If you are looking at creating a Y splitter (actually the best way for this setup), then be sure to only connect ground and the signal going to the magloop controller. As someone has mentioned, you do not want to have two devices driving a data signal simultaneously. At some point one will go to +12V, the other to -12V. They will argue and one will win, the other will cease to function.
We were very careful when designing the devices that need to “sniff” the RS-232 cable. The KRC2 has an internal multiplexer that allows it to share driving the signal to the radio in parallel to the one from the computer. Even still, we advice folks to set one or the other for sending commands to the radio. The KPA500 has an internal relay to enable or disable the data being sent out the PC port. this is controlled by the menu system, allowing the KPA to perform serial polling (PC port TxD will be enabled) or pure sniffing (TxD disabled). Note that enabling both devices (computer and antenna controller) to poll the radio can be problematic, even with a multiplexing device. There are some PC applications that can be greatly surprised if they receive a response they didn’t specifically ask for. The surprise generally ends in a crash. Most programs have been rewritten to accept whatever comes there way. I won’t embarrass the problematic program’s authors, but they are aware. There is one other thing to consider. If you always use the radio and magloop with the computer running, then you are fine. But at some point if you don’t want to use the radio then you will need a source to poll the data. In that case just set the radio to output changes as they occur. That should do the job quite nicely, keeping the magloop controller happy with more data than probably needs to get the job done. 73, Jack, W6FB > On Jul 8, 2018, at 2:00 PM, Stephen Rector via Elecraft > <elecraft@mailman.qth.net> wrote: > > Hi Dick: > > Thanks - the diagram makes things very clear. I initially didn't think of > accomplishing the split at the KXPA 3.5mm connector, but it makes sense. > > Thanks, 73, > > Steve NU7B > > >> On Jul 8, 2018, at 1:38 PM, d...@elecraft.com wrote: >> >> Typically "sniffers" don't have the TX side connected. RS-232 can't have >> multiple transmitters on either wire. >> >> This is done with SteppIR controller, for similar reasons. SteppIR >> describes a splitter cable for DE-9 connectors. The same principle (with a >> much simpler cable, just tip and ring) applies to the 3.5mm connector to the >> KXPA100. >> >> http://www.steppir.com/wp-content/uploads/2011/10/Y-Cable.pdf >> >> 73 de Dick, K6KR >> >> >> -----Original Message----- >> From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> On >> Behalf Of Stephen Rector via Elecraft >> Sent: Sunday, July 8, 2018 12:31 >> To: elecraft@mailman.qth.net >> Subject: [Elecraft] [KX3] RS232 xcvr control when serial ports are occupied >> >> Hy home station is a KX3 + KPXA100, and I can control the radio via the >> RS232 port on the KXPA. However, recently I added a Ciro Mazzoni magloop to >> the station, and its controller plugs in to the KXPA serial port to sniff >> for frequency information, allowing re-tuning on the fly. This leaves no >> RS232 port left for remote control of the radio. >> >> How do I modify this arrangement to add an extra serial port for KX3 >> control? My first thought is that, since the antenna controller just sniffs >> for data, I could add a DB-9 Y-cable to provide the extra port at the >> controller serial port location. However, packets could still collide >> ...does the protocol handle this? Is there some sort of multiplexer >> available? >> >> Thanks, >> >> Steve >> >> NU7B >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html Message >> delivered to d...@elecraft.com >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to jackbrin...@me.com ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
