On Sun, 15 Jul 2012 21:24:57 -0700 (PDT), "hr(bob) "
wrote:

Jeff - I installed antennas in the mid-1950's in Ft Pierce, FL.
Nearest tv broadcast station was Miami @ 125 miles. We used antenna-
mounted signal vacuum tube boosters, and 300 ohm twinlead with
standoffs to get the maximum possible signal to the tv sets. When
West Palm Beach came on the air, only 50 miles away, we were able to
drop the boosters, but kept the 300 ohm twinlead. There was also a
hollow tube 300 ohm twinlead that claimed slightly lower losses in wet
weather, but that required sealing the tube at the top or it could act
like a small pipe and be worse than regular flat twinlead. Coax
losses were just too great at those signal levels/distances.

In the 1950's, antenna mounted tube amplifiers were all you could buy.
In the mid 1970's, I inherited some Jerrod tower mounted amps (6AG5
tubes) that I used for the local do it ourself CATV system receivers.
They worked, but when proper dual gate MOSFET amps arrived, I junked
them.

According to theory, as long as your antenna mounted amplifier has a
reasonable noise figure, and your amplifier gain is a few dB more than
your coax cable losses, it will work as well as if the receiver was on
top of the tower. The purpose of the RF amp (not normally called a
booster) is to eliminate the effects of the coax cable. Had you left
the amp up the tower, you would not have needed to squeeze every last
dB out of the twinlead. Coax would have worked.

However, since you enjoy living in lightning country, I suspect that
tower mounted electronics have a short lifetime. Maybe mounting the
amplifier a few feet below the top the of the tower might be better.

Incidentally, I worked with the low loss twinlead. The center "core"
was filled with some kind of foam rubber. Judging by the density, it
was probably open cell foam. Left open to the atmosphere, it would
absorb water from the air, wick it into the coax, and eventually fill
with water. I used some of that stuff in the Smog Angeles area. That
was when I was into using the best, not matter how much it cost my
parents. I sealed the top of the twinlead, but didn't think I needed
to seal the bottom. After a few months, it was dripping water out the
bottom. Oddly, the reception wasn't affected, but we were in a strong
signal area, so a few dB didn't matter.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558