[Elecraft] KX3 Computer Interface for digital modes

[Joe Subich, W4TV]

"Pin 1" problem refers to an issue originally identified in professional
and broadcast audio equipment where "pin 1" of the XLR connector was not
connected directly to the shielded case *at the connector* but instead
connected to the circuit common elsewhere in the device in question.

> On SUB-D-25 pin 1 is shield, so I guess you refer to shielding/ground
> loop problems? The now much more common SUB-D-9 only has data ground,
> on pin 5... and pin 1 there is DCD.

A properly installed DB25 (RS-232C) bonds the shell, pin 1 (shield) and
pin 7 (signal ground) to the circuit board ground plane and device case
at the connector.  A properly installed DB9 (EIA/TIA 574) bonds the
shell and pin 5 (signal ground) to the circuit board ground plane and
device case at the connector.

Any device that does not bond the shell of a DB series connector and
all "grounds"/signal returns to the chassis and circuit board ground
plane *at the connector* has a potential "pin 1 problem".  In the case
of the Signalink USB, the "pin 1 problem" is on the RJ-45 since both
audio and circuit (PTT) returns float on the circuit board before
returning to the ground plane via long/thin traces.  The device
violates proper design principles by *not* properly bonding all
"grounds" and circuit returns.

73,

    ... Joe, W4TV


On 7/28/2012 5:55 AM, Holger Schurig wrote:
> What do you mean with "Pin 1 problem" ?  On SUB-D-25 pin 1 is shield,
> so I guess you refer to shielding/ground loop problems?  The now much
> more common SUB-D-9 only has data ground, on pin 5...  and pin 1 there
> is DCD.
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