[RFI] Direct TV DVR problems

[Jim Brown]

On 11/2/2010 1:07 PM, Howard Lester wrote:
> Jim, are you referring to the number of turns required as a function of the operating frequency?

I'm referring both to the winding instructions and also the various 
discussions of how RFI occurs and how to kill it.

> And yes, the Amidon ferrites I bought long ago were FT-240's.

They are NOT Amidon ferrites, they are Fair-Rite toroids, with a VERY 
high markup added by Amidon. AND the cores you bought from Amidon are 
almost certainly not #31.   The wholesale cost of these cores is about 
$4 in lots of 100 or more.  Last I heard, Amidon and other ham vendors 
were selling them for something like $15.  Not a fair price.

Appendix One of that tutorial includes advice about how and where to buy 
ferrites and which ones to buy.

73, Jim K9YC