Definitely, as I'd mentioned, less site-to-site variability would be shown
with a full-size efficient transmitting type antenna, whether a vertical
over a good ground system or a high (>150 ft. elevation) horizontal dipole
/ yagi.
Smaller receiving loops and active whips exhibit the greatest influence
due to surrounding ground conductivity and elevation profiles. This is
particularly the case on groundwave or very low angle skip. High angle
skip is largely unaffected by the nature of the surrounding landscape;
certainly by the time you get to Near Vertical Incidence, that can work
even if you are surrounded by tall buildings or mountains.
Why would it matter?
The receiving antenna does not matter, provided it responds to the wave
angle at the receive site. It doesn't matter if it is loop, a 10 foot
vertical, or a 200 foot vertical so long as the antenna does not null the
primary wave angle for the incoming signal. It does not matter if it is a
large receiving array or a whip, provided each are not nulling the primary
signal arrival.
When broadcast station are measured, the engineer walks around with a hand
held loop. The loop is calibrated in volts. If someone changes TX antenna
pattern or power or efficiency, it shows as exactly the same change no
matter what the soil under the test meter. As a matter of fact, as long as
you don't need to know absolute levels (which Hams virtually never need to
know) the meter does not need to be calibrated to any voltage reference.
You can throw a 20 dB pad in the system, and as long as the internal
sensitivity and noise does not limit the reading, the change would still be
linear.
The only critical thing is the transmitting reference signal we are
comparing with, and filtering out QSB and selective fading with a lot of
averaging. Any of us who grew up in the AM days are likely to remember all
about frequency selective fading. :)
73 Tom
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