The following info or parts thereof have been in the
ARRL handbook for the past 15 years. Someone asked for
a table of values for frequencies including the WARC bands.
I have provided some equations instead that allow you to
select the freq. of choice that best suits you. A
one-to-one balun is good practice but not necessary
in a pinch. A tuner is not required either. The antenna
and feed are efficient, light enough for camp use, and
broadbanded relative to a light gage single wire.
|---------------A-----------------|
_________________________________
|______________ _______________| 300 twin lead ends tied together
| |
| |
| | Any length 300 ohm
| | feed down to stub match
| | capacitor
| |
+-||+ ----Cs silver mica across feedline
| | or open stub of 300 ohm twin lead
| | B
| |
|___|-----
| |
50 ohm into 1:1 balun
or 50 ohm feed direct.
A(ft.) = 468/F(MHz)
B(ft.) = 49/F(MHz)
Cs(pf) = 1085/F(MHz)
silver mica
-or-
Cap.(ft) = 140/F(MHz)
stub lgth.
With some imaginative construction one can come up with a
multiband system consisting of plug in sections, etc. Some
additional trimming may be required to put the minimum SWR
point exactly where you want it.
Here's hoping my mail sender or your mail reader does
not scramble the ascii art.
72/73,
Clay N4AOX
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