[Antennas] Coaxial feed line question.

[Sam Morgan]

I have a question related to the length of a coaxial feedline for a 40m 
antenna. I want to use a length equal to 1/2 wavelength electrically. The 
velocity factor of the feedline is 66% (RG-213) So using 7.1 mhz. as the 
frequency, I come up with 45.84 feet. Seems I remember this 'multiples of a 
1/2 wavelength feedline' as some magical thing that effectivly places the 
antenna feedpoint in the shack at the end of the feedline??? Been way to many 
years since I did this stuff, lol. Comments please.

I have seen a chart in the handbook that says for 7 mhz a coil of RG-213 of 22 
ft in 10 turns will be an effective choke for this setup. Or a coil of 10 ft, 
  in 7 turns would work for 3.5-30 mhz.

1st question is, if either coil is added on the end of the basic 1/2 
wavelength 45.84 foot feedline...... will this defeat my purpose and change 
the length of the feedline? Or is the coil some how just a blackbox kind of 
thing, not effecting the 1/2 wave length calculation?

2nd question:
If I tried to use the above '40m 1/2 wave feedline and coil' on any other 
bands, by running it thru a tuner in the shack,.... I blow the entire thing 
and the feed line radiates... yes/no?

-- 
GB de ka5oai,
Sam Morgan

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