Ed Bailen wrote:
I don't know that I buy your statement that ground losses aren't
extremely important for receiving applications. Antenna systems are
bi-directional. If you lose xdB of transmitted sigal due to ground
losses, then you are also going to lose xdB of received signal due to
ground losses.

Your statement about the "bi-directionality" (usually called
reciprocity) of antennas is true. But what counts when receiving is the
signal to noise ratio. If you lose x dB at the transmitter, the person
receiving the signal gets a signal that's now x dB lower than it was
before, and the noise is the same. So the S/N ratio has been reduced by
x dB. Therefore it's desirable to minimize loss at the transmitter antenna.

But what happens when the receive antenna has x dB loss? At HF, the
dominant source of noise is atmospheric (and QRM). Adding x dB loss at
the receive antenna reduces both the signal *and* the noise by x dB. The
result is the same S/N ratio as before. That's why efficiency isn't
important for HF receiving antennas. Of course, you could reach a point
where the efficiency is so bad that the receiver noise dominates. Beyond
that point, lowering receive antenna efficiency will reduce S/N ratio.
But this point is usually a long way down. Likewise, at VHF and above,
where atmospheric noise is low and receiver noise dominates, high
receive antenna efficiency is desirable. But the original question was,
I believe, in reference to HF receiving.

A more important issue is that ground losses are very important when
receiving a lightning strike. It may be effective to bury several
runs of bare #6 copper in trenches radiating from your "ground
point". The QTH here is located on a solid rock slab. All grounding
is through buried #6 wires and a few ground rods driven laterally
between the rock layers up by the tower base.

Lightning protection and mains safety grounding are separate issues with
somewhat different requirements. Although a good lightning ground
probably usually constitutes a reasonably efficient RF ground, that's
not always the case, and the reverse isn't necessarily true either.

Roy Lewallen, W7EL