Elecraft

K3S RS232 "Y" Connector causing port conflict

Classic

List

Threaded

4 messages Options

charles-2

K3S RS232 "Y" Connector causing port conflict

I have an OM2500A amp that works perfectly with my K3S when it is the
only thing connected to the RS232 of my K3S.

I am using LP-Bridge and Na3P to create a panadapter and this works
perfectly when the computer is the only thing connected to the RS232 of
my K3S.

The manual shows how to use a RS232 "Y" splitter so that two devices can
share the RS232 port of the K3S, but when I use the "Y" splitter (one
side to the OM2500A amp and one side to the computer) the following
malfunctions occur:

1. The OM2500A display rapidly changes from the correct VFO frequency to
an out-of-band frequency over 2 Mhz away.
2. The pandapter frequency readout ceases to function.

I assume there is a port conflict, and I wonder if anyone knows the
correct pin-out of the RS232 line to the OM amp so that it will be a
passive listener on the DB9 cable?

Thanks,

Charles K5UA

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Josh Fiden

Re: K3S RS232 "Y" Connector causing port conflict

Have you tried passing through the amp instead of using the splitter? OM-Power has two RS232 ports for computer & transceiver.

73,
Josh W6XU

Sent from my mobile device

> On Dec 13, 2015, at 7:52 AM, [hidden email] wrote:
>
>
>
> I have an OM2500A amp that works perfectly with my K3S when it is the
> only thing connected to the RS232 of my K3S.
>
> I am using LP-Bridge and Na3P to create a panadapter and this works
> perfectly when the computer is the only thing connected to the RS232 of
> my K3S.
>
> The manual shows how to use a RS232 "Y" splitter so that two devices can
> share the RS232 port of the K3S, but when I use the "Y" splitter (one
> side to the OM2500A amp and one side to the computer) the following
> malfunctions occur.....

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Don Wilhelm-4

Re: K3S RS232 "Y" Connector causing port conflict

In reply to this post by charles-2

Charles,

I don't know the specifics of your OM2500A amplifier, but I do know
about RS-232.
First, RS-232 is a point to point system. The use of "Y" connectors is
not the norm and are applicable only under certain specific conditions.
Those conditions are that the device added by the "Y" connection has no
active drivers on the RS-232 signals - only line receivers are permitted.

Think of it this way - a driver on an RS-232 line can have a negative
voltage of up to -25 volts, and a positive voltage of up to +25 volts.
Imagine that one driver is trying to produce -25 volts while the other
driver is trying to produce +25 volts. In other words, they 'fight'
with one another, and the result is 'confusion' because the receiver
listening on that RS-232 signal line will not respond to a voltage that
is less than 3 volts positive.

In other words, use a "Y" connector only when the added device is
capable of being put into a "listen only" mode (with its drivers disabled).
Look at your amplifier information carefully to see if it can be placed
in a "listen only" mode. If not, you cannot use it with a "Y" connector.

The SteppIR is one example of a device that can be placed in listen only
mode, so the use of a "Y" connector is possible, but that is not the
general case.

Bottom line, you can connect only *one* RS-232 device to another in the
general case. Introducing a 3rd RS-232 device (with a "Y" connector)
requires special conditions be present in that 3rd device - it must only
listen to the data traffic and not attempt to transmit data.

73,
Don W3FPR

On 12/13/2015 10:52 AM, [hidden email] wrote:

>
>
> I have an OM2500A amp that works perfectly with my K3S when it is the
> only thing connected to the RS232 of my K3S.
>
> I am using LP-Bridge and Na3P to create a panadapter and this works
> perfectly when the computer is the only thing connected to the RS232 of
> my K3S.
>
> The manual shows how to use a RS232 "Y" splitter so that two devices can
> share the RS232 port of the K3S, but when I use the "Y" splitter (one
> side to the OM2500A amp and one side to the computer) the following
> malfunctions occur:
>
> 1. The OM2500A display rapidly changes from the correct VFO frequency to
> an out-of-band frequency over 2 Mhz away.
> 2. The pandapter frequency readout ceases to function.
>
> I assume there is a port conflict, and I wonder if anyone knows the
> correct pin-out of the RS232 line to the OM amp so that it will be a
> passive listener on the DB9 cable?
>
>

Josh Fiden

Re: K3S RS232 "Y" Connector causing port conflict

The OM2500A has 2 serial ports. It is designed to be patched inline between a computer and the K3.

73,
Josh W6XU

Sent from my mobile device

> On Dec 14, 2015, at 5:11 AM, Don Wilhelm <[hidden email]> wrote:
>
> Charles,
>
> I don't know the specifics of your OM2500A amplifier, but I do know about RS-232.
> First, RS-232 is a point to point system. The use of "Y" connectors is not the norm and are applicable only under certain specific conditions.
> Those conditions are that the device added by the "Y" connection has no active drivers on the RS-232 signals - only line receivers are permitted.
>
> Think of it this way - a driver on an RS-232 line can have a negative voltage of up to -25 volts, and a positive voltage of up to +25 volts.
> Imagine that one driver is trying to produce -25 volts while the other driver is trying to produce +25 volts. In other words, they 'fight' with one another, and the result is 'confusion' because the receiver listening on that RS-232 signal line will not respond to a voltage that is less than 3 volts positive.
>
> In other words, use a "Y" connector only when the added device is capable of being put into a "listen only" mode (with its drivers disabled).
> Look at your amplifier information carefully to see if it can be placed in a "listen only" mode. If not, you cannot use it with a "Y" connector.
>
> The SteppIR is one example of a device that can be placed in listen only mode, so the use of a "Y" connector is possible, but that is not the general case.
>
> Bottom line, you can connect only *one* RS-232 device to another in the general case. Introducing a 3rd RS-232 device (with a "Y" connector) requires special conditions be present in that 3rd device - it must only listen to the data traffic and not attempt to transmit data.
>
> 73,
> Don W3FPR