[RFI] Tower/Antenna Reradiation

[David Eckhardt]

We tried a rather large common mode choke to little avail.  It did
"something" but not enough.

Yes, 31 material is the preferred material, especially for 160 and 75/80
meters.  40-meters is roughly the break-even frequency.  15-meters on
upward, yes, 43 material is best.  I spent almost the whole month of
January and into February measuring various CMCs using both 43 and 31
material.  I used the HP 8753C to evaluate some 35 different common mode
chokes wound in a bifilar manner.  My conclusions are based on that
testing.   A summary of that testing is posted in the archives of the
Nanovna-users group.

Dave - WØLEV

On Wed, Dec 22, 2021 at 8:40 PM Jim Brown <jim at audiosystemsgroup.com> wrote:

> On 12/22/2021 11:07 AM, David Eckhardt wrote:
> > Ultimately,
> > an aggressive line filter (Corcom or equivalent) was installed with the
> > case of the filter bonded to the metal support of the opener, itself, and
> > that in turn bonded to the "ground" of the opener circuitry.
>
> A multi-turn ferrite common mode choke wound on a #31 toroid or through
> a #31 clamp-on would have likely solved the problem. #43 is the wrong
> mix below about 100 MHz.
>
> http://k9yc.com/2018Cookbook.pdf
> http://k9yc.com/KillingReceiveNoise.pdf
>
> We also had
> > to install several ferrites (43 material) with several turns through each
> > on the lines going from the opener to the sensors at the bottom of the
> > garage door opening.
>
> 73, Jim K9YC
>
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-- 
*Dave - WØLEV*
*Just Let Darwin Work*