[RFI] Clamp-on Ferrites

[Michael Aust]

Had very good luck with FT-240-31 
Cores with multiple turns thrust them
73 Mike
WB6DJI 
-------------- next part --------------


Sent from my iPhone

> On Jun 26, 2022, at 2:26 PM, Dave (NK7Z) <dave at nk7z.net> wrote:
> 
> ?https://www.nk7z.net/rfi-now-house-cleaning/
> 
> Fair Rite part numbers are about 3/4 of the way down...
> 
> 73, and thanks,
> Dave (NK7Z)
> https://www.nk7z.net
> ARRL Volunteer Examiner
> ARRL Technical Specialist, RFI
> ARRL Asst. Director, NW Division, Technical Resources
> 
>> On 6/26/22 13:11, Dan K2YWE wrote:
>> We have a TV whose audio is seemingly susceptible to HF RF in every port.
>> It hums in time with ICW pulses on the HF ham bands. The picture is
>> unaffected.
>> Using HDMI input from wi-fi Roku device.
>> The hum is barely perceptible using internal speakers but loud enough to be
>> obnoxious when using cheap passive earbuds on a long extension cord. It's
>> still there but much less when the earbuds are plugged directly into the TV.
>> Unplugging the HDMI cord at the TV end has no effect.
>> Unplugging the HDMI at the Roku end makes it louder. That might rule out
>> the Roku except that unplugging the Roku wall wart makes it better,
>> I have only one clamp-on ferrite to experiment with and I have no idea what
>> material it is. It has no when effect placed on the earbud extension cord
>> except that when the clamp is almost closed (small gap in mag path) around
>> the earphone cord the interference drops. Fully closed, it's back to full
>> interference. It's hard to imagine I'm saturating the core, so it may be
>> somehow tuning with the cord inductance.
>> I want to isolate the TV as much as possible by choking all the I/O, namely
>> the AC line cord (no waart), HDMI , and earphone jack. I'd prefer a snap-on
>> core with a big enough hole in which to put 2 or 3 turns of the line cord
>> and the earbud extension, but a smaller hole will suffice for
>> experimentation and maybe using a few tandem. Freq is 2-0 MHz.
>> Any suggested snap-on cores or other ideas?
>> Dan Z
>> _______________________________________________
>> RFI mailing list
>> RFI at contesting.com
>> http://lists.contesting.com/mailman/listinfo/rfi
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi