Topband: Core for K9AY loop transformer

K9AY k9ay at
Wed Mar 28 10:54:24 EST 2007

>>I almost exclusively use 73 materials for broadband .5 to
>>30MHz receiving applications.
>>73 Tom
> I use a pair of large type 43 toroids with 10 turns of RG6 feedline
> through them for my common mode suppressors on my Beverages.
> Are you saying this is a poor choice?
> 73, Richard - K5NA


For a common mode suppressor, you simply want enough inductive reactance to 
impede current flow. The type of core does not matter -- air, low mu or hi 
mu materials -- as long as the result is at least a few hundred ohms 
reactance. 10 turns through 43 material is roughly 1000 ohms at 160M, which 
should work well.

On the subject of transformer cores, Fair-Rite 77 material is also excellent 
for 160M. It has similar mu and lower loss specs than 73, although the 
difference may be hard to measure in an actual transformer.

73, Gary

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