Using an electrical 1/2 wave length of coax (or whole number multiple) will give the same impedance at the 'other' end as it 'sees' at the antenna end. That's handy when checking the antenna's input impedance. If that length isn't too long it won't hurt anything just to leave it as the normal feed line. If it would mean way too much 'extra' cable, replace it with the length needed to reach.
That's really the only benefit to using an electrical 1/2 wave length. It doesn't 'do' anything toward making the impedance match correct, it only tells you what the match is at the 'other' end of it as if you had placed the SWR meter there.
There are 'catches' though. Figuring the electrical length of any cable depends on you knowing what that cable's velocity factor is. And, the quoted velocity factor of any cable is always given as a 'characteristic' value, not an exact one. That characteristic value should be ball-park close, but don't expect it to be exact because there are too many manufacturing variables no one can account for. Ain't nothing perfect. Right?
- 'Doc
That's really the only benefit to using an electrical 1/2 wave length. It doesn't 'do' anything toward making the impedance match correct, it only tells you what the match is at the 'other' end of it as if you had placed the SWR meter there.
There are 'catches' though. Figuring the electrical length of any cable depends on you knowing what that cable's velocity factor is. And, the quoted velocity factor of any cable is always given as a 'characteristic' value, not an exact one. That characteristic value should be ball-park close, but don't expect it to be exact because there are too many manufacturing variables no one can account for. Ain't nothing perfect. Right?
- 'Doc
