On 1/27/2012 11:41 AM, Steve Hunt wrote:
Jim,
What "bugs" me most about this issue is that it isn't Rocket Science -
simple application of Ohm's Law will give you the answers.
Yes
Some may think that's an insignificant difference and that we are
"nit-picking"; but now imagine you are running a long length of that
ladderline at high VSWR based on an Antenna Book loss prediction of 2dB
- would you be happy if you discovered that the real loss was at least
4.8dB? Or that what you thought was a 4dB loss was actually nearer 10dB?
Exactly my point as well. One option that smart engineers always
consider for very long runs are open wire lines. Anyone who has had the
opportunity to visit one of the WW!! vintage HF broadcast and
communications stations or a high power AM broadcast transmitter has
seen LOTS of open wire lines feeding rhombics, Sterba curtains, vertical
radiators. Some are/were balanced, and some are/were in a coaxial
configuration. They are typically supported on rigid poles with a
U-shaped bracket and insulators at the top. In a typical coaxial
configuration, there might be four closely spaced parallel wires
functioning in parallel as the center conductor and four or more wires
at much wider spacing surrounding the center conductor as the shield.
73, Jim Brown K9YC
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