| Author | Message | ||
     Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 285 Registered: 08-2003 |
I just installed a Cobra 75 WX ST CB in my disco. I have a Wilson "Little Wil" hooked up to it. My coax cable runs from the antenna directly above me, down the pillar, in the car through the rubber boot (behind and to the left of the brake), and then under my seat where the connector box is. I have noticed that when I turn my engine on, I can hear the the static increase/decrease with the RPM's of the engine. It isn't that bad, but it still makes it hard to hear some conversations. Is there anything I can do to stop this interference? The radio and antenna are tuned also. Channel 1 reads 1.4 SWR's and channel 40 reads 1.4 SWR's I have a feeling there's nothing I can do, but any suggestions would be greatly appreciated. Matt | ||
| Gabriel Guay (Gearhead) Member Username: Gearhead Post Number: 64 Registered: 04-2002 |
Mat, Try two things. 1. disconnect the antenna and see if you still hear the static rise and fall with the engine RPM. ( you may need to turn up the volume )If you do and I suspect you will, it's coming in from the power lead to the radio. If you don't, it's most likely from spark plug wires. If it's as I suspect, coming from the power lead. you can run a power cable directly to the bat or simply add a noise filter to the pos & neg leads. I personally like my radios to shut off when the key is off. I use a add a line fuse on the acc fuse and run that lead to a Hella 30 amp relay. Wire the positive lead direct from the bat with a fuse at the bat to the relay and the out put of the relay runs all my radio's with no noise. That's probably more trouble than you want to get into, so the other option is to buy a 20 amp noise filter from Radio shack or a CB store. Most truck stops have these as well as mail order like HRO or AES radio dealers. These typically cost around $30. I like not having a high amp draw on the Lucas box err I mean fuse box, so I always set-up a relay to switch power on & off directly from the bat. Hope this helps. By the way, mount the relay next to the bat not under the dash, that way when the key is off, you don't have a live wire into the cab. GG | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 286 Registered: 08-2003 |
Thanks Gabriel, I have the positive lead from the CB directly hooked up to my battery (with an inline fuse). The ground is hooked on one of the bolts holding down the front shock tower to the chassis. I wanted it this way so I could use it regardless if the car was on or not. Do you think just hooking up a Hella 30 amp relay would cause this to go away? Or should I go the other route and use the noise filters on the positive and negative leads? Thanks, Matt | ||
| Gabriel Guay (Gearhead) Member Username: Gearhead Post Number: 65 Registered: 04-2002 |
you should'nt get alt noise off the bat. You can try a noise filter but there is a reason for the noise. Is it a poping sound or just a electric motor noise. A poping sound would be plug wires. Alt noise is usually due to a weak bridge rectifier in th alt ( that's what changes the alt output from AC to DC). Aslo your ground should be on the bat @ neg terminal. This way the bat acts as a filter. The shock tower may not be a very good ground and if your running your wires close to the ignition, it will pick it up. The relay only alows me to make a separate power strip for my accories without loading the factory fuse box. If you don't have any luck grounding to the bat, let me know. We can look at other causes. GG | ||
| Craig Kobayashi (Koby) Dweb Lounge Member Username: Koby Post Number: 823 Registered: 02-2002 |
Matt- I thank Gabriel is right and what you're hearing is actually coming from the power source rather than the antenna assembly. If you connect the CB directly to the battery and run the ground to the common ground points close to the battery in the engine compartment you should be able to avoid most of the alternator noise you're describing. I've never had luck with noise when I've power and grounded CBs or stereo amplifiers aft of the firewall. | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 287 Registered: 08-2003 |
The positive runs along the back of the engine bay, where the back of the hood seals. I'll just run the neg. along side the positive, and hook it up to the neg. on the battery. The instructions said to hook the ground up to a good grounding point. So I figured the shock tower is bolted directly to the chassis, so that would be a great spot. I'll try hooking the ground up to the battery today or tomorrow. Almost forgot, the noise is just a light whining sound that rises and falls with the RPMs of the engine. When I press the gas and RPMs go up, it gets louder with it. It's not that loud, but it does interfere with recieving transmissions. There is no popping sound. Thanks Gabriel and Craig, Matt | ||
| Jamie (Rover_puppy) Senior Member Username: Rover_puppy Post Number: 673 Registered: 05-2003 |
Matt, My last CB did that. It was hooked up to one of the "hot" wires in my fuse box. It was AWFUL off road when I had to keep throttle high to retain traction in deep mud ruts. It screamed and whined terribly. If I could have let my hands off the steering wheel, I would have thrown it out the window. My newer CB bypasses the stock electrical system and goes to the battery. Whining and screaming stopped (even before I broke my CB). BTW, that tiny firestick external speaker fits perfectly in the D2 right above the cigar lighter. It is convenient, stays hidden, and is out of the way. Jamie | ||
| Craig Kobayashi (Koby) Dweb Lounge Member Username: Koby Post Number: 826 Registered: 02-2002 |
Matt, I'm 100% sure you're hearing alternator whine coming in through the power wires. Your ground point on the shock tower was probably fine for most electrical accessories and would pass a continuity test, but audio equipment like radios and amplifiers can be picky about stuff like alternator whine and ground loops. let us know how it works out after you relocate your ground. | ||
| Andrew Maier (Newman) Senior Member Username: Newman Post Number: 482 Registered: 04-2003 |
So Jamie, the only whining and screaming heard inside your truck is from you?  (kidding) | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 288 Registered: 08-2003 |
I hooked up the ground to the battery today, and it still whines a little. I have the wires too close to the spark plug wires, that's the only thing I can think of. Since it runs along the top back part of the hood, that just puts it too close to those wires. I guess I'll have to run it from the rubber boot I talked about earlier, around the front of the engine and to the battery. Do you guys think I should just find a constant power source inside my disco, and hook it up to that? I have a genuine LR CD changer under my seat that hasn't worked since I bought the car. Should I just hook it up to that power source? Maybe I'll just have to live with the whining sound. Matt | ||
| Craig Kobayashi (Koby) Dweb Lounge Member Username: Koby Post Number: 828 Registered: 02-2002 |
I think that if you find a power source inside the car you will find the whining will get worse. | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 290 Registered: 08-2003 |
OK, I'll just run the wires around the front of the engine away from the spark plug wires. Hopefully that will do the trick. | ||
| Jamie (Rover_puppy) Senior Member Username: Rover_puppy Post Number: 685 Registered: 05-2003 |
Andy, I'm sure it's the music - I get yelled at ALL THE TIME because I keep it so loud that I can't hear my radios or phones ring. oh well... | ||
| Gabriel Guay (Gearhead) Member Username: Gearhead Post Number: 67 Registered: 04-2002 |
Hi Matt, sorry to hear you still have alt whine. If your + & - are connected directly to the bat, you should be fine. Unless you hear poping static that increses in speed with motor RPM, That would be spark plug wires. Alt whine sounds like a high pitch whine. When you said static, it makes me think spark plug noise. That could be worn plug wires, power lead too close to plugs and plug wires. Cobra's are usually filtered internally for Alt noise but not all CB's have very good filters. Sounds like a filter might clean it up but, check that the Alt has good ground, good ground straps on the motor and good clean connection on the + lead of the alt. Poor connections here will make a noisy alt even though it still chages Ok. If all alse fails, a good line filter can be purchased at most CB shops, truck stops &Radio shack. Although don't expect anyone at Radio Shack to know anything about it. Seems they only sell toys, Cell phones and CD player these days. Sorry I coudn't pin point it for you. Let us know how you made out. GG | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 297 Registered: 08-2003 |
"Sorry I coudn't pin point it for you." No need to be sorry at all Gabriel. I learned a lot from you, Craig, and Jamie. I'm just glad you guys took the time to help. I did some freeway driving, and it sounds OK. I'll do some other test to see what setup works best. I'll also look into the noise filters if all else fails. I've got a good feeling that the wires are just too close to the spark plug wires. I'll move them soon, and see what happens. I really appreciate the help, Matt | ||
| Craig Kobayashi (Koby) Dweb Lounge Member Username: Koby Post Number: 833 Registered: 02-2002 |
Matt- to expand on Gabriel's point regarding different CB units. My Cobra 75WXST seems to have the gain set very high. I previously owned a Midland which had an adjustable RF gain. My 75WXST with its non-adjustable gain is extremely sensitive to ETC activity. By turning the gain down on my Midland radio, I was able to block the noise generated by the ETC system. With my Cobra I just have to put up with it or squelch up very high. I guess what I'm trying to say is that there are CB radios out there that can be tuned to suit your situation. You may want to investigate other radios if you absolutely cannot get the Cobra working. I love my 75WXST and have learned that some of its features are worth more to me than some of the deficits this stealthy CB does indeed have. | ||
| Josh Gorman (Jgdds) New Member Username: Jgdds Post Number: 39 Registered: 02-2003 |
Craig I have the same problem, but was told it was because I ran my power/ground leads through the rubber grommet on the pass side of the firewall where the ETC wires run. I was told to relocate and the problem would go away. Where do you have your power leads run through the firewall. Thanks, Josh | ||
| Craig Kobayashi (Koby) Dweb Lounge Member Username: Koby Post Number: 843 Registered: 02-2002 |
I have my power cables running through a grommet on the driver's side of the firewall. Interesting theory. I wonder if there are any ETC wires running near the driver's side of the firewall. | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 314 Registered: 08-2003 |
I routed the CB wires around the front of the engine today. I did a little testing in my driveway reving the engine, and there wasn't any noticable interferance. It sound a lot better now that the CB wires are away from the spark plug wires. Craig, I asked you some questions in another post about your tent cot. I have one more. Have you ever slept up there when it's been really windy? It gets pretty damn windy here in NV, so I'm a little curious what it would be like up there on a windy night. Thanks, Matt | ||
| Craig Kobayashi (Koby) Dweb Lounge Member Username: Koby Post Number: 865 Registered: 02-2002 |
I imagine that with the rainfly camping in windy conditions is not bad at all. When I was in Death Valley we only encountered 25mph winds that created a 30F wind chill... The tent was pretty quiet and definitely stable on the roof rack. With a rain fly I think it'd be warmer. I haven't been in super-windy (>50mph)conditions with the TentCot so I can't really say, but it can't be worse than any other tent. The only thing that I can think would be different would be air flowing under the TentCot, but if you're on a Thermarest I doubt even that would be an issue. | ||
| Darryll Mills (Emnat) Member Username: Emnat Post Number: 71 Registered: 11-2003 |
Matt, I have the same problem you had. I installed my cobra 75 today. Mounted the firestik antenna on the front rht of the ARB bumper. Ran the + power through the rubber hole next to the break then down to the front and then behind the winch to the battery. The - is wired into a ground stud next to the fuse box. I have a little whine with the car running and a BIG whine when I turn the A/c on. Do you think running the - to the battery will help?? What does yours sound like with the a/c on?? | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 323 Registered: 08-2003 |
Darryll, I would hook the neg. up to the battery. I have both wires hooked up to the battery, and it sounds better. Gabriel said (4th post from top) that the battery acts as a "filter." It seemed to work for me. I use to have my wires routed across the back of the engine, and they were too close to the spark plug wires. I now have them routed around the front and it sounds great. I haven't used my a/c in a long time so I'll check that and let you know. Did my answer to your "How do you test the SWR on a antenna??" post help? Matt | ||
| Darryll Mills (Emnat) Member Username: Emnat Post Number: 72 Registered: 11-2003 |
Matt Sure did, I am going to a truck stop tomorrow to see if I can find a SWR reader. I have turned the CB on but have not transmitted yet. I have chatter on all channels and some of it is FAR away. | ||
| Darryll Mills (Emnat) Member Username: Emnat Post Number: 73 Registered: 11-2003 |
Matt Something else I did was mount an on/off switch under the stearing wheel so if I ever want to kill the power to the unit I just flip the switch. | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 324 Registered: 08-2003 |
That sounds like a good idea. Where do you have the connection box mounted? I mounted mine under the seat on a croos bar. The plug comes out underneath my right knee on the side of the plastic box/compartment under the seat. I mounted the handset to the left of the cdl on that little "hump" so it faces up at an angle to make it easy to hear and read. Where did you put your handset? | ||
| Darryll Mills (Emnat) Member Username: Emnat Post Number: 74 Registered: 11-2003 |
I mounted the box under the seat like yours on the cross bar, than ran the cable behind the seat them back up next to the seat and the center console. The handset just lies next to the hand break for now. I might mount it some where but not sure yet. Next time you are in the truck run the A/c and let me know if the whining gets worse. | ||
| Craig Kobayashi (Koby) Dweb Lounge Member Username: Koby Post Number: 869 Registered: 02-2002 |
Darryll, FYI, the SWR has nothing to do with how well your antenna receives signals, so how much chatter you pick up is not a good indicator. SWR indicates how effectively your antenna and associated wiring is radiating the signal your CB transmits. The only effective way to measure this is by using a SWR meter. You can get a SWR meter at Radio Shack if you can't find one at the truck stop. | ||
| Darryll Mills (Emnat) Member Username: Emnat Post Number: 75 Registered: 11-2003 |
Craig Thanks I will be going to a truck stop today. If I can't do it there I saw one at Radio Shack for $30.00. Thanks | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 331 Registered: 08-2003 |
Ran the A/C, and there was no whining at all. Had no effect. | ||
| Darryll Mills (Emnat) Member Username: Emnat Post Number: 76 Registered: 11-2003 |
Matt I guess I will have to change my wires out to get rid of the whine. BTW I had the antenna tuned today so I can start using it. | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 350 Registered: 08-2003 |
How did it work out Darryll? Still have the whine? | ||
| Darryll Mills (Emnat) Member Username: Emnat Post Number: 78 Registered: 11-2003 |
Matt Still have not changed the wire, I was called out of town so have not been able to get to it. I hope to get to it this week, I also want to get out on some trails soon just have not had any time. | ||
| Matthew A. Barnes (Discoveryxd) Senior Member Username: Discoveryxd Post Number: 353 Registered: 08-2003 |
Yah, I know what that's like. When you get it taken care of, let me know how it turns out. |
