CDM1250 Tx without PL on data, help

[Vercomm]

Hey Guys,

Trying to get a CDM1250 to Tx without PL when its keyd for data.

I have the 16 pin connector PTT set for data and the audio is going into pin 5, flat Tx.

Some how these radios are still sending PL, do I need to also change something with the emphasis selection?

Sould I have that setting to:
None
De-emphasis
Pre-emphasis
De-emphasis & Pre-emphasis


Or does this setting matter.

The repeater is an MTR2000 and I have the wildcard tables set properly to Disable Tx PL unless Rptr Qual are met.

The system works 100% when I have the subscribers turned off. If the master station sends out requests the repeater doesn't repeat it. The master is currently programmed for Tx CSQ. Once the mobiles respond we hear the data on the voice channel.

Any ideas?????

[Al]

Have you programmed accessory pin 6, 8,12, or 13 for Tx PL inhibit and applied the appropriate logic level for your hardware's interface?

[ve3nsv]

I did this on a CM200 and just tied the PTT and Tx PL inhibit on the accessory jack to the same point and programmed both for active low and it worked great. This was done for a local company that did both data and voice on the same frequency.

[Vercomm]

Right now I'm using the flat audio and data PTT. As I understood it you could inject audio into the flat audio port and that would transmit without PL. I've had some other tips to try, but if they don't work I'll have to use pin 6 and tie that to the PTT and label it PL disable.

[Vercomm]

Well, I've tried programming a pin for PL inhibit but no luck, still keying the repeater on the voice side.

Any ideas or thoughts would be welcome!!


PM sent to ve3nsv about cm200's

[HLA]

can you create a 2nd channel identical but without pl?

[Al]

Tx PL inhibit *must* be active before PTT goes active in order for PL to be inhibited. So the pin you've programmed for Tx PL inhibit is latched by PTT(either from control head or accessory connector). If PL inhibit goes inactive while PTT is still active, PL will not be transmitted until PTT goes inactive then active again.

[Vercomm]

I could create a second channel and use data revert, but we are using channel steering so I can use I revert channel. I actually tried it to findout it wouldn't work.

Al,

could you elaborate a bit more on the "latched by PTT". I have an external Kantronics modem that is controlling the radio for the data. I understand what you are saying about the PL inhibit going low first.

[Al]

If tx PL inhibit pin is active, asserting PTT will inhibit tx PL.
If tx PL inhibit pin goes inactive while PTT is still asserted, PL will still not be transmitted until PTT is deasserted and then reasserted.
If tx PL inhibit pin is inactive, PTT going active will tx PL.
If the tx PL inhibit pin goes active while PTT is asserted, PL transmission will not be inhibited until PTT goes inactive and then gets reasserted again.

So the action of asserting PTT latches whichever state the tx PL inhibit pin is in into the controller, and merely changing the state of the tx inhibit pin while PTT is active will not disable or allow PL transmission.

I don't know which version of the radio firmware you have in your units, but this is the way it works on R05.05.15 thru R05.05.19. Likely it works the same way if you have earlier firmware.

[Vercomm]

Hey Al,

I'm running R05.05.19. So, how would I make sure that the PL inhibit goes active each time before the external PTT is pressed? Would connecting the two to the same PTT work, or would that be "ify"?

[Al]

If you don't have any external PTT hardware where the timing can be adjusted, a simple RC circuit between the PTT accy line and the Tx PL inhibit line might be used(with the external PTT control applied to only the tx PL inhibit line). You wouldn't need much delay - just half a millisecond or so - to insure that the radio's controller sensed the active state of the inhibit line before the RC circuit applied the PTT signal.