[Elecraft] [K3] Why do they still use 1/4 inch phone jacks?

[Fred Jensen]

On 9/17/2010 11:49 AM, Barry wrote:
>    I presume, historically, it was so there would be enough spacing to
> prevent arcing for the 300VDC on the keying line, etc.  Nowadays, most
> headphones come with 1/8 inch plus, paddles/keyers are low voltage, etc.

I've wondered that myself.  The phone and key jacks on my K3 and FT-847 
are all 1/4" as was the key jack on my S-Line and on KWM-2A's.  Mic jack 
on my S-Line was a 2-ckt telephone jack [smaller than 1/4"] which I 
swapped out for a 1/4".  In fact, my K2 and KX1 are the only rigs I can 
name that don't/didn't have 1/4" key jacks.  I guess some things just 
stick around whether there's a reason or not.  Why didn't RCA phono 
plugs show up on headphones, they became ubiquitous for other audio 
lines?  Still are to look at the back of our TV and DVR.

Re Key Voltage:  When I first started at the coastal marine station 
while in high school, the keying lines were 120VDC on metallic pairs to 
the TX site.  You quickly learned to put the shoe from your bug right 
side up into the straight key on the desk and push your bug around the 
desk with the eraser on the end of your pencil.  They switched to 48VDC 
which you could still feel but a much smaller jolt.  Cathode keyed rigs 
were also good for a moderate knock if you grabbed the key behind the knob.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2010 Cal QSO Party 2-3 Oct 2010
- www.cqp.org