Curious why you would choose mix 43 over 31 for HF interference? Is there a
specific advantage in this situation? I thought 43 were more effective at
higher frequencies.
73
Dave wo2x
Sent from my waxed string and tin cans.
> On Jun 20, 2024, at 8:26 AM, Dave (NK7Z) <dave@nk7z.net> wrote:
>
> Hi Jim,
> Thanks for the reply, and suggestions... I have six mix43 FT240s in stock
> now... I also have a pile of mix31s, but in this case, I think the 43s will
> be better...
>
> Can either you, or Dave (W0LEV), suggest a commercial unit that can be
> purchased, that I can have an electrician install?
>
> If it were my unit, I would install however, being a neighbors unit, I want
> an electrician to install due to liability issues. I am fairly sure I can
> get the HVAC folks to wrap a 43 core on the control lines at both ends...
>
> 73, and thanks,
> Dave (NK7Z)
> https://www.nk7z.net
> ARRL Volunteer Examiner
> ARRL Technical Specialist, RFI
> ARRL Asst. Director, NW Division, Technical Resources
>
>> On 6/20/24 00:01, Jim Brown wrote:
>>> On 6/19/2024 6:08 PM, David Eckhardt wrote:
>>> Dave, install ferrites on BOTH the input AND output.
>> I think you mean on both the mains power side and the control lines.
>> Strongly agree. BUT -- it's going to take more than single-turn clamps that
>> peak around 140 MHz to make much of dent between 17 and 29 MHz.
>> Couple of thoughts. First, dedicated twisted pair for the current carrying
>> conductors.
>> Second, look for anything that would divide some of the return current with
>> a random ground path, like building structure. The logic -- when forward and
>> return current can form a transmission line, their fields cancel as long as
>> they're equal, (and are confined to the narrow region between the conductors
>> that make up the line), AND the transmission line is a much lower impedance
>> than the wider random path, so all the current goes to it. But if their is
>> no transmission line, the return current in that random path creates a large
>> magnetic field, and also radiates as an antenna.
>> Henry Ott got me to see this light years ago, and I got the same analysis
>> with an EMC engineer I encountered when he showed up as a friend of the
>> client at a church in Dayton for which I was designing a sound system. The
>> first thing he said after I'd outlined the issue was "twisted pair."
>> 73, Jim K9YC
>> _______________________________________________
>> RFI mailing list
>> RFI@contesting.com
>> http://lists.contesting.com/mailman/listinfo/rfi
>
> _______________________________________________
> RFI mailing list
> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|