feedback

[rickybobby]

Im having a problem with feedback, but only with the AC on. I have to turn the squelch about 3/4 of the way up to get rid of it. I an running a noise supressor in the positive wire. Im not sure what else i can do, but with the squelch that high i cant really pull in any incoming signals, so i cant run the AC when on a trail run, and it gets friggin hot in a rig moving at idle speeds

[rizzjc]

First thing I'd look at is where the power wire is running, or where the radio is location, or the antenna wire. Is it the AC, or the fan in general? I assume you mean NOISE, not feedback.

[rickybobby]

I guess noise would be a more accurate description. It is worst when the AC is on, but i noticed today it is there any time the engine is running. I tapped into the fuse box for power. Would it be better to run it straight from the battery?

[The DB]

Originally Posted by rickybobby

I guess noise would be a more accurate description. It is worst when the AC is on, but i noticed today it is there any time the engine is running. I tapped into the fuse box for power. Would it be better to run it straight from the battery?

Yes, the battery is a more stable power source. The electrical system is connected to the battery so you may still get some noise, but it should noticeably less if you hear any at all. Also run your radios power line as far away from anything with a motor as well. If the noise is coming from the electrical system this should help minimize it as much as possible.

Where is your antenna located? Is it on the hood as some people like to mount them or elsewhere on the vehicle? If the antenna is on the hood it is possible it is picking up the noise from the engine/AC. If that is the case I would consider moving it to the roof.


The DB

[Maniak]

I don't know if it really helps, but I always run a power and ground wire right from the battery to my CB (on hard mounted units).

I put the wires into a drill and twist them together too. Supposedly it helps cut down on noise (no idea if it really does but it doesn't take long to do it).

I actually run no squelch on the CB in the X and I have the RF gain turned 3/4 up.

~Mark

[Rick]

Another tip is to avoid running audio system power cables parallel to other wiring, to avoid inductive coupling.

[rickybobby]

Originally Posted by Maniak

I don't know if it really helps, but I always run a power and ground wire right from the battery to my CB (on hard mounted units).

I put the wires into a drill and twist them together too. Supposedly it helps cut down on noise (no idea if it really does but it doesn't take long to do it).

I actually run no squelch on the CB in the X and I have the RF gain turned 3/4 up.

~Mark

twisting the wires sounds easy enough, just have to get a 2nd color lol. The unit i have now doesnt have RF gain, but the one that is in the mail does. I decided to go with a better unit rather that buy a SWR meter for about the same cost. The new one also has noise filters built in which im hoping that combined with a re-wire will help me get rid of most of the noise

[rickybobby]

Originally Posted by Rick

Another tip is to avoid running audio system power cables parallel to other wiring, to avoid inductive coupling.

I will try to keep that in mind, but it amp be hard to do since the power cable for my amp also runs straight to the battery. If i drill a new hole that will allow me to keep the power wires for the CB and brake controller away from the amp wire for the most part though. for some reason they say that having the power wire for the brake controller too close to an amp power wire can cause problems too

[The DB]

Originally Posted by Maniak

I don't know if it really helps, but I always run a power and ground wire right from the battery to my CB (on hard mounted units).

Always a good idea.

Originally Posted by Maniak

I put the wires into a drill and twist them together too. Supposedly it helps cut down on noise (no idea if it really does but it doesn't take long to do it).

The twists act as an inductor, the distance between the wires acts as a capacitor. The problem is this only really works on an AC circuit, not DC power leads. Computer network cables are an example, as is some phone wire (not the cheap stuff). Computer networks and your voice operate on an AC circuit where the voltage constantly changes over time. This change reacts with the inductance and capacitance in a twisted pair of wires forming a natural filter which stabilizes the circuit. With DC the voltage does not always change (doesn't change really at all even when you factor in the noise that sometimes exists on a DC circuit), and thus there is no reactance so the wires never get the chance to work as a filter.

Originally Posted by Maniak

I actually run no squelch on the CB in the X and I have the RF gain turned 3/4 up.

Your choice, however turning your RF Gain down turns down the sensitivity of the receiver in your radio. The more you turn it down the stronger the signal has to be for you to receive it. The Squelch kind of does the same thing, except it only blocks the weakest signals, not turning down all of them. Because of this it allows you to turn it up just enough to block the noise (static) and not affect much else. The RF Gain attenuates all incoming signals, making all of them weaker as far as the radio is concerned. I only turn the RF Gain down when someone is right next to me over driving my system with to much power.

Originally Posted by Rick

Another tip is to avoid running audio system power cables parallel to other wiring, to avoid inductive coupling.

Yes a lot of car audio systems put a lot of noise into the cars electrical system, even the high dollar high quality ones. This can be helped by putting an electrolytic capacitor across the power leads as close to the audio system as possible, as well as any audio amplifiers you may have. Doing this with your radio may also help reduce noise some as the capacitors tend to stabilize the voltage for the device attached.

Also, for the record, you are talking about capacitive coupling. Inductive coupling happens when two coils are to close together causing their magnetic fields react with each other. Lengths of wire running together act somewhat like a capacitor, and thus capacitive coupling.


The DB

[Maniak]

Originally Posted by The DB

Computer networks and your voice operate on an AC circuit where the voltage constantly changes over time. This change reacts with the inductance and capacitance in a twisted pair of wires forming a natural filter which stabilizes the circuit.

That is where I got the idea.. I have lots of experience with Cat 3/5/6 (even 10 base 2 and 10 base t) and ran into all kinds of issues with network cables.. Interference has always been interesting. Of course, It didn't occur to me that I'm dealing with DC now so it doesn't help.. Oh well, it at least looks neat and makes it easy to run.

Your choice, however turning your RF Gain down turns down the sensitivity of the receiver in your radio. The more you turn it down the stronger the signal has to be for you to receive it.
<snip>

I went with lower RF gain only because I can never get the squelch set the way I like. If I turn it up some I end up with people being cut off when I'm listening to them. With the RF rain down a some and no squelch I can at least hear the entire broadcast. When I'm wheeling I do turn up the gain a little more since I don't mind hearing some of the noise. I just wish the squelch worked better.. It seems like it goes from nothing to way too much squelched too quickly (Cobra 29 with weather). No idea if that is normal or if having a peaked/tuned radio has anything to do with it.

Good info though. I know just enough about CBs to be dangerous..

[The DB]

Originally Posted by Maniak

I went with lower RF gain only because I can never get the squelch set the way I like. If I turn it up some I end up with people being cut off when I'm listening to them. With the RF rain down a some and no squelch I can at least hear the entire broadcast. When I'm wheeling I do turn up the gain a little more since I don't mind hearing some of the noise. I just wish the squelch worked better.. It seems like it goes from nothing to way too much squelched too quickly (Cobra 29 with weather). No idea if that is normal or if having a peaked/tuned radio has anything to do with it.

What squelch does is in essence set the minimum amount of signal strength the radio is sensitive to. Anything below that point you simply don't hear. Its main use is to set high enough to cut out the static.

If the static in your vehicle is loud you might consider doing some RF bonding. In most vehicles this will drastically lower the amount of static you hear, as well as let you hear those weaker signals that would normally be in static.

Originally Posted by Maniak

Good info though. I know just enough about CBs to be dangerous..

I was that way once... Everyone has to start somewhere.


The DB

[4x4junkie]

Originally Posted by Maniak

I went with lower RF gain only because I can never get the squelch set the way I like. If I turn it up some I end up with people being cut off when I'm listening to them. With the RF rain down a some and no squelch I can at least hear the entire broadcast. When I'm wheeling I do turn up the gain a little more since I don't mind hearing some of the noise. I just wish the squelch worked better.. It seems like it goes from nothing to way too much squelched too quickly (Cobra 29 with weather). No idea if that is normal or if having a peaked/tuned radio has anything to do with it.

Good info though. I know just enough about CBs to be dangerous..

It's not necessarily your radio, it's just the nature of how squelch has to work for AM signals (and is why I also use the RF gain on mine the same way you do).
Say you get into an area of high interference, and your radio suddenly bursts into static noise, you turn the squelch up higher, but you've now blocked out weaker signals, even once you've left the area of interference. With the RF gain down slightly, I'll usually still hear a weak signal (or the noise), it'll just be faint, in which case I can just turn it up a little if it's an actual signal I want to hear. If the signal isn't enough to pop open a closed squelch however, then I'd never be aware of it. (it's kindof like Squelch but with a very soft "threshold").

If the FCC had not had their head up their you-know-what, they would've allowed FM to be used on the CB band (like many other countries do ). The squelch circuit in a FM receiver is able to work on an entirely different principle than for AM (noise-quieting, which is what virtually all HAM VHF/UHF FM radios use, and is partly why they seem so interference-free. Such static noise on the band usually cannot trip the squelch open, only an actual signal can).

[rickybobby]

well, over 6 months later i found the problem, went to start the truck and the battery was dead. Had it tested and it was bad. New battery and all of the noise issues are gone. I can now turn the squelch all the way down and the RF gain most of the way up before i get too much noise

[The DB]

Good to hear.


The DB