The following lumped element circuit is
equivalent to a quarter wave of 75 ohm line:
------CAPACITOR----------CAPACITOR-------
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INPUT INDUCTOR OUTPUT
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------CAPACITOR----------CAPACITOR-------
(Set your font to Courier for this ASCII art!)
The series capacitors have a reactance of 37.5 ohms
and the shunt inductor has a reactance of 75 ohms.
As shown, the circuit gives a 90 degree phase
lead, whereas a 1/4 wave line gives a 90 degree
phase lag. If you swap the open wire line
connections to one side, you can add a 180
degree phase shift so that the lumped element
network gives a 90 degree lag like the 1/4
wave line. You can also build it with four
inductors and one capacitor, then you don't
have to swap the connections to get a lag.
I use seven of these circuits in my seven
element driven array, and they work perfectly.
Rick Karlquist N6RK
> Well, I have searched in vain for a source of the old style 72-75
> ohm brown
> twin lead with no success. My current project needs a 1/4wave 75 ohm
> balance feedline transformer, but I don't seem to be able to find one.
> Anyone got any ideas?
>
> Mel Farrer
> Director of Engineering
> Tality Corporation
> 555 River Oaks Parkway
> San Jose, CA 95134
> 408 456-8254
> 408 944-8000 FAX
> mfarrer@tality.com
>
>
> List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
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List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 100 feet for under $1500!! http://www.anwireless.com
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
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