2 meters
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2 meters is a popular amateur radio band. It is so named because the wavelength of the radio waves is very close to 2 meters in length. It ranges in frequency from 144 to 148 MHz in the United States and Australia, and from 144 to 146 MHz in most other parts of the world. The 2-meter band is part of the VHF spectrum, and is primarily used for local communications, within a range of about 100 miles. Because it is local and reliable, and because in many parts of the world, the licensing requirements to transmit on the 2-meter band are easy to obtain, this band is one of the most popular non-HF ham bands.
Much of 2-meter FM operation uses a radio repeater, a radio receiver and transmitter that retransmits a signal over a longer distance. Simple radios for FM repeater operation have become plentiful and inexpensive in recent years. A fully-functional FM transceiver and antenna can be obtained for under $200 US.
While 2 meters is best known as a local band, there are opportunities for long distance communications. Occasionally, bending in the atmosphere's troposphere (ducting) can allow 2-meter signals to carry hundreds of miles. In rare cases, Sporadic E propagation can bring contacts well over 1000 miles. 2 Meters is also utilized in conjunction with 70 cm (Mode B or V/U) on some amateur radio satellites, giving distances of up to around 3000 miles with a Low Earth Orbit satellite.
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[edit] Atmospheric interference
Since the 2-meter band is mostly line-of-sight communications, worldwide communications can not be achieved with this band, without the aid of Earth-Moon-Earth (EME, a.k.a. "Moonbounce") or satellite communications. The 2-meter wavelength is not affected by the ionosphere like High Frequency ("HF") frequency bands which have easy worldwide communications. However, it is affected by the troposhere, quite often opening up communication paths sometimes exceeding 1,000 miles (1,600 km), like VHF/UHF TV, and FM Radio. This is referred to as "troposheric ducting" or "troposheric scatter".
The ionosphere can sometimes affect this band in the form of "Sporadic E". This refers to the "E" layer in the ionosphere getting charged up by a solar flare or similar activity, then shooting the MUF (Maximum Usable Frequency) from lower frequencies up to VHF frequencies for a short time. Meteor scatter can also have a shorter lasting but similar effect.
[edit] FM
Most communications on this band, unlike HF bands (CW/SSB), is done with frequency modulation (FM) (except on the bottom of the band which is CW/SSB or satellite). FM repeaters are found to be quite useful in extending communications on this band, and helping with emergencies. These repeaters are the same kind of devices used for commercial and public communications, like police departments and such.
Frequencies like 145.550 MHz have been used for amateur radio contact with projects setup on former Russian space station MIR, The International Space Station, and STS (Shuttle) Missions.
[edit] Common uses of 2 meters
- FM simplex (direct, radio-to-radio communications)
- FM repeater operation
- Packet radio
- SSB voice operation
- Morse code (CW) operation
- Satellite communications
[edit] Band plan
Below is a common band plan for 2 meters. Note that in some areas (generally whole states) the channel spacing is 20 kHz, not 15.
Please note, this is the band plan for the USA.
In the UK, the band extends from 144 MHz to 146 MHz.
To summarize:
- 144.000 to 144.400 narrowband modes.
- 144.500 to 145.000 is an "all mode" section.
- 145.000 to 145.200 are VHF repeater inputs.
- 145.200 to 145.600 are Simplex channels (12.5kHz spacing).
- 145.600 to 145.800 are the outputs.
Space communications are above 145.800 to the band edge.
[edit] Sample band plan
| 144.000–144.100 MHz | CW only, as restricted by FCC Part 97 |
| 144.100–144.275 MHz | CW and SSB |
| 144.275–144.300 MHz | CW propagation beacons |
| 144.300–144.500 MHz | Satellite |
| 144.510–144.890 MHz | FM repeater inputs (600 kHz splits)
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| 144.910–145.090 MHz | Packet and FM simplex
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| 145.110–145.490 MHz | FM repeater outputs (600 kHz splits)
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| 145.510–145.790 MHz | FM simplex, digital and satellite
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| 145.800–146.000 MHz | Satellite |
| 146.010–146.385 MHz | FM repeater inputs (600 kHz splits)
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| 146.400–146.595 MHz | FM simplex
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| 146.610–146.985 MHz | FM repeater outputs (600 kHz splits)
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| 147.000–147.390 MHz | FM repeater outputs (600 kHz splits)
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| 147.405–147.585 MHz | FM simplex
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| 147.600–147.990 MHz | FM repeater inputs (600 kHz splits)
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[edit] Frequencies of note
- CW and SSB calling frequency is 144.200 MHz.
- APRS frequency is 144.390 MHz in the United States, 145.175 MHz in Australia and 144.800 MHz in Europe.
- FM simplex calling frequency is 146.520 MHz.
- In some areas, 146.415–146.505 MHz are repeater outputs with inputs +1 MHz at 147.415 - 147.505 MHz, spaced 15 kHz apart.
| Very high frequency (VHF) and Ultra high frequency (UHF) Amateur radio bands | |||||||
| VHF | UHF | ||||||
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| 6 m | 4 m | 2 m | 1.25 m | 70 cm | 33 cm | 23 cm | 13 cm |
| 50 MHz | 70 MHz | 144 MHz | 219-220 MHz | 420 MHz | 902 MHz | 1.24 GHz | 2.3-2.31 GHz |
| 54 MHz | 70.5 MHz | 148 MHz | 222-225 MHz | 450 MHz | 928 MHz | 1.3 GHz | 2.39-2.45 GHz |
