NX-5700/5800 Audio Issues - Rapid Clicking

[mikelimayankee]

Kenwood Gurus, I'm looking for help with a persistent audio issue. I have an NX-5700/5800 dual deck setup with a KCH-20R advanced head, installed in my truck. I have an annoying, high-amplitude rapid clicking sound in the background of all transmissions made from these decks in NXDN and DMR modes. I first noticed it while testing my audio on a parrot talkgroup in DMR and assumed it was a TDMA artifact, but the same sound is present in simplex NXDN conventional operation as well. I have NX-800 and NX-300 units configured the same (as close as they can be with KPG-111D vs KPG-D1N) in operation and none of them have this issue.

I have tried:

• KMC-65 and KMC-27B microphones.
• Cycling through audio settings such as ANR, microphone profiles, microphone gain, etc.
• Different power sources, including vehicle start battery, vehicle lithium house battery, Jackery power pack, and AC/DC power supply
• Turning over-the-air alias off
• Switching signaling from Fleetsync to MDC1200 and back

Here is a video example of the sound, including dead air and a voice transmission. Any help would be appreciated.

 

[mikelimayankee]

Two more tests:

• I switched to a KCH-19 basic control head I had lying around, no change. Same issue.
• Here is a similar clicking sound from the VHF deck, this time on an analog conventional channel with a PL tone and no additional signaling.

 

[Vern]

KW mics in the ham world were notorious for this, especially knock-offs from China. It's usually a poorly crimped RJ45 at either end of mic cable. There's a data line in mic circuit and that's bleeding over onto the mic audio line. Sometimes simply recrimping the RJ45's can cure it.
Give it a shot.

 

[buddrousa]

Does this happen with the motor running and the motor turned off or just with the motor running.

 

[kd4efm]

Going to be a little crazy here, but this sounds like a bad spark coil or wire (you didn't state vehicle info other than a truck)
BUT, that being said, GROUNDS and coax check, for a bad crimp, fray ground, loose chassis ground, anything that would
create RFI. Diesel truck? again, would say the alternator may have a diode going south.

ANYTHING in the area of grounding and or B+ where the RFI is getting into the deck(s) <in this case your UHF Deck> since you state
NX300/800 (UHF).

Good luck, report back!

 

[mikelimayankee]

Thank you all for the suggestions, I’ll give all of that a try and get back to you!

 

[mikelimayankee]

Update: I swapped the mic cable out for another one I had lying around and think I had a counterfeit/chinese knockoff cable originally. The markings are slightly different and the second cable feels more flexible. The new cable has noticeably reduced the volume of the interference, but not eliminated it.

I've repeated all my tests with the engine running and with the car turned off. I've also run power from a bench power supply in the garage and plugged both decks into that. The power source does not seem to have any effect on the interference.

 

[AM909]

Sounds like RF getting back into the radio. Do you have a dummy load? If so, does it happen when transmitting into a dummy load instead of the antenna?

 

[W3AXL]

You're not using a mic extension correct? That's a surefire way to get mic clicking. The standard KW RJ45 mic pinout puts the mic line and one of the serial data lines on the same twisted pair when you use a standard T568B ethernet cable.

 

[mikelimayankee]

Thank you all for the help. I have solved the issue. Turns out, both mic cords I had were counterfeit/knockoff ebay items, one of which was totally unshielded and one of which was inadequately shielded, but better. I purchased a cable directly from a Kenwood parts supplier and that fixed the issue completely.

W3AXL, thank you for your comment about the extension, as I am planning to extend the cable when I finish this install and that definitely would have caught me out. I'm planning to use double shielded CAT 8 ethernet cable now and make sure the mic input line is not paired with a serial data line.

 

[AM909]

Is T568A organization better/usable?

 

[mmckenna]

Is T568A organization better/usable?

The only difference between 568A and 568B is that the Green and Orange pairs are swapped in position. As long as the correct pair is shielded and the connectors are installed correctly, it won't matter for an LMR microphone.

 

[AK9R]

The only difference between 568A and 568B is that the Green and Orange pairs are swapped in position.

The positions are different in the plug between 568A and 568B, but the wires in the cable are still green/white-green, orange/white-orange, blue/white-blue, brown/white-brown.

To the OP, this is a well-known problem with Kenwood's TM-D710 and TM-V71 amateur radio mobiles but I wasn't aware that the NX-5000 mobiles had the same problem. The issue is that Kenwood sends serial data down the mic cable and uses one of the wires in the mic cable to pass a clock signal. In gen-you-wine Kenwood mic cables, the microphone audio on pin 6 (MIC) has it's own shield on pin 5 (MIC-E). See image below. A mic cable with an overall shield often won't help because the clock signal is inside the cable. You need a cable that shields the mic audio. There was a company doing business as Greenlight Labs who found a source for cable similar to what Kenwood uses and sold mic extension cables for TM-D710 and TM-V71 users, but he's no longer in that business.

Among the solutions for ticking in the transmit audio on TM-D710 and TM-V71 radios were to make sure the connectors are clean, both male and female at both ends. Also, make sure that the cable isn't stressed or pulled one way or the other at the connector.