CB and Scanner antenna proximity

[outoffocus]

I currently have the Radioshack magnet mount scanner antenna on my car to hook up my Pro-95 to while out and about. I tried (and returned) the Radio Shack handheld CB w/ a CB magnet mount antenna. First thing I noticed with the CB is that it got a ton of car interference making me turn the squelch almost all of the way down. My scanner on the otherhand, even with the rubber duck pointing straight at the engine the way it sits has never gotten any noticable intereference from my car.

The second, not so major problem is that when I would transmit on the CB, it seemed like it would sometimes break squelch on the scanner channels around 152MHZ (sometimes I get quiet skips on the channel).

I wasn't sure if this had to do with the cheap CB itself, or the antennas. I had them both placed on my trunk about two feet apart. After looking at the mobile setups on the forum I've noticed many of you have a CB in your setup.

Any recommendations to avoid this problem in the future? I've been looking at some of the regular CBs that have built-in noise limiters and noise blankers. I'm assuming these help eliminate the noise from the engine and other electronics rights? A few specific CBs of interest are:

Cobra® 40-Channel NightWatch™ Chrome CB Radio with SoundTracker®
Uniden® Bearcat PC78 Elite CB Radio
RS Deluxe Chrome-Faced 40-Channel Mobile CB Radio with Weather Alert


Thanks for any info.

 

[N_Jay]

. . .. First thing I noticed with the CB is that it got a ton of car interference making me turn the squelch almost all of the way down. My scanner on the otherhand, even with the rubber duck pointing straight at the engine the way it sits has never gotten any noticable intereference from my car.

1) you turn the squelch UP to quiet a radio

2) AM (CB is much more susceptible to noise than FM (Most Scanner Bands)

3) Lower frequencies (27 MHz CB) is much more susceptible to typical automotive (and most other) interference than higher bands.

4) You scanner "Rubber ducky" is LEAST sensitive to signals in the direction it is "Pointed". It receives from the sides.

The second, not so major problem is that when I would transmit on the CB, it seemed like it would sometimes break squelch on the scanner channels around 152MHZ (sometimes I get quiet skips on the channel).

The CB is putting out about 4 watts. That is +36 dBm.
You scanner is listening for signals at about -90 to -110 dBm.

Wide-band noise from a transmitter is typically only -60 to -100 dB from the carrier.

I wasn't sure if this had to do with the cheap CB itself, or the antennas. I had them both placed on my trunk about two feet apart. After looking at the mobile setups on the forum I've noticed many of you have a CB in your setup.

Any recommendations to avoid this problem in the future? I've been looking at some of the regular CBs that have built-in noise limiters and noise blankers. I'm assuming these help eliminate the noise from the engine and other electronics rights? A few specific CBs of interest are:

Move the antennas further apart.

Learn to live with it.

 

[outoffocus]

Gee, thanks for all of the great information. What I was trying to say about the rubber duck is that it was much closer to the engine (the likely cause of the problem right?) than any other antennas. It did not have any interference even in the CB band. I should have changed the subject name, I was really trying to make sure buying a better mobile CB would help solve this problem. I took the CB and antenna back soon after trying them, therefore I don't have to live with it. I was attempting to ensure that I wouldn't have another problem on my hands with something that would be wired to my car this time.

Thanks again.

 

[N_Jay]

Gee, thanks for all of the great information. What I was trying to say about the rubber duck is that it was much closer to the engine (the likely cause of the problem right?) than any other antennas. It did not have any interference even in the CB band. I should have changed the subject name, I was really trying to make sure buying a better mobile CB would help solve this problem. I took the CB and antenna back soon after trying them, therefore I don't have to live with it. I was attempting to ensure that I wouldn't have another problem on my hands with something that would be wired to my car this time.

Thanks again.

Some of the noise could have been coming in the power connection if the CB was on car power and the scanner had batteries.

Just because the scanner was on the CB band, was it also set for "AM" signals?

Is the scanner a s sensitive as the CB is in that band?

 

[outoffocus]

Some of the noise could have been coming in the power connection if the CB was on car power and the scanner had batteries.

Just because the scanner was on the CB band, was it also set for "AM" signals?

Is the scanner as sensitive as the CB is in that band?

At the time both were running on batteries, the scanner now runs on car power sometimes, but I haven't noticed any interference at all from it.

The scanner goes to AM automatically when searching the CB band. With the stock antenna it was not very sensitive at all to CB traffic, rarely got anything unless very, very close to source. With the external antenna it has improved greatly.

I ran the handheld CB ran on an external antenna which seemed to transmit well, but I had to turn the squelch so far up that receiving probably wasn't much better than with it's stock antenna. I noticed little difference in the amount of interference between the stock antenna or the external one and it got slightly better if I set the unit in the back seat which wasn't very practical for use. That led me to believe it was likely the unit itself.

I also checked my spark plugs and wires to ensure they were ok and connected properly. Had horrible reception once when riding in someone elses vehicle and that was the cause.

After looking around at some "regular" CB's, it looks like if I decide to try another one, I would at least want it to have a noise blanker in it right?

Thanks.

PS: Didn't realize until re-reading my first response a few hours later that I had such a smart@$$ attitude, sorry.

 

[N_Jay]

PS: Didn't realize until re-reading my first response a few hours later that I had such a smart@$$ attitude, sorry.

No problem!

My Smart @ss attitude is kind of permanent. (Just some good old sarcastic humor that does not translate well to text).

 

[twolf816]

i used to have a pricy cb and antenna, it was maybe 2 and a half feet away from the scanner antenna and i never once had any interference from the scanner on the cb or vice-versa, your problem may be in the connections or the cb itself, if its an elcheapo, then your gonna have more problems. but check the connections

 

[Al42]

After looking around at some "regular" CB's, it looks like if I decide to try another one, I would at least want it to have a noise blanker in it right?

That would probably help, but there are good noise blankers and bad noise blankers. Good ones turn the receiver off during the noise pulse - which can be bad if there's enough noise. Bad ones cause distortion even when there's no noise.

What you really want to do is eleiminate as much noise as possible and to do that you have to find out where it's coming from. It can come from the wheels. If there's noise that only occurs when the car is moving, you need static eliminators for the wheels, which are almost impossible to find these days. They're springs that sit in the hub caps, with a little pointed thing that presses against the axle, so the noise on the wheels (and hubcaps) is grounded to the axles. If you have CV joints, and they're well-greased, that might not work. If the static is from the alternator (kind of a grinding noise), you want to stick a coaxial capacitor in the line coming from it. If it's from the ignition system (popping at idle, reving up when you give it gas) you'll need ignition suppressing wires, etc. You can also be getting noise from a guage (like the gas guage), the car's computer, the fuel pump if it's electric. You'll almost definitely get noise from the heater/AC blower.

If you connect the CB set to the car's electical supply, connect it directly to the battery - both wires - positive and negative. The battery is the biggest noise filter in the car - it's a dead short for noise. Connecting the positive lead to the battery and the negative lead to ground somewhere (or, worse, depending on the antenna cable for DC ground) is asking for noise no blanker will eleiminate. Be certain to fuse the positive lead - it's sitting on a source of hundreds of amps (read:heat if it shorts).

In modern cars there are about 2 dozen distinct noise sources, and you have to tackle each one individually. (a fender not grounded to the frame can be a noise source.) A noise blanker that can handle all of them at once is bigger than a CB set and it'll probably blank just about everything you want to hear.

 

[Voyager]

If you connect the CB set to the car's electical supply, connect it directly to the battery - both wires - positive and negative.

VERY bad advice. I saw a cement truck almost burn up (and toasted a new radio completely) because they did what you said, and they lost the ground from the battery to the chassis. When they started the truck, those 'hundreds of amps' went the only path they had left - RIGHT THROUGH THE RADIO.

That will teach them for going to our competitors to get radios! :wink:

While it may be good for eliminating noise, noise will be the last thing on your mind if your car catches fire and your radio fries.

If you insist on connecting the negative lead to the battery, AT LEAST FUSE IT! But, you are better off connecting it to a good chassis ground anyway.

Joe M.

 

[K5MAR]

If you connect the CB set to the car's electical supply, connect it directly to the battery - both wires - positive and negative.

VERY bad advice. I saw a cement truck almost burn up (and toasted a new radio completely) because they did what you said, and they lost the ground from the battery to the chassis. When they started the truck, those 'hundreds of amps' went the only path they had left - RIGHT THROUGH THE RADIO.

That will teach them for going to our competitors to get radios! :wink:

While it may be good for eliminating noise, noise will be the last thing on your mind if your car catches fire and your radio fries.

If you insist on connecting the negative lead to the battery, AT LEAST FUSE IT! But, you are better off connecting it to a good chassis ground anyway.

Joe M.

That's why you use fuses no higher than recommended. Even the 30 and 60 amp fuses used on the old Motorola radios will blow when starter current passes through them. All my radios (6, currently) are wired directly to the battery. Soon, I intend to install a battery isolator and second battery, so this won't even be a problem.

Mark S.

 

[Voyager]

If you connect the CB set to the car's electical supply, connect it directly to the battery - both wires - positive and negative.

VERY bad advice. I saw a cement truck almost burn up (and toasted a new radio completely) because they did what you said, and they lost the ground from the battery to the chassis. When they started the truck, those 'hundreds of amps' went the only path they had left - RIGHT THROUGH THE RADIO.

That will teach them for going to our competitors to get radios! :wink:

While it may be good for eliminating noise, noise will be the last thing on your mind if your car catches fire and your radio fries.

If you insist on connecting the negative lead to the battery, AT LEAST FUSE IT! But, you are better off connecting it to a good chassis ground anyway.

Joe M.

That's why you use fuses no higher than recommended. Even the 30 and 60 amp fuses used on the old Motorola radios will blow when starter current passes through them. All my radios (6, currently) are wired directly to the battery. Soon, I intend to install a battery isolator and second battery, so this won't even be a problem.

Mark S.

Most people don't think a fuse is required in the negative line. Really, it isn't unless you are going directly to the battery.

Mark, you should really consider a RigRunner. 8) It will cut down on a lot of wiring. Less chance of shorts, opens, Etc.

Joe M.

 

[cdenton]

CB Noise

I have a Cobra 25 WX NW ST with the Noise Blanker that I run on a
K-40 antenna along with my Pro 96 on a duck ... I have a TINY bit of ignition noise that I usually can't even hear over ambient. I hard-wired the CB and my amplified scanner speaker to the wires leading to the cigarette lighter just to see if I could get away with that install, and it works great.

I don't think those hand-held CBs are worth much - you want at least a dynamic mic IMHO. I only got the CB 'cause the scanner will only pick up CB Tx for a mile AT BEST, and I like to hear where the piggies (pardon me: heros) are hiding. I get great scanner Rx with the stock duck (urban area, though).

The down-side of good Rx on CB, of course, is that I can hear everything (I'd estimate that 90% of those Tx-ing on CB are jerks, idiots, in serious need of some therapy for their mommy issues, or some combination of the three).

As I still scan the rest of the CB freqs, I did have to lock out channels 18, 20, and 21 on the scanner or every Tx with the CB would bleed right over.