2M (VHF)
2M BAND
The 2-meter amateur radio band is a portion of the VHF radio spectrum, comprising frequencies stretching from 144.000 MHz to 148.000 MHz in International Telecommunication Union region (ITU) Regions 2 (North and South America plus Hawaii) and 3 (Asia and Oceania) and from 144.000 MHz to 146.000 MHz in ITU Region 1 (Europe, Africa, and Russia). The license privileges of amateur radio operators include the use of frequencies within this band for telecommunication, usually conducted locally within a range of about 100 miles (160 km).
The 2-meter amateur radio band is a portion of the VHF radio spectrum, comprising frequencies stretching from 144.000 MHz to 148.000 MHz in International Telecommunication Union region (ITU) Regions 2 (North and South America plus Hawaii) and 3 (Asia and Oceania) and from 144.000 MHz to 146.000 MHz in ITU Region 1 (Europe, Africa, and Russia). The license privileges of amateur radio operators include the use of frequencies within this band for telecommunication, usually conducted locally within a range of about 100 miles (160 km).
OPERATING ON 2M BAND
Because it is local and reliable, and because the licensing requirements to transmit on the 2-meter band are easy to meet in many parts of the world, this band is one of the most popular non-HF ham bands. This popularity, the compact size of needed radios and antennas, and this band's ability to provide easy reliable local communications also means that it is also the most used band for local emergency communications efforts, such as providing communications between Red Cross shelters and local authorities. In the US, that role in emergency communications is furthered by the fact that most amateur-radio operators have a 2-meter handheld transceiver (HT), handie-talkie or walkie-talkie.
Because it is local and reliable, and because the licensing requirements to transmit on the 2-meter band are easy to meet in many parts of the world, this band is one of the most popular non-HF ham bands. This popularity, the compact size of needed radios and antennas, and this band's ability to provide easy reliable local communications also means that it is also the most used band for local emergency communications efforts, such as providing communications between Red Cross shelters and local authorities. In the US, that role in emergency communications is furthered by the fact that most amateur-radio operators have a 2-meter handheld transceiver (HT), handie-talkie or walkie-talkie.
REPEATER AND FM USE ON 2M
Much of 2-meter FM operation uses a radio repeater, a radio receiver and transmitter that instantly retransmits a received signal on a separate frequency. Repeaters are normally located in high locations such as a tall building or a hill top overlooking expanses of territory. On VHF frequencies such as 2-meters, antenna height greatly influences how far one can talk. Typical reliable repeater range is about 25 miles (40 km). Some repeaters in unusually high locations, such as skyscrapers or mountain tops, can be usable as far out as 75 miles (120 km). Reliable range is very dependent on the height of the repeater antenna and also on the height and surroundings of the handheld or mobile unit attempting to access to the repeater. Line of sight would be the ultimate in reliability. The typical hand held two meter FM operator has about 5 watts of transmit power. Stations in a car or home run higher power, 25 to 50 watts, and may use a simple vertical antenna mounted on a rooftop.
However, even without repeaters available, the 2-meter band provides reliable crosstown communications throughout smaller towns, making it ideal for emergency communications. Antennas for repeater work are almost always vertically polarized since 2-meter antennas on cars are usually vertically polarized. Matching polarization allows for maximum signal coupling which equates to stronger signals in both directions. Simple radios for FM repeater operation have become plentiful and inexpensive in recent years.
Much of 2-meter FM operation uses a radio repeater, a radio receiver and transmitter that instantly retransmits a received signal on a separate frequency. Repeaters are normally located in high locations such as a tall building or a hill top overlooking expanses of territory. On VHF frequencies such as 2-meters, antenna height greatly influences how far one can talk. Typical reliable repeater range is about 25 miles (40 km). Some repeaters in unusually high locations, such as skyscrapers or mountain tops, can be usable as far out as 75 miles (120 km). Reliable range is very dependent on the height of the repeater antenna and also on the height and surroundings of the handheld or mobile unit attempting to access to the repeater. Line of sight would be the ultimate in reliability. The typical hand held two meter FM operator has about 5 watts of transmit power. Stations in a car or home run higher power, 25 to 50 watts, and may use a simple vertical antenna mounted on a rooftop.
However, even without repeaters available, the 2-meter band provides reliable crosstown communications throughout smaller towns, making it ideal for emergency communications. Antennas for repeater work are almost always vertically polarized since 2-meter antennas on cars are usually vertically polarized. Matching polarization allows for maximum signal coupling which equates to stronger signals in both directions. Simple radios for FM repeater operation have become plentiful and inexpensive in recent years.
LONG DISTANCE 50+ MILES
While the 2-meter band is best known as a local band using the FM Mode, there are many opportunities for long distance (DX) communications using other modes. The typical 2 meter station using CW (Morse code) or SSB (single side band) modes consists of an exciter (radio) driving a power amplifier generating about 200-500 watts of RF power. This power is usually fed to a multi-element horizontally polarized, directional beam antenna knowns as a Yagi. Stations that are located in relatively high locations with views clear to the horizon have a big advantage over other stations at lower elevations. Such stations are able to communicate 100–300 miles consistently and it is not unusual to be heard at distances much further; beyond line of sight. These distances can be traversed on a daily basis without any noticeable help from known "Signal Enhancements". However, when coupled with these well known signal enhancements, astonishing distances can be bridged.
To traverse these distances, directional Yagi antennas are almost essential and are generally horizontally polarized. These antennas provide huge signal gains over a dipole or simple vertical and make short work of several hundred miles providing reliable communications. Meteor scatter, Sporadic E, and Tropospheric Ducting are the most common forms of VHF signal enhancement and are described further below.
Tropospheric ducting:
Occasionally, signal bending in the atmosphere's troposphere known as tropospheric ducting can allow 2-meter signals to carry hundreds or even thousands of miles as evidenced by the occasional 2-meter contact between the west coast of the United States and the Hawaiian Islands, the northeast region to the Florida coast and across the Gulf of Mexico. These "Openings" as they are known, are generally first spotted by amateurs operating SSB and CW modes since amateurs using these modes are always alert for ducting or signal enhancement events. Completion of contacts using these weak signal modes involves the exchange of signal level reports and location by grid square which is known as the Maidenhead Locator System. Two way ducting contacts can have very strong signals and are often made with moderate power, small antennas and other types of modes. Long distance ducting contacts do occur using FM modes as well but for the most part go unnoticed by many FM operators.
Sporadic "E":
Another VHF propagation event called, Sporadic E propagation; is a phenomenon involving radio reflections off highly ionized segments of the ionosphere which can bring contacts well over 1,000 miles (1,600 km) with very strong signals received on both ends of the conversation. Unlike some other long distance modes, high power and large antennas are not required to "Work" some distant stations via a sporadic "E" event. Low power, even as low as one watt can sustain a two-way conversation over hundreds of miles or more. Sporadic-E events can last for hours or can last for minutes. Sporadic-E is a rare and completely random propagation phenomenon.
Satellite communications:
The 2-meter band is also used in conjunction with the 70-centimeter band, or the 10 meter band and various microwave bands via orbiting amateur radio satellites. This is known as cross band repeating. On board software defines what mode or band is in use at any particular time and this is determined by amateurs at so-called earth stations who control or instruct the satellite behavior. Amateurs know what mode is in use via published internet schedules. For instance, a favorite mode is Mode "B" or "V/U" which simply indicates the uplink and downlink frequencies or bands the satellite is currently using. In this example, V/U means VHF/UHF or VHF uplink with UHF downlink. Most amateur satellites are Low Earth Orbit satellites, or LEO's as they are affectionately known, and generally are about 450 miles high. At that height amateurs can expect reception distances of up to around 3,000 miles (4,800 km). However, there are a few amateur satellites that have very high elliptical orbits. These satellites can reach altitudes of 30,000 miles above the earth where an entire hemisphere is visible providing outstanding communications capabilities from any two points on the earth within line of sight of the satellite; distances that are far beyond the reach of the LEO's. Satellites are basically orbiting repeaters.
Trans-equatorial propagation:
Trans-equatorial propagation also known as (TEP) is a regular daytime occurrence on the 2-meter band over the equatorial regions and is common in the temperate latitudes in late spring, early summer and, to a lesser degree, in early winter. For receiving stations located within +/− 10 degrees of the geomagnetic equator, equatorial E-skip can be expected on most days throughout the year, peaking around midday local time.
Moon bounce (EME):
To communicate over the longest distances hams use moon bounce. VHF signals normally escape the Earth's atmosphere, so using the moon as a target is quite practical. Due to the distance involved and the very high path loss getting a readable signal bounced off the moon involves high power ~ 1000 watts and steerable high gain antennas. Receiving these very weak return signals, again involves the use of high gain antennas (usually the same ones used to transmit the signal) and a very low noise front end RF amplifier and a frequency stable receiver. However, new and recent technological advances in weak signal detection has allowed the successful reception of signals off the moon using much smaller or less well equipped stations allowing reception of signals that are "in the noise" and not audible to the human ear. One of these modes is JT65 which is a digital mode. Due to the delay of the signal traveling to the moon and back (travel time approx. 2.5 seconds), a person transmitting may hear the end of his own transmission returning.
While the 2-meter band is best known as a local band using the FM Mode, there are many opportunities for long distance (DX) communications using other modes. The typical 2 meter station using CW (Morse code) or SSB (single side band) modes consists of an exciter (radio) driving a power amplifier generating about 200-500 watts of RF power. This power is usually fed to a multi-element horizontally polarized, directional beam antenna knowns as a Yagi. Stations that are located in relatively high locations with views clear to the horizon have a big advantage over other stations at lower elevations. Such stations are able to communicate 100–300 miles consistently and it is not unusual to be heard at distances much further; beyond line of sight. These distances can be traversed on a daily basis without any noticeable help from known "Signal Enhancements". However, when coupled with these well known signal enhancements, astonishing distances can be bridged.
To traverse these distances, directional Yagi antennas are almost essential and are generally horizontally polarized. These antennas provide huge signal gains over a dipole or simple vertical and make short work of several hundred miles providing reliable communications. Meteor scatter, Sporadic E, and Tropospheric Ducting are the most common forms of VHF signal enhancement and are described further below.
Tropospheric ducting:
Occasionally, signal bending in the atmosphere's troposphere known as tropospheric ducting can allow 2-meter signals to carry hundreds or even thousands of miles as evidenced by the occasional 2-meter contact between the west coast of the United States and the Hawaiian Islands, the northeast region to the Florida coast and across the Gulf of Mexico. These "Openings" as they are known, are generally first spotted by amateurs operating SSB and CW modes since amateurs using these modes are always alert for ducting or signal enhancement events. Completion of contacts using these weak signal modes involves the exchange of signal level reports and location by grid square which is known as the Maidenhead Locator System. Two way ducting contacts can have very strong signals and are often made with moderate power, small antennas and other types of modes. Long distance ducting contacts do occur using FM modes as well but for the most part go unnoticed by many FM operators.
Sporadic "E":
Another VHF propagation event called, Sporadic E propagation; is a phenomenon involving radio reflections off highly ionized segments of the ionosphere which can bring contacts well over 1,000 miles (1,600 km) with very strong signals received on both ends of the conversation. Unlike some other long distance modes, high power and large antennas are not required to "Work" some distant stations via a sporadic "E" event. Low power, even as low as one watt can sustain a two-way conversation over hundreds of miles or more. Sporadic-E events can last for hours or can last for minutes. Sporadic-E is a rare and completely random propagation phenomenon.
Satellite communications:
The 2-meter band is also used in conjunction with the 70-centimeter band, or the 10 meter band and various microwave bands via orbiting amateur radio satellites. This is known as cross band repeating. On board software defines what mode or band is in use at any particular time and this is determined by amateurs at so-called earth stations who control or instruct the satellite behavior. Amateurs know what mode is in use via published internet schedules. For instance, a favorite mode is Mode "B" or "V/U" which simply indicates the uplink and downlink frequencies or bands the satellite is currently using. In this example, V/U means VHF/UHF or VHF uplink with UHF downlink. Most amateur satellites are Low Earth Orbit satellites, or LEO's as they are affectionately known, and generally are about 450 miles high. At that height amateurs can expect reception distances of up to around 3,000 miles (4,800 km). However, there are a few amateur satellites that have very high elliptical orbits. These satellites can reach altitudes of 30,000 miles above the earth where an entire hemisphere is visible providing outstanding communications capabilities from any two points on the earth within line of sight of the satellite; distances that are far beyond the reach of the LEO's. Satellites are basically orbiting repeaters.
Trans-equatorial propagation:
Trans-equatorial propagation also known as (TEP) is a regular daytime occurrence on the 2-meter band over the equatorial regions and is common in the temperate latitudes in late spring, early summer and, to a lesser degree, in early winter. For receiving stations located within +/− 10 degrees of the geomagnetic equator, equatorial E-skip can be expected on most days throughout the year, peaking around midday local time.
Moon bounce (EME):
To communicate over the longest distances hams use moon bounce. VHF signals normally escape the Earth's atmosphere, so using the moon as a target is quite practical. Due to the distance involved and the very high path loss getting a readable signal bounced off the moon involves high power ~ 1000 watts and steerable high gain antennas. Receiving these very weak return signals, again involves the use of high gain antennas (usually the same ones used to transmit the signal) and a very low noise front end RF amplifier and a frequency stable receiver. However, new and recent technological advances in weak signal detection has allowed the successful reception of signals off the moon using much smaller or less well equipped stations allowing reception of signals that are "in the noise" and not audible to the human ear. One of these modes is JT65 which is a digital mode. Due to the delay of the signal traveling to the moon and back (travel time approx. 2.5 seconds), a person transmitting may hear the end of his own transmission returning.