[TowerTalk] Identifying Teflon Cable

[Jim Brown]

On Sat,9/12/2015 10:02 PM, Jim Thomson wrote:
> 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.

Yes.

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

Maybe it's semantics, but the correct arrangement is the 1:4 transformer 
matching the 200 ohm Yagi to 50 ohm coax, then the choke in the 50 ohm 
section.

> I wouldn’t call any of the various xmfrs a choke.

RIGHT!  More examples of why I strongly object to use of the word 
"balun" -- it is used to describe nearly a dozen objects or products 
that are VERY different from each other.

73, Jim K9YC