[Elecraft] Common mode chokes

[Dave Cole]

On Sun, 2016-08-07 at 15:50 +1000, Gary wrote:
> Hi,
> I have an inverter generator producing S9 noise on 3.5Mhz, and S7
> noise on 7Mhz. Higher frequencies are clear.
> If I were to use a trifilar wound choke on the lead from the
> generator, what would be the best mix...43, 77 or?....
> I can source ferrite cores here in VK, whether I can obtain what I
> will need is unknown but likely. Failing that, Mouser?
> I spent a lot of time searching the web but unsure still.
> If the learned group could help out with advice it will be greatly
> appreciated.
> 
Hello Gary,

I have had good luck using mix31 material in the FT-240-31
configuration.  

See:
http://www.fair-rite.com/design-tools/materials/

For an explanation of what each mix does, also see:
http://audiosystemsgroup.com/RFI-Ham.pdf

and:
http://audiosystemsgroup.com/SAC0305Ferrites.pdf

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

for more information.
-- 
73's, and thanks,
Dave (NK7Z)
For software/hardware reviews see:
http://www.nk7z.net