[Elecraft] K2 "serial" connector and PA KEY output (was: KPA1500 and K2)

[Geert Jan de Groot]

[Submitted this earlier today with a picture attached of "how I made 
mine", however it seems the picture is causing the message to bounce, so 
now sending w/o picture]

> Is your K2 one with a PA Key out?  If so, just an RCA cable and a coax
> jumper.

If your K2 is a K2/100 then it will have PA key out as the KPA100 
provides it. If your K2 is a K2/10 (without KPA100), then, to ponder:

On 
https://ftp.elecraft.com/K2/Mod%20Notes%20Alerts/K2%20Amplifier%20Keying%20Circuit.pdf 
there is an application note from Wayne on how to build a simple circuit 
to get this PA KEY output. The application note suggests adding a small 
PCB inside the K2.

Notice that the connector of the KIO2 ("do not connect a straight 
through cable") has all the signals that Wayne's circuit needs. So, it 
is possible to build this PA key out circuit on a small PCB that fits 
inside the hood of a DE9 connector, the one that connects to the KIO2 
connector.
Hence, it is possible to build a "KIO2 special cable" that houses the PA 
KEY circuit, and also provides connectivity to pin 2, 3, 5 (only these 
pins!) so that a RS232 device can be connected, and not make any change 
to the K2 itself.

And there would not be a need to drill a hole in the K2 casing, find 
place for Wayne's circuit - it all fits in the cabling that connects to 
the K2, and, at the same time, protects the non-RS232 signals of the 
KIO2 connector.

In my "special cable dongle", sharp eyes will see some deviations: I did 
not connect the RS232 pins because my transverters don't need it, but I 
did add a 3rd transistor (2nd 2N2222) and a LED to indicate when the PA 
KEY circuit is activated. A red LED now lights when the K2 activates the 
TX PA circuit.

And if you have done the Unspeakable and connected a RS232 device via a 
full-wired straight cable, then you may find 
http://folk.uio.no/sverre/LA3ZA/blog/K2/N0SS/k2_wrong_ser_cbl_damage.pdf 
of interest. Note that updating a K2 to the "B" revision makes a number 
of changes that, at least in theory, should reduce some of the damage 
done. It is still best to NEVER make this mistake, though.


73, Geert Jan PE1HZG