Need help keying in radio with a serial cable

[dcp2232]

Hi,

I'm kind of new to Labview but I'm working on a project where I have to key-in a Motorola radio automatically using an RS-232 cable. Does anyone know how to go about doing that or have experience with that? I'm using Labview 2010. Your help with this is appreciated.

Thanks,

dcp2232

[GovBob]

First which Motorola radio model are you using? By "key-in" do you mean to cause the radio to transmit? I've worked with some models and found by grounding the PTT line will cause the radio to TX. A TTL low has worked for me in the past.

[dcp2232]

Hi,

I'm using the Motorola XTS 5000. Yes, I mean transmit through the Labview program rather than pushing the button manually. When you say grounding the PTT line, do you mean connecting the PTT line with the ground wire on the serial cable? What is a TTL low? Is there a particular toolbox to use to transmit the signal to the radio. I need it to "key-in" constantly for six minutes each hour for 96 hours.

Thanks.

[SteveChandler]

I worked as a radio technician a long time ago. I remember one GE mobile radio that had an LCD and keypad on the front panel. The front panel was electrically connected to the main chassis with an internal DB9 connector. Guess what the communications protocol was between the front panel and main radio chassis. Yep. TTL 300 baud RS232.

What does this have to do with the question? Nothing. It just reminded me of that. It would have been cool to interface LabVIEW to that radio.

But it depends on the radio. You may be able to just use TTL but I would highly recommend using a relay. Especially if you are using an RS232 signal to activate. Use a solid state one or something like a 4066 bilateral switch. If you use a mechanical relay make sure you use a diode accross the coil or the driver circuit will only work once. Some relays have the protection diode built in.

[johnsold]

dcp2232,

From your reply to GovBob it is apparent that you have very little practical electronics experience.

Grounding the PTT line means connecting the PTT line to a switching device which will connect it to ground when you transmit and disconnect it from ground when you receive.  The switching device can be the mechanical switch in the microphone, a relay, or an electronic device like a transistor. To select an appropriate switch you must know two things: What is the voltage when the switch is open (receive mode)? and What is the current when the switch is closed (transmit mode)?

The output of a serial RS-232 driver will NOT work.  It never switches to ground and it only switches for milliseconds or microseconds while characters are being transmitted.

I recommend that you find a good electronics technician or engineer to assist you so that you do not damage your radio or your computer.

Lynn

[SteveChandler]

I think you can use the DTR signal as a digital output. But yes you definately need some kind of electrical interface and you need to isolate your radio from your computer as much as possible. Nothing like a mechanical relay for isolation.

[GovBob]

First I never said I used the RS232 to key the radio. I use 5v ttl logic levels from the test port of Aeroflex service monitors.

Is it possible to use a serial port. Yes. Motorola does using their Astro 25 Radio Tuner application and a RKN4106a interface cable. You would have to get the command set from them and they might not be very forthcoming. As to " my electronics background".. no comment.

[SnowMule]

I guess my question is... What are you trying to accomplish by interfacing an HT to a PC?  Passing audio?  Passing data?  OTA Programming?  Stun/Kill?  Some systems (NTS Commander comes to mind) will let you do a lot of that sort of thing remotely through the interwebs.

Some licenses don't allow for data messages on leased channels.  Some also limit what you can connect the radios to.  Make sure you're within the boundaries of applicable licenses before you go too much further, fines from the FCC can be pretty hefty.

All the radios I've worked with have a technical manual that goes along with them that usually contains schematics, signal descriptions, programming codes, etc.  I'd highly recommend going through that to familiarize yourself with what's available at the connector and what you can do OTA from a console.

[dcp2232]

We would like to measure the power of the "keyed-in" radio for an extended period of time so that it can be tested at various temperatures. It would be much preferrable to do this automatically rather than transmitting manually. Is there a much easier way to do this? Is there a relay made by NI that would make this task easier? Let me know.

[johnsold]

I do not know if NI makes one, but I have heard of RS-232 devices with relay outputs.  A search on line should find something for you.

Lynn