The type 77 material is notorious for having a poor loss
tangent, hence the 60 deg phase angle. Type 61 material
is much better, but the mu is much lower so you need
bocque beads to get the same series impedance as with
type 77. One design worth looking at is WX0B's 1:1 balun.
He winds RG-142 on a large torroid and puts it in a plastic
box. With this method you get a lot more inductance per
pound of ferrite as compared to the beads, so you can use
a lower mu material with better loss characteristics than
type 77. It would be interesting to measure the choking Z
of Jay's balun and compare it with one of those type 77
bead baluns.
73 de Mike, W4EF............................
----- Original Message -----
From: "Jim Lux" <jimlux@earthlink.net>
To: "Pete Smith" <n4zr@contesting.com>; <towertalk@contesting.com>
Sent: Friday, July 11, 2003 3:06 PM
Subject: Re: [TowerTalk] Balun filler
>
> The beads show a phase angle of 60 odd degrees, implying that the XL is
> about 1.7 times the R.. .. from that you could calculate the heat
> dissipated, for a given amount of power incident in the choke. I wonder
> why the Z is so high below 14 MHz.. Do you happen to know what material it
> is? Maybe the mu starts to drop off above 14 MHz, so the inductance
starts
> to drop, making the resistive losses more significant?
>
>
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