Hi Scott,
That is the idea... I will use Jim's curves from his cookbook in the
event my curves differ from his... I trust his data more than mine, as
this will be the first test run of the standardized test bed I have been
working on for far too long! :)
I want low Q, frequency range to cover is wide, 18 to 28, or 10 MHz...
My intent is to put one CMC at each end of the power to the Fan,
assuming that is the culprit.
I will build a small probe to find out where the RFI is coming from
within the HVAC unit... My preference would be an RFI kit from
Mitsubishi, next is a commercial filter, (yet to be located), and third
is snap on cores... If you know if a good commercial filter, I am all
ears...
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
On 6/21/24 14:15, K9MA wrote:
On 6/21/2024 3:56 PM, Dave (NK7Z) wrote:
No problem on winding turns, and thanks!!! I will tune the ferrite to
24 MHz., and see how that works... I am setting up a test jig to hold
a ferrite out in the closest I can get to free space, being fed as it
would be in the real world. I will adjust the resonant frequency to
be 24 MHz., that should give me the best shot at using this to kill
this mess... THANKS again!
I'd be surprised if you could get enough turns on it to resonate, unless
it's a really big core. If it does resonate, the Q should be very low,
as that material is supposed to be lossy. (A pure reactance might just
reflect the current to radiate from somewhere else, rather than turn it
into heat.) There may be published curves for the core showing impedance
vs frequency for various number of turns. In any case, you want the
maximum impedance you can get at that frequency, and it should be mostly
resistive.
73,
Scott K9MA
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