[TowerTalk] EFHW core

[Richard (Rick) Karlquist]

AFAIK, the answer in this case (choke or xfmr) is:
none of the above.

Only an autotransformer (or a transformer connected
as an autotransformer) could possibly work, utilizing
the coax shield as a counterpoise.  Unless there is a
separate counterpoise connection point, which is not
evident in the description.

BTW, I use #61 ferrite cores in my 50 ohm to 450 ohm
transformers.  However, if I was going to go from 50
ohms to 1000's of ohms, #67 or even #68 would probably
be necessary at legal limit power.  The EFHW of 35
years ago that I posted about did not use a transformer,
just an LC network.

Rick N6RK

On 9/30/2020 10:36 AM, Jim Brown wrote:
> On 9/30/2020 9:00 AM, Jim Thomson wrote:
>> ##  Danny  Horvat is beyond a smart cookie.   How many  CM chokes do 
>> you see that cover  160-10m,
>> with 8-12 K of  RS..and  RS  >  XS  ?   No  Z  bumps  either.   
>> Ingenious staggered core design.   And  no,
>> you wont blow em up with  4 kw.
> 
> The obvious question is, "is the winding on the ferrite core a choke or 
> a transformer?"  Their behavior is VERY different. That it's being used 
> at a hi-Z feedpoint suggests the latter. N6RK, also a very smart 
> engineer, has used Fair-Rite #67 for high power transformers.
> 
> NA6O, another very sharp engineer who has done some serious lab work of 
> chokes inside enclosures, emailed me directly questioning the 
> dissipation issues with practical windings on Fair-Rite #61 and #54.
> 
> 73, Jim K9YC
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