[CQ-Contest] CW Keying Cable

[Art Boyars]

Well, yes, I've had a few transistors fail, too.  I remember in 1973 my Heathkit AR-19 Receiver (AM-FM-Stereo) started distorting as it warmed up.  I held an ice cube against the various transistors in the chain until I found the culprit, and replaced it.

In my career I even spent one year in Failure Analysis, delidding and depotting transistors and ICs and peering at them with the SEM.

In my post I was really just facetiously shilling for the K3KU circuit and my hoard of early-1960's transistors.  I'm sure opto-isolators are a fine solution.  I just don't happen to have any on my junkbox.

73, Art K3KU


----- Original Message ----- 
From: Dennis Vernacchia 
To: Art Boyars 
Cc: cq-contest at contesting.com 
Sent: Wednesday, November 12, 2008 3:34 AM
Subject: Re: [CQ-Contest] CW Keying Cable


I have had several transistor types fail over last 13 years

No failures with the Opto type circuits

No keying problems

( W1GEE Opto units ) 

U got lucky

others mileage may vary

stick with the Opto units

My 2 cents

N6KI 


On Tue, Nov 11, 2008 at 12:08 AM, Art Boyars <art.boyars at verizon.net> wrote:

  N6KI said "Be sure the one U buy uses an Opt Coupler typr device and not descrete transistor(s) - The Optos are far more reliable !!!"

  Gee, the 2N398A germanium PNP and the whatever NPN used in the original implementation of the "K3KU circuit" for keying pos or neg have been in use for over 30 years w/o failure.  They may well pre-date optocouplers AND computer keying.

  I still have a few 2N398A's if anybody wants to build the circuit, though the MPSA92 used by Logikey in their CMOS4 and by MFJ in their 490 would work fine. (Note that Logikey and MFJ both use it as a separate neg keying output, not the K3KU circuit.)

  73, Art K3KU

  _______________________________________________
  CQ-Contest mailing list
  CQ-Contest at contesting.com
  http://lists.contesting.com/mailman/listinfo/cq-contest