[Elecraft] K2 AUX I/O connector

[Don Wilhelm]

Paul and all,

Yes, you can fry some circuits in the K2 and KPA100 by connecting a PC
serial port to the K2 with a commonly available 9 pin cable - the connectors
fit, but it is wrong, and it is not a K2 unique problem.

We should all take the KIO2 and KPA100 'AUX I/O' designations that the K2
uses for that DE-9 connector seriously and explicitly - THIS IS NOT AN
RS-232 CONNECTOR - (and neither does it state that it is an RS-232 or a
serial connector).  The fact that it just happens to be a connector that is
commonly used in the PC world as a connector for RS-232 serial port
connector does not make it one, and furthermore that does not say that any
and all similarly looking connectors are for the same use.  As an example, I
work regularly with a sound mixer board that has DB-25 connectors on the
rear panel, but never would I make any assumption that they are RS-232
connectors - especially when they are marked something to the contrary. To
throw another fact into the pot and stir it a bit: the DB-25 connector on
many PC type computers is a printer port, even though that specific
connector is defined as an RS-232 connector, and similarly, all RCA jacks
are not for audio signals!  One should never assume that a particular type
connector contains any particular configuration of wires - that is machine
specific information and the machine manual must be consulted before
reaching any conclusion about the use of a particular connector.

As a side note, RS-232 is a signalling protocol, and yes the oficial
standard does define some connectors (DB-25 and RJ-45), but the DE-9
connector is NOT defined in the RS-232 standard.  The K2 AUX I/O connectors
use 3 pins that are RS-232 compatible, but even that does not make it an
RS-232 connector - one must check the machine documentation to determine the
pinout and directional usage of the connectors before cabling to them unless
you are following the machine manufacturer's specific instructions or using
the manufacturer's supplied cables.

Just as with multi-pin power connectors and microphone connectors, one
should know that the plug (or jack) and cable are compatible before
connecting them (that should be true for all cases, not just for the K2).
The KPA100 and KIO2 manuals give explicit instruction on the proper cable
configuration and provide suitable warnings about avoiding the use of a
'standard' (really means common) computer serial cable.

Apologies about the rant, but if it saves just one K2, it was worth it.

73,
Don W3FPR


> -----Original Message-----
>
> I've heard you could fry the K2 RS232 board by using the wrong serial
> cable - which I think is a design flaw as these cables (null modem vs
> straight through) are not marked differently so it's easy to make a
> mistake.
>
> Should I open the cable I'm going to use up and make sure only three
> pins are connected?
> thanks and 73,
> Paul
>