> obtained with 135 degrees phasing, but I would like to
know how to obtain
> 135 degrees phasing with the length of the phasing lines;
90 degrees is easy
> because it uses 1/4 wave electrical length for the phasing
lines, which can
> be calculated using the velocity factor of the lines used,
but 135 is not as
> easy.
>
> I can obtain 90 degrees phasing using two 1/4 wave RG-11
and one 1/4 wave
> RG-8 for the phasing that will be switched using 2 relays,
but 135 degrees
> is another story.
The delay of a transmission line is equal to the electrical
length **only** when:
1.) The line is terminated in unity SWR
---or---
2.) When the line is a multiple of 1/4 wave long.
The error peaks when the line is an odd multiple of 1/8th
wave long. If we cut a transmission line for 3/8th wave
electrical length and the SWR is not 1:1 the phase error is
maximum.
This is why feedlines from the phasing system to antenna
elements in unidirectional phased arrays should be multiples
of 1/4 wl, and why the phasing line system should be
designed as a unit to match certain element and feedline
combinations.
You can use lines with standing waves, but lengths have to
be adjusted for the errors for best performance.
Roy Lewallen W7EL pioneered designs of very simple phasing
systems using only coax. I would look for his information.
Roy is one of the most competent engineers I have ever met.
73 Tom
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