Recommended frequencies Edit
Below 87.5 MHz (obscure)
- 87.5 to 87.9 MHz (lots of FM radios receive these ones, the recommended frequencies for in-vehicle use, not too many personal transmitters support these ones)
- 88.1 to 88.7 (The most commonly supported frequencies for personal transmitters, but these frequencies are taken in some locales)
- 88.9 to 105.9 MHz (Frequencies in-between on some transmitters, lots of these frequencies are unavailable in some locales)
- 107.1 to 107.9 MHz (the second most commonly used frequencies for personal transmitters, sometimes unavailable for personal use)
- 108.1 to 108.9 MHz (somewhat usable)
- above 108.9 MHz (obscure)
Personal FM transmitters serve as a workaround dongle for allowing some electronics equipped with an AM/FM receiver to support features and functions not native to the stereo itself.
Examples of applicationsEdit
- AM radio AM R
- Bluetooth audio receiver R
- Cordless headphones (headphones with integrated FM tuner) AM C CF F R T W
- hands-free cellular M N S
- HD radio receivers F* O R
- Internet radio F* I N
- Mac/PC desktop/laptop computers CF USB
- portable CD player C CF
- portable media players (e.g. iPod) CF
- Protection of playback equipment from watery environments, such as if a shower radio were to be used when hearing one's MP3 player, or non-waterproof satellite or HD radio system CF R W WP
- tape player (cassette/8-track) T
- turntables (45/LP vinyl records) A
- Satellite radio (XM Sirius) O R
- smartphones CF
- tablet computers (e.g. iPad) CF
- USB/SD card MP3 players CF USB
- voice advertising for soapboxes M
- cordless transmission of AUX in W
- other FM radios F** R
Note: some parameters are to be observed when using FM transmitters:
A NOT RECOMMENDED for use in automobiles, due to tactile force
AM a workaround for if an FM radio without AM support is being used
C Workaround for if a stereo doesn't support CD insertion
CF grants support for audio formats of computer files [e.g. MP3, WAV, FLAC, ATRAC (proprietary Sony format), etc.], such as using portable CD players on car radios with a CD player of their own that doesn't support MP3s, and also solid-state devices that support these file formats.
F this tactic makes it possible to hear FM radio stations on other frequencies, and a * indicates that this standard is largely a "mirror" of most analog FM frequencies. A ** indicates liability for "feedback" if the receiving frequency was the same as the transmitting frequency for this type of setup.
I supplies streamable content from the Internet.
M a microphone is also required for this application
O this device offers a future opportunity to decommission analog FM frequencies
R Addition of another radio standard
S Ensures more safety to the driver
T recommended for AM/FM radios without a tape deck (8-track/cassette)
USB externalizes USB support to radios that don't natively support it
W an optional measure for radios, even if they already have AUX in so as to ensure a "wireless" connection instead. Bluetooth can be an alternative to this in some cases.
WP An application where non-waterproof devices on the transmitting end are transmitting to a water-resistant AM/FM receiver (such as a shower radio)
Procedures on usage of FM transmittersEdit
Note that FM transmitters are largely recommended for AM/FM (sometimes FM-only) systems that don't have TRS connector or RCA jack AUX in, seeing as AUX inputs are to be used if they are available, since FM transmitter use can be troublesome depending on parameters, although first-time use of FM transmiters using AM/FM systems as a testbed even with AUX input availability is recommended to ensure reliability in future applications where AUX inputs are unavailable.
Use of FM on devices that don't natively support FMEdit
The opposite tactic of using an FM transmitter to use AM/FM radios without AUX inputs, is taking advantage of AUX inputs on stereos that don't internally support FM reception. For instance, things like inexpensive stereos made for iPods (iHome for instance) and MP3 players in general can simply take advantage of the built-in FM tuner on MP3 players, and also computer speakers generally don't internally support FM either, so they can be used in conjunction with computer-based devices such as PCs, laptops, iPods, smartphones, and other devices that supply radio reception to utilize the speakers. Sometimes FM transmitters can be tested for reliability using an iPod on FM reception mode utilizing stereos that don't internally support FM.
Special applications where both an external FM receiver, and an FM transmitter would be used would be special scenarios where USB/SD flash drive MP3 players with a built-in FM transmitter (but no headphone out port) were to be used with stereos that didn't have a built-in FM tuner.
- The relatively low power output of FM transmitters sometimes makes it unsuitable for use in some large urban areas because of the number of other radio signals. This is compounded by the fact that strong FM signals can bleed over into neighboring frequencies making the frequencies unusable with the transmitter. Removing a car's radio antenna has been found to significantly improve transmitter reception. Some frequencies below 88.1 have even been supported as reception frequencies on some car stereos, and some indegeneous FM transmitters even take advantage of those unused frequencies which are generally more reliable as no frequency below 88.1 is used for mainstream broadcasters in the US.
- Some models which connect via ports other than the headphone jack have no means of controlling the volume, which can force the sound to transmit out from the device harshly (causing over modulation, audio distortion and possible radio interference), or too low. In theory a device could use an automatic level control or audio limiter circuit to overcome this problem although there are few (if any) devices with such a facility available out on the market yet.
- When trying our FM transmitters for the first time, it is recommended to test them on any FM radio (outside of a car), and to nominate them for radios without AUX inputs when testing them on first available FM receivers (regardless of AUX input presence), since being lenient about parameters is the best approach to ensuring reliability in the beginning, as per these limitations.
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