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Re: [RFI] Travel trailer converter RFI solutions

To: Jim Brown <jim@audiosystemsgroup.com>, rfi@contesting.com
Subject: Re: [RFI] Travel trailer converter RFI solutions
From: nm8rmedic via RFI <rfi@contesting.com>
Reply-to: nm8rmedic <nm8rmedic@rocketmail.com>
Date: Fri, 22 Jul 2022 15:57:26 -0400
List-post: <mailto:rfi@contesting.com>
I was suspicious of it too!   The growl started inside the converter when I 
placed a mix 31 ferrite on the DC line.  I immediately removed the ferrite 
core.The ferrite core on the DC line indeed caused the growl to become audible 
from the converter.The growl from the converter when the ferrite was in place 
on the DC line was disconcerting enough that I didn't take time to check if it 
reduced the spurious  HF output.The core was only on the positive line, so not 
in common mode.I have a mix 31 core that's about 4 in in diameter. I could 
probably get a couple of turns of both the positive and negative DC lines 
through it, if that warranted a try.  Go with a CM choke.The mix 31 I placed on 
the AC line at the input of the converter was common mode. But as noted in my 
initial post, it had no effect whatsoever. Nor did an isobar power strip with 
its filtering components.I also did try a large value electrolytic (87,000 
microfarad) across the DC line, but no effect.Smaller value capacitors across 
the DC line likewise made no change.Jim has me wondering if focus on the DC 
line with a common mode choke holds promise.  The growl from the converter with 
the choke only on the positive lead made me abandoned that, pronto. Perhaps 
prematurely.Per WA2LBI's suggestion I also have an inquiry in with Iota 
regarding their converters.Thanks to everyone who's responded. It is very much 
appreciated. ScottSent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Jim Brown <jim@audiosystemsgroup.com> 
Date: 7/22/22  14:53  (GMT-05:00) To: rfi@contesting.com Subject: Re: [RFI] 
Travel trailer converter RFI solutions On 7/22/2022 11:42 AM, 
k1ttt.dave@gmail.com wrote:> I would be very suspicious of the growl caused by 
ferrites on the dc line,Dave,That "growl" (great description) is harmonics of 
rectangular waves produced by switched-mode power supplies and power control 
electronics like the controllers for variable speed motors. Growl is not CAUSED 
by ferrites, SUITABLE ferrite chokes can SUPPRESS it on circuits that carry 
those currents. The 2-wire transmitting chokes in this link are also suitable 
in this application. http://k9yc.com/2018Cookbook.pdf73, Jim 
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