[Elecraft] K3S Microphone Cable

[Jim Brown]

The nature of the shield matters a lot. Back in 1994, Neil Muncy, 
ex-W3WJE (SK), published the landmark AES paper in which he exposed both 
The Pin One Problem and Shield Current Induced Noise (SCIN). The Pin One 
Problem is the (now) well known equipment design defect, whereby the 
cable shield fails to contact the shielding enclosure, first going to 
the circuit board, where shield current is coupled to the circuitry.  
SCIN is a defect in the construction of "rack cable" having a foil/drain 
shield, whereby the drain wire is twisted at the same rate as the signal 
pair and is much closer (along the cable) to one signal conductor than 
the other. This causes shield current to induce a differential voltage 
on the signal pair.

Neil did his work on how these mechanisms coupled at audio frequencies, 
but in multiple bar conversations when we met at conventions, he said 
that both were also very strong causes of RFI, and that Pin One was the 
dominant cause. In 2003, I did research that confirmed this. Audio 
old-timers may recall that in the late '80s and early '90s, Mackie 
mixers were almost certain to pick up AM broadcast stations that were on 
the high end of the band. My work on susceptibility of equipment showed 
that they suffered both from Pin One Problems AND that the bandwidth of 
their audio circuitry extended past 1 MHz!  In attempting to use one of 
these mixers to test condenser mics for RFI from FM and TV broadcast, I 
found that these mixers themselves strongly detected RF from TV channel 
2, and were thus unusable!

I also tested the RF rejection of quad cables, including Canare, and 
found that they were inferior in that regard to a good braid-shielded 
cable like Belden 8412. Gotham Audio cable (an EU cable then imported by 
the Neumann distributor) also performed quite well.

All of that work was published as AES papers. You can buy them for $10 
each at aes.org, or you can download them without the AES logo from my 
website for free. :)  k9yc.com/publish.htm  Scroll down to find the AES 
papers.

As to the Heil cable -- I've never seen it, don't know its construction. 
As Don notes, additional conductors can be useful for control functions.

73, Jim K9YC

On 1/16/2018 8:59 AM, Don Wilhelm wrote:
> The Heilwire is IMHO the best wire for ham applications because it 
> contains additional conductors for PTT as well as a shielded twisted 
> pair and is soft and flexible.