TK-790H Tx audio from accessory connector- audio terrible

[WX5812]

I am using my tk-790h as a temporary transmitter on a vhf repeater. I have pins 2-ptt,13-mic audio, and 7-ground going to the controller. It keys up as it should but the audio coming out is horrible. Sounds like a ton of background noise and cannot hear any voice just mostly hiss and static. Did I possibly make a mistake on which pin is tx audio? Any other suggestions?

 

[mmckenna]

Pin 13 is the microphone input. Make sure you have the right interfaces.
Pin 25 is "Mic Earth". Shouldn't matter, but I could be wrong.

The input needs to meet the following specs:

MIC/Data signal input 1 (Default : DI)
Input impedance

DI : 10kΩ or more​

MI : 600Ω​

Coupling

DI : DC coupling​

MI : DC coupling​

Frequency response

DI : ~9.6kHz +1/–3dB (1kHz=0dB)​

MI : Compliance with TIA/EIA-603​

Deviation

DI : 60% deviation or more​

(1kHz 2.5Vp-p input)​

MI : 60% deviation​

(1kHz 5mV ±1.5mV input)​

​

Not sure what kind of repeater controller you are using, but making sure the specs on the interface meet that of the radio.

 

[mmckenna]

Looking at what I posted, make sure you have the input set for MI, not DI. The DI input is for data, and will have poor sounding audio. Setting it for MI will give you better audio response, if you haven't done that already.

 

[WX5812]

I will check that first thing this morning! I will report back with the results. Thank you!

 

[WX5812]

Repeater controller is an acc rc-96

 

[WX5812]

I cannot see where it gives me an option to switch between mi or di. Do you by any chance know how to switch that?

 

[ramal121]

To select between DI and MI is done with jumpers on the control board. You would look for 0 ohm resistors. For MI R640 needs to be in and R641 needs to be out.

But it appears your radio is correct as what you describe sounds like the mic (MI) input is grossly over driven. Look again at the specs again and see it only takes 5 mV for 60% deviation. That's pretty darn low. I find some external equipment can't really go that low or the adjustment is just too touchy. I always add a 10K resistor to the mic line for Kenwoods. This pads down the audio and raises the TX audio adjustment of your device up into a more medium range where it is easier to get it dialed in.

 

[WX5812]

To select between DI and MI is done with jumpers on the control board. You would look for 0 ohm resistors. For MI R640 needs to be in and R641 needs to be out.

But it appears your radio is correct as what you describe sounds like the mic (MI) input is grossly over driven. Look again at the specs again and see it only takes 5 mV for 60% deviation. That's pretty darn low. I find some external equipment can't really go that low or the adjustment is just too touchy. I always add a 10K resistor to the mic line for Kenwoods. This pads down the audio and raises the TX audio adjustment of your device up into a more medium range where it is easier to get it dialed in.

I will try that!
I had a Motorola mts2000 as my transmitter and audio was fine when taken out. This is my first go around with a Kenwood in its place. Thanks for the tip

 

[WX5812]

First of all thank you to everybody that has responded so far I appreciate all the help.

Update on this project.

Rx radio is a TK-790H (bad pa)
TX radio is a TK-790 mid power model


I put a 10k resistor at the mic input. The audio from the controller and out of the transmitter is crystal clear and beautiful (courtesy tone,cw id and speech synthesizer) . But for some reason it does not pass voice audio. I know the receiver is hearing because the controller is Acknowledging all my DTMF commands. Every single digit. So as of right now I am stumped as of why voice audio is not being passed through. Any thoughts?

 

[WX5812]

Forgot to add the controller is an ACC RC-96

 

[KK6ZTE]

First of all thank you to everybody that has responded so far I appreciate all the help.

Update on this project.

Rx radio is a TK-790H (bad pa)
TX radio is a TK-790 mid power model


I put a 10k resistor at the mic input. The audio from the controller and out of the transmitter is crystal clear and beautiful (courtesy tone,cw id and speech synthesizer) . But for some reason it does not pass voice audio. I know the receiver is hearing because the controller is Acknowledging all my DTMF commands. Every single digit. So as of right now I am stumped as of why voice audio is not being passed through. Any thoughts?

Where are you getting RX audio from the receive radio?

 

[WX5812]

Pins 17 rx audio, 23 cos from the db25 accessory port

 

[KK6ZTE]

Is JP1 present in the RC96? Have you adjusted the RX level (R102)

Is the output from the controller is good I'd look into the RX path into the unit (even though it's decoding DTMF).

 

[WX5812]

I will look at the controller and see about that. Today I hooked it to a Motorola GR1225 And it worked just fine. It possibly could be the Kenwood receiver radio bad

 

[KK6ZTE]

Per the service manual, the audio level from pin 17 is 125mV so JP1 should be present.

 

[WX5812]

Upon inspection JP1 is not Connected. I will put a jumper in that tomorrow and report back. Are you familiar with ACC controllers?

 

[KK6ZTE]

Not at all. I'm just reading the manual online as we go back and forth.

I suggest going onto the Repeater-Builder site and groups.io list for more help.

 

[WX5812]

Ok gotch ya. Thanks for your help!