I am using a Folded Dipole which I bought when I first got my General License. It was advertised as an all band antenna. My results with it were less than the claims made by the makers to say the least. At a height of about 40 feet above local ground level and a manufactured length of 90 feet I could not make many contacts on any band. I began to believe that what the ad meant when it described the antenna as "Quiet" was actually deaf.
I was given a Yaesu FT-1000 by a member of my radio club after a field day during which I logged for him whenever he was operating. I read the manual even though that is supposed to be some sort of violation of some sacred rule and found out that it had an internal antenna tuner. The manual and other sources said the internal tuner would bring any SWR up to 3:1 down to 1.5:1 or better.
Since much of what I read about the Terminated Folded Dipole called them by such uncomplimentary names as "Bird foot warmers" and my experience with mine had been so unrewarding I thought I would give the tuner in the FT-1000 a try at making the beastie perform more effectively. I did some reading and took it as gospel that the impedance of a folded dipole without the 600 Ohm resister and the 12:1 balun would be 300 Ohms at resonance. I then ran the usual formula for Resonance and got ~5.464 MHz for my 90 foot long folded dipole. I knew that wouldn't be exactly right because the antenna is not strung at quite >45 feet but I thought it might be close enough to try the FT-1000 internal tuner on. The tuner would not match the antenna anywhere I tried it. I concluded that the SWR had to be greater than 3:1 and thus beyond the tuners limit. I figured I could get the antenna to an actual 50 Ohm load with 300 Ohm window line down to a 6:1 balun. Suddenly the tuner likes the antenna from 160 Meters to 6 meters because the indicators said the the tuner was getting a match.
As it is know there is ~25 feet of Times Microwave Systems LMR-400, 1:6 balun, ~30 feet 300 Ohm window line, feed point of 90 foot long folded dipole.
Here is the heart of my question. Does it seem at all likely to those of you with more theoretical acumen that the tuner is getting a match through that wide a range of Wavelengths?
If I take my club's AEA HF Analyzer and hook it up to the 6:1 balun will it show me what the tuner is actually seeing? Would their be any benefit to using the more recently designed RigExpert AA-200 instead?
What is the proper technique to measure the impedance of an antenna with a balanced feed line using an analyzer with in imbalanced input?
I would be grateful for any help that anyone cares to offer.
-- Tom Horne W3TDH