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TNC Connection to Portables

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Nickdap
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TNC Connection to Portables

Postby Nickdap » Wed Jul 28, 2004 9:24 pm

Hey All,

Can some one actually draw me a picture of how I can connect my KPC3 TNC to my MTS2000? I still can't get my head around how to key the radio from the TNC.

Thanks Guys.

Nick

P.S. I want to make up a cable to work with the audio adapter and also one just using an old speaker mic cord.

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kcbooboo
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Postby kcbooboo » Thu Jul 29, 2004 3:36 am

Many portable radios put DC on the mic input signal line, as well as mic audio. This lets them use an electret (i.e. powered) mike by providing the DC from the radio. Push-To-Talk is accomplished by grounding another line, or this same mic input line through a resistor, so the DC level shifts closer to ground. The radio senses the change in DC voltage and begins transmitting. There's still enough power left to run the mic.

Your TNC probably has separate audio out and PTT lines. You may have to use a 10uF capacitor from the audio out line to a common radio input point to pass the audio, and then use a resistor from this point to your KPC PTT line to make the radio transmit. The capacitor keeps the DC out of the KPC while the resistor makes the radio think the external mike's PTT button was pressed. It's all very radio-dependent.

If the radio has discrete mic audio and PTT inputs, then connecting the KPC's PTT line directly to the radio's PTT input should work just fine. But I'd want to verify that the signals really do go to ground first, by checking the schematic of a radio or microphone.

Bob M.

kmoose
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Postby kmoose » Thu Jul 29, 2004 7:24 am

I take he is not talking about TNC, as in the connector type? What is a TNC?

Alan
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Postby Alan » Thu Jul 29, 2004 7:40 am

He is talking about a KPC3 Kantronics wireless modem (TNC= Terminal Node Controller).
I don't have any connection information.

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Monty
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Postby Monty » Thu Jul 29, 2004 8:41 am

[img]What is a TNC?[/img]

A TNC is a [ Threaded BNC style Cconnector ] ???

Monty

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Postby kmoose » Thu Jul 29, 2004 9:45 am

Monty wrote:[img]What is a TNC?[/img]

A TNC is a [ Threaded BNC style Cconnector ] ???

Monty


Yeah, Monty........that is what I thought, when I first read the thread. But then I saw his comment about not knowing how to do PTT from the TNC, and I knew he couldn't be talking about a TNC RF connector. At least, I hoped he wasn't. :wink:

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Cam
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Postby Cam » Thu Jul 29, 2004 11:08 am

kmoose wrote:
Monty wrote:[img]What is a TNC?[/img]

A TNC is a [ Threaded BNC style Cconnector ] ???

Monty


Yeah, Monty........that is what I thought, when I first read the thread. But then I saw his comment about not knowing how to do PTT from the TNC, and I knew he couldn't be talking about a TNC RF connector. At least, I hoped he wasn't. :wink:


Isn't it like a data deal that hams us?

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Postby va3wxm » Thu Jul 29, 2004 12:25 pm

Yes, it's called a Terminal Node Controller and interfaces a radio with a computer. Kind of like a smart modem. It controls packet flow and tx/rx operations of the radio.

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Re: TNC Connection to Portables

Postby Nand » Thu Jul 29, 2004 2:52 pm

Nickdap wrote:Hey All,

Can some one actually draw me a picture of how I can connect my KPC3 TNC to my MTS2000? I still can't get my head around how to key the radio from the TNC.

Thanks Guys.

Nick

P.S. I want to make up a cable to work with the audio adapter and also one just using an old speaker mic cord.


Keying a Jedi radio requires both OPT SEL 1 and 2 contacts on the accessory side connector to be grounded at the same time. OPT SEL 1 is grounded permanently to activate the external speaker. OPT SEL 2 now functions as the PTT line when grounded.

http://www.batlabs.com/images/mt2kpin.gif shows the side connector layout.

Pins are numbered from the top down; pins 1 and 2 in the top group and pins 1 to 13 in the bottom group.

OPT SEL 1 is pin 1 in the bottom group of contacts.
OPT SEL 2 is pin 5 in the bottom group of contacts.
Pin three is external mic input.
Pin 2 is external speaker out. (Do not ground!!!)
Pin 6 is speaker common. (Do not ground!!!)
Pin 8 is ground.

The easiest way to connect to these pins for TNC use would be to get a external speaker/mic cable and use the RJ11 ??? connector that normally connects the cable to the mic head and plug it into a RJ11 wall box.
You can pick up RX audio between the speaker output and ground; just do not load it too much since it’s not designed to be used that way.

The OPT SEL pins have several features that are not documented. These pins can both sink and source current. In the JT1000 these pins allow programming from the front panel if a diode is placed across them. I also believe that they are used to switch the radio to low power in a MVA box, but I didn’t verify this.

Nand.

Looks like the above RJ11 is a RJ45.
Last edited by Nand on Sat Jul 31, 2004 7:20 pm, edited 1 time in total.

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Nickdap
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Postby Nickdap » Thu Jul 29, 2004 4:25 pm

Thanks guys for the help.

Sorry about ambiguity of my post. I was talking about the data modem not the RF connector. I'm not a HAM but I do find TNC's to be very useful on the non HAM bands.


Anyway.....Now that I know how to use the speaker mic cable to do this job, how about setting it up on a HT1250 (GP338) I don't have access to a speaker mic cable but I do have an audio adapter. So I'm guessing it would be just like hooking up a radio modem to a GP300.


Any takers?

Nick

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Nickdap
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Postby Nickdap » Thu Jul 29, 2004 11:07 pm

Ok I found this.... In re: to the GP300/HT1250 audio (adapter) interface:

Image

If I were to pull Pin 5 to ground on the service cable, would this cause the radio to tx?


Thanks,

Nick

Nand
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Postby Nand » Fri Jul 30, 2004 2:41 am

Nickdap wrote:Ok I found this.... In re: to the GP300/HT1250 audio (adapter) interface:

If I were to pull Pin 5 to ground on the service cable, would this cause the radio to tx?


Thanks,

Nick


Yes it will PTT if pin 5 is grounded. Also not that the speaker is floating.

Nand.

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Nickdap
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Postby Nickdap » Fri Jul 30, 2004 9:27 pm

Great this has all been a great help.

My only problem now is the MIC input on the JEDI connector/speaker mic.

I used my multi meter to map out the pin outs between the JEDI connector and the RJ45 connector on the other end, everything went well, except that the MIC Input pin (pin 3) on the JEDI connector has no corrosponding pin on the RJ45 side. I find this to be impossible. I've tried this with two known working speaker mic cables and yet I still can't find it!!

Any help with this last hurdle?

NAND: In regards to the floating Speaker out (Waris), can it some how be isolated so as to allow the audio to be found between the SPK Hot and regular GND? If I'm not mistaken, and not to much of a novice this is the same as the JEDI, so I should be able to pull some audio from it just by hooking it up the same?


I'm using a small RJ45 to DB9 connector which is designed to be custom wired and snaped together, however this neat little package doesn't leave much room.


Thanks guys!

Nick

Nand
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Postby Nand » Sat Jul 31, 2004 5:52 am

Obviously there has to be a connection for the mic at the RJ45 end. There is some simple circuitry on the radio connector end perhaps a capacitor. You can remove the cover and have a peek there or just inject audio into the RJ45 where you suspect the mic may connect.

As for the Warris, it is similar to the Jedi. Both use a push-pull arrangement.

The RJ45 to DB9 connector makes a nice setup since it connects directly to the TMC that way.

Nand.

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Nickdap
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Postby Nickdap » Sat Jul 31, 2004 5:21 pm

Thanks Nand,

I hope I can pull it off. Your right it does make a neat little package. It's just a pitty I may have to make changes to a skr mic cable. I was hoping I could leave it all standard. Hmmm thinking about it now, I don't believe all the RJ45 connections are used perhaps I can pick up the mic audio from an unused wire....if they have left any unused in the cable....we shall see.


Regards,
Nicholas

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Nickdap
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Postby Nickdap » Sat Jul 31, 2004 6:03 pm

Hmm how about modifiying this to do the same. This way I can just use an audio adapter.

Image

Thanks,
Nick

Nand
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Postby Nand » Sat Jul 31, 2004 7:18 pm

For the Jedi, you should be able to get mic audio into the blue wire at the speaker/mic RJ45. There are some resistors and a choke inside the other end. These should not cause a problem. There also is about 3.8 volts at that point, so use a small capacitor (0.1uF) to feed the audio in.

Nand.

Nand
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Postby Nand » Tue Aug 03, 2004 3:18 pm

Here is the pinout and their functions at the mic head end. With the gold RJ45 pins facing you and the cable downwards, the firts pin on the left I call pin 1. It has a black wire running from it.

Pin 1 Black - Option B+ ( 7 Volts, current limited in the radio by a 68 Ohm resistor.)
Pin 2 Brown - Speaker
Pin 3 Violet
Pin 4 Red - Ground
Pin 5 Blue – Mic (About 3.8VDC present.)
Pin 6 Orange – PTT (if grounded)
Pin 7 Green
Pin 8 Yellow – Speaker

Nand.


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