Re: Steve R., Eversharp, et al Ferrite antenna? - FARMERIK


Steve Ratzlaff
 

Thanks, good info there, especially the link to the Fisher manual. Too bad the parts list doesn't give details such as the turns ratio for the AM input transformer and the tuning cap values for AM. It appears the external loop inductance is being stepped up by the input transformer and then resonated at the transformer secondary. The transformer could be most any turns ratio though integral turns ratios (2,3,4,5, etc.) don't yield inductances at the secondary that one would like, so they probably use non-integral turns ratio for the transformer.

Remember that for the a ferrite rod, inductance is max with the coil in the center and decreases as the coil moves toward either end. Since you indicate Peter is your repairman, it sounds like you should just pay him to do all the experimenting to try this idea (he or someone mentions that idea).
I doubt many turns would be needed to get 47 uH on a ferrite rod with 125 permeability (-61 mix, normal AMBC ferrite rod type). That might mean it would turn out to have poorer sensitivity than a much larger air loop.

(Photos need to be uploaded into the Photo section of the Files.)

Steve

On 10/4/2015 2:42 PM, farmerik@... [ultralightdx] wrote:
 

Thanks. Yes I still have the LC meter, but less use of my hands and poorer eye sight.

I tried to upload photos of the tuner and Litz loop here, but it would not go.

Here is some discussion about it by Pete who does my repairs-

Antique Radio Forums • View topic - AM loop antenna for Fisher AM-80 or 80-T

 

-FARMERIK


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