Hi Dave,
I know I should also model this thing in EZNEC, but have not taken the
time
to learn how to use it yet. Seems a little daunting when I look at it.
When you do have the time to try EZNEC you will find that it is quite easy
to use. Transmission line programs are also very useful because once ENZEC
gives you the value of the feedpoint impedance of an antenna at some
frequency, you can enter this value into the transmission line program as a
load, along with the characteristics or type of feeder, and read off the
values of resistance and reactance at any point along the length of feeder.
The results are reasonably accurate and can save a lot of time otherwise
spent cutting off lengths of feeder to obtain a suitable load for a balun or
matching unit. One program that I use is TLW which came with the ARRL
Antenna Handbook 20th edition.
Plus, I'm a
little confused as to how it seemed to work so well in that configuration.
Probably just dumb luck on my part ;-)
Both the resonant frequency and the feedpoint impedance at the resonant
frequency of an Inverted V change quite rapidly as the included angle
between its legs is decreased. With decreasing angle the resonant frequency
increases and the feedpoint impedance at the resonant frequency decreases
IIRC, so the load that your balun or tuner saw in the first antenna
configuration could be very different from that seen in the second if the
included angle between their legs is different. The height of the top is
another factor as is the length of feeder.
Yesterday, I was tuning around 40m when I heard a station calling CQ - QRP
on 7.059. He was a 479 here so I thought I would give him a call back. He
answered and gave me a report of 359. After the initial exchange, he
stated
he could not copy me - we tried a couple more times and then signed off.
He
was a definite solid copy on my end with the S-meter hitting S1-3 at times
with some QSB. It was like this the whole time.
- with all the great receiver reports I've read on the K3 - could it be
that I was simply hearing him better with my K3 than whatever he was using
(unfortunately I don't know what he used as we never got that far in the
QSO)?
Assuming that he was not having trouble with QRN nor QRM (which you could
not hear due to skip conditions), this could be a instance where the law of
reciprocity is not obeyed - quite common on 40m especially during the summer
on East-West paths. One reason for this is that the path followed by a
signal going from A to B can be different from the path B to A. After
sorting out the feeder etc it takes time to evaluate properly the
performance of an antenna!
73,
Geoff
GM4ESD
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