You can replace a delay line of theta degrees with a lumped
equivalent consiting of a pi network having a series inductor with
a reactance of Zo sin theta and two shunt capacitors
with reactance of Zo/[tan (theta/2)]. You can build what
appears to be an antenna tuner using two air variable
capacitors and a roller inductor. You will need to put
calibrated dials on the three components and then set them to
the correct values for the delay you want. (You would want
to make a lookup table using the formulas above). Alternately,
you could have a three gang rotary switch that selects
fixed capacitors and coil taps, again based on the formula
I quoted above. Additionally, you could simply use lumped
pi networks to replace coax in the binary line configuration
you mentioned.
Rick Karlquist N6RK
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com]On Behalf Of Rob Frohne
> Sent: Wednesday, March 21, 2007 8:09 PM
> To: towertalk
> Subject: [TowerTalk] Variable phasing networks?
>
>
> Hi All,
>
> You guys are giving me such good advice today, that I can't resist
> another question.
>
> I'm considering trying to phase a four element quad at 40 feet on one
> tower with a four element 20 meter monoband yagi on another tower at 90
> feet. In order to do this, I need a variable delay line. Is the best
> way to do this using a set of coaxial delay lines whose lengths are
> related to one another in a binary fashion, or are there other better
> ways of doing this?
>
> 73,
>
> Rob, KL7NA
> --
> Rob Frohne, Ph.D., P.E.
> E.F. Cross School of Engineering
> Walla Walla College
> 100 SW 4th Street
> College Place, WA 99324
> (509) 527-2075
> http://www.wwc.edu/~frohro/
>
> _______________________________________________
>
>
>
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>
>
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