CB Feedback thru Radio

[Brentbba]

Coming home from SnT yesterday I started getting feedback thru the radio speakers while I was transmitting. Weird hearing your own voice. I've had the CB installed under the radio for over a year now w/o issues. It's the intermitent problem. No humming and no issues receiving transmissions, just when I que up the mike and transmit.

Wondering if in the crammed in space behind the radio if I'm now getting some sort of crossover in the wiring between the CB and the radio head unit???

Outside of removing the radio, which we all know that have done it is a PITA, what options do I have? What could be causing the problem?

 

[Cruiserdrew]

Pretty standard stuff. Is the antenna in close proximity to the radio antenna?

The cases of cheap CBs often leak RF, so it isn't really surprising it would feed into your radio. My CB sometimes bleeds into my 2m (possibly the other way around), solved by leaving the CB off. Cheap radio=cheap receiver=cheap RF amplifier. Once you ditch the CB, you'll never look back.

 

[FJ40_owner]

Coming home from SnT yesterday I started getting feedback thru the radio speakers while I was transmitting. Weird hearing your own voice. I've had the CB installed under the radio for over a year now w/o issues. It's the intermitent problem. No humming and no issues receiving transmissions, just when I que up the mike and transmit.

Wondering if in the crammed in space behind the radio if I'm now getting some sort of crossover in the wiring between the CB and the radio head unit???

Outside of removing the radio, which we all know that have done it is a PITA, what options do I have? What could be causing the problem?

Check all your ground connections at the antenna, PL259 and make sure your power connection is tight and clean.

Is the CB antenna bonded to the frame?

If this problem just started then I suspect some of what I wrote is true. If always a problem then what Drew said most likely applies.

Good Luck

 

[Brentbba]

Uniden 520.
Wilson 5000 mag mount at the rear of the truck. Truck antenna down and Garmin Streetpilot 2730 hockey puck antenna mounted on the middle of the front dash at the windshield so not even close to each other.
Not many of us down here using 2m yet Andy.
Power connections I can check, but they are nowhere close to each other.
Will be a PITA to recheck the antenna connection at the back of the cb w/o removing the radio, but I'll see what I can reach.
Hope I don't have to replace the CB. I've got it mounted very nicely under the single din radio in the pocket and there's not much room for the wiring that comes with the aftermarket Eclipse head unit and the CB.

thanks for the suggestions.

 

[FJ40_owner]

So what has changed? Figure that out and correct it.

I run 11 and 2 meters side by side with no problem Both on at the same time. I can xmit on either radio with no interference.The CB is a cheapo radio Trash model, the 2 and 70 radio is a Kenwood D700. Ny antennas are about 4 feet apart.

Another thing to check. Try unplugging the remote speaker and see what that does.

Have fun.

JB

 

[Brentbba]

That's what's frustrating, I've changed nothing since the install.

Unplugging anything in the 80 is a PITA as tightly jammed as things are behind the dash and all but inaccessable w/o removal.

 

[Kofoed]

Check all your ground connections at the antenna.

Good Luck

x2 and try running a seperate ground wire from the chassis.

 

[Brentbba]

x2 and try running a seperate ground wire from the chassis.

It's a mag mount. Where would you connect a separate ground wire at the antenna?

 

[Bob_Garrett]

If you have a meter, check the SWR. An increase in reflected power can cause the problem. Should be less than 2:1. With the Wilson, you shouldn't have more than 1.5:1 or so.

Any splices in the coax? Does it change if the stereo is off?

 

[Brentbba]

There are two splices in the coax between the antenna and the radio. One about 6 feet from the antenna so I can remove it and the second up near the driver's seat that's an extension so I could reach the radio.

 

[Bob_Garrett]

Are the connectors pre-installed or did you do them yourself? Are the splices inside or outside? What brand of coax?

For starters, I would suggest buying some good quality coax and eliminating the splice up front. Use good quality connectors and be sure to install them correctly.

Since this started after a wheeling trip, my first suspicion is that a connection has loosened up or the coax was kinked somewhere, causing a partial break in the shielding.

 

[Brentbba]

One set of connectors my FIL and I installed. Did it right with the solder and all. Most of the length of the coax is what came with the Wilson 5000. The little 6 foot extension is Radio Trash. All the splices are inside the truck. After checking the connections, if the problem still exists, I may get one length of coax and eliminate one of the connections.

I'll definetly check the connections first as it started after some serious wash boards on the dunes. I was told my rear end was off the sand several inches, so the bouncing was good!

 

[FJ40_owner]

Coax Slice

I hope you did not splice the coax like a piece of wire and that you used 2 PL259's and a barrel connector.

If you spliced the coax like ordinary wire the Impeadance of your coax will change dramatically and your SWR may go off scale, in addition to most likely being the cause of your problem.

Having an improper splice invites spurious radiation to get into your radio and allows it to be emitted as well. All your RF is not being radiated by the antenna.

read up on the "characteristic Impeadance" of coax. For 11 meters it should be 50 Ohms.

I suggest you lose the splice and connect direct.

You loose probably 1/2 a db per connector also. So your ERP will be much lower as well as your ability to receive an already noisey week (in most cases) AM signal.

Good luck

JB

 

[Brentbba]

JB - I am using PL259's. Thought the solder comment would have given that one away. I know there are a couple of ways to do it and the solder method seemed more permanent.

 

[Kofoed]

It's a mag mount. Where would you connect a separate ground wire at the antenna?

Ground the radio chassis to the vehicle.