Vehicle mounted scanner interference

[nschaffer 0]

Does anyone know how to prevent interference on a scanner.

It only occurs when I turn on my emergency lights.

Thanks.......

[FFLieu 70]

It's probably feedback from the strobe pack. Is the pack located near the scanner?

[PEMO3 523]

Many things can cause this. First check and make sure you have a good solid ground both on the scanner and on the light pack. If all else fails a ground loop isolator may reduce the issue. You can get this at Radio Shack, most larger auto part stores and most radio install locations, e.g. Best Buy and the smaller shops.

Good Luck

[Guest 40-32 Comms]

First question- Are your emergency lights strobes and, if so, are the shield wires on the cables from the power supply to the heads properly grounded? By "properly grounded" I mean connected to chassis ground at the power supply end only, with as short of a jumper as possible, using soldered connections rather than cheap Radio Shack crimp on connectors.

Secondly,how are the devices powered? Ideally the ground wire should be as short as possible and connected to the body as close as possible to the piece of equipment. The positive lead should be powered directly from the battery, or from a high current distribution point, connected directly to the battery. Also, make sure that the vehicle has an adequate jumper between the battery negative and the vehicle body. If a lot of additional equipment has been added, the ground bond size may need to be increased.

Third, you need to figure out if the noise is RF being picked up through the antenna, or power line noise coming in through the power cable. If the noise goes away when you disconnect the antenna, then the odds are it is RF being picked up by the receiver. If that is the case, no amount of power filtering will help you. You will need to suppress the RF at the source (i.e. shielding strobe cables). If the noise does not correlate to the antenna, try running the scanner using an AC wall adapter plugged into an extension cord, removing it from the vehicle's power system. If that cleans it up, then a power line filter may help the issue.

[IzzyEng4 427]

Do you have your scanner hooked up to the fuse box inside of the car or directly to the car's battery? Any radio communication or receiving equipment should not be hooked up directly to the fuse box as that is your major source of electrical interference. What everyone here said about strobe packs and such are true, but if everything is hooked up through the fuse box and going through the alternator then you are going to get interference.

Now having that said, if you have your lights hooked up directly to the battery like the proper installation instructions suggest and also have your scanner hooked up this way, then you may / will still get some interference. Grounding is a must and also you may have to put in a ground loop isolator and maybe a choke in the power lines and also the ground lines of your scanner. If you connect your scanner up to the battery directly, then you negative should be also connected to the negative side of the battery. I would advise against grounding the equipment close to where it is mounted as that may not be the best grounding location in a vehicle.

The best place to start looking is the wiki on Radio Reference, ARRL and Strong Signal's websites and follow the way HAM radio operators and also professional communication installers set up radios in emergency and commercial vehicles.

Also another major thing to look ate is where your antenna is located and where the co-axial cable is running. If its is running near the power supply or even the cables to the strobes, that will also give off enough RF to drive you N-V-T-S NUTS!

If you have any pics how everything is set up now, it may help all of us here in trying to give you a better explanation how to try and correct the problem.