Topband: Short Receive Antennas

[Earl W Cunningham]

Jerry, K3BZ wrote:

"Talking about "noise cancelling", what about the MFJ-1025 which claims
to provide a "60 db null to wipe out noise and QRM" using a separate
external receive antenna (maybe a beverage or a small loop??). It even
has an "RF sense T/R switch" that "automatically bypasses the receiver
when transmitting".  Has anyone tried one of these things? Does it work
at all?"
========== 
Yes, they DO work if the noise is a pinpoint source, however I recommend
you pay the few extra dollars and buy the MFJ-1026.  The 1025 needs a
large "sense" antanna because there is not enough gain in the unit for a
small sense antenna.  On my 1025, I had to use a preamp in the sense
antenna feedline to get the signals from both antennas equal (equal
strength signals on both inputs is essential to get a good null).

The 1026 has a built-in whip for the sense antenna and it has a built-in
preamp for that antenna.  It has provisions so that you can instead use
an outboard sense antenna (and still use the built-in preamp with it).

73, de Earl, K6SE