> Since Derek feeds HIS dipole with 450 ohm line, feedline
loss due to
> mismatch is not really much of an issue.
>
> de K1HI.
That's an incorrect assumption. If you look at the link I
posed, it is for "ladder line" with large conductors. We
also cannot dismiss or ignore tuner losses when matching
short antennas, even if they are fed with some sort of
"magic line".
It's a popular but untrue assumption feedline losses can be
ignored when using 450 ohm line. At HF, most losses in dry
lines are I^2 R losses in the conductors. The worse possible
scenario in a case of using a modest length 450 ohm line at
lower frequencies is to mismatch it with greatly increased
current in the line. It is especially bad if the line uses
small diameter conductors, like #18 or 20.
It's a fact that shorting a dipole to the lengths Cebik
suggests creates both matching and feedline loss problems.
That a big price to pay just to keep a "good figure 8
pattern" on higher bands. especially when almost no pattern
is textbook clean anyway in a typical cluttered Ham
installation.
73 Tom
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|