[Elecraft] KIO2 noise update

[Scott T Emery]

	Hello Michael,

	I will take you up on your kind offer!

	With a little bit more measurement I found out that the serial
cable itself appeared to be an antenna picking up the hash. Here is
my train of logic.

	I measure the output of the computer on pins 2, 3 and 5 referenced
to computer case ground. It was all pretty flat.

	I attach the serial cable to the computer port an measure at
the free end to the scope ground. I see a pulse a little less than
6 ms (166+Hz?)  ~96 V/p-p. 

	I then measured the case ground and saw a similar wave.  I didn't
believe this, so I measured the difference between the scope ground
and the computer ground with a DVM using and came up with 32VAC. Something
is wrong *HERE*.

	I plugged the scope into the same PDU as the computer and the
"noise" went away when meaured with the scope or the DVM as above.

	Plugging the K2 into the same PDU as the computer made the noise
problem go away.


	To explain things a little better.  There are two outlets in
the computer room.  One has a Power conditioner feeding some PDUS
feeding some computer related equipment connnected to it.  The other
was conveniently unused.   I saw the difference in ground potential
when I connected the O'scope to the unused outlet and measured the
computer system.   Plugging the test system (and the K2) into the
computer's PDU made the problem go away.

Scott Emery
emery@nas.nasa.gov

"Masleid, Michael A." writes:
In message <475537F51AB2D211959D0001FA7EAAED0C6C238C@synt1.inland.com>, 
>Hi Scott,
>
>>	I took a look at the ground pin (5) signal coming from the computer.
>>It had a large square wave clocking away on it. Quite disturbing. Nothing
>>to do with the K2 or KIO2. 
>
>This is a bit odd.  I have seen things like this, however, when something
>else was really the culprit.  Figuring out that kind of thing requires
>more detail about the overall system - what else is connected - networks,
>printers, hard drives, monitors, and on and on and on.
>
>So, exactly what did you measure and how did you measure it?
>
>What is the K2 chassis ground connected to?  What is the computer chassis 
>ground connected to?  Is the shell of the (DB9?) serial port on the
>computer connected to the computer chassis ground?  What kind of probe
>do you have on your 'scope?  Does it have a ground clip?  When you measured
>a square wave on pin 5, where was the 'scope probe ground connected?
>
>What did you see on the 'scope?  Amplitude, rise time, period (or frequency)
>and so on.  What are you hearing (seeing) on the K2?
>
>What else do you have connected to the computer(s)?  Is there a network
>connection?
>
>73, de Michael, AB9GV
>