• To anyone looking to acquire commercial radio programming software:

    Please do not make requests for copies of radio programming software which is sold (or was sold) by the manufacturer for any monetary value. All requests will be deleted and a forum infraction issued. Making a request such as this is attempting to engage in software piracy and this forum cannot be involved or associated with this activity. The same goes for any private transaction via Private Message. Even if you attempt to engage in this activity in PM's we will still enforce the forum rules. Your PM's are not private and the administration has the right to read them if there's a hint to criminal activity.

    If you are having trouble legally obtaining software please state so. We do not want any hurt feelings when your vague post is mistaken for a free request. It is YOUR responsibility to properly word your request.

    To obtain Motorola software see the Sticky in the Motorola forum.

    The various other vendors often permit their dealers to sell the software online (i.e., Kenwood). Please use Google or some other search engine to find a dealer that sells the software. Typically each series or individual radio requires its own software package. Often the Kenwood software is less than $100 so don't be a cheapskate; just purchase it.

    For M/A Com/Harris/GE, etc: there are two software packages that program all current and past radios. One package is for conventional programming and the other for trunked programming. The trunked package is in upwards of $2,500. The conventional package is more reasonable though is still several hundred dollars. The benefit is you do not need multiple versions for each radio (unlike Motorola).

    This is a large and very visible forum. We cannot jeopardize the ability to provide the RadioReference services by allowing this activity to occur. Please respect this.

Kenwood TK-760 to David Clark Headsets

Status
Not open for further replies.

traingeek087

Member
Joined
Jan 31, 2008
Messages
19
Hello,

This is my first post here in a while but I have been a member for some time. I am not very smart with radios but I need a little help. I bought a used Kenwood TK-780 with the KCT-19 wiring kit already installed in the radio. I want to integrate it in with some David Clark 3800 series headsets I have. To do this, David Clark makes a interface cord - C3821 is the number. One end has a plug and the other has open wires.

The KCT-19 has 15 female pins on the connector. I see Molex makes a male connector for it that I can use. My problem is I do not know what wires I am suppose to connect. I have the information for what each pin is for the radio and for the interface cord, but I still don't know what ones need to go together.

Here is what I found for the pin outs:
KCT-19
1 - RXD (Smarttrunk) or DTC (MDT)
2 - Mic Ground
3 - Ignition Sense
4 - RX Discriminator Output
5 - External Mic Input (ME)
6 - Ground
7 - Switch B+
8 - External PTT
9 - Data Module Input
10 - Horn Alert Output
11 - Squelch Detect (MDT)
12 - Speaker Audio
13 - Speaker Mute Input
14 - Mic Mute Input
15 - Emergency Input or TX sense output

David Clark Interface Cord:
Green - Audio High
Black - Audio Low
Red - MIC High
White - MIC Low
Yellow - PTT High
Blue - PTT Low

All I want is to be able to broadcast over the headsets when I push the PTT button. I wouldn't mind having an external speaker that worked with it when I don't have the headsets on, but if that is not possible then I don't mind. Can anyone help me out please?

Thanks,
Stu
 

ramal121

Member
Joined
Dec 5, 2008
Messages
1,636
Location
Sonoma, CA
Hello,

This is my first post here in a while but I have been a member for some time. I am not very smart with radios but I need a little help. I bought a used Kenwood TK-780 with the KCT-19 wiring kit already installed in the radio. I want to integrate it in with some David Clark 3800 series headsets I have. To do this, David Clark makes a interface cord - C3821 is the number. One end has a plug and the other has open wires.

The KCT-19 has 15 female pins on the connector. I see Molex makes a male connector for it that I can use. My problem is I do not know what wires I am suppose to connect. I have the information for what each pin is for the radio and for the interface cord, but I still don't know what ones need to go together.

Here is what I found for the pin outs:
KCT-19
1 - RXD (Smarttrunk) or DTC (MDT)
2 - Mic Ground
3 - Ignition Sense
4 - RX Discriminator Output
5 - External Mic Input (ME)
6 - Ground
7 - Switch B+
8 - External PTT
9 - Data Module Input
10 - Horn Alert Output
11 - Squelch Detect (MDT)
12 - Speaker Audio
13 - Speaker Mute Input
14 - Mic Mute Input
15 - Emergency Input or TX sense output

David Clark Interface Cord: KCT-19
Green - Audio High PIN-12 SP
Black - Audio Low PIN-6 E
Red - MIC High PIN-5 MI
White - MIC Low PIN-2 ME
Yellow - PTT High PIN-8 PTT
Blue - PTT Low PIN-6 E

All I want is to be able to broadcast over the headsets when I push the PTT button. I wouldn't mind having an external speaker that worked with it when I don't have the headsets on, but if that is not possible then I don't mind. Can anyone help me out please?

Thanks,
Stu
OK, there ya go. You'll need to scare up a 15 circuit Molex plug and male pins size .063". Easy enough to do. Note that if the speaker SP line is connected to the KCT-19 the internal speaker will be disabled. You can add an external speaker, just wire across the DC green and black leads. Also you'll have to move a couple of jumpers inside the radio to enable the MI mic line. Default the MI line is disconnected.

The connector pins are small and you see there will be some with double wires. Hard to do and still look nice. Best to break out the KCT-19 to a terminal strip and make the multiple connections there.
 
Last edited:

traingeek087

Member
Joined
Jan 31, 2008
Messages
19
Thank you for the help. If I add an external speaker, will it always broadcast whenever I speak using the PTT button or whenever someone broadcasts via the narrowband radio? I am going to make sure I have everything I need before I do the project, but I am sure I will have more questions to come soon later.

Thanks,
Stu
 

traingeek087

Member
Joined
Jan 31, 2008
Messages
19
OK, there ya go. You'll need to scare up a 15 circuit Molex plug and male pins size .063". Easy enough to do. Note that if the speaker SP line is connected to the KCT-19 the internal speaker will be disabled. You can add an external speaker, just wire across the DC green and black leads. Also you'll have to move a couple of jumpers inside the radio to enable the MI mic line. Default the MI line is disconnected.

The connector pins are small and you see there will be some with double wires. Hard to do and still look nice. Best to break out the KCT-19 to a terminal strip and make the multiple connections there.
I have it all wired up correctly I think.

Everything works except for the mic on the headsets. the hand mic makes a aweful noise in the headsets when in use, but I can hear others talking to me. They just cannot hear me talking to them.

The jumper that I need to move IN THE RADIO is where I am confused. I think it is why I cannot get the mic on the headset to work. The link has the manual to the radio, look on Page 21, is this saying I have to jumper it to make the mic work? I am not a radio guy, is there anyway of doing that?


LINK http://www.ko4bb.com/Manuals/Kenwood/Kenwood_TK-780h_880hver2.pdf
 
Last edited:

tlitt019

Member
Joined
Aug 19, 2011
Messages
2
Location
Barry County
I have it all wired up correctly I think.

Everything works except for the mic on the headsets. the hand mic makes a aweful noise in the headsets when in use, but I can hear others talking to me. They just cannot hear me talking to them.

The jumper that I need to move IN THE RADIO is where I am confused. I think it is why I cannot get the mic on the headset to work. The link has the manual to the radio, look on Page 21, is this saying I have to jumper it to make the mic work? I am not a radio guy, is there anyway of doing that?


LINK http://www.ko4bb.com/Manuals/Kenwood/Kenwood_TK-780h_880hver2.pdf
I talked to a engineer from David Clark. He said all that was needed is a jumper wire from the white wire to the blue/black wire. So basically some sort of jumper wire before the KCT-19, from pin 2 to pin 6.

I haven't tried this yet, but I am in the same boat you are currently in. I am going to try it first thing tomorrow.However I have a TK-760HG, but the wiring seems very similar.
 

mmetalworks

Member
Joined
Jan 26, 2016
Messages
8
David Clark interface to Kenwood TK790

HI I'm new here so take it easy on me. I have read several posts in regards to this topic but I just wanted to be sure I have all my ducks in a row here is the set up I have a David Clark U3800 module with a Jumper to the David Clark U3815 radio interface module I am wanting to interface a Kenwood TK790 radio to the David Clark system. The U3815 module has a C3821 cable coming from it with 6 leads which will tie into the Kenwood TK790 via the DB25 connector on the back of the Kenwood radio

The radio should be programmed as follows (posted by another member)

"go into the software and read the radio. Then at the top of the screen, left click on the "EDIT"
selection on the top line. Then left click on the "FUNCTION PORT" selection. In the "INPUT" tab,
the line that says "RADIO 1 AI1" should be set to "EXT PTT".

Mic mute should be set to off in programming EXT PTT as well (correct?)

just looking for some confirmation at this point on my wiring connections they are as follows
wires coming from the C3821 cable

Red wire (Microphone High) connects to Pin 13 on DB25
White wire (Microphone Low) connects to Pin 25 on DB25
Yellow wire (PTT High) can connect to pin 2-6 depending on programming (Correct?)
Blue wire (PTT Low) connects to Pin 7 on DB25
Green wire (Receive Audio High) connect to pin 17 on DB25
Black wire (Audio Low) (I think this connects to pin 18 which is ground is that correct?)

It has been recommended to use a 1.0 uf cap on the green wire connection to pin 17 (correct?)

I am wanting to use an external speaker (Motorola HSN4038A External 7.5W) I believe this gets wired into the Green and Black wires if that is the case do the green and black still need to tie into the DB25 ( I would assume Yes in order to receive transmissions on the external speaker and the headsets)

Internal radio modifications that need to take place are as follows
remove the R641 and close the R640 circuit

Will this modification still allow me to use the hand mic or only the headset mic and while receiving messages will they be received on both the external speaker and headset?

I know there are a lot of questions here I have put this together from other's posts but still had a few questions thanks for any help
 

ramal121

Member
Joined
Dec 5, 2008
Messages
1,636
Location
Sonoma, CA
I'll answer in the order you asked questions

Yes you'll need to program an input for external PTT to key the radio. You can use AI1 through AI5. AI1 is a good choice and will be on pin 2 of the DB-25 connector of the radio. Be aware AI1 shows in two places in the program software, the control head or the radio. Since it sounds like you want to connect to the radio chassis, be sure you select that.

Mic mute should never be checked. This is for data operations only, like a GPS modem or something. A lot of guys think this is something else and check it. Just leave it alone for headset ops.

For wiring, you are correct for mic high and low, also PTT high and low. For receive audio green and black wires, it depends. Pin 17 (AFO) and 18 (ground) is a constant low level receive audio that is unaffected by the volume control. Now what depends is, if your 3815 is a newer style or older style. Open it up and look for two blue volume controls on the board. If both are there you have a new one and you can use the receive audio from pin 17 but you'll have to turn the receive volume pot all the way up to make it usable (don't hold me to this as older Firecoms may be the only ones that have enough gain to utilize pin 17, can't really remember). If you only have one blue pot then this is for transmit audio and the receive (green and black) will have to tied to the speaker leads that come out of the white molex connector of the radio to give you usable receive audio to the headsets as it is not adjustable.

A coupling capacitor is a safe prophylactic in most instances, but David Clark systems use transformer coupled audio in both transmit and receive so the capacitor is not needed.

An external speaker would come off of pins 2 and 6 of the white molex connector on the back of the radio. Depending where you want the green and black wire to go, you can just parallel across the speaker wires or go to the DB-25 connector.

Pin 13 is dual function, either mic input or data input. You want microphone. Yes, for this jump R640 needs to be installed and jump R641 removed. If you are somebody reasonably well versed at soldering, go for it. Any doubts then a solder bridge or lifted trace can make for a real bad hair day.

Both the speaker and headset will work along with hand mic and headset mic, no problems there. A cravat though. The TK-790 microphone element is always hot. What this means is when you key the radio from the headset both the headset mic and hand mic are live at the same time. Depending where you hang the hand mic, in can interject excessive engine/road/siren noise into your transmissions. There is a mod to the mic to switch out the element unless the thumb button is pressed. Requires cutting a trace and installing a transistor and resistor in the mic.

You will lastly need to set the audio levels inside the 3815. The blue volume pots are multi-turn, I think 20 maybe. With a very small screwdriver, turn both many turns counter-clockwise to the bottom. When you reach the bottom, you'll hear a faint click from them as you rotate around. Now unsquelch the radio to blow white noise. Pick a pot and start turning clockwise. The receive volume should increase. Keep adjusting until you reach a point it won't get any louder in the headset. Back off and try again, get to the point where volume increase just ceases and quit. If you don't hear anything you picked the wrong pot. Turn it all the way back and adjust the other. Now do the transmit. Have a helper monitor on another radio. Press headset PTT and give a test count in a medium to high voice. Turn the transmit pot clockwise until the volume doesn't get any louder and stop. Any further will just give you more distortion and background noise making it harder to understand. Go back and forth a couple of times to make sure you're at the right point. Due to Kenwoods high mic sensitivity, only a few turns are necessary, Compare it with the hand mic as both now should sound about the same.

A lot of questions, yes, and a beefy answer in response. Anything else, chime in.
 
Last edited:

mmetalworks

Member
Joined
Jan 26, 2016
Messages
8
David Clark interface to Kenwood TK790

Wow! thanks for such a detailed and organized answer I'm still acquiring all my components for this interface I'm sure once I get started on it I will have some more questions. I'm thinking it might be easier to just tie the green and black wires into the molex connector with the external speaker (Green to pin 6 and black to pin 2) but is there a downside to this if my 3815 is the newer style with two volume controls?

I'm not too concerned about reversing the R640 and R641 jumpers I am still awaiting the arrival of my radio do you by chance have a diagram with the location of these jumpers or is it pretty self explanatory once the unit has been opened?

I'm thinking the hand mic mod would be a nice feature I could see that becoming an issue transmitting a bunch of background noise while transmitting via the headsets is there a forum that gives the details on this?

Okay just to be sure I understand this: a newer 3815 will have 2 volume controls on the inside a receiver volume control (turned all the way up if I want to use Pin 17 on the DB25) the second volume control will be used to fine tune transmission volume levels
an older 3815 will only have one volume control on the inside and it is therefore the one used to fine tune transmission volume levels (correct?)
 

ramal121

Member
Joined
Dec 5, 2008
Messages
1,636
Location
Sonoma, CA
No problem. Done a few DC's in my time.

No real downside to hooking the green and black wires to the speaker as this is the way it was designed. The only difference is the headset volume goes up and down with the radio volume. Using this method you would set the radio volume at a normal level and then adjust the 3815 receive to a point you'd like for an audio level in the headset.

For R640 and R641 see attached visual.

Here's a link for the hand mic mod. Not real detailed. Scroll down to section that explains this. I do it slightly different but don't have any pictures (yet) that show how. Maybe I'll attempt a quick tutorial now that you ask. http://static1.1.sqspcdn.com/static/f/1281716/16765525/1330023216150/TK90SERIES.pdf?token=3/58AaeZV+sV6irmsbHTH/BU14A=

Yes you have it. Newer 3815's have adjustment for transmit and receive levels while the older ones only adjust transmit level.
 

Attachments

mmetalworks

Member
Joined
Jan 26, 2016
Messages
8
Kenwood interface

Thanks for the attachments I ordered a few components as per the vague instructions on doing the Kenwood hot Mic mod. I would be interested if you end up doing a tutorial on this. The attachment detailing the location of the R640 and 641 is perfect thanks! Still awaiting the arrival of the radio I will post a follow up once the interface is complete in the mean time Here are a few photos of my project the David Clark intercom set up is already installed they will be used in a small rail car Speeder (Fairmont MT-19) and one photo of the tool I built to hold the "cannon" MS connectors while disassembling and or soldering
 

Attachments

ramal121

Member
Joined
Dec 5, 2008
Messages
1,636
Location
Sonoma, CA
Kenwood KMC-27 hot mic mod

Way cool. A David Clark system will make this project stand out. I've installed radios into a couple of speeders, and after my efforts was offered a ride. Somehow this never came to fruition. Drat! And yes I understand speeders are very noisy, hence the need for headsets.

OK. Since I think this would be useful info and I needed to make one for stock, here's how to mod a KMC-27 to switch the mic audio to prevent excessive noise on transmit when using a headset or anything else connected to the accessory connector.

First you need to scare up any old general purpose PNP transistor (ie 2N3906) and a 1K resistor.

PIC #1; Remove the mic cord, split the mic housing and extract the printed circuit board. Locate the trace indicated in the picture. Gently scrape the green mask off about 1/4 inch either side of the bend to expose the copper trace. Tin the trace with solder. Now you need to remove a small portion of the trace right at the bend to open the circuit. I score the trace with a razor and then use a hot soldering iron to lift it. A Dremal tool can chew through it also if you're careful.

Pic #2; Take your transistor and bend the lead to the angle shown. The idea is to have the emitter and collector leads to line up on the copper trace.

Pic #3; Once the leads line up with the trace, trim them down, tin them and tack solder to the copper traces. Lay the resistor on top of transistor and solder to the middle base lead of the transistor. Connect a chunk of wire to the other side of the resistor (I use a piece out of some CAT5 cable).

Pic #4; Now run the wire to the other side of the PCB and tack solder it to the pin shown of the PTT switch.

Pic #5; That's all there is to it. I use dabs from a hot glue gun to secure the components and loose wire to make sure things don't break loose as the mic is banged around.

To test, with the headset unplugged, key the radio from the 3815 but speak into the hand mic. Nothing should be heard. Then press PTT on the hand mic and give a test, all should be normal.
 

Attachments

Last edited:

mmetalworks

Member
Joined
Jan 26, 2016
Messages
8
Kenwood interface hot mic mod

Okay I got it thanks to your instructions and pictures. Basically you are splicing into a normally closed circuit and In my simple terminology installing a small relay (the transistor basically serves as a "relay or remote switch) the pnp transistor I'm assuming is basically in the "normally open" position until it is triggered by the PTT switch which triggers the transistor "Relay" to close and re establish the connection just like it was before the mod. "That's ingenious!" Correct me if I'm wrong but am I understanding that correctly? It seams Kind of Dumb that Kenwood didn't set these microphones up this way when they were manufactured I don't see any downside to this modification and again have to wonder why didn't Kenwood make these like this from the get go.

Thanks again for the photos and instructions I don't think I would have figured this out on my own based on the vague instructions from the previous attachment. I will post my progress once all the components I have ordered arrive

Quick question: since I only own one radio (the Kenwood TK-790) and need another one to not only fine tune the transmission volume on the David Clark 3815 but to also confirm that everything is working correctly once it has all been interfaced I ordered one of these on amazon "BaoFeng BF-F8HP 8-Watt Dual Band Two-Way Radio (136-174Mhz VHF & 400-520Mhz UHF)" any thoughts on these? you can be brutally honest. Also since I am not a certified Ham operator I was planning on broadcasting on the Narcoa channels (151.625, 151.505, 158.400) which is the sanctioning body over the rail speeder clubs Narcoa stands for national association of railcar operators of America. Am I breaking any laws broadcasting on these channels to test this set up or is there perhaps another frequency I could use to be in compliance, and finally one more question the guy I am purchasing the radio from agreed to program the channels I will be needing and program it accordingly for the David Clark interface, however should I need to do any additional future programming what all do I need to know. I see programming cables are available for about $30 (FTDI USB Programming Cable Kenwood TK-790) I believe the "FTDI chip" cables are the better ones? can the software be downloaded or purchased? any recommendations? do you have to subscribe? I think I heard you have to purchase a 3 year subscription for the Motorola stuff or is it not even worth messing with the programming and easier to source this out to someone else. Thanks again for your time and expertise on all things radio.
 

Attachments

mmetalworks

Member
Joined
Jan 26, 2016
Messages
8
David Clark interface to Kenwood TK790

Just a quick follow up the interface was a complete success! I was able to locate and switch the two jumpers inside the radio and perform the hot mic. Mod. Thank you to all the members who contributed to this post and walk me through all the steps. I was going to post pics but had a heck of a time getting them to work
 

mmetalworks

Member
Joined
Jan 26, 2016
Messages
8
Rail speeder ride

There is an excursion on February 20th at the Fillmore and Western Railway. Fillmore Ca. I'll be there enjoying the new radio and intercom. Your are welcome to come and check it out and of course go for a ride in a rail speeder. Here is the web page address for all the details (Motorcar Operators West (MOW)) Thanks again for all the help!
 

mmetalworks

Member
Joined
Jan 26, 2016
Messages
8
Kenwood TK-790 Squelch adjustment

This is a follow up message / question in regards to the Kenwood David Clark interface set up in my Fairmont Mt 19 rail speeder. The set up is working fantastic with one annoying exception I have to crank the squelch all the way up to 14 or 15 in order to clear the static. at first I thought I had perhaps messed up on the antenna PL 259 connection so I ordered a new antenna cable with the connection already installed and discovered the antenna was not the problem the new cable created the same problem as the original cable. Upon further investigation I discovered this is a bit of known issue with the older Kenwood 790 radios. I found some info showing how to put the radio in "test mode" and adjust the "squelch tight" and "squelch open" setting using the PF1 - 5 buttons, there is even a neat video on YouTube showing how to do this and some "general" settings to use, here is the link:

https://www.youtube.com/watch?v=16zh85wNi8U

(I'm positive there are many others that are well aware of this adjustment and have seen this video)

Now here's my problem: according to the instructions in order to enter test mode, turn off radio, hold down PF1 and at the same time press the power button the radio now comes on in a test mode, now press the group up button once, the display shows "frequency-xxx" now click the channel button one click clockwise and a small "N" should show up on the display, now press PF1 twice the display should read squelch tight. and the appropriate settings can be made from that point and programmed by pressing the PF5 button.

My problem is no matter how many times I try I cannot get my radio to enter into test mode by holding down the PF1 button and pressing the power button. The radio just turns on like normal and no additional adjustments can be made. Am I missing something what do I need to do in order to put my radio into the test mode to make these adjustments.

Thanks in advance for any help or suggestions,
John
 

KA2FWN

Member
Joined
Jan 2, 2007
Messages
21
Location
central ny
if you have the programing cable and software you can put it in test mode and make the adjustments.
if you want to use panel tuning you will need to enable it in the programing.

just did one today :)

I found the headset mic to very hot add a 10k resistor to mic input
 

mmetalworks

Member
Joined
Jan 26, 2016
Messages
8
Thanks for the reply in regards to the Squelch adjustment and putting the radio into test mode I do not have a programming cable or the programming software. Lately I have just been turning the squelch all the way up, not exactly ideal but functional. I know there are several programming cables available is there one that is a better choice than others? Also how do I acquire the programming software I purchased my radio pre programmed and don't really need to change any of the channels at this point in time but I can see it being useful in the future and adjusting the squelch would be an added bonus.

Thanks, John
 
Status
Not open for further replies.
Top