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View Full Version : Help Needed w/ Cobra 29 ltd bt and dual firestik antennas



Oxymoron
09-21-2016, 10:30 AM
Hello again. I posted a thread a day or two ago but apparently the site crashed and the thread was lost. I'm running a Cobra 29 ltd bt radio with dual firestik mirror mounted antennas. Radio is hooked up straight to the battery with inline fuse and correct gauge wire. Mirror mounts are metal and grounded to the body of my van. I'm getting this weird laser like sound when on the highway. The sound increases when I accelerate. Could this be from me grounding the antennas? It's not letting attach the video I took. So I'll have to come back and edit the post with a link.
Ok got the link here :

https://youtu.be/32LWnQ1rpsc

222DBFL
09-21-2016, 11:15 AM
Something isn't right. Never heard a radio do that before. I thought you meant engine whine, I'm not sure what the heck that is you have there. I would make sure that the mounts for the antennas are well grounded to the mirror itself. Remove all paint to have bare metal on bare metal. Adding a ground wire from the antenna to the frame can make that grounding wire become part of the antenna so to speak. You want the mount itself to have a good ground. To accomplish this, all paint and such should be removed from where the mirror mounts attach to the mirrors. You will need some no-ox or some other rust inhibiting agent to place between the mirror mounts and the bare metal of the mirrors. Adding wire from the antenna to the frame doesn't always work like you would think it does. Especially with RF. I suggest you go back and make sure both antennas are put on the brackets correctly and that your coax harness is good and has no pinches or cuts or has been shorted somewhere. Also make sure all paint between the mirror mounts and the mirror itself is removed. And then make sure the antennas are installed correctly. Like I said, I've never heard the noise you are having. Definitely not good!! Hope you get it resolved!! Be safe and have a good one!!

Oxymoron
09-21-2016, 11:38 AM
Thanks for the response. I did remove a good amount of paint on the mirror frame and coated it with cold gal. Maybe I'll go back and just make sure but I was pretty thorough. Antennas are installed correctly as well as the coax. No pinches and I inspected the coax before installing to make sure there were no cuts. Maybe defective ? It was bought new but the seller didn't exactly go all out on packaging when he shipped it. May be damaged while in transport. I see your pretty versed when it comes to cb's. So the fact that you've never heard anything like this before makes me nervous. In hindsight. He might have dumped a defective set up on me. He was pretty vanilla when I inquired about certain things. Damn ebay.

222DBFL
09-21-2016, 12:53 PM
It would help if you had another radio to test it with. Just to rule that out as well. Unplug your coax from the radio and see if the noise goes away or if it stays. Don't try to talk on the radio without the coax plugged in, just use it for receive to trouble shoot. Are you receiving any other stations? And what is your VSWR (SWR) readings at the radio?? All kkkmt

Oxymoron
09-21-2016, 01:28 PM
I have received a couple other stations but the quality isn't great. I can't afford to buy another radio and don't know anyone with a radio. Does anyone know of someone in the Long Beach /Los Angeles or Orange County areas that is versed in these?

doughboy
09-22-2016, 11:04 AM
i agree if you pull the antenna wire out and its still there at least you know its some sort of ignition noise or something through the power wires

doughboy
09-22-2016, 11:04 AM
could also be the fuel pump

Oxymoron
09-22-2016, 11:20 AM
Ok thanks. I'm doing a turn around tomorrow or Sat going up North. I'll disconnect it and see what happens. I really appreciate the help.

SiCk_DiAbLo
09-22-2016, 12:56 PM
Sounds like alternator noise, or dist noise...Sometimes if ya add another fuse protector to the ground side...It could go away, cheap fix if it works...

Oxymoron
09-22-2016, 01:19 PM
I'll keep you posted.