CB Radio noise

Yesterday I saw some kind of city vehicle (1st gen Prius) with a large whip antenna mounted on the rear fender. I know other official agencies, cops and taxis are using Prius now. They all have some kind of two way. Maybe the problem is CB. I'm no radio expert, but I see lots of Prius with extra communication antennas.

 

Hi Subarutoo,

Those are most likely Ham Radio operators. Many Hams like the Prius.

Hams typically use FM for vehicle communications, which is more operationally resistant to vehicle noise. It was invented just prior to WWII for application in the American gas-engined tanks. Which had lots of ignition noise compared to Diesel tanks. This was done by a man considered the father of modern radio, even today, Edwin Howard Armstrong. His life story makes good reading for any newly minted engineer, about the evils corporations sometimes do. This history was the beginning of the downward slide of engineering as a profession in the USA. Which might be contributary to why USA car companies lost the hybrid car race, even after having USA engineers invent all the key sub-system technologies, and prototype hybrid cars largely funded by the US government.

CB on is much lower in frequency, where the noise levels are higher, and AM, which is much less resistant to noise. CB Radios cannot be had in remotable units. So, the power leads have to be run from a fuse box or battery all the way to the radio. This allows for extra pickup of extraneous signals.

Many Ham mobile radios can have the radio box remotely located. And in the Prius, the battery in the rear lends itself for very short power lead and antenna lead runs. Which cuts down on the noise pickup, reportedly. Then the control head is on a well shielded wire, which runs up to the front of the car.

Whip antennas are usually used for CB (27 MHz), but can also be used for the State Patrol long range low band VHF (approx. 40 MHz), or ham 6 meter band (50 MHz). The higher the frequency the shorter the whip antenna. Although a whip can have a coil attached which allows it to be shorter for its operating frequency. Even longer whips, usually with large plastic enclosed coils are used for Ham mobile short-wave operations (2 to 30 MHz).

 

You may not be able to -completely- eliminate the noise, however, steps to take include:
1. Twist your power cables (which are usually two wires side by side). The twist tends to cancel noise pickup.
2. Put a large capacitor at the power pickoff point in the vehicle to a -good- ground point and/or use a "noise suppressor" device (available at Radio Shack). These consist of a coil and capacitor to filter out the noise from the power source. They must be well grounded to work effectively.
3. Make sure the antenna cable is well grounded to the vehicle body at the antenna. Use "braid" for the ground connection if a wire is needed.
4. Make sure all grounds mentioned above are to the nearest point with a short direct cable - no coils in it.

 

Most departments just use a portable Handi-talkie, the media carry nextels.....

CB in a Prius, thats cool .. I used to sell CB radios & emergency lighting products...

I would think the ant would make the car look like a remote :lol:
I think they sell the on-gless cb antennas now, they kinda look like a celluar ant. They are good for the hwy.
As for noise, noise suppresser.. radio shack or Copper Electronics

I have found Copper to be a very good company to deal with & their resonably priced.... check them out here: http://www.copper.com/

 

Jose,
I just moved my CB from my Wrangler to my Prius. I was expecting some noise, but was surprised at the level that I hear. I just 'stuck' it in the car first to see how bad it was before I spend a bunch of time or money on it. My next step is to run a good power wire from the battery in the back to the radio in the front. I will first try shielded cable, like what we use for long audio runs in our sound system. It is 18ga, 2 conductor wire with a foil shield and a drain wire (good audio cable). This should all but eliminate any noise coming in through the power wire, but I fear that more noise is getting in through the antenna. Right now, I am using a decent (K40) magnet mount antenna. I might need to use a more permanent mount that can be directly grounded near the mast. I don't want to do that if I can avoid it. I don't like poking holes in body panels (neither the cars nor my own).

Incidently, our family radios (FRS/GMRS) work just fine, but that is due to their operating frequency and more importantly the fact that they are FM instead of AM.

I find it interesting to hear the sounds that the hybrid system makes, though. Once the battery is charged and the cruise control is leveled out, it stays relatively quiet. I can hear the throttle servo motors operate when I change the throttle position, and when I decelerate, it gets really noisy. I can dampen most of the noise by turning down the RF gain on my CB, but that greatly reduces my effective listening range.

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