Like Jim N2EA, there are many that understand propagation, fading and such
better than I. This year I've had the pleasure of using diversity with an
ORION II and a K3 on top band. Antennas were beverages and a Tee top
vertical. Just as Jim observed diversity saved the day frequently as the
signal in one ear faded as the one in the opposite ear peaked.
The military used to use various forms of diversity reception with RTTY HF
communications. The most common forms of diversity were frequency and space.
Frequency diversity was typically used on ship and ashore. Space diversity
was used at shore stations in combination with frequency diversity. The Navy
typically used the URA-17 comparater/converter as the demodulator. It had
two audio inputs and the obvious job of the comparater was to select the
best of the two signals.
With space diversity the two antennas were separated by a fairly large
distance, so it would be difficult to use it on board most ships.
In the case of Jim's experience, I wonder how far apart the loop and dipoles
were and if space diversity might have accounted for some of the difference.
Regardless of how it works, application of some ancient military techniques
on top band sure makes a difference!
73 de Lar K7SV
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