Difference between revisions of "Offset"
From The RadioReference Wiki
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|800 MHz||806-896||-45 MHz|| | |800 MHz||806-896||-45 MHz|| | ||
|- | |- | ||
| − | |900 MHz|| | + | |900 MHz||935-940||-39 MHz||4 |
|- | |- | ||
|33cm Ham||902-928||-12 MHz or -25 MHz||1 | |33cm Ham||902-928||-12 MHz or -25 MHz||1 | ||
| Line 57: | Line 57: | ||
*'''2.''' There are some paired channels in the VHF high band (paging, taxi, old RCC mobile phone channels) but no standard offset. | *'''2.''' There are some paired channels in the VHF high band (paging, taxi, old RCC mobile phone channels) but no standard offset. | ||
*'''3.''' The 406.1-420 MHz federal land mobile band began changing to a +9 MHz offset a few years ago. Many older systems remain with non-standard offsets. | *'''3.''' The 406.1-420 MHz federal land mobile band began changing to a +9 MHz offset a few years ago. Many older systems remain with non-standard offsets. | ||
| + | *'''4.''' There are other paired channels (paging, PCS and Part 101 microwave) with different offsets in the 896-960 MHz band. | ||
<br> | <br> | ||
[[Category:RR Glossary]] | [[Category:RR Glossary]] | ||
Revision as of 18:54, 6 December 2011
Offset is the difference between receive and transmit frequencies of a radio channel. Most commonly it refers to the separation between the input frequency and output frequency of a repeater or other type of full duplex system.
For example, a mobile radio receives on 146.94 and transmits on 146.34 in order to operate on a repeater.
146.94 - 146.34 = .6 (.6 MHz or 600 kHz)
Since in this case the transmit frequency is lower than the receive frequency, it is said to have a negative offset of 600 kHz or -600 kHz.
Certain bands and frequency ranges in the United States have standardized offsets.
| Band | Frequency Range | Offset | Notes |
|---|---|---|---|
| 10m Ham (repeater subband) | 29.5-29.7 | -100 kHz | |
| VHF Low Band | 30-50 | No standard offset | |
| 6m Ham | 50-54 | -500 kHz or -1 MHz | 1 |
| VHF High Band | 138-174 | No standard offset | 2 |
| 2m Ham | 144-148 | +600 kHz or -600 kHz | 1 |
| 220 MHz | 220-222 | +1 MHz | |
| 1.25m Ham | 222-225 | -1.6 MHz | |
| 380 MHz Federal LM | 380-400 | +10 MHz | |
| Federal UHF | 406.1-420 | +9 MHz | 3 |
| 70cm Ham | 420-450 | +5 MHz or -5 MHz | 1 |
| UHF Canadian border area | 420-430 | +5 MHz | |
| UHF | 450-470 | +5 MHz | |
| UHF T | 470-512 | +3 MHz | |
| 700 MHz | 746-806 | +30 MHz | |
| 800 MHz | 806-896 | -45 MHz | |
| 900 MHz | 935-940 | -39 MHz | 4 |
| 33cm Ham | 902-928 | -12 MHz or -25 MHz | 1 |
| 23cm Ham | 1240-1300 | -12 MHz or -20 MHz | 1 |
Notes
- 1. Ham radio offsets can vary in certain areas of the country.
- 2. There are some paired channels in the VHF high band (paging, taxi, old RCC mobile phone channels) but no standard offset.
- 3. The 406.1-420 MHz federal land mobile band began changing to a +9 MHz offset a few years ago. Many older systems remain with non-standard offsets.
- 4. There are other paired channels (paging, PCS and Part 101 microwave) with different offsets in the 896-960 MHz band.