[Elecraft] Balun with a G5RV?

[Ron D' Eau Claire]

> I don't believe for a moment your observations of signal strength are the
> result of changes in your feed arrangement. The change in loss would be
> too small to be noticed.
> Bill Coleman, AA4LR

It is certainly true that it is very hard to see the differences in received
signal strength, although in theory the differences are there.

I have been comparing various antenna combinations for some time and
investigated ways of using received signals as a reliable indicator of
antenna effectiveness. It is certainly easier to tune around the bands and
compare received signals than it is to make contacts and trust the report
from "the other end". The "S-Meter" on the K2 is useless for this sort of
comparison, unless one is only interested in huge differences in signal
strength.

I have discovered that I can use received signals with some success using
Spectrogram. What I do is to watch signals using Spectrogram with the
receiver AGC OFF, so the AGC is not trying to manage the audio output and
keep it at a constant level. The RF gain is backed well below the point
where the output starts to compress, so the computer is getting audio level
out that changes linearly according to the to r-f signal level at the
antenna connector.

Then it's a matter of finding a signal and "averaging" it on the Spectrogram
display, setting the marker, swapping the antennas and monitoring it again.
How long I have to "average" the signal and how often the measurement must
be repeated depends upon how fast I can switch antennas and band conditions.
QSB will normally cause variations in strength far exceeding the differences
between any two decent antennas. Also, when using a CW signal that does not
have a steady carrier, the keying will affect the displayed signal level.
For those reasons a lot of signals are useless. Even so, useful readings can
be made on many signals.

I can reliably see as little as 2 or 3 dB of difference in antennas by
repeatedly checking a signal over a period of five or ten minutes. That's
below what most ops can see to report on the air without spending a great
deal of time swapping back and forth between the antenna during a QSO.
Spectrogram does a better job of averaging the signal over time than one can
do by eye watching the S-meter as well.

Comparing my readings vs. distance between a "cloud warmer" horizontal and a
vertical on 40 meters, my reception results agree very well with the on-air
checks that I have done with a few reliable ops on the other end.

Ron AC7AC
K2 # 1289