# Frequency offset

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Intentional frequency shift in broadcasting

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In [radio engineering](/source/Radio_engineering), a **frequency offset** is an intentional slight [shift](/source/Frequency_shift_(disambiguation)) of the broadcast [radio frequency](/source/Radio_frequency) (RF), to reduce [interference](/source/RF_interference) with other transmitters.[1][2] Carrier frequency offset arises from mismatches between the received signal's carrier frequency and the receiver's local oscillator, often due to synchronization errors and Doppler shifts.[3]

## Interference

The most important problem encountered in broadcasting via terrestrial transmitters is the interference from other broadcasters. In principle, each broadcaster has a different radio frequency (planned by the public authority) in a common reception area to avoid interference from each other. However, there are still two problems: spurious radiation of adjacent channels and fringe reception.[1][2]

[Fringe reception](/source/TV_and_FM_DX) is unintended reception under certain weather conditions. The exceptionally long-range reception means that the receiver may be tuned to more than one transmitter (transmitting at same frequency) at the same time. These transmitters may transmit programs of different broadcasters as well as the programs of the same broadcaster. In analogue transmission, even the transmitters transmitting the very same program interfere each other because of phase differences of the incoming [signal](/source/Signal_(electronics)), but in [digital](/source/Digital_data) transmission the transmitters transmitting the same program in the same channel may reinforce each other.[1][2]

## The shift in RF

In order to reduce the interference from the fringe area transmitters transmitting in the same channels, a method named frequency offset is often used. By this method, a slightly shifted RF is assigned for a transmitter which may experience interference from other transmitters.

In TV transmission, the shifted RF is calculated by the formula;

- f o s = f c h + f L ⋅ p 12 {\displaystyle f_{os}=f_{ch}+{\frac {f_{L}\cdot p}{12}}}

where,

- f o s {\displaystyle f_{os}} is the offset RF,

- f c h {\displaystyle f_{ch}} is the standard channel frequency,

- p {\displaystyle p} is an integer such that − 12 < p < 0 {\displaystyle -12<p<0} or 0 > p > 12 {\displaystyle 0>p>12}

- f L {\displaystyle f_{L}} is the line frequency. (**15625 Hz.** for [625-line](/source/625-line) systems, **15750 Hz.** for [System M](/source/CCIR_System_M) and System J and **20475 Hz.** for [system E](/source/Analog_high-definition_television_system))

**Precision offset** is the same as frequency offset, except that in this case, the offset frequency is produced by a [cesium](/source/Cesium) controlled oscillator.

## Example

**8p** offset of channel **9** in system B can be found readily

The standard visual [carrier frequency](/source/Carrier_frequency) is **203.25** MHz The line frequency is **15.625** Hz.

- f o s = 203250000 + 15626 ⋅ 8 12 ≈ 203260417 {\displaystyle f_{os}=203250000+{\frac {15626\cdot 8}{12}}\approx 203260417}

**8n** offset of the same channel is likewise

- f o s = 203250000 − 15626 ⋅ 8 12 ≈ 203239583 {\displaystyle f_{os}=203250000-{\frac {15626\cdot 8}{12}}\approx 203239583}

## References

1. ^ [***a***](#cite_ref-:0_1-0) [***b***](#cite_ref-:0_1-1) [***c***](#cite_ref-:0_1-2) ["What are Frequency Offset and Clock Slips? How to measure Clock Slips"](https://kb.veexinc.com/en/knowledge/what-are-frequency-offset-and-clock-slips). *kb.veexinc.com*. Retrieved 2025-03-07.

1. ^ [***a***](#cite_ref-:1_2-0) [***b***](#cite_ref-:1_2-1) [***c***](#cite_ref-:1_2-2) ["Frequency Offset Mode"](https://helpfiles.keysight.com/csg/N52xxB/FreqOffset/Frequency_Offset_Mode.htm). *helpfiles.keysight.com*. Retrieved 2025-03-07.

1. **[^](#cite_ref-3)** Kotb, Moatasem Mohammed Elsayed; Mohamed, Maha Raof Abdel-Haleem; Fahmy, Ashraf Yahya Hassan Ali; Mohra, Ashraf Shawky Selim SayedAhmed (2025-05-05). ["Fine carrier frequency offset estimation for OFDM and MIMO-OFDM systems: A comparative study"](https://pmc.ncbi.nlm.nih.gov/articles/PMC12050312/). *Scientific Reports*. **15** (1): 15622. [doi](/source/Doi_(identifier)):[10.1038/s41598-025-98233-3](https://doi.org/10.1038%2Fs41598-025-98233-3). [ISSN](/source/ISSN_(identifier)) [2045-2322](https://search.worldcat.org/issn/2045-2322). [PMC](/source/PMC_(identifier)) [12050312](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12050312). [PMID](/source/PMID_(identifier)) [40320441](https://pubmed.ncbi.nlm.nih.gov/40320441).

v t e Analog television broadcasting topics Systems 180-line 343-line 375-line 405-line (System A) 441-line 455-line 525-line (System M) 625-line (System B, System C, System D, System G, System H, System I, System K, System L, System N) 819-line (System E, System F) Color systems NTSC NTSC-J Clear-Vision PAL PAL-M PAL-S PALplus SECAM Video Back porch and front porch Black level Blanking level Chrominance Chrominance subcarrier Color burst Color frame sequence Color killer Color TV Composite video Frame (video) Horizontal scan rate Horizontal blanking interval Luma Nominal analogue blanking Overscan Raster scan Safe area Teletext Television lines Vertical blanking interval Vertical interval timecode White clipper Sound Multichannel Television Sound NICAM Sound-in-Syncs Zweikanalton Modulation Frequency modulation Quadrature amplitude modulation Vestigial sideband modulation (VSB) Transmission Amplifiers Antenna (radio) Broadcast transmitter/Transmitter station Cavity amplifier Differential gain Differential phase Diplexer Dipole antenna Dummy load Frequency mixer Intercarrier method Intermediate frequency Output power of an analog TV transmitter Pre-emphasis Residual carrier Split sound system Superheterodyne transmitter Synchronization of TV transmitter and receiver Television receive-only Direct-broadcast satellite television Television transmitter Terrestrial television Transposer Digital television transition Frequencies & bands Frequency offset Microwave transmission Television channel frequencies UHF VHF Propagation Beam tilt Distortion Earth bulge Field strength in free space Noise (electronics) Null fill Path loss Radiation pattern Skew Television interference Testing Distortionmeter Field strength meter Vectorscope VIT signals Zero reference pulse Artifacts Dot crawl Ghosting Hanover bars Sparklies

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