Have you ever tried to filter out alternator whine from your CB receiver? In severe cases, this whine is transmitted over the air. Even ignition spark noise is carried along the power leads. There are several power line filters available.
Radio Shack has them, Pyramid makes one, and there are other filter manufacturers in various current ratings. Some involve trying different wiring combinations to achieve the best results.
All require splicing them into the power cord: some work well, and others not at all. The best filters have been by Marine Technology Incorporated (MTI) until now. Magnum designed this filter because many drivers encountered a lot of noise on their CB rigs while the vehicle was running.
Although much noise comes in through the antenna, a great deal follows the radio power leads, and most radios don’t filter it all out. An alternator with a bad bypass capacitor across the windings will produce a high level of whine that increases in pitch as the engine runs faster.
Why replace an otherwise working alternator, and at what cost? Other interference can come from the vehicle’s computer, electric fuel pump, ignition system, electric fan, and more. There is no guarantee that a power line filter will work on some, all, or any of this interference.
It is determined on a case-by-case basis. In most cases, one test that gives a clue as to how the interference is getting into the radio is to disconnect the antenna. If you still have noise without the antenna connected, the noise is definitely coming in through the power source.
However, this doesn’t always mean that if the noise isn’t present while the antenna is disconnected, a power line filter won’t help. It has helped in many cases of this type, reducing the overall receiver noise.
To my knowledge, Magnum is the first company to manufacture a replacement CB/10-meter radio power cord. Up until now, it has been cut and spliced to add one of these in line. Now it’s a matter of replacing the power cord with this new gem.
My installer and I were the first to run tests on two different power filters for Magnum. One was a very expensive high-end amateur radio filter; the other was the unit they now produce.
To everyone’s surprise, the high-end filter worked poorly on all types of noise. The other filter worked even better than the MTI filter that we’ve stocked for years. The results were better than any of us had hoped.
The Magnum PLF-10 filters are a heavy-duty 7-foot long replacement power cord made with 14-gauge wire. They are equipped with a 10 Amp inline fuse, which you should replace with the one from your original power cord if it’s rated for less than 10 amps. There are two models available. The PLF-10C is a three-pin cord for Cobra, Uniden, Galaxy, and other similar radios.
The PLF-10M is a two-pin Magnum-type power cord. Both filters will handle 10 Amps, which is fine for all the radios they currently fit. The filter block can easily be mounted with screws or with double-sided mounting foam tape. These filters are available in many CB shops.
If your local dealer doesn’t carry them, have them contact their distributor or Magnum International; it’s low-cost insurance against noise.