[Elecraft] KIO2/KPA100 Serial Comm Problems

[VR2BrettGraham]

N0SS continued:

>Well, I think I've found the culprit of my K2 serial comms problem... and
>it's the laptop!!!  Unfortunately!
>
>My IBM ThinkPad 380D shown the following voltages:
>
>Voltages:
>
>    TXD line (from K2PA100):
>       Quiescent:  -15VDC
>    Sending data:  +5VDC
>
>
>    RXD line (from IBM ThinkPad 380D):
>       Quiescent:  -5VDC
>    Sending Data:  +1.0VDC
>
>Given data provided by Jack Brindle, W6FB, the TXD line appears to be about
>1.4VDC under the minimum required voltage.

That is likely to remain flaky.

I can't find my copy of EIA/TIA-232-F, but ITU-T V.28 mentions the 3
volts as the minimum that I always remember.

5 volts may be what a driver should produce, as I did find some mention
of 2 volts allowance for noise at the far end.

Interesting - the usual culprit is something to do with a software
driver, as had been suggested.  Now is this some sort of intermittent
hardware fault, or could it be that one can't assume that an IBM
ThinkPad's RS-232 port(s) don't do real RS-232?  I was counting on
getting a ThinkPad as it's on of the few decent laptops that can still
be had with a real serial port!

Speaking of serial control of the K2, a few months ago I was looking
at the chirp (cricket sound when polled for frequency data by a
computer) & the data received by the K2 does get serious radiated by
the ribbon cable - though no amount of dressing of the cable made a
difference, suggesting rather than induced by the ribbon into
surrounding circuitry, it's induced into the lines in the ribbon itself
(power?).

Have a look with a 'scope probe around the ribbon & note the
difference in RXD & TXD-induced spikes coming from the ribbon.
Anybody have any idea why RS232-in-converted-to-TTL should
be worse than TTL-converted-into-RS232-out?

73, VR2BrettGraham