Batboard

Anyone know the "answer" or have ideas on this subject.

Background:
Any flavor of Motorola Radio (but specifically GM300, Maxtrac's, Spectra's or CDM1250).
A Windows PC with XP.
E-Com work

Ok, so now that the "background" is out of the way...Does anyone or has anyone, ever completed a cable to connect any of said radios to a "virtual" TNC like AGWPE. If so, how hard was it? What accessories did you need?

Regards,

-Frank C.

I havent done it with a moto, but all you should need is a way to interface a device such as a rigblaster to the radio. The only trick would be making sure the jumpers are set correctly on the rigblaster.

Normally the company that made the TNC should have some interface connection information.

Have you tried their site to find the radio your trying to use and get the connections and if you have to make any software changes to the radio?

Jim

From what I understand, AGWPE is "TNC"-less and the TNC is the COMPUTER! No extra doo-dads or whatcha-macall-its except a cable between the radio and computer!

Now with Mother /\/\ gear, I assume, that the required cable would probably have to run through the RIB perhaps? I'm ok with that as the RIB is a permanent feature in the mobile rig.

Further thoughts??

Regards,

-Frank C.

fchrist16 wrote:From what I understand, AGWPE is "TNC"-less and the TNC is the COMPUTER! No extra doo-dads or whatcha-macall-its except a cable between the radio and computer!

Now with Mother /\/\ gear, I assume, that the required cable would probably have to run through the RIB perhaps? I'm ok with that as the RIB is a permanent feature in the mobile rig.

Further thoughts??

Regards,

-Frank C.

The short little bit that I read about the AGWPE is that it is a terminal program that you run on your computer to work through what ever TNC you have that then interfaces with the radio. In short, the TNC converts the packet audio from the radio into a format and level that a computer can use. Then you need some sort of terminal software to take the digital information coming from the TNC and put it into information that you can use. Normally this is in a text format. If you have the AGWPE, then this is the terminal software that does most of the translation to the text on the screen.

Getting back to the radio audio output. You need to obtain the most direct and unfiltered audio output you can get. Normally this is from the descriminator of the radio. The different radios may or may not have this available directly on the connector of the radio. Each radio is different and in dealing with some of the Motorola models, you may even have to change some settings in the radio software programming.

If you can provide some details on just what radio your using, them there may be someone on here that can provide the exact pin connections and if there has to be any software settings changed in the radio. Making up the connection from the radio to the TNC is a piece of cake. No RIB is required. Just the connection at the radio accessory connector is all that should be required. There will be a common ground, the TX PTT line, and RX audio out of the radio. It would be best to use a shielded cable pair for the TX audio.

In the Motorola radios, there is a DC bias on both the RX audio and the TX audio lines. You need to make sure that the TNC has a coupling capacitor in line with the connections. If not, then you will have to add an external capacitor to the lines it is missing on. Otherwise, you will load down the line and it won't work. Remember in the Motorola radios, never ground one side of the speaker output.

A TNC will not work well trying to use the speaker audio output. The audio is filtered too much for the TNC to decode the tones used by the packet communications. The TNC is looking for raw audio like right off of the receiver discriminator. Again, you should be concerned with loading from the TNC. Not all TNC inputs use a high impeadance. Some have a very low impeadance and will load down the source too much. It will take adding a series resistor in many cases to get around this issue. Something like a 5 to 10 K resistor might be needed. It is a ballance between loading down and having enough signal for the TNC decoder to work. I have spent a few trials and changing in the past to find the right combination that works.

Your other problem will be trying to get the correct audio level to feed the transmitter. Most people end up using a level that is too high and this causes distortion on the transmitted signal. Your better off starting with too low of a level and slowly increasing it. The best way to set this is with a service monitor. If you don't have one, then it is trial and error with a friend that is looking at your message being sent. Find the low end level where it just starts to work and the high end where it stops working, Then set it in the TX audio in the middle.

Jim

Here is a link describing how KB0NLY did a very clean job of interfacing a TNC to a SABER.

http://kb0nly.info/saber_to_tinytrak.html

May give you some ideas.

Ken - N7QQU

Sorry but I gave the incorrect credit for the article. It is on KB0NLY's websiet but the work was done by Kelvin Helmick: N7XVB and Ron Parks: WB5DYG.

Got to give credit where credit is due:)

Ken - N7QQU

@Jim: Thanks. I was told by someone who used it before, as did his elmer that it was "TNC"-less. Guess I'll have to go back and ask again. As far as the radio goes, I'm leaning towards a GM300 which I know is easily modified for Packet as I use it for my APRS in the mobile. I think I have a Maxtrac 5 Pin radio laying around that I could use as well, but I was hoping to set that up as the house APRS station for RX-only.

@Ken: Thanks for that link. I think I had seen it before but Saber's are out of the question for now, for two reasons. 1) No Sabers in my collection. 2) Want a bigger than 5w output if I do go into the TX side of Packet.

Right now I'm looking into the RX only side of packet as I have enough on my plate for radio stuff that I want to take a quick look at the packets and see what's it's all about before I invest too much into it.

Regards,

-Frank C.

Jim,

Not meaning to disagree with you, but I have used motos for RX only on packet using the EXT SPKR port or pin, and it has worked fine. In fact, I havent ever used a radio with a discriminator tap for my 1200 baud packet ops.