"dave" wrote in message
m...
David Eduardo wrote:


At the populated areas, not the mountain, but this was a single bay, so
it really was only optimized to comply with downward radiation for OSHA
purposes. This was just too little power. Everything was designed right,
and over the course of a number of years, three different antennas, both
side and pole mount, were tried. It was so obvious that it was simply too
little power... so moving down to the valley floor produced the right
results and within one survey period saw a dramatic increase in
listening.

Single bays don't work. You put as much energy into the sky as anywhere
else with a single bay. A 3 bay, with null-fill, tilted to the beach, low
VSWR 1.06:1 or better at +/- 600 kHz, and a properly constructed
transmission line should work well.

All multi-bay antennas do is narrow the radiation beam. Were I to have the
choice, and cheap electric power too, I would always use single bay
antennas. There is no need for beam tilt, since the radiation angle is so
wide. And the focused beam of multi bay arrays tends to be jagged, and is
observed to be a contributor to increased multi-path.

I did extensive experimentation with my FMs in Ecuador, which was possible
due to lack of regulation and the fact that we built our own antennas (and
even the towers) locally. In a very mountainous terrain among the Andes, I
found that single bays did the best, and even developed a system to put
several single bays on the same plane with reflectors separating them so we
had 4 bays, at the same height, on a pole, each covering a 90 degree arc. Of
course, we decided to use vertical polarization only, which significantly
reduced multipath, also.

The optimal for cost and efficiency is likely a 2-bay system... unity gain,
and a wide, fairly rounded, beam.