[Elecraft] KIO2/KPA100 Serial Comm Problems

[Tom Hammond]

Hi Folks:

For quite a while I've blamed my KIO2 _and_ my KPA100 (s/n 0008) for some 
serial communications problems I've been experiencing... I can SEND data to 
the PC with no problem, BUT I cannot RECEIVE data FROM the PC...

Today, while getting a local's K2/100 (s/n 4224) ready for Field Dat (and 
PC logging) I think I've determined that the problem may not be my K2, but 
the PC!

The PC I've been using as an IBM ThinkPad 380D Laptop which USED TO 
communicate very reliably with the K2... however, since about a year ago, 
communications have been 'flakey' at best... sometimes on, sometimes off... 
with no rhyme or reason (that I've been able to determine) to the failures.

I've now tried this laptop with two K2/100's and two different serial 
cables of my manufacture and verified to be properly wired (in case someone 
wants to ask). Serial comms work fine if the K2 is sending data, but fails 
if the PC is sending it back to the K2.

I'm beginning to thing that maybe (and I've not yet scoped it to confirm) 
that the signalling voltage on the RXD (K2 side) line may be marginal and 
that the serial adapters in the KPA100s just can't quite decode the voltage 
changes. Guess I'll hang a scope on it later today and see what's going on 
there.

Last time I did this, I HAD data going into the MAX1406 (pin 6, R3IN/RXD), 
but nothing coming out on R3OUT/K2 RX, which tends to imply that the 
MAX1406 wasn't (or couldn't) decode the incoming data for one reason or the 
other. I swapped out the MAX1406 and there was no change, BUT then, 
sometime a bit later, all of a sudden serial comms picked back up and all 
was well... and no, I'd not changed anything. At that point I blamed myself 
for a poorly soldered connection somewhere in the serial comms section, BUT 
since the problem also shows on a completely different K2, I now absolve 
myself of that onus.

Has anyone else experienced a serial comms problem with their Laptop PC? I 
know some Laptops tend to use RS232 voltages quite a bit less than those 
used on desktop PCs, voltages which might cause problems under certain 
circumstances.

Suggestions are ALWAYS most welcome.

73,

Tom Hammond   N0SS