coax is the
best place to install it?
Bill
PS  Thanks to all for getting back to me about my many many many other
questions.

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