[Elecraft] K3 TVI on 40 meters only

[Jim Brown]

On 8/26/2017 10:58 AM, Lynn W. Taylor, WB6UUT wrote:
> First, he's reporting that his CW signal interferes with his TV, not 
> the other way around.  It's not the VHDSL (probably) signal getting 
> out, but his 40 meter signal getting in. 

Doesn't matter -- thanks to the principle of reciprocity, any passive 
system that radiates will also receive, and all of that interface 
(wiring, transformers, cable termination, Pin One Problem) is passive. 
Take my post and substitute the word "receive" for "radiate." 
Reciprocity is the principle that causes antenna gain and directivity to 
be the same on receive as on transmit.

Further, electronics at both ends of these systems are noise sources, 
and both are susceptible to interference, and both input and output 
stages can be susceptible to interference. RFI often comes into audio 
power amplifiers on their loudspeaker wiring, which couples back to the 
input of the stage via the feedback network, where it is detected and 
amplified.

Pin One Problems inject any current on cable shields onto the signal 
common bus (traditionally called "ground"), where it gets injected into 
gain stages at the whim of the PC layout artist, detected, and amplified 
(or breaking up the digital signal). Study the tutorial material on my 
website. Neil Muncy, ex-W3WJE (SK) published work documenting this in 
1994. In bar conversation, he observed that most RFI issues are caused 
by Pin One Problems. In 2003, I published research showing that 
statement to be entirely correct with respect to audio gear. Those AES 
Papers are on my website. There's also tutorial material that's easy to 
read.

Because Pin One Problems are putting the interfering signal onto the 
signal return bus (signal ground), there's no logic between which gain 
stage detects it and the cable it came in on. The RF could be on an 
output cable, or on the cable for input #3, but turning the gain for the 
input or for mic #10 could cause the RFI to increase in level.

73, Jim K9YC