Re: Common Mode Chokes


Hi there,

<< You will wind each toroid with 35 turns and they are connected in series, not stacked >>
With 35 turns, what is the "frequency coverage" ?
How many turns would be required for this setup to be effective in the range 500-1200 kHz ?


Le ven. 15 nov. 2019 à 12:14, Everett N4CY via Groups.Io <> a écrit :

You will wind each toroid with 35 turns and they are connected in series, not stacked.


In a message dated 11/14/2019 10:54:48 AM Central Standard Time, writes:

Thanks Everett.  Fantastic information.  However, I'm having trouble envisioning the configuration using two toroids in each individual common mode choke.  Are the TDK N30 and FT240-31 toroids 'stacked' together, with the RG-316 looped through the 'stack' to tie them together?  Do you have a simplified drawing or photo of the configuration you use?

Thanks again.  Also, a belated Veterans Day thank you for your military service in the Air Force.

Ken, WBØOCV East Falmouth, MA USA
41.5997N, 70.5614W  FN41ro

On Thursday, November 14, 2019, 08:55:20 AM EST, Everett N4CY via Groups.Io <> wrote:

Hi Ken,

You need only one of the TDK N30 and one FT240-31 cores, each must be wound with 35 turns of RG316. Also as Paul said you will need one at the antenna and one at the receiver. Also another thing that will help is a isolation transformer between the coax and your receiver, which can be made using a BN73-202 binocular core with 6 bifilar turns. One winding will go to your coax and the other to your receiver.

You can get all of the ferrite from Mouser Electronics. You have the part number for the TDK core and the part number for the FT240-31 is 2631803802, the part number for the BN73-202 is 2873000202.. So you will need 2 of the FT240-31 and 2 of the TDK30 and you might want to get several of the BN73-200 cores as they are great for making up matching transformers.

Your best bet for the RG316 coax is eBay...


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