[RFI] Finally located my RFI

[Dave (NK7Z)]

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
>