At 4/12/2007 06:26 PM, you wrote: >Antenna is a Cushcraft AFM-44 4bay. feedline is LMR400 abt 50ft run. >all N connectors. > >Dan
2 problems: one is the LMR400. If it's brand new & the connectors are correct (made especially for LMR400 & properly installed), it should be OK for now but expect problems later. The other, probably more severe problem is the Cushcraft antenna. Unless I'm mistaken, that model hasn't been produced in several years, so the phasing harness is automatically several years old. The braided shield of the phasing harness is not made with silver-plated coax, so it will generate duplex noise. Replacing the antenna is the only good solution. If that simply can't be done, you might be able to cure the problem by stacking several pass cavity filters on the TX to strip off as much noise off of your TX as possible. When there's no TX phase noise, there's no noise to convert back to the input to cause the scratchy noise you hear. However, IMD from other sources may still be a problem. Bob NO6B
