"What's the frequency, Kenneth??"

The small amount of power the iPhone FM transmitter produces, though, is often less than needed to produce clear, crisp, CDor MP3-quality music.

An FM transmitter adapter is the only choice for cars without USB or audio-input connections.

Play music through your car's stereo

If you have an iPhone, it might not transmit if you use a non-iPhone endorsed FM transmitter.

Look for the iPhone logo next to the iPod logo to ensure the unit will be more compatible with your device. Don't expect to save a few dollars to get a non-iPhone compatible FM transmitter and have to return it back to the store. A waste of time. This is also true for other iPod accessories. They may not with iPhone unless it is stated on the box.

Get a charge while you play

Choose an FM radio transmitter that also charges your iPhone or iPod while it is playing. Otherwise, the battery will drain while it plays. It may be worth it if you want to use your iPhone/iPod on long trips or don't want to keep charging your iPhone throughout the day.

When the iPhone/iPod is connected to the cigarette lighter (AC adapter), it can be recharged while the motor is on.

Selecting the best FM transmitter for your iPhone, iPhone 3G or iPod

The two most popular producers of FM transmitter car kits that work with iPhones and iPods are Belkin and Griffin.

EMOL.org just purchased a Belkin TuneBase FM for the iPhone. At this time, it was the only iPhone 3G compatible FM transmitter with both a cradle and charger. This model, released in August 2008, has nearly all the bells and whistles- wireless player, charger, dashboard mount and ClearScan. The ClearScan feature automatically finds the clearest FM radio station on your dial to tune in for the best reception. This model also has a Pro setting to improve audio and boost volume. Our review of this device is still pending as we test it on a long drive outside of the country soon. Check our FM ttransmitter reviews on this page.

How your iPhone or iPod becomes a radio station

When your mobile device is connected to an FM transmitter, either by cradle or cable, the music, videos and audio recordings are broadcast over FM radio waves. But the power is so low, that it only reaches a few meters. Just enough to transmit it to your car stereo.

The problem with FM transmitters

The biggest challenge with any FM transmitter is getting a clear sound to the car stereo. Most people complain about the reception. Since such a low power is send out from the transmitting device, competing signals for the same frequencies tend to overcome the weak output from FM transmitter.

When you drive near a phone cell tower, past a radio station, or other transmitters, your car stereo picks up those sounds and they become interferences. Features like ClearScan or SmartScan on the Griffin iTrip look for an open frequency to tune for best reception. But, drive a few blocks and someone else using the same or nearby frequency may interfere with your weak iPhone or iPod.

How to improve your FM signal

There are several suggestions to improve, or boost, the output of the FM transmitter. While there is no way to entirely eliminate the outside noise coming through your speakers, you can reduce the interfering broadcasts from invading your space. But, some areas may not be able to provide a suitable reception despite anything done.

Tune to the lowest radio frequencies. ClearScan and SmartScan often find available channel space on the lower end of the FM radio spectrum 87.9-88 FM. But, the car stereo dial needs to also be able to go that low. Some car models might not able to pick up the low end of the FM dial. Check for a list of your local radio stations to see what frequencies might be open. Stay away from high power stations, as they will drift into your space.

Remove your car antenna. While this may limit your other AM and FM radio reception, this will reduce your car from being an antenna for outside FM broadcasts. Why be an FM lightening rod? Some people have found this helpful to improve sound.

Turn off "Airport Mode" on your iPhone. This turns your iPhone into an iPod and shuts off all cellular and Internet activities. The iPhone has a "push" mode that check email, phone messages, voice mail and other apps. When your iPhone updates, it sends a signal from your phone to a nearby cell tower to look for new email and voice mail. When you are in a foreign country, or on an airplane and still want to use the device as an intelligent iPod, turning off Airplane Mode prevents additional cell or international charges. The downside: this shuts off all cellular and Internet activities.

Find an open frequency in your area and stick with it. Many of these devices now let you store one or more frequently used frequencies. This way you don't have to keep searching for a new frequency when interruptions intrude or the signal fades.

Boost your FM antenna. Some handy people have been able to increase the power of their transmitter by adding coil, additional circuits or extending the device's antenna. This means opening the case to add components.

FM Transmitters for iPhones and iPods:

These FM transmitters work on both iPhones, iPhone 3G and iPods. Be sure to check for the Made for iPhone logo to indicate the item is compatible with the iPhone.