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2-meter band
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(Redirected from 2 Meters)
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 ITU Regions 2 (North & South America plus Hawaii) and 3 (Asia and Oceania) and from 144.000 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 100miles (160km).
Operating on 2 meters
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 U.S., that role in emergency communications is furthered by the fact that seemingly every amateur-radio operator has a 2 meter mobile radio or walkie-talkie.
Much of 2-meter FM operation uses a radio repeater, a radio receiver and transmitter that instantly retransmits a signal over a longer distance. However, even without repeaters available, it provides reliable crosstown communications throughout smaller towns and that makes it ideal for emergency communications. 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 US$200 new and far less used for a modern one.
DX
While 2 meters is best known as a local band, there are many opportunities for long distance (DX) communications. Occasionally, bending in the atmosphere's troposphere (ducting) can allow 2-meter signals to carry hundreds of miles. This is called a lift.
In rare cases, Sporadic E propagation can bring contacts well over a 1,000miles (1,600km). 2 meters is also utilized in conjunction with 70cm (Mode B or V/U) on some amateur radio satellites, giving distances of up to around 3,000miles (4,800km) with a Low Earth Orbit satellite.
A set of 2 long Yagi antennas for the 2 meter band fed in phase to obtain more gain and narrow main lobe of radiation (WA6PY)
By speeding up Morse code using an audio tape recorder, or using a computer, very short bursts of signal can be bounced off the ionized gas trail of meteor showers allowing DX. This is often called Burst transmission.
Another phenomenon that produces upper atmosphere ionization suitable for 2M DXing are the auroras. Since the ionization persists much longer than meteor trails, regular audio signals can be used, but the constant movement of the ionized gas leads to heavy distortion of the signals causing the audio to sound 'ghostly' and whispered.
To communicate over the longest distances hams use moonbounce. This involves high power and good antennas to reflect the VHF signals off the moon. VHF signals normally escape the earth's atmosphere, so using the moon as a target is quite practical. Due to the delay of the signal traveling to the moon and back, a person transmitting may hear the end of his own transmission returning.
Links to 2m propagation sites
DX-Sherlock's real-time 2m propagation maps
DX-Sherlock's real-time VHF&up propagation ticker
References
^ US Amateur Radio Frequency Allocations. http://www.arrl.org/FandES/field/regulations/allocate.html accessed 12 May 2008.
^ RSGB UK band plan. http://www.rsgb.org/spectrumforum/bandplans/RSGB Band Plan master.pdf or http://www.rsgb-spectrumforum.org.uk/Papers/RSGB Band Plan master.htm Accessed 14 May 2008.
^ Sharing spectrum with other services a ham radio reality. The ARRL Letter, Vol. 20, No. 2. http://www.arrl.org/arrlletter/01/1102/ Accessed 14 May 2008.
^ http://www.rsgb.org/getlicence/#foundation RSGB licensing guide
^ http://www.rsgb.org/emergency/ RSGB Radio Emergency & Public Service Communications website
Very high frequency (VHF) and ultra high frequency (UHF) amateur radio bands
VHF
UHF
6 m
4 m
2 m
1.25 m
70 cm
33 cm
23 cm
13 cm
50 MHz
70 MHz
144 MHz
219220 MHz
420 MHz
902 MHz
1.24 GHz
2.32.31 GHz
54 MHz
70.5 MHz
148 MHz
222225 MHz
450 MHz
928 MHz
1.3 GHz
2.392.45 GHz
Categories: Amateur radio bands(and so on) To get More information , you can visit some products about health protecction instrument, virtual digital multimeter, . The Wine Thermometer (JWW) products should be show more here!
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Is it feasible to construct a vacuum tube AM receiver capable of tuning into the VHF or even UHF bands?
If so, how? If not, why not? This is for all the hams and amateur radio techies out there.
Wow, great question...
It was generally not done, only FM was/is used in the VHF and UHF bands. You typically only see AM in the SW bands and up to 30Mhz (is this still SW?). I think VHF starts around 50Mhz and is where TV begins (less channel 1).
So your question is can a reciever decode an AM signal on those higher frequencies... simple answer is YES but it's not practical due to the fact that higher frequencies tend to become "line of sight". ie, they do not curve with the earth or bend around structures. So I would think that normal everyday interference would alter the Amplitude of the Carrier you are receiving, increasingly so on the higher frequencies.
If you are considering a mobile type transmiter/reciever then just forget it, as you drive the carrier amplitude will peek and plunge as you pass buildings if it were tuned to VHF. Hence the need to go to Frequency Modulation (FM) on those higher bands.
This is just my best guess... I would love to hear some HAMs opinion on this.
