Roy, W7EL wrote:
"No, that`s not true. The radiation at zero elevation angle is zero for
any antenna height and ground conductivity, even "extremely low"."

We need no simplified quotes nor formulas. Reflection requires a
"discontinuity". The resistance of free space is 377 ohms. As long as a
traveling wave in space encounters 377 ohms, its velocity and trajectory
are not altered.

"Extremely low" could include a soil that for practical purposes appears
to the wave as 377 ohms. Surely the earth could be absorbent and not
highly reflective. In that case, the reflected wave reaching a distant
observer or antenna would come practically from the incident wave alone.

377-ohm earth may be hard to come by. Sheets impregnated with carbon
were invnted by Winfield Salisbury at the Harvard Radio Research
Laboratory during WW-2. These cloth sheets are patented and are called
Salisbury sheets.

A similar technique was contemporaneously developed in Germany by J.
Jaumann.

So it`s not likely to just happen upon completely non-reflective soil.
But, surely most soil absorbs some energy from the wave striking it. So,
the reflection from the soil will be weakened and will be unequal to the
task of completely canceling the incident wave. Cancellation at zero
degrees will be incomplete.

Best regards, Richard Harrison, KB5WZI

In article ,
VE says...
hi,

I am taking a trip on a dive boat to Cocos Island off of Costa Rica.
I'm thinking about trying to bring an HF rig. What suggestions have
you for an antenna? It would have to fit into a reasonably "standard"
suitcase, or go as carry-on luggage, since packing space is limited.


You've little description of the vessel you'll be in. If it has a
stayed mast of any height a common practice is to load the backstay thru
a tuner. If the stay is conductive to a metal mast and to a metal hull
at the lower end tune it from a gamma match. If the stay is insulated
tune it as a marconi. The taller the mast the lower the freq you can
easily match.