Radio Signal Amplifiers
Many people think they need a signal amplifier because they experience noisy radio reception, and in reality, the problem may be noise induced by the vehicle itself, or due to improper installation of high-powered audio amplifiers or equalizer equipment.
When installing ANY audio equipment, it is important to run a separate heavy-duty ground (–) wire to the battery, and not just attach negative wires to the vehicle chassis. If you install a signal amplifier on a vehicle that has an electrically noisy electrical system, you will invariably make the problem worse. It is therefore very important that you correctly identify the problem before you attempt a "solution". This article (and those referenced with the hyperlinks) hopefully addresses all possibilities.
BASICALLY: You need a signal amplifier if the radio station you want to listen to is weak, or fades in and out while the vehicle is standing still with the engine off, AND the CD / DVD / iPod (aux jack) is functioning properly regardless of whether the engine is on or off. You need to run a separate heavy-duty ground wire to the battery negative terminal if your CD /DVD / iPod (aux jack) is picking up hum, static, or high-pitched whining with the engine running.
UNFORTUNATELY, some of you have correctly identified the problem as a weak radio signal in a fringe area, or not enough gain from a shorter antenna you might have installed to make your vehicle more "bush-worthy", but have attempted to fix that problem with a BOGUS solution; a cheap antenna "amp"
HUNDREDS OF THOUSANDS of these units are being sold by sellers all over the Internet, No doubt, many of these sellers are not aware that the product is a ten cent P.O.S. that CANNOT POSSIBLY WORK, doesn't work, and contains no components that could be called "signal amplifier" or "signal booster" in any sense of the word.
Many people have devoted hours to installing this thing, and some have convinced themselves that it made a difference because they invested so much effort into its installation, but it is ABSOLUTELY IMPOSSIBLE that the device can amplify a radio signal, because there are NO TUNED CIRCUITS, and absolutely NO SEMICONDUCTOR COMPONENTS in the device at all.
If you installed a short radio antenna or rubber "trail antenna" on your vehicle to prevent it thrashing about as you drive on back-woods trails, or are simply in or travelling through a fringe area where your radio reception sucks, there IS a solution to the problem, but it ISN'T the $3.89 piece of crap advertised on eBay, which is the same piece of junk you can get from a host of other sellers on the Internet.
A signal amplifier has nothing to do with eliminating noise caused by the alternator or other components in your vehicle. An RF (Radio Frequency) signal amplifier is designed to operate on a specific band of frequencies, and it requires tuned circuits and transistors or tuned circuits and integrated circuits. This is the least of what you should expected to find in the "amplifier" built into the aluminium tube
When you open these up and look inside you will see
a 10uFd, 25WVDC capacitor and two resistors on a circuit board.
While this circuit might filter out some alternator whine, it is definitely NOT an amplifier of any sort. In addition, the Working Voltage (25 Volts) on the capacitor is much too small; voltage spikes on the vehicle's electrical system could cause the capacitor to short out, and while in this circuit, a shorted capacitor is unlikely to start a fire, your radio reception if this happens will suddenly be next to nothing.