CB Radio

When you get it all hooked up and working right, I'd be interested in hearing the details on where you put it etc. Maybe a few pictures if you have them.

I'm definitely going to install one in my Prius, but it's too new right now, I want to wait until I've run it through the first couple of dealer inspections before I start taking things apart (so if anything goes wrong with the car initially, they don't say I did something to it).

I'm still thinking along the lines of using my Prius FM radio antenna and the little multiplexer box I mentioned in my previous post (#11). That worked fine in my truck. Who knows what the antenna pattern is going to look like, but the Prius roof should make a nice ground plane. I suspect that due to the angle of the FM antenna, the pattern is going to be aimed upward a bit, but who knows...

Are you hearing any of the Prius hybrid electronics noise?

 

Take magnetic antenna. take one with kind of flat magnet and they come with quite long cables and you can feed it along the edge of 5th door.
For actual CB radio that Uniden 520 sounds like good choice.

 

Regarding using the prius antenna as a stealth CB antenna using a multiplexer/tuner box, you can't do it. See my edit on post #11. There's a little AM/FM antenna amplifier between the radio and the prius antenna base.

'Guess I'll have to figure something else out.

 

I just installed a CB in my girlfriend's 2008 Prius, option #3, and I'm getting a constant 2-3 bars of RF signal while the car is running. The signal strength varies slightly with acceleration and deceleration but "coasting" produces no signal. There is no sound coming from the speaker and I have not yet received a CB transmission to my knowledge. Will this thing work only on strong signals above 2-3 bars? Does anyone out there have experience with CB's in a Prius? The radio works fine in my Pontiac Bonneville.

 

a) what are you using for an antenna?
b) did you tune the installed antenna using an SWR meter?
c) what is the location of the antenna?
d) where are you taking DC power from?
e) do you have a good ground attachment on both the power supply negative lead (-) and on the chassis of the radio itself?

If you paid attention to all of the above during the installation, then try putting some clamp-on ferrite beads around the antenna coax and on the power supply leads. That will help keep noise from getting into your radio.

Ferrite bead - Wikipedia, the free encyclopedia

 

Antenna is a Radio Shack #21-994. I do not have a SWR meter. Antenna location is on the roof, rear right side 12" from the AM/FM radio antenna. Powered from an aux. 12 VDC outlet (cigarette lighter type) in the center console, using a plug-in connector. Power is factory grounded at this connector, the radio chassis is not separately grounded. Wouldn't that potentially cause a ground loop? Those are not good in LAN designs (I used to be a network design consultant).

 

Okay, based on that, I think it might be your antenna is mismatched. If it is severely mismatched, then you won't hear any CB signals from outside. You will eventually also degrade your transmitter if you are transmitting into it. If your radio is picking up noise from the car at 27 MHz (and other spurious frequencies), then that's what you're hearing instead. There are a couple of things you can do. If you have another CB radio, you can have someone transmit from a distance and adjust your antenna until you can hear the signal the loudest. You can also get an el-cheapo CB SWR meter on ebay for about 20 bucks. Channel 19 is the best channel to tune your antenna with, since it's roughly in the middle of the band.

In your LAN, multiple/indirect/combined signal returns will corrupt the data on your signal lines, but on the radio, the RF/DC will choose the path of least resistance to the car chassis. The antenna also uses the car chassis as a reference. It would be better for you to provide a local ground to the car chassis very close to the radio than to go through the wiring harness. If you have a (+) and or (-) connection through the (very noisy) wiring harness, then it's a good idea to loop the wire through a ferrite bead to keep noise from getting into/out of the radio.

 

C'mon, hog, go whole hog!

Trail an 80-meter longwire behind the car and stick a CW key onto the console!

 

Thanks for the help. I'll try a few things next time I get my hands on the car. The radio/antenna combination work just fine installed in my Pontiac Bonneville. I'll hunt down what's different in the Prius using your suggestions. Thanks.

 

Thanks for the tip on isolating the path of the noise. Next time I'm in her car I'll try your tip. I just assumed it was coming down the antenna. Is the RF filter a ferrite donut loop or do I need to buy a choke (coil) designed for CB frequencies?

 

It's a short antenna and that makes it very sensitive to changes in it's environment. You'll probably need to tune it. An SWR meter will also tell you if by chance, you have a short or an open in the antenna coax that you can't see.

My thought is this: If the only ground the radio has is through the wiring harness, and the antenna is referenced against the roof of the Prius, then the ground reference has to go through the wiring harness to the car chassis, then to the roof (that's a big ground loop). Any noise induced on to the ground wire as it goes through the wiring harness will be imposed on the RF signal, which is AM modulated, so you will hear it. When I finally get around to installing my CB radio in my car, I'll test that theory since I plan to power it through the plug in the center console like you did. It's just a theory, but it makes sense to me...

Good luck. Let us know if you resolve the problem and how it worked out.

 

Thanks Neo, you've been very helpful. This radio/antenna combination works just fine in my Pontiac Bonneville. I temporarily set it up there before installing it the Prius.

I need to do some additiional tests to isolate the path of the noise. Wa1hog (funny animation by the way) recommended disconnecting the antenna while the car is operating to see if the signal noise goes away. That would tell me if the noise is coming through the antenna or the power source. The signal meter (5 or 6 LED lights) are lit up to #3 during breaking and #2 most of the time, but there is no sound coming from the speaker until I turn the squelch almost to off, then the standard radio noise comes out. It's like someone is keying but silent. That's what I thought at first. I won't have access to the car/radio until this weekend and I will be testing everything that I can. I'll let you (all) know what I find. Thanks again guys.

 

I'm back. First of all, the stray radiation from the Prius' electrical systems is coming through the antenna. Disconnect it and the signal "meter" goes dead. The power is clean. The car's AM radio, tuned off-station, does not sound differently with the car's drive train operating or shut down. I grounded the radio's chassis using 2' of copper wire to the seat frame which is bolted to the car's chassis and no detectable resistance on the ohm meter. This had zero affect on the received RF interference.

I got a closer look at the RF signal "meter" on the radio. It consists of 5 LEDs labeled 1,3,5,9 and 30+ db. Normal cruising in the car is a solid 3db with occasional blinking of 5db. Breaking will cause 5 to 9 db bursts. Occasionally very rapid bursts of 30+ db will occur. I was not able to correlate these 30 db bursts with the operation of the car. Also noted, "coasting" the car (no energy moving on the drive train display) will stop the RF interference. Also note that the RF interference only shows up on the signal meter and does not produce any audible sounds from the radio.

Any suggestions out there on what to do next? Do you think that ferrite beads or donuts on the antenna cable will help? My next step is to contact Midland and Toyota for their 2 cents. I'm not hopeful that they will be of any help. I did contact a CB dealer's support line, out west somewhere, and he just said the problem was due to a cheap radio and he really doesn't deal with "4-wheelers".

 

If your antenna is not tuned and you have high VSWR, then the shield of your coax will have standing waves on it. You can try the clamp on ferrite bead around your coax to see if it helps (it can't hurt). I had a similar problem in the past and clamp on ferrites around the coax cable made a big improvement (but my problem was a transmit problem and not a receive one). RF is a funny thing, even when you have the proper test equipment, sometimes it's hard to find where the problems are. When you don't have any equipment, all you can do is try different things and see what works and what doesn't.

If filtering on the power supply lines doesn't work and the clamp on ferrite on the coax doesn't work, then Wa1hog is probably right - it's inherent in the radio. Some radios are designed better than others, have different filtering, shielding etc... inside. If the radio has poor front end filtering, then you get "mixer spurious" where other frequencies other than the one you want enter the radio through the antenna and are converted to the wanted IF, along with the signal you want. That shows up as a higher noise level.

The lack of sound from the audio is puzzling though.

 

Check this out! I installed the radio/antenna back on my Pontiac Bonneville... works great. I got stuck in crawling traffic this morning, on the way to work, next to a Prius. The radio registered lots of RF interference every time he was moving and we passed each other. A few days ago, as I passed one at high speed there was a noise blip, but I wasn't sure the Prius caused the blip. Now I'm sure. Prius' are a little hotbed of RF noise that deffinitely can affect CB radios.

Another response that I received yesterday from the editor of a CB magazine said to use a Wilson 1000 antenna and see what happens. He has no confidence in cheap compact antennas. But I don't want to throw more money at this problem based on a hunch or bias against inexpensive products. That's why I'm here. Has anyone successfully installed a noise-free CB in a Toyota Prius? And if so, what did it take to do it?