Difference between revisions of "Radio Bandwidth Frequency Offset"

Revision as of 12:56, 4 June 2015

Refer to Radio Frequencies, Bands, and Channels for your place on the Electromagnetic Spectrum. The spectrum is a finite resource. It has limited space and humans fill it up fast. Bandwidth consumption reduction is a way of conservation made possible by advances in radio electronics. Digital communication also helps to dramatically reduce bandwidth consumption.

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Radio Communication Methods

• Frequency Division Multiple Access (FDMA)
• Time Division Multiple Access (TDMA)
• Code Division Multiple Access (CDMA).

FDMA is the conventional communication method that is widely used for frequency band of under 1GHz.

Band Nomenclature

The new APCO standard for FM is Narrow Band +/-2.5 KHz. For amateur use set the radio to Wide Band +/- 5 KHz.

The new Land Mobile Radio standards of "wideband" vs "narrowband" refer to the bandwidth of the signal. Older analog wideband FM business band signals are 25 kHz wide. The new mandated narrowband signals are only 12.5 kHz wide.

• super or ultra narrow (2.5kHz deviation)
• narrow, and regular narrow (5kHz) wide.
• two way wide is 15kHz
• amateur wide is 15kHz
• amateur narrow is 5kHz
• commercial super FM narrow (2.5kHz) narrow and 5kHz standard narrow.

• normal 2 meter FM is considered wide band at about 5khz for amateur use.
• wide/narrow setting on newer ham radios: 25KHz (wide) or 12.5KHz (narrow).
• VHF private land mobile narrow band uses 7.5 kHz spacing.
• Old VHF radios are based on 5 or 6.25 kHz channel step size.

Narrowbanding

The FCC is trying to enact a maximum 12.5 kHz bandwidth across the private land mobile bands between 150-174 and 421-512 MHz, and increases available channels by creating new ones between existing channels. As of 2013 the FCC mandated that all current licensees must be fully operational on 12.5 kHz equipment.

While 12.5 kHz channel spacing is widely mentioned in communications media, there is usually no corresponding mention of the difference in channel spacing between VHF and UHF, which leads to the erroneous assumption that 12.5 kHz will be the standard channel spacing across the board. In truth, 12.5 kHz channel spacing (and eventually 6.25 kHz) only affects UHF between 420 and 512 MHz.

• An old police scanner that tunes 5 kHz steps will still receive the 7.5 kHz spaced channels if you program the next higher or lower 5 kHz channel. If the older police scanner is limited to 12.5 kHz steps on UHF it will not be able to receive the new 6.25 kHz channels.
• The FCC private land mobile narrowbanding rule only affects Part 90 Public Safety Pool and Industrial/Business Pool frequencies in the 150-174 MHz, 421-430 MHz Canadian border area, and 450-470 MHz bands. It excludes frequencies used only for paging such as 152.0075, 154.625, 157.45, 157.74, 158.46 and 462.75-462.925 MHz.
• The FCC private land mobile narrowbanding rule does not affect the federal government land mobile bands (138-144, 148-150.75, 162-173.2, 173.4-174, and 406.1-420 MHz). They were nawrrowbanded years ago. Their deadline was in 2008.
• The FCC private land mobile narrowbanding rule does not affect VHF low band 30-50 MHz, mid band 72-76 MHz, the 216-222 MHz, 700 MHz, 800 MHz or 900 MHz bands.
• The FCC private land mobile narrowbanding rule does not affect 800 MHz and is not the same as rebanding.
• The FCC private land mobile narrowbanding rule does not mandate the use of P25 or any other digital mode. Some grant funding or interoperability plans may require public safety agencies in some areas to use P25 equipment.
• The FCC private land mobile narrowbanding rule does not require changing frequencies, only changing the emission mode of existing ones.
• The FCC private land mobile narrowbanding rule does not affect amateur radio.
• The FCC private land mobile narrowbanding rule does not affect CB.
• The FCC private land mobile narrowbanding rule does not affect GMRS.
• The FCC private land mobile narrowbanding rule does not affect FRS.
• The FCC private land mobile narrowbanding rule does not affect MURS.
• The FCC private land mobile narrowbanding rule does not affect the VHF marine band.
• The FCC private land mobile narrowbanding rule does not affect the VHF aircraft band.
• The FCC private land mobile narrowbanding rule does not affect the NOAA weather channels.
• The FCC private land mobile narrowbanding rule does not have anything to do with digital television.