cb transmission

[LawnCowboy]

Maybe a little off topic but curious as to why when using a mobile cb in my vehicle, my tx comes across on the radio speakers! Whether I'm listening to a cd or radio.... Know it's happened in the past off and on but recently seems it's constant. Volume on radio has no effect... if I turn off the radio that cures the problem. Would like to run with both on though at times!

 

[jonny290]

some diode in your system is rectifying the RF and turning it back into audio

google "bypass capacitors" and you should be able to get a start on the situation.

 

[CherokeeKid]

Easy answer. Its a couple things.
1. Ground your antenna system better
2. get your equipment tuned and aligned
3. if running a linear, learn to live with it(sometimes if your running enough power(over 200 watts) your speaker wires will act as an antenna and the modulated RF in the air is converted to audio via the speaker!)

 

[LawnCowboy]

hmmm, ok... I'm thinking it's more along the lines of the bypass capacitor idea... don't have a linear and 99% sure my antennas are grounded well and the cb is tuned to the antennas.

 

[kb2vxa]

That's a fairly unusual problem unless you're fibbing about the leenyar. (;->) Seriously, is the stereo a 0.5 gluteus maximus after market installation or stock? If the former and likely messed up but working the installers just slap and shove the mess out of the way so it looks nice until you look up under the dash, you'll have to clean up the sloppy wiring. If it's stock I really don't know what to tell you, the factory is pretty good about wiring.

Slapping in bypass caps willy nilly will get you nowhere, do you really know what you're doing? If there's ANY doubt in your mind ask for help from a local ham or radio club. No, the average CBer is NOT technically skilled except maybe skilled in BS but sometimes you get lucky.

If that's OK you may have radiation from the coax likely from a bad ground or a ground that's not a ground, maybe more sloppy wiring. There are many things that can cause common mode currents on the outside of the coax and too much to go into here so check the grounds and routing, it may be just that obvious.

"...and 99% sure my antennas are grounded well and the cb is tuned to the antennas."

That backward comment makes me 99% sure you're in the dark, go seek some help. Somewhere along the line you'll find out you tune the antenna, not the radio. As for it there's "no user serviceable parts inside" so keep your fat fingers and the infamous golden screwdriver out of it. Sarcasm admitted, no insult intended, just fed up with fixing the mess left behind by the Saturday afternoon driveway mechanics.

 

[LawnCowboy]

lol Ok, well... thanks for the input... yep, I don't claim to know all there is so that is why I was asking... I probably have a little more knowledge on the scanner subject but am by no way an electrical engineer or guru on most subject matter here and was searching for an answer to a topic somewhat still related to communications and possibly the antenna system if not the radio.

Ooops, pardon my mistake for the mixed up sentence... yes, I believe you are right, antennas are tuned to the radio... I was the one that did it and yeppers, I'm the one that worked on the aftermarket radio in the vehicle too. Possibly the wires close to something I guess could be a possible place to look.... sounds simple enough for this driveway mechanic. Would also maybe explain why it would happen (as stated originally) occasionally in the past but constantly now. Wires have moved?

All I was stating in last post was that I didn't have a linear (no winking about it - just want to communicate economically on the road during trips - w/o the bleed over from my fm radio!) and I was fairly certain because of antenna tuning and also double checking grounds on the antennas that grounds weren't a problem in that area... perhaps I will double check the ground to the radio? Just looking for some non-technical ideas.... If it's technical (possibly a radio problem) then I guess I'll have to buy something newer? I'm fairly detailed but even the most detailed person misses something once in a while. Thanks for everyone's help in reading and trying to figure it out. Sorry if I leave a mess behind... lol

 

[kb2vxa]

Hi again,

What's a lawn cowboy? Grazin' in the grass, can you dig it?

Before this Laugh In gets out of hand let me explain you're asking too much of me. I'm not there to see the mess and I can't master the psychic art of remote viewing. This really requires a hands on approach by someone familiar with the problem so like I said go for help. Then again just monkeying around might fix it, works for me more often than not.

Consider yourself lucky, a trucker friend had a weird experience with a CB that drove the digital dashboard nuts and killed the engine. That's not good while driving down the Interstate looking for Smokey.

Now was my subtle humor lost on you? Maybe you're too young to remember the 60s and Rowan and Martin but eeeeh, you should recognize a song by The Fifth Dimension. (;->)

 

[CherokeeKid]

I am actually an electronics tech for a local company. I am an avid 11 meter DX enthusiasts. Ive delt with this problem of bleed over TONS of times. 75% of the time its a bad ground. Whats the VSWR? What coax are you using? What kind of radio is it? Did you get the radio aligned? Peaked? Clipped? Is the radio stock? How old is your car FM/AM radio? Many times car stereo systems/speakers and wires are just not of good quality and bleed over is common. Its part 15 of the FCC. What KIND of antenna are you using and where/how is it mounted. Tell me these and Im sure we can narrow it down further.

 

[kb2vxa]

"I am an avid 11 meter DX enthusiasts."

You're a baaaaad boy! If you want to work DX get a ham license and work the world, legally. Peaked? Clipped? Oh brother, one of THOSE.
BTW, how many of you are there being you're an "enthusiasts"? (;->)

 

[CherokeeKid]

"I am an avid 11 meter DX enthusiasts."

You're a baaaaad boy! If you want to work DX get a ham license and work the world, legally. Peaked? Clipped? Oh brother, one of THOSE.
BTW, how many of you are there being you're an "enthusiasts"? (;->)

1st: Tell me something I dont know
2nd: I am the only enthusiast, lol
3rd: I dont get on the HAM bands cause they are better people then me (like you) and the rest of the CB crowd
4th: STICK TO THE QUESTION AT HAND, and get off the ham wagon ASAP, itll make you a bitter old man whos hobby is gonna die with them.....

 

[klogd]

cherokee kid has the right advice.

One thing about transceivers in general.. they need to be wired directly to the battery, both + and -. Another this is the quality of your vehicle chassis as an image plane for your CB antenna. This is improved by whey they call bonding using braided copper straps. This bonding helps you get out better, and helps prevent RF from getting into vehicle electronics, and reduces RFI from your engine to your CB receiver. The bonding becomes more important the bigger leenyar you run.

If you still hear yourself in the stereo, then you need to grab some split bead ferrites like 31 or 43 mix, take the radio and and experiment placing them on various wires on the stereo and you might find what wire(s) are bringing in RF into your stereo. The ferrites absorb radio energy.

 

[CherokeeKid]

Real quick: the braided straps dissipate RF as it travels across them, and increasing the ground plane is also not a bad idea for tx. Check your coax too, RG-58, RG-58/U, RG-8, it all leaks quit a bit. Get some LMR-400 and Ill bet that will solve the problem. Also, if the radio HAS been clipped, reattach the resistor. And get the radio on a scope to check for any splatter/over-mod. Some hillbillys get inside these radios, turn pots till the needle on the meter is in the red and close them up.... Then you got a super whammy, whack packed, peak and tune for only $50!?!? and as we, i mean I, say "ALWAYS CHECK YOUR SWR!!" bleed over is sometimes a dead giveaway that your SWR is sky high.It may be from a bad antenna ground or bad antenna mount ground depending on your antenna. good luck

 

[rvawatch]

back to the non technical answers like you asked....

do you have any other audio equipment (axillary players, subwoofers, etc) connected to your head unit? Where do you have your coax cable run? Make sure your cable isn't crossing any wire (or near for that matter) that connects to your stereo. try taking out the wiring for your antenna and have it in hand going straight from the cb to the antenna (without having the wiring snaked around the car. it really might just be a simple fix. mine does this from time to time since i have my coax next to a sub amp. sometimes it bumps against it and i hear myself blaring across my own speakers. a simple push of the cable fixes it all perfectly.

as the marines say... kiss. keep it simple, stupid



at least until you know it's something more complicated.