Date: Tue, 23 Jul 2013 03:55:04 +0200
From: "Peter Voelpel" <dj7ww@t-online.de>
To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Which Balun with the TH7DXX
One turn is quoted by Fair-Rite with 190 ohms at 10MHz, 290 ohms at 25MHz
31 mix would not be my choice for a balun anyway, at least not with decent
power.
It?s curie temperature ist just over 130?C.
73
Peter
### dunno what the heck u are Reading. For a standard 2.4 inch od x 1.4 inch
id x .5 inch thick,
the Z at 10 mhz = 40 ohms...and 63 ohms at 25 mhz. (type 31 ) This is with
one turn, IE one pass,
through ONE
core.http://www.fair-rite.com/cgibin/catalog.pgm?THEAPPL=Suppression+Components&THEWHERE=Cable+Component&THEPART=Round+Cable+EMI+Suppression+Cores#select:onepart
## stack 4 x cores and it’s now 160 ohms at 10 mhz.....and 252 ohms at 25
mhz.....same deal, one
pass of coax through the 4 x cores. Ok, now wrap 4 turns of coax through 4
cores..and Z goes way up...
up to the square of the turns. IE 4 squared = 16. 16 x 160 ohms = 2560
ohms at 10 mhz.
16 x 252 ohms = 4042 ohms at 25 mhz. Use 8 x cores in a stack, or 4 cores
on each side, and you can
double the above Z figures again .
## per their very last graph, at bottom of page, 14 mhz = 50 ohms, one core,
1 pass of coax.
4 x cores = 200 ohms. With 4 turns, it now becomes 16 x 200 = 3200 ohms @
14 mhz !!
And 6400 ohms with 8 cores and 4 turns.
## Curie temp is a moot point at best. 31 is good for > 130 C. Type 43 is
the same >130 C.
The Z at 10-15-20 mhz is slightly less with type 43.
## Although type 61 has a sky high >300 C curie temp... it’s a moot point. The
Z is way too low with type 61
material, and 2.4 inch od torroids are not available from fair rite in
type 61.
You wont blow this stuff up either, or over heat it. The TH7DXX traps will
be long gone destroyed 1st.
Jim VE7RF
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