[TowerTalk] Identifying Teflon Cable

[Jim Thomson]

Date: Fri, 11 Sep 2015 16:19:27 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Identifying Teflon Cable

On Fri,9/11/2015 3:17 PM, Richard (Rick) Karlquist wrote:
>
>
> On 9/11/2015 1:24 PM, Jim Brown wrote:
>
>> Which is a terrible choke, because the Q of #61 material is far too 
>> high.
>>
>
>> 73, Jim K9YC
>> _______________________________________________
>
>
> There is a tradeoff regarding power handling.  61 material will have
> far less heating than, for example, 43, or 31.  Depending on what
> you are trying to do, 61 might make sense.  I use it in my
> 50 ohm to 450 ohm bal-bal transformer.

You're talking about a TRANSFORMER to handle RF power, where higher Q is 
desirable. My comment was on use of the core for a choke.

Important fundamental principle:  Chokes want LOW Q material, lots of 
resistance, transformers want HIGH Q if they need to handle power.  #61 
high Q below 10 MHz, low Q at UHF, so it is a good choke material at 
UHF, a good transformer material below 30 MHz. This is true of nearly 
all ferrite materials -- materials have low loss at lower frequencies, 
so can handle power, much more loss at higher frequencies, so can't 
handle power but are good as chokes. A key difference between materials 
is WHERE they transition from low loss to high loss.

73, Jim K9YC

##  Even then, you would still want to follow up immediately with a good  CHOKE balun. 
IE:  1:1  choke balun using type 31....followed by  the 1:9 xfmr using type 61.

##  same deal if a 1:4  xfmr used...like on a 200 ohm yagi.   1:1 choke  1st, then the 1:4 xfmr. 

I wouldn’t call any of the various xmfrs a choke.    No big deal to insert a choke b4 any xfnr.

Jim   VE7RF