From: "Jim Brown" <jim@audiosystemsgroup.com>
Subject: Re: [TowerTalk] Baluns/tutorial/notes.
On Sat, 22 May 2010 13:59:27 -0700, Kevin Normoyle wrote:
>Am I wrong there?
Yes, you're wrong. :) #61 is a poor core material, because its Q
is too high. For all the reasons discussed in my tutorial, we want
RESISTANCE, not reactance, and we want it to be as broadband as
possible (i.e., low Q).
We ALWAYS want common mode chokes to be low Q with a high value of
resistance at all frequencies. This makes them relatively
insensitive to the length of the line they're suppressing.
On the other hand, we generally want TRANSFORMERS to be LOW LOSS
(high Q) if they're handling high power. However, when we're
widning broadband transformers that don't handle power, as in the
case of interstage transformers and Beverage transformers, loss
doesn't matter, and low Q may help broadband the circuit.
73,
Jim K9YC
## OK, what abt #77 ferrite ?? It comes in large beads [1" OD x .5" ID x
1" long, that
will slide over 213] and also toroids. [2.4" OD x 1.4" ID... and also 2.9" OD
x 1.53" ID]
## the idea here is to supplement my existing type 43 bead baluns. The existing
type 43 bead
baluns are 17" [24" long on 80m].. with a 7-16 female din on the end. I
could slide some type 31/77/43 beads
over the 393 coax... before installing the male 7-16 din connector. Put some
heat shrink over the beads,
then plug the mess into the back end of the existing balun. That would make
for a simple, clean install.
## Plan B is to wind 2-3 turns of 393 around 4-6 x stacked type 31 cores....
then install the 7-16 male Din
connector.... then pug into the back end of existing bead balun..as above.
Type 31 ferrite comes in 2.4" OD x
1.4" ID... and also 4" OD x 3" ID x 1" high . I could also use type 43
toroids.... or type 77 toroids.
## I believe 31/77 material would provide the biggest increase in Z.. vs
type 43. The bead idea is less bulky,
and just tape to boom for the yagi's... [and mast for the 80m rotary dipole] .
The existing type 43 bead baluns don't heat
up.. and adding additional beads [31/77] at the back end of the existing
balun... the additional beads won't heat up either.
## The toroid approach is bulky. Either way.. which is the better material
for this particuar supplemental application... type 31
or type 77 ?? Ants are 80m rotary dipole... 40m yagi.... a 20m yagi... and
a 17/15m yagi. 393 teflon coax is aprx .391" OD
on the jacket. If toroids are used... coax wrapped 1st... THEN the 7-16 male
din plug installed.
Tnx... Jim VE7RF
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