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[Towertalk] Common-mode choke at 430 Mhz

To: <towertalk@contesting.com>
Subject: [Towertalk] Common-mode choke at 430 Mhz
From: Larry Bush" <w5ncd@bigfoot.com (Larry Bush)
Date: Wed, 17 Jul 2002 14:09:27 -0500
Building a couple of 8 element 430 MHz Yagi on 1 inch PVC boom.=20

The driven element is a dipole with direct feed of 50 ohms. From the =
driven element I have 3 foot of RG-58A terminated into a type N female =
connector.



I thought a common-mode balun wound with the RG-58 around the 1 inch OD =
PVC boom would be neat so I computed the reactance needed  at .4 =
micro-Henry, which is five turns on the boom. During my research I was =
could not find the use of common-mode baluns on frequencies higher than =
6 meters. I have three questions:



1 Will a common-mode choke work on 430 MHz?



2   Will the capacity coupling between turns of the balun at 430 MHz =
make the choke ineffective and if so would winding the balun by spacing =
the turns the diameters of the RG-58 help?



3   How would one check the common-mode currents on the yagi models?

=20

=20

Larry Bush, W5NCD



P.S. Yes I know about ferrite beads, etc.



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