Topband: Common mode chokes

[Pete Smith]

These are fair points, Jim.  One of the purposes if this series of 
tests is to see if Clifton Labs' super-duper center-tapped choke, 
which combines 2 different wound cores on each side of the center 
ground, will give significantly better performance for 160-10 
meters.  That's coming up.

The reason I used beads (aside from having ON4UN's design to go by) 
was that I had a piece of RG-59 and 100 #73 beads, and I figured it 
would be a lot easier to use the beads and wrap them in tape than to 
figure out how to weatherproof two cores and a bunch of windings.

73, Pete

At 02:22 PM 7/4/2009, Jim Brown wrote:
>On Sat, 04 Jul 2009 10:16:23 -0400, Pete Smith wrote:
>
> >Take a look, and tell me what you think!
>
>Good work! Several comments. First, since your primary interest is
>HF, you'll get FAR more bang for the buck with WOUND chokes, as
>opposed to a string of beads. The reasons why are well documented in
>my tutorial, so I won't go into it here. Second, although the #73
>beads have relatively low choking impedance as compared to a wound
>choke, you make them do more by turning the common mode circuit into
>a sort of voltage divider by taking it to ground. Third, for even
>more noise suppression (if you haven't already hit the limit), I
>suggest the same centertapped configuration combined with wound
>chokes using the guidelines in my Cookbook. It's simply "if a
>little;s good, more's better." Fourth, if you are going to use
>beads, #73 is a good choice, since they are primarily resistive, not
>inductive, at HF, which means that their interaction with feedline
>length is minimal.
>
>If you're going to do a wound choke, I'd suggest 7 turns of the coax
>through the "big #31 clamp-on" specified in my Cookbook.
>
>73,
>
>Jim Brown K9YC