[RFI] Old wives tail, or true?

[Tim Duffy]

Hello Alex,

I can tell you that this test opened my eyes to how noise is propagated to
our radio receivers. Like K9YC, W1HIS and many others I have embraced these
findings. There is a reason the noise floor here at K3LR is below S0 on all
bands. This is science - nothing more.

I have significant common mode impedance chokes at every antenna feedpoint
and at the connection to each amplifier (11) - so end to end on the
feedlines. The results speak for themselves.

This is not a wives tale. Do your own research and report your results.

73
Tim K3LR
-----Original Message-----
From: RFI [mailto:rfi-bounces+k3lr=k3lr.com at contesting.com] On Behalf Of
alex at kr1st.com
Sent: Thursday, April 8, 2021 3:21 PM
To: Alan Higbie
Cc: Rfi List
Subject: Re: [RFI] Old wives tail, or true?

Let me challenge that test because I'm not convinced that the test is 
valid.

I watched that video and it only shows the signals before and after the 
choke has been applied, on the outside of the coax. The conclusion is 
then drawn that all those signals make it into the receiver and causes 
noise. Can someone explain why that would be a valid conclusion? 
Shouldn't he be showing that those signals are indeed making it into the 
receiver and then showing that the application of the choke indeed make 
these signals disappear?

I mean, I can make such measurements on any cable attached to a receiver 
and would probably be horrified by what I would see, but that doesn't 
mean that those signals actually make it into the receiver and cause 
noise.

Like someone else wrote, the best test is probably to apply the choke 
and if it doesn't make a difference, ask for a refund from DXE. :)

This inquiring mind would like to know.

73,
--Alex KR1ST

On 2021-04-08 10:35, Alan Higbie wrote:
> In 2019 K3LR presented such a test at the Dayton Contest University.
> 
> Tim describes it @ 15:30 into the presentation.
> Here is the YouTube link:  https://www.youtube.com/watch?v=wd5B5qPHI_U
> 
> The relevant slides are at pages 41050 of his Power Point presentation.
> CTU 2019 14-K3LR-Contest-Station-Optimization-PLUSROTATOR.pdf
> 
> 73, Alan K0AV
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