Batboard

Hello, work for Highway Patrol and have a Astro 800 (motorola) in my 2002 tahoe. I am getting a sound coming across my radio, dispatcher is advising me of this that sounds like a clicking sound, almost like horses running? Sometimes they have a hard time understanding me. I have heard this also in 2 other of our camaros. Anyone heard of this, does seem to happen on the Crown Victorias. I have a whelen power pack running 4 strobes in the truck, 4 LED lights in the back and a visor light (strobe) over the passenger visor. Of course I do have a mobile vision camera. Mine doesnt do is constantly when it occurs the lights and camera are always on. Trying to figure out if it is the radio or some other interference on the truck.

Any help would be appreciated!

Thanks in advance

Have a NexTel?

Often the noise-making devices will transmit to the system, and in doing so the EMI will get back into the microphone of the radio... I hear it mostly coming from Dispatch consoles though, but I foresee it being possible to occur on the mobile end too.

-Josh

Sounds like you have it partially isolated. Next step would be to duplicate the problem then narrow it down by disconnecting the mentioned items one at a time while running the others. I'd start with the strobes.

i've ran into that problem with a vhf cdm1250. it was mounted in a console and someone put the relays in the console about 3 inches away from the radio and you can hear the clicks over the radio when transmitting and they are in sync with the strobes and wigwags. we moved the relays and put a noise filter on the power to the radio and it went away.

have a friend with a tahoe, used a Nextel on speakerphone, had the same clicking noise. Upgraded his phone recently and no more clicking.

I have run into this problem with some of the installs I have fixed for people. Check your grounding on the strobe power supply, and how they ran the power for the supply and the radio. What I have found, is depending on the grounding, the radio would echo the strobe pack over the air. When they talked, you would here the clicking of the strobes firing.
Another thing you might want to check is how the radio antenna wires are run. I had one where the antenna sheathing was rubbed off by bare metal, and was run along a strobe cable that was the same way. Every time he keyed the mic, all you heard was clicking.

Hope that helps.
SH

Make sure the EMI ground leads on the strobe supplies are grounded solidly. Many "installers" do not connect these for some reason. Also, if the radio's power is coming from a common point with the lighting power feed, the feed may be too small and the sound is from a voltage drop. You may need a larger common power feed and main ground.

As for the LEDs. We have seen many EMI problems with Whelen LEDs that have a self-contained flasher (POS Talon being the worst offender) cause clicking noises. Neither 911EP or Tomar's LEDs do this and besides, they are a better light.

RF Noises I've encounted have come from strobes and NexTels. Nextel is obvious. It is rapid clicking whenever the phone is doing something. Strobes would only be when the strobes are on and it is often silenced when you do as Jim suggests and actually ground the shield drain. Nobody ever does that for some reason.

I believe I've run into your problem before, radiouser.

Does the sound almost resemble a helicopter going "tick tick tick tick tick tick tick" in the background when you're talking?

What version of host firmware is in your radio? This problem is corrected in recent firmware revisions. I had an XTS3000 doing this with host version R05.51.00/DSPN06.04.12, but no matter what I could not clear up the problem with physical shielding/testing.

When I updated the firmware, the problem went away.

I still hear users with older firmware having this issue on a daily basis.