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Re: [TowerTalk] Which Balun with the TH7DXX

To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Which Balun with the TH7DXX
From: "Peter Voelpel" <dj7ww@t-online.de>
Date: Tue, 23 Jul 2013 12:55:28 +0200
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
I used their table with the snap-its cores.

The 2.4 inch 61 core is part number 5961003821.
I use them for stack match transformers from time time or for small baluns
wound with RG142. 
13 turns of RG142 on a single core give me 30µH, same as my solenoid chokes.

 
73
Peter


-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Thomson

###  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,

##  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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