[TenTec] OT

[Steve Hunt]

John,

It's very difficult to get decent common-mode impedance across a 4:1 
frequency band with an air-cored choke - they are too "High-Q".

A further problem caused by their high Q is that their impedance is 
almost totally Reactive away from the SRF. Depending on the impedance of 
your common-mode path, the choke Reactance can actually increase the 
common-mode current. Check out an EZNEC example which illustrates the 
problem, towards the bottom of this page:

http://www.karinya.net/g3txq/chokes/

As Jim said, Ferrite-cored chokes with a predominantly Resistive CM 
impedance are a much better solution.

73,
Steve G3TXQ



On 17/11/2010 05:30, John Molenda wrote:
> Does anyone have the dimensions for a air-core choke balun  to be use
> for 160 - 40 mtrs .  thanks John kb2huk
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