What is the best FM frequency for a transmitter?
What frequency range is used for FM radio transmission? A. Very Low Frequency: 3 kHz to kHz. B. Low Frequency: 30 kHz to kHz. C. High Frequency: 3 MHz to 30 MHz. D. Very High Frequency: 30 MHz to MHz. E. None of the above. Answer: Option D. Mar 18, †Ј The FM broadcast band, used for FM broadcast radio by radio stations, differs between different parts of the world. In Europe, Australia and Africa, it spans from to megahertz (MHz) - also known as VHF Band II - while in the Americas it ranges from 88 to MHz. The FM broadcast band in Japan uses 76 to 95 MHz.
The FM broadcast band, used for FM broadcast radio by radio stations, differs between different parts of the world.
In Europe, Australia and Africait spans ranbe Americas it ranges from 88 to MHz. The International Radio and. Television Organisation band in Eastern Europe is from Some other countries have already discontinued the OIRT. If you want how to make your own website that makes money to hear your broadcast, or at least as many people as possible, use the 88Ч MHz band.
Audio distortion: 0. We test them in the open real by ourselves. Hello Willard, you could connect a Mic or some audio equipment to the FM transmitter directly for Drive in service, any help needed, please email us freely at support retekess.
Sign In. Close Menu. What is the best FM frequency for a transmitter? Some other countries have already discontinued the OIRT band and have changed to the If you want everyone to hear your broadcast, or at least as many people as possible, use the 88Ч MHz band, that's where all the commercially made, personal radio receivers work and all the commercial broadcast radios work.
Pls eange the type as you need. If you want to get more information, pls email us to support retekess. Where to buy FM Broadcast Transmitter? Oct 30, Oct 31, Willard Delaney. Sep 19, Sep 21, Leave a comment. Chat Now Inquiry.
A typical example is:
If 50 Watt ERP is used, it's very likely that 20 miles of range will be achieved. This is because 50 Watt ERP is ample power to propagate a strong signal 20 miles. If 1 Million Watts of power is used, it is very likely that signal will only propagate just over 20 miles. This because the .
FM broadcasting is a method of radio broadcasting using frequency modulation FM. Invented in by American engineer Edwin Armstrong , wide-band FM is used worldwide to provide high fidelity sound over broadcast radio. FM broadcasting is capable of higher fidelityЧthat is, more accurate reproduction of the original program soundЧthan other broadcasting technologies, such as AM broadcasting. Therefore, FM is used for most broadcasts of music or general audio in the audio spectrum.
FM radio stations use the very high frequency range of radio frequencies. Usually The frequency of an FM broadcast station more strictly its assigned nominal center frequency is usually a multiple of kHz. In most of South Korea , the Americas , the Philippines and the Caribbean , only odd multiples are used.
Some other countries follow this plan because of the import of vehicles, principally from the United States, with radios that can only tune to these frequencies. In some parts of Europe , Greenland and Africa , only even multiples are used.
In the UK odd or even are used. In Italy , multiples of 50 kHz are used. In most countries the maximum permitted frequency error of the unmodulated carrier is specified, which typically should be within Hz of the assigned frequency. There are other unusual and obsolete FM broadcasting standards in some countries, with non-standard spacings of 1, 10, 30, 74, , and kHz. To minimise inter-channel interference, stations operating from the same or geographically close transmitter sites tend to keep to at least a kHz frequency separation even when closer frequency spacing is technically permitted.
The ITU publishes Protection Ratio graphs which give the minimum spacing between frequencies based on their relative strengths. Frequency modulation or FM is a form of modulation which conveys information by varying the frequency of a carrier wave ; the older amplitude modulation or AM varies the amplitude of the carrier, with its frequency remaining constant. With FM, frequency deviation from the assigned carrier frequency at any instant is directly proportional to the amplitude of the audio input signal, determining the instantaneous frequency of the transmitted signal.
The maximum frequency deviation of the carrier is usually specified and regulated by the licensing authorities in each country. Random noise has a triangular spectral distribution in an FM system, with the effect that noise occurs predominantly at the higher audio frequencies within the baseband. This can be offset, to a limited extent, by boosting the high frequencies before transmission and reducing them by a corresponding amount in the receiver.
Reducing the high audio frequencies in the receiver also reduces the high-frequency noise. These processes of boosting and then reducing certain frequencies are known as pre-emphasis and de-emphasis , respectively. The amount of pre-emphasis and de-emphasis used is defined by the time constant of a simple RC filter circuit. For stereo, pre-emphasis is applied to the left and right channels before multiplexing.
The use of pre-emphasis becomes a problem because of the fact that many forms of contemporary music contain more high-frequency energy than the musical styles which prevailed at the birth of FM broadcasting. Pre-emphasizing these high-frequency sounds would cause excessive deviation of the FM carrier.
Modulation control limiter devices are used to prevent this. Systems more modern than FM broadcasting tend to use either programme-dependent variable pre-emphasis; e. Pre-emphasis and de-emphasis was used in the earliest days of FM broadcasting. Long before FM stereo transmission was considered, FM multiplexing of other types of audio level information was experimented with.
These FM multiplex transmissions started in November and consisted of the main channel audio program and three subcarriers : a fax program, a synchronizing signal for the fax program and a telegraph "order" channel. These original FM multiplex subcarriers were amplitude modulated. Two musical programs, consisting of both the Red and Blue Network program feeds of the NBC Radio Network, were simultaneously transmitted using the same system of subcarrier modulation as part of a studio-to-transmitter link system.
These transmissions consisted of two-channel audio programs, binaural audio programs and a fax program. The individual systems were evaluated for their strengths and weaknesses during field tests in Uniontown, Pennsylvania , using KDKA-FM in Pittsburgh as the originating station. The Crosby system was rejected by the FCC because it was incompatible with existing subsidiary communications authorization SCA services which used various subcarrier frequencies including 41 and 67 kHz.
The Halstead system was rejected due to lack of high frequency stereo separation and reduction in the main channel signal-to-noise ratio. The GE and Zenith systems, so similar that they were considered theoretically identical, were formally approved by the FCC in April as the standard stereo FM broadcasting method in the United States and later adopted by most other countries.
A stereo receiver will add the difference signal to the sum signal to recover the left channel, and subtract the difference signal from the sum to recover the right channel. This composite signal, along with any other sub-carriers, modulates the FM transmitter.
The terms composite , multiplex and even MPX are used interchangeably to describe this signal. Slight variations in the peak deviation may occur in the presence of other subcarriers or because of local regulations. Another way to look at the resulting signal is that it alternates between left and right at 38 kHz, with the phase determined by the 19 kHz pilot signal.
Converting the multiplex signal back into left and right audio signals is performed by a decoder, built into stereo receivers. Again, the decoder can use a switching technique to recover the left and right channels. In addition, for a given RF level at the receiver, the signal-to-noise ratio and multipath distortion for the stereo signal will be worse than for the mono receiver.
As with monaural transmission, it is normal practice to apply pre-emphasis to the left and right channels before encoding and to apply de-emphasis at the receiver after decoding.
In the U. A handful of radio stations around the country broadcast stereo in this way, under FCC experimental authority. It may not be compatible with very old receivers, but it is claimed that no difference can be heard with most newer receivers.
At present, the FCC rules do not allow this mode of stereo operation. In , Louis Dorren invented the Quadraplex system of single station, discrete, compatible four-channel FM broadcasting. There are two additional subcarriers in the Quadraplex system, supplementing the single one used in standard stereo FM.
The baseband layout is as follows:. The normal stereo signal can be considered as switching between left and right channels at 38 kHz, appropriately band-limited. Early efforts to transmit discrete four-channel quadraphonic music required the use of two FM stations; one transmitting the front audio channels, the other the rear channels. Following this experiment, a long-term test period was proposed that would permit one FM station in each of the top 25 U.
The test results hopefully would prove to the FCC that the system was compatible with existing two-channel stereo transmission and reception and that it did not interfere with adjacent stations.
The original Dorren Quadraplex System outperformed all the others and was chosen as the national standard for Quadraphonic FM broadcasting in the United States. Various attempts to add analog noise reduction to FM broadcasting were carried out in the s and s:.
The pre-emphasis change compensates for the excess treble response that otherwise would make listening difficult for those without Dolby decoders. It was based on the Telefunken High Com broadband compander system, but was never introduced commercially in FM broadcasting. Yet another system was the CX -based noise reduction system FMX implemented in some radio broadcasting stations in the United States in the s. FM broadcasting has included subsidiary communications authorization SCA services capability since its inception, as it was seen as another service which licensees could use to create additional income.
SCA subcarriers are typically 67 kHz and 92 kHz. Initially the users of SCA services were private analog audio channels which could be used internally or leased, for example Muzak -type services.
There were experiments with quadraphonic sound. If a station does not broadcast in stereo, everything from 23 kHz on up can be used for other services. If there is stereo, there will typically be a guard band between the upper limit of the DSBSC stereo signal 53 kHz and the lower limit of any other subcarrier. Digital services are now also available. A 57 kHz subcarrier phase locked to the third harmonic of the stereo pilot tone is used to carry a low-bandwidth digital Radio Data System signal, providing extra features such as station name, Alternative Frequency AF , traffic data for commercial GPS receivers  and Radio text RT.
This narrowband signal runs at only 1, A few proprietary systems are used for private communications. In Germany the analog ARI system was used prior to RDS to alert motorists that traffic announcements were being broadcast without disturbing other listeners. RDS is designed to be capable of being used alongside ARI despite using identical subcarrier frequencies.
This in-band on-channel approach, as do all digital radio techniques, makes use of advanced compressed audio. The proprietary iBiquity system, branded as " HD Radio ", currently is authorized for "hybrid" mode operation, wherein both the conventional analog FM carrier and digital sideband subcarriers are transmitted. Eventually, presuming widespread deployment of HD Radio receivers, the analog services could theoretically be discontinued and the FM band become all digital.
The output power of a FM broadcasting transmitter is one of the parameters that governs how far a transmission will cover.
The other important parameters are the height of the transmitting antenna and the Antenna gain. Transmitter powers should be carefully chosen so that the required area is covered without causing interference to other stations further away.
Practical transmitter powers range from a few milliwatts to 80 kW. As transmitter powers increase above a few kilowatts, the operating costs become high and only viable for large stations. Efficiency drops dramatically if any digital HD Radio service is added. VHF radio waves usually do not travel far beyond the visual horizon , so reception distances for FM stations are typically limited to 30Ч40 miles 50Ч60 km. They can also be blocked by hills and to a lesser extent by buildings.
Individuals with more-sensitive receivers or specialized antenna systems, or who are located in areas with more favorable topography, may be able to receive useful FM broadcast signals at considerably greater distances.
The knife edge effect can permit reception where there is no direct line of sight between broadcaster and receiver. The reception can vary considerably depending on the position. This is still less than the range of AM radio waves, which because of their lower frequency can travel as ground waves or reflect off the ionosphere , so AM radio stations can be received at hundreds sometimes thousands of miles. This is a property of the carrier wave's typical frequency and power , not its mode of modulation.
The range of FM transmission is related to the transmitter 's RF power, the antenna gain , and antenna height. Interference from other stations is also a factor in some places. S, the FCC publishes curves that aid in calculation of this maximum distance as a function of signal strength at the receiving location. Computer modelling is more commonly used for this around the world. In such instances, however, this technique is often surprisingly effective in increasing the station's useful range.
General Electric sold the station in the s. Today this station is WRVE.