Topband: RFI on TB

[Rob Atkinson]

>This has got to be on a case-by case basis.  I don't have any listening antennas, so i listen on my transmit vertical.  It works fine.  For me.  Most of the time. Would I hear more stuff with listening antennas?  I bet the answer is yes under certain conditions.

Yes under certain circumstances using the tx antenna is okay for rx,
the most obvious example being local communications with a ham a few
miles away.  But I don't know of any serious 160 m. operator who does
not have separate receive antennas.  The reason is that the
reciprocity that allows the tx antenna to also work on rx starts to
break down as we go lower in frequency, beginning on 75 m. but by the
time we tune down to medium wave, it is very noticeable and receiving
becomes more about signal over noise than pure signal strength.  As
new hams, we probably all had the experience of mistakenly tuning
across 160 with the wrong antenna, maybe a 40 m. dipole, and wow, we
hear a lot.   We excitedly hooked up our 160 m. antenna only to hear
nothing, or a lot less.  What went wrong?  Ah, the education begins.

The other problem with the same tx/rx antenna for anyone except the
few lucky ones with no noise sources, is transmitting on top of a QSO
without realizing it.

73
Rob
K5UJ