[RFI] Old wives tail, or true?

[alex at kr1st.com]

Hi Tim,

My point is that the test in the video shows that a RF resistor works as 
a RF resistor, nothing else. It's proving Ohm's law. It doesn't show the 
effect on the receiver, yet it makes a claim about what its effect is on 
the receiver. If that is the point to make, then show that with a test 
that actually proves the point. That can be easily done with the 
cheapest of RTL-SDR dongles and free software.

Inductively coupling a SA to a long feedline it would be a wonder if it 
didn't show enormous amounts of signals, and it should not be a surprise 
to anyone that the signals will be greatly reduced if you put a choke in 
place.

Note that I'm not saying the choke is ineffective, I'm saying that the 
test in the video is invalid for the claim being made. Selecting a 
proper test is also part of science.

73,
--Alex KR1ST


On 2021-04-08 23:45, Tim Duffy wrote:
> 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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