|Tuning in an FM signal isn't the same as tuning in an AM station. For one thing, FM transmissions are line-of-sight. That means that obstacles between you and the transmission that you're trying to receive can block the signal and leave you with poor reception. A hill, big buildings - all these things could get in the way of your FM reception and could even leave you hearing the effects of multipath interference. You get multipath interference when a signal meets an obstacle of some sort, let's say a mountain. Depending on the signal strength and the conditions of the mountain, the signal might get absorbed or reflected. You'll end up with poor reception, as the different paths taken by the reflected signal arrive at your receiver at different intervals.|
Fortunately, multipath interference usually happens when you're in your car, so it tends to be pretty easy to overcome by finishing your drive around a city loop or the base of a mountain. Still, some people might experience all sorts of interference at home as well, and that's where a better antenna might do the trick.
Most portable radios have whip, or telescoping antennas that work fairly well when the radio is set close to a window and away from sources of significant interference. If you always have your whip antenna fully extended, however, you may not be getting the reception you're expecting. Sometimes you'll get better reception for a certain station when the whip antenna isn't fully extended. Occasionally, to pull in the cleanest signal you'll have to go by trial and error - experimenting with extending the antenna to different lengths, and also pointing it in different directions (only if your antenna is designed to rotate, of course). Sometimes moving the Radio near a window will help receptionů
If playing around with the antenna and moving the radio around doesn't improve your reception as much as you like, you may need to move toward a more powerful indoor or outdoor antenna. An outdoor unidirectional antenna, also known as a yagi, is the most powerful option. A yagi looks like rooftop TV antenna, and is ideal for tuning in distant stations, or for reducing multipath interference. By aiming the yagi at the signal you want to capture, you can basically tune out most types of interference - be it from competing signals, buildings, or a weak signal.
Another alternative in outdoor antennas is an omni directional FM antenna. Though omnidirectional antennas might not reduce interference as much as unidirectional antennas, their ability to pickup stations cleanly from all directions make them a good choice if you're not aiming for a specific, distant station.
If you don't have access to the outside of your building, you might want to go for a good dipole antenna. T-shaped, these antennas offer pretty decent reception indoors, and are also easy to hide if necessary.
Which ever antenna you chose, be sure you're not getting more than you need. Sometimes just switching to mono rather than stereo or putting a portable radio in a different spot can improve reception - you might also be lucky enough to improve your reception by just attaching a simple wire to the external FM antenna jacks. If these quick and easy solutions don't work for you, however, or if you can hear a signal in your car but not when you go inside, you may want to consider one of the antennas mentioned here.
Ref: Crane Radio Company