Topband: RX antennas

[Michael Tope]

> jimjarvis at comcast.net writes:
> Your friend is right about the coax loop vs. simple inverted vee.
> Except, of course, the ability to get a null.
> I agree with all the comments about the coax "magnetic" loop limitations
but
> it can still be quite effective in allowing DX qso's especially from a
noise
> compromised environment like a suburban neighborhood. I have Pennants and
Flags
> here which work well and a magnetic loop - Ive worked VK6 with the mag
loop
> and countless Euros when I could'nt hear them as well with the other low
noise
> antennas on certain mornings or evenings.. I'd say the mag loop is
effective
> this way less than 50% of the time but in a 160 unfriendly place I think
one
> need several noise antennas - i.e. all the help you can get...  you'll
hear
> nearly as well as JI but you'll hear none the less some stuff...


When I was still back in college in Ohio, I shunt-fed my
grandmother's TV tower for 160. I had an A3 tribander on top,
along with an 80 meter dipole, and a 40 meter inverted-vee.
Quite by accident I discovered that the 40 meter inverted-vee
was an excellent topband receiving antenna, but only if the
coax running to the 160 meter shunt-feed was shorted-out in
the shack by the BW coax switch which shorted its unused
inputs (this must have detuned the tower). The inverted-vee
routinely delivered a 10dB SNR improvement on topband
signals, and no it wasn't intercept point related. I had a step
attenuator in front of my R-4C which allowed my to switch
in any amount of attenuation between the TX antenna and
the receiver. The inverted-vee clearly delivered an SNR
improvement. I wish I could claim that this was based on
some brilliant engineering insight on my part, but in truth it
came about totally by accident :). I can still remember the
thrill of listening to UG6GAW's Q5 signals on that inverted-vee
while at the same time he was barely readible on the TX
antenna.

Seems that it is true that you can never have too many
antennas.

73 de Mike, W4EF.....................................