On Tue, 07 Mar 2006 15:18:33 GMT, "Jerry Martes"
wrote:


"Mike Newman" wrote in message
.. .
Any advice on which grade of ferrite would be most useful for a
feeedline balun choke effective at 70 cm?
Thanks de miken zl1bnb

Hi Miken

I've been using the tubular, high permeability ferrites designed for RFI
suppression slipped over the RG-223 coax for a balun for vhf antennas. I am
aware of the high loss with those ferrite tubes. I have been hoping the
high permeability would present a high reactance to currents along the
outside of the coax. So far, the tubes are working OK for my needs.
Your mileage may vary.

Jerry

That's exactly what I intended doing, feeding a moxon rectangle in
this case, my win4nec model gives 50+0.1j.

Given the correct grade of ferrite, it should probably be ok on
UHF.

But how to to determine the effectiveness? Maybe a small bead with a
couple of turns to pick up voltage nodes on the coax feedline, with
and without the choke balun beads.

MikeN