[Elecraft] Common Mode chokes to reduce noise

[Jim Brown]

On 11/28/2021 11:05 AM, Ed Cole wrote:
> K, kind of what I was thinking.  So either go on search for noise source 
> or try reducing the noise at the receiver.  K3 NB does not improve SNR 
> on 6m.

The K3 NB has lots of tweaks. Depending on the modes you use, it might 
help in some situations.
> 
> On HF noise varies: 80m its S7 from an inverted-V; on 20m its S3 from a 
> yagi (both have baluns).

Of course -- noise sources vary widely in their spectral content, and 
how much we hear will depend on what they are using for TX antennas and 
how those TX antennas are coupled to the noise sources. Likewise, how we 
hear them will depend on our antennas -- their location, directivity, 
and whether they are well choked at the feedpoint.
> 
> 6m noise at S5-S7 is the most troublesome because I do weak-signal 
> operating (eme, ms, FT8). InnovAntenna 6m baluns are many ferrite beads 
> in series.  6m yagis are LFA7 from InnovAntenna (UK).

Is that S5-S7 on a well calibrated S-meter?  That's HUGE.
> 
> Shack is grounded via No. 8 wire to ground post adjacent to shack. 
> Aluminum plate coax thru-wall panel is grounded by it, as well.

You need to STUDY N0AX's ARRL book on Grounding and Bonding, to which I 
contributed, and/or this slide deck pdf.
http://k9yc.com/GroundingAndAudio.pdf

Also these to chase down and kill the noise sources. The first is text, 
written for National Contest Journal, the second is a slide deck.
http://k9yc.com/KillingReceiveNoise.pdf
http://k9yc.com/KillingRXNoiseVisalia.pdf

73, Jim K9YC