[Elecraft] Parts for compact loop antenna - toroid help

[Charles Greene]

Well Dan,

A F-114-43 should work ok for a transformer.  I don't know of any design 
data.  When I said the iron core was for tuned circuits, I meant a coil and 
condenser type.  The ferrite cores are better for broadband transformers.

73,  Chas

At 10:24 AM 10/7/2004, Daniel Reynolds wrote:
>I'm just posting this so that someone can tell me ... NO - DON'T DO THAT - 
>or -
>DO THIS.
>
>I know I could use a loop inside of a compact loop, but a toroid is more
>appealing for me because of the size and appearance. It looks like the
>consensus is that I need an Iron Core Toroid ... something along the lines 
>of a
>T-50-6 (or larger size diameter T-114-6). This will be used as a 'transformer'
>between a turn (or a few turns) of wire run between the center conductor and
>shield of my coax, and a single turn of a compact loop. I plan to use this for
>80-20m.
>
>When I inquired with the original author of the webpage (aa5tb) - he 
>thought he
>used a ferrite core ... FT-114-43 maybe - he didn't know for certain. It 
>sounds
>like from some of you - that a ferrite core has significantly less coupling

Probably the other way around.  The ferrite core has a lot more 
permeability, which means you can get more inductance with fewer turns.

>than an iron core.
>
>Can I safely assume that if a core is of a low density (reduced coupling), 
>that
>I can make up for it with more turns on the primary/coax side - however, if it
>is a high density core - it would be very hard to reduce coupling since the
>secondary/compact loop side is already limited to one turn?
>
>Finally - many of you were able to tell me about the cores - BUT - what core
>would you use for this application (coupling your transmission line to a
>compact transmitting loop)?

To tell the truth, I wouldn't use any core.  I'd use a coax or copper 
tubing coupling loop.


>Thanks again - and sorry about the Off Topic post (albeit - it is for a
>QRP/Elecraft radio).
>
>- Daniel / AA0NI