> place. I added wire and lowered the freq of each (measured at the end
> of the transformer lines) to 6.085 and flat SWR. When the 2
> transmission lines are connected to a Tee the resonant freq rises to
> the target freq but so does the SWR to 1:7. When the 50 ohm phasing
> line is added the resonant freq drops to 6.900 and the SWr rises to
> 3:1. Would trimming the phasing line in the field raise the target
> freq and lower the SWR ?? Mny Tnx Mark K8FU
Hi Mark,
You are going about this absolutely wrong, unless your main goal
is a certain SWR!
What you are doing is adjusting the elements and phasing to
obtain a certain impedance in the system and living with phase and
current distribution errors, and that is totally the opposite of
traditional goals.
While it may not be what you want to do, most people adjust
phasing and element lengths or design the system for a certain
pattern. They then add a matching system that brings impedance
(SWR) of the **system** to the desired value at the desired
frequency, without messing with the element lengths or phasing.
You really need to read some of the articles by Roy Lewallen
(W7EL) or Forrest Gerke (K2BT) about phasing systems and lean
how to design the system, or find a good proven design and copy
it. MOSt articles I have read, and even some patents, actually have
things wrong. It seems phasing is one of the least understood
things people write about.
Short of doing that, the easiest system to make work would be to
cut the elements for EXACT resonance with the other element
removed or totally detuned. Then you feed each element through an
exactly equal length of coaxial cable to the shack, with the line an
odd-multiple of 1/4 wl long.
You can then experiment with delay lines of various lengths and
impedances (or use a "T" network antenna tuner in place of the
delay line) you find one that gives you high F/B ratio at the desired
frequency on RECEIVING!!!
Then, after you have the high F/B ratio, you use another tuner to
match impedances to the radio.
If you start cutting antennas and feedlines to get a certain SWR or
resonant frequency, actual antenna performance with almost
always be less than optimum. At times people are happy with
whatever performance they get by luck, but optimum performance
only comes from a lot of cut and try (which is why I suggested
moving the phasing system into the house) or by careful design
(which is why I suggested articles by Lewallen or Gerke).
73, Tom W8JI
W8JI@contesting.com
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