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
|