Tom,
Air cored chokes tend to be quite narrow-band - that means using the
right number of turns of the correct diameter is critical to getting
high choking impedance at your operating frequency. Even then, they are
Reactive and can actually increase CM current in some applications.
The safer option is to wind the coax on a ferrite core - the number of
turns is then less critical and its impedance will be Resistive if you
choose the correct material. There are some choke designs here which may
be suitable:
http://www.karinya.net/g3txq/chokes/
Those charts also indicate how narrow-band the air-cored chokes are.
Winding the coax on a ferrite core will have no effect on its
differential-mode operation, so it will still operate OK as a matching
section.
73,
Steve G3TXQ
On 25/02/2011 19:26, Tom Osborne wrote:
> H
> This might seem like a silly question, but I just put up a 15 meter delta
> loop and wanted to wind a RF choke coil at the antenna.
>
> I am matching the antenna with a 1/4 wave matching section. Is is OK to
> wind this section into a coil for the RF choke, or wind it through a
> torroid? I don't see where it would hurt anything, but not sure. Thanks
> and 73
> Tom W7WHY
>
>
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