Need some help with whistling/squealing

[oneeyebear]

Just installed an old cb radio in my car, it is receiving pretty well but has a high pitch whistling/squealing sound that it is making... this seems to get louder with the rev of the engine and occurs when turning the key to accessory and while the car is on. Another important thing to note is that this noise was only happening on channels 1 through 5. Then I went through and put 3 more grounds in the system. This helped, now the noise is only on channel 4. Not sure what is causing this but channel 4 is not even listenable.

The 4 foot antenna is trunk mounted (hole drilled, not magnet or lip mount). the grounds I added were one from the coax (antenna end) to the inside of the trunk (I do not think the trunk door itself was actually grounded). One was grounded from the middle of the negative battery wire to under the dash. The last ground I drilled a hole into the back of the radio to the left of the antenna plug in spot and I put a ground wire from there to the negative side of the battery. I would say it is good but there is still that noise on channel 4. Any help is appreciated.

 

[mmckenna]

Just installed an old cb radio in my car, it is receiving pretty well but has a high pitch whistling/squealing sound that it is making...

How old a radio are we talking about? Was it working well when it was last used? What year/model car is it installed in?

Not to sound flippant here, but last time I turned on a CB, all I heard were people whistling, cussing and making weird sounds.

The grounds are a good start. I'd recommend running a ground from the frame of the trunk lid to the body.
Do the same with the hood.

Noises when the engine is running, or just in accessory mode could be numerous. Make sure you are powering the CB directly off the battery to eliminate as much of the internal electrical noise as you can. Many of the accessories on cars can make a real racket, and tapping into convenient power sources under the dash can often be problematic.

Fuel pump noise can be an issue on some GM cars. Some of the fuel injected cars have a fuel pump in the tank. There have been many reports of these generating noise. Ignition noise is a common issue with CB since it uses AM modulation, you can hear no end of racket from a vehicles ignition system.

As to why you are only hearing it on certain channels, that sounds a lot like normal CB racket to me, and without actually hearing it, I'm not sure what to tell you.

 

[oneeyebear]

Thanks for the quick reply and the great points you brought up

How old a radio are we talking about? Was it working well when it was last used? What year/model car is it installed in?

Well the radio is a Midland 77-118 I got it from my father-in-law after he past away. He hadn't used it in a good few years so I am not sure when it was last used. It is installed on a 2003 ford crown victoria

Not to sound flippant here, but last time I turned on a CB, all I heard were people whistling, cussing and making weird sounds.

I know what you mean haha but this is definitely not random cb bs, this is a noise that specifically only happens when in acc or when the engine is running... it is a constant noise and fluctuates in severity with acceleration.

I'd recommend running a ground from the frame of the trunk lid to the body.

This ground has been run it was the first one I listed, sorry if that wasn't clear.

Noises when the engine is running, or just in accessory mode could be numerous. Make sure you are powering the CB directly off the battery to eliminate as much of the internal electrical noise as you can. Many of the accessories on cars can make a real racket, and tapping into convenient power sources under the dash can often be problematic.

The unit is wired directly to the battery, no shortcuts here =)

Fuel pump noise can be an issue on some GM cars. Some of the fuel injected cars have a fuel pump in the tank. There have been many reports of these generating noise. Ignition noise is a common issue with CB since it uses AM modulation, you can hear no end of racket from a vehicles ignition system.

I'm glad you brought this up because I think it could be a fuel pump issue, when I turn the car to acc the fuel pump primes and I have noticed that the noise on channel 4 only last for the duration of the fuel pump priming. Any ideas on how to fix it if this is the issue??

 

[mmckenna]

So, noise that fluctuates with acceleration can be alternator noise. You can try moving the negative connection at the battery to a fire wall grounding point. This worked to fix alternator noise on a VHF radio in one of my trucks. I originally had the power directly off the battery. Turns out it didn't like have the negative wire grounded there. I moved it to the bolt where the battery is connected to the chassis. Sounds weird, but that worked.

Fixing the fuel pump noise can be difficult. First step would be to try running the power feed that goes to the fuel pump through a torrid. They look like big black metal donuts, and you should be able to find them at Radio Shack. Install it as close to the fuel tank as possible, if that is where the fuel pump is on those.
I'd also be sure that the power wire from the CB doesn't run along next to any of the existing wiring. This can cause inducted noise on the power feed to the CB.

Also, make sure your battery posts are clean and the connections at the alternator are clean. Corrosion at these points can cause all sorts of headaches.

Not impossible to fix this stuff, but it will take some work. This is always the interesting and challenging part of installing a radio in a vehicle.

 

[oneeyebear]

I did originally attempt to ground the negative connection on the battery to the firewall with no success. This was before the other grounds were added though so maybe it will like that change this time.

If it does turn out to be a fuel pump issue I think I might just leave it because 39/40 channels is satisfying for me, if it was an easy fix that would be different. Gonna keep trying, any more ideas let me know! Thanks

 

[oneeyebear]

Alright so I ruled out the fuel pump being the cause of the noise by turning it off with the kill switch and still the radio squealed. I also tried using a Toroid Choke behind the radio on the red power wire and that didn't help. I know it has to be something in the electronics just need to figure it out.

 

[oneeyebear]

So I found out that fuse 8 on my car is the problem which goes to
"Powertrain Control Module (PCM) power
relay, Coil-on plugs, Radio noise capacitor,
Passive Anti-Theft System (PATS)"

 

[oneeyebear]

Update: I stopped the squealing by taking the out all the wiring except for the antenna and I wired the power to the fuse box under the steering wheel and the ground to under the dash board. Bad thing is there is a new sound... it sounds kind of like a Printer/Morse code thing going on. Here is how I have it wired from CB red and orange combined to red to the fuse box, black to ground. ....there is the toroid choke on the red wire right before the orange and red are combined.

Can anyone confirm if this setup is correct?? should the red and orange be separate? ....also the radio does not turn on until the key is turned now.

 

[LtDoc]

There are two ways for 'noise' to get into a radio. One is by radiation through the antenna. The other is by conduction through the power line. Both can be 'cured', the difficulty of doing so depends on exactly what's making the noise to start with.
All noise is either AC or a 'pulse' of some kind (it amounts to it being AC just of very short duration). One way of stopping AC on the power line is by the use of an inductor (coil) in series with that power line. It isn't always effective. Another way is by 'directing' that AC to ground through a capacitor. (Capacitors won't pass DC so you would only be 'shorting' the AC to ground.) A combination of those two thingys is how most noise is 'neutralized'. (That torroid/coil is called a choke by the way.) If one 'set' of choke and capacitor doesn't 'cure' the problem, but it does reduce it a little, then add another combination of coil/capacitor until the noise is 'acceptable'! (Wrapping that power line through that torroid as many times as it will go is the way to do that. Add more wire to the power line if you have to.)
Stopping radiated noise from getting into the radio is a bit harder. The best way of doing that is by stopping the device that's radiating from radiating anything. Or, shield it (keep it in a 'box', sort of). that's were grounding comes in. Connecting all the body panels together in effect put's the noise producing thingy in a 'box', or shields the radio from it. I think GM's solution to fuel pump noise was to add a capacitor to ground from the pump's power line _AT_ the fuel pump (or as close to it as possible). It works (in most cases) but is a real PITA to do.
About those by-pass capacitors. The 'size' of the capacitor makes a difference, but the voltage rating makes a much bigger difference. The voltage rating should be at least 2 or 3 times (or more!) than the amount of voltage encountered. For a typical 12 volts system something like a 50 volt (or larger) capacitor is nice. That's to keep the thing from blowing up (literally). the capacitance of that capacitor is frequency related. Bigger usually means better, but don't get carried away with it! Something like 0.47 uF or larger ought to work fine. Don't think in terms of 'farad' sized capacitors! It's just not needed and is dangerous. Figure a capacitor as a chunk of 'comp-C'. The bigger they are the louder the bang. If a 1 farad cap ever goes off, you don't wanna be anywhere near it!
You are going to have such fun with all this!
Good luck.
- 'Doc

 

[oneeyebear]

Still havent figured this out. I did add a capacitor on the power line and it didnt help. Next thing i will try is attaching the body panels together

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[jfhtm350]

If you have another cb radio try it and see if it does the same thing or if you have a spare 12volt car battery laying around, charge it and hook the cb up to it without hooking the battery up to the car and see if the noise persists. Another option is unhook the coax cable from the cb and turn it on and see if the noise is still there. Do not key up the radio while you have your coax unhooked. Another thing is unplug the mic from the cb and see if it still makes that noise.

 

[oneeyebear]

If you have another cb radio try it and see if it does the same thing or if you have a spare 12volt car battery laying around, charge it and hook the cb up to it without hooking the battery up to the car and see if the noise persists. Another option is unhook the coax cable from the cb and turn it on and see if the noise is still there. Do not key up the radio while you have your coax unhooked. Another thing is unplug the mic from the cb and see if it still makes that noise.

Just to update this, I don't have an extra cb or car battery. Taking out the coax from the cb stops the noise. Taking out the mic from the cb stops it as well, but no radio chatter is transmitted either.

So far I am just learning to deal with it and avoid using channel 4.

 

[jfhtm350]

What kind of coax are you using? There should be some numbers on it. RG-58 etc. Have you tried to run the cable from the cb out the door away from the car and to the antenna like that? What about unhooking the coax just from the antenna?

Take a multimeter and set it to the resistance reading and touch the metal of the antenna with one probe and then touch the other probe to a good ground. There should be no reading. If there is a reading then the bushing that separates the antenna from ground is missing.

If you dont know your coax length should be in 3 foot segments. Such as 9 foot long or 12 foot long or 18 foot long (probably what you should have). That is not your problem just letting you know that. You say you have a 4 foot antenna and that doesnt sound like the right length to me and I would say your swr's are way off also.

 

[oneeyebear]

What kind of coax are you using? There should be some numbers on it. RG-58 etc. Have you tried to run the cable from the cb out the door away from the car and to the antenna like that? What about unhooking the coax just from the antenna?

Take a multimeter and set it to the resistance reading and touch the metal of the antenna with one probe and then touch the other probe to a good ground. There should be no reading. If there is a reading then the bushing that separates the antenna from ground is missing.

If you dont know your coax length should be in 3 foot segments. Such as 9 foot long or 12 foot long or 18 foot long (probably what you should have). That is not your problem just letting you know that. You say you have a 4 foot antenna and that doesnt sound like the right length to me and I would say your swr's are way off also.

The coax I am using is 15' of RG-58. Yes I have tried running it on the outside of the car away from the vehicle. I have not tried disconnecting the coax on the antenna end though.

There is good ground, no reading was given in the multimeter test.

I have not tuned the antenna I am going to get a meter soon but I didn't think the swr had anything to do with the noise.

 

[jfhtm350]

The coax I am using is 15' of RG-58. Yes I have tried running it on the outside of the car away from the vehicle. I have not tried disconnecting the coax on the antenna end though.

There is good ground, no reading was given in the multimeter test.

I have not tuned the antenna I am going to get a meter soon but I didn't think the swr had anything to do with the noise.

It shouldnt have anything to do with noise, but your liable to burn up the finals in the cb if your swr's are too high and your cb will get out further.

A cb radio setup needs these things: A decent cb radio, good coax, tuned antenna (changing coax length will affect swr's also), good ground on antenna mount.

If the noise doesnt bother you, then get your swr's check by a cb shop and just run it.

 

[oneeyebear]

Yea i will get them checked, i plan on getting a top load antenna as well when i figure out what one is good to go with

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[LtDoc]

Here are some things that are nice to know.

Feed line length makes no difference in SWR if the antenna is really tuned correctly. SWR is simply a way of telling how well impedance is matched. The ideal is 50 ohms. The further away from that 'ideal' the higher the SWR. The feed line length in multiples of 3 feet is pure hog-wash.
If you don't know what the SWR is (impedance match) then how can you make any meaningful changes of that impedance match (SWR)? It's a very good idea to know how to operate that SWR meter, not just the 'hands-on' part, but why this is better than that. Sorry, but the lowest reading isn't always the best.
Checking for 'shorts' with an ohm meter isn't very reliable with all antennas. Some will show a direct DC short normally. That does not mean that 'short' is a short at radio frequencies, all RF is AC. An antenna that uses an impedance matching thingy at it's input (usually a coil) will show a DC short. That DC short isn't always a short at AC.
This stuff really isn't as simple as it may seem...
- 'Doc

 

[KC4RAF]

+1 with Ltdoc

The length myth is still alive and well I see...

 

[oneeyebear]

Soo, decided to take apart my mic because it has channel changing buttons on top the up worked but the down button did not... when I got the mic apart about half of the wires inside were burned and the insulation was melted... it was pretty horrifying ...I am currently in the process of rewiring the mic the best I can...if this doesn't work I will just buy a new one.