[Elecraft] K3S RS232 "Y" Connector causing port conflict

[Don Wilhelm]

Charles,

As Fred Cady said in a recent post, it is "all mixed up" and the safest 
way to check is to look at the schematic.
It all depends on whether you are a DTE or a DCE device.  Prior to the 
IBM PC, all was well defined and an RS-232 interface used a DB-25 connector.
AFAIK the IBM PC was the first to use the DE-9 connector for the serial 
port connector, and they initially envisioned the PC being used as a 
terminal device connected to a large mainframe - so the mix-up began 
there - thus the PC is a DTE device, and when things are run from a PC, 
the signals are "backwards".
This state of affairs was adopted

In any case, pin 2 is the DE-9 signal line for data *TO* the PC.  So the 
proper check is for a driver on pin 2 in your amplifier.   If your 
amplifier also implements other RS-232 signals that use drivers in the 
amp, it is likely that those should be disabled as well - check for 
drivers on pins 1, 6, 8 and 9 of the DE-9 connector.

And just another twist on the connector designation - the 9 pin 
connector commonly used is properly a DE-9.  References to it as DB-9 
anre quite common, but are incorrect.  If you look at the general 
category of D-sub connectors, the first letter is properly "D", but the 
2nd letter refers to the shell size - "B" is the long connector 
typically seen in computer parallel ports, "E" is the smaller shell 
commonly used in PC serial ports.
It is usually not important until you get to the typical 15 pin video 
port on computers - that is properly a DE-15HD connector. DB-15 
connectors also exist, but it is longer and has 2 rows of pins rather 
than the 3 rows of the DE-15HD.

Standards are standards, but many manufacturers do not conform to those 
standards.  Never make the mistake of thinking "it looks like a computer 
serial connector, therefore it should be one" - that thought can lead to 
damaged equipment.  Check the equipment manufacturer's manual.  If it is 
not marked RS-232, it is not likely to be RS-232.

73,
Don W3FPR

On 12/14/2015 2:50 PM, charles at k5ua.com wrote:
>   
>
> Thanks for the detailed explanation Don. It seems like that is what is
> happening, the OM2500 may be sending info back on the line into the "Y"
> connector, confusing Na3P on the computer end on making the OM2500 jump
> frequency rapidly back and forth between the correct frequency and the
> out-of-band phantom frequency. From the responses, there may be 3
> possible solutions:
>
> (1) I read N8LP's comment under a different thread heading than this
> one. I am using his LP-Bridge program and LP-Pan hardware. Larry said
> that I could use one of the extra serial ports in LP-Bridge to send data
> to the OM2500A. I think that will work if I put a Serial to USB
> converter coming out of the RS232 port on the OM2500A going back to a
> USB port on the computer.
>
> (2) If all else fails, I have used DDUTILl in the past to talk to the
> OM2500A using the CI-V format into the CI-V port of the OM2500A. I don't
> really want to use two virtual serial port programs (DDUTIL and
> LP-Bridge), but I might have to try that.
>
> (3) I will email OM Power to ask if I can put the OM2500A into "passive
> listener" mode only. I thought that I might be able to accomplish the
> same thing by removing the wire in the DB-9 cable that would carry
> signals from the OM2500A back to the "Y connector, thereby making it a
> "passive listener" by default. If you look at the K3S DB-9 wire
> definitions in the manual, one of the wires is RX and one is TX. I was
> thinking that if I removed the Line 3 TXD OUT pin from the cable going
> to the OM2500A, any signals coming from the OM2500A would never get back
> to the "Y" connector to confuse the computer that is listening on the
> same line.
>
> On page 18 of the manual there is a table of the DB-9 pin-out. Although
> the names of the pins seem counter-intuitive to me.....
> Pin 2 (RXD IN) is used to _SEND_ data from the K3 _TO_ the PC and the
> OM2500A.
> Pin 3 (TXD OUT) is used to _RECEIVE_ data _FROM_ the PC or the OM2500A.
>
> I'm thinking that removal of Pin 3 from the side of the "Y" splitter
> that goes to the OM2500A will allow the OM2500A to _RECEIVE_ signals
> from the K3S/PC _BUT NOT SEND_ signals to the K3S/PC. Does that make
> sense? Would like to receive comments on these three possibilities.
>
> Thanks for all who responded.
>
> Charles K5UA
>
>   
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