Nate, I looked in my KPC-3+ manual and they do call out a DCD line on both the RS232 DB25 connector, pin 8, and also on the 9 pin radio connector. However, I cannot find any reference to it in the manual. Probably there, but cannot find. Wonder why they could put in a simple chart saying "pin 1, does this, lo or high to turn on/off".
In the RS232 spec the pin 8, known as CD, is Receive Line Signal Detector. It does take the unit on/off line. So I am assuming if the CD (DCD here) is in off state then the TNC will not do anything including receive or transmit??? >From the inital question this probably would work since little data might be >going thru the system. 73, ron, n9ee/r >From: Nate Duehr <[EMAIL PROTECTED]> >Date: 2007/08/03 Fri AM 03:08:44 CDT >To: Repeater-Builder@yahoogroups.com >Subject: Re: [Repeater-Builder] Connecting Multiple TNCs > > >On Aug 2, 2007, at 7:03 PM, Ron Wright wrote: > >> Nate, >> >> Would just disabling one PTT while the other is txing mean the >> disabled would think it was transmitting, but not really. > >That's not what I recommended. I recommended tying one's PTT signal >to the other's RECEIVE signal so it would hold off and not transmit. >(TNC's won't transmit over an incoming received signal.) > >As someone else and myself both pointed out, you have to rely on >having a real COS signal from the radio and have your TNC's set up to >use that, and not use a "software" DCD (data carrier detect) that >looks for real tones, you have to do it the "old fashioned" way with >a hardware COS line from the rig. > >> Unless there is some sort of feedback to tell a TNC to wait then >> its data would be lost. I guess some TNCs have this wait line >> INPUT allowing one ptt to talk to the other TNC commanding a wait. > >No, TNC's "buffer" data all the time. If the channel is busy when >the computer connected to them sends data to them, they buffer and >wait. Then when the channel's clear, they transmit that data. So >it's not really a separate "WAIT" line, you're just tricking TNC #2 >to think that the channel is busy when TNC #1 is really transmitting, >and vice-versa. > >This is kinda off-topic for RB, so I'll stop now -- but suffice it to >say, hooking two TNC's to the same rig would be pretty simple... as >long as you're not relying on the TNC to determine if the channel is >busy, and you're using the "old-fashioned" system that simply watched >the squelch circuit of the receiver... if the squelch was open, the >TNC knew it shouldn't transmit. > >(Once upon a time, there were endless debates about the benefits of >doing busy-channel detection by either method, and which one was >"better" over the last couple of decades... real "squelch" circuits >will also give way to voice traffic on the same frequency... software >DCD's won't... etc. etc. etc.) > >-- >Nate Duehr, WY0X >[EMAIL PROTECTED] > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
