Amateur Radio Wiki - User contributions [en]

2 metres

2010-08-12T23:29:21Z

KJ6EUO:

Other VHF/UHF/Microwave wiki pages : [[13 centimetres]], [[9 centimetres]], [[6 centimetres]], [[3 centimetres]] [[1.25 centimetres]] and [[Bands above 24GHz]].

{{Band
|band=2m
|USG=144.000-148.000
|USE=144.000-148.000
|USA=144.000-148.000
|UST=144.000-148.000
|UK=144-146
}}

2 metres is probably the most heavily-used amateur band in the United States. Most newly-licensed [[Technician|Technician-class]] operators get their start in amateur radio on 2 meter [[Modes#Frequency Modulation (FM)|FM]].

==Equipment==
Equipment for operation on two meters is plentiful; many well-known manufacturers produce new base, mobile and hand-held transceivers intended specifically for the 2 meter amateur radio band. In some cases, additional bands (most often [[70 centimeters]] but occasionally also additional VHF bands) will be supported.

Much of the early equipment deployed by radio amateurs on 2 meter FM was surplus, built originally for commercial land-mobile use on bands elsewhere in the 130-174MHz spectrum and converted to the 144-148MHz amateur band. Users of adjacent spectrum range from marine radiotelephone and public safety to dispatch radios used by taxis and service vehicles. As commercial two-way radio frequencies became more crowded, spacing between channels was reduced, leading to many existing radios becoming available as surplus. The oldest of this equipment was crystal-controlled and provided use of a limited number of FM voice frequencies; modern equipment is frequency-synthesized and often also capable of receiving out-of-band services such as weather and marine radio.

Commercial land-mobile base station equipment has also been adapted readily to construct repeaters, although factory-built repeaters designed specifically for amateur use are now commercially available. This ready availability of a wide selection of equipment at reasonable cost has made 2 meters the most commonly-used amateur band for mobile voice communication.

==Modulation==
The most common application of 2 meter radio is in FM voice transmission, either operated directly between stations or via automated [[repeater]]s. Individual FM channels are normally spaced at 15kHz or 20kHz intervals. Repeater inputs below 147MHz are typically set 600kHz below the output frequency; above 147MHz this pattern is reversed.

The 2 meter band is a popular choice for digital packet transmission, with 144.39MHz (North America) and 144.8MHz (Europe) commonly used for [[APRS]] operation.

==Propagation==
Signals in this band travel primarily line-of-sight or slightly further. It is not uncommon for a powerful, well-situated repeater to be accessible to mobile stations at up to fifty miles distance. During unusual atmospheric conditions (such as temperature inversion) the VHF signals' range may be significantly but temporarily increased.

==Australian Bandplan==

[[Image:vk4yeh_vk_2m_bandplan.jpg]]

{{bands}}

Random Wire Antenna

2010-08-12T23:09:46Z

KJ6EUO: /* Advantages and Uses */

A "Random Wire" antenna is an end-fed antenna that is operated against ground or an artificial ground system - much like a vertical antenna. The "Random Wire" must normally be coupled to the transmitter by an [[Impedance_matching|ATU]] (except if it happens to be in resonance on some amateur band).

A popular length is 7m. This does not provide excessive impedances for the ATU to tune out for bands between 80 and 10m.

Jack Clarke VE3EED adds that for optimum performance, "random length" antennas should not be multiples of half wavelengths in the intended bands. The following table reproduced with permission from his [http://www.jackclarke.net/hamdnld.htm website] details half wave lengths that should be avoided.

<table border="1" cellpadding="6" cellspacing="0" width="58%">
<tr>

<td width="20%" align="center">Frequency
MHz</td>
<td width="20%" align="center">1/2
Wave</td>
<td width="20%" align="center">2nd
Multiple</td>
<td width="20%" align="center">3rd
Multiple</td>
<td width="20%" align="center">4th
Multiple</td>
</tr>

<tr>
<td width="20%" align="right">1.9</td>
<td width="20%" align="right">246</td>
<td width="20%" align="right">492</td>
<td width="20%" align="right">738</td>
<td width="20%" align="right">984</td>

</tr>
<tr>
<td width="20%" align="right">3.8</td>
<td width="20%" align="right">123</td>
<td width="20%" align="right">246</td>
<td width="20%" align="right">369</td>
<td width="20%" align="right">492</td>

</tr>
<tr>
<td width="20%" align="right">7.2</td>
<td width="20%" align="right">65</td>
<td width="20%" align="right">130</td>
<td width="20%" align="right">195</td>
<td width="20%" align="right">260</td>

</tr>
<tr>
<td width="20%" align="right">10.1</td>
<td width="20%" align="right">46</td>
<td width="20%" align="right">92</td>
<td width="20%" align="right">138</td>
<td width="20%" align="right">184</td>

</tr>
<tr>
<td width="20%" align="right">14.2</td>
<td width="20%" align="right">33</td>
<td width="20%" align="right">66</td>
<td width="20%" align="right">99</td>
<td width="20%" align="right">132</td>

</tr>
<tr>
<td width="20%" align="right">18.1</td>
<td width="20%" align="right">26</td>
<td width="20%" align="right">52</td>
<td width="20%" align="right">78</td>
<td width="20%" align="right">104</td>

</tr>
<tr>
<td width="20%" align="right">21.3</td>
<td width="20%" align="right">22</td>
<td width="20%" align="right">44</td>
<td width="20%" align="right">66</td>
<td width="20%" align="right">88</td>

</tr>
<tr>
<td width="20%" align="right">24.9</td>
<td width="20%" align="right">19</td>
<td width="20%" align="right">38</td>
<td width="20%" align="right">57</td>
<td width="20%" align="right">76</td>

</tr>
<tr>
<td width="20%" align="right">28.5</td>
<td width="20%" align="right">16</td>
<td width="20%" align="right">32</td>
<td width="20%" align="right">48</td>
<td width="20%" align="right">64</td>

</tr>
</table>

Further calculations by Jack led him to produce the following list of "preferred" list of antenna lengths, to avoid half wavelengths and their multiples (measurements in feet):

29 35.5 41 58 71 84 107 119 148 203 347 407 423

== Advantages and Uses ==
A random wire Antenna is used in conjunction with an antenna tuner to achieve resonance over a range of bands. The advantage being that it can be used without the need to make physical reconfigurations to the antenna system in order to change bands.

== Basic Construction ==
The basic design of a random length wire Antenna consists of a driven wire of a length that does not correspond to the wavelength of the intended Band and a grounded plane of conductive material such as steel. It differs physically from a Vertical in that ???.

{{antennas}}

Vertical antenna

2010-08-05T00:02:23Z

KJ6EUO: /* 1/2 Wave Vertical */

Related wiki pages: [[Antennas]], [[Propagation]], [[Feedlines]]

Vertical antennas, often simply known to amateurs as "verticals," are [[antennas]] in which the [[driven element]] is vertical. Most common verticals are simply a piece of wire or aluminum tubing mounted vertically, but others, such as those designed for [[mobile antenna|mobile]] use, are significantly more complex.

== 1/4 wave Vertical ==

A quarter wave vertical is electrically equivalent to one half of a center fed dipole that is oriented vertically rather than horizontally. The other half of the dipole is in effect a reflection in the ground-plane of the vertical element.

[[Image:Quarter_vert.jpg | 400px]]

The ground-plane need not actually constructed of solid material. Just as effective is four radials or "arms" at right angles to each other.

For best results the radials may be perpendicular to the vertical element or angled downwards at about 45 degrees.

== 5/8 Wave Vertical ==

== 1/2 Wave Vertical ==
A half wave vertical is electrically equivalent to a center fed dipole that is oriented vertically rather than horizontally. The other half of the dipole is in effect a reflection in the ground-plane of the vertical element.

==Slim-Jim and J-Pole antennas==

[[Image:Slimjim_jpole_pix.jpg | 600px]]

===Indicative dimensions for Slim-Jim and J-Pole antennas===

* Note that the Slim-Jim only uses dimensions A, D, F and C

[[Image:Slimjim_jpole_meas.jpg | 700px]]

== Importance of Ground ==

=== Ground Radials ===

=== Elevated Ground Plane ===

== Efficiency ==

Refer to KE4UYP's [[Vertical Antenna efficiency]] article for more discussion.

== Loaded Verticals ==

Antenna loading is the practice of shortening antennas to less than the length that [[resonance]] would normally require, then adding [[reactance|reactive elements]] to bring them back to resonance. They are very useful when the space a full-size antenna would require is not available. All verticals designed for mobile use must use some type of loading.

See [[antenna loading]] for a detailed discussion.

== Phased Vertical Arrays ==

{{antennas}}

Vertical antenna

2010-08-05T00:01:59Z

KJ6EUO: /* 1/4 wave Vertical */

Related wiki pages: [[Antennas]], [[Propagation]], [[Feedlines]]

Vertical antennas, often simply known to amateurs as "verticals," are [[antennas]] in which the [[driven element]] is vertical. Most common verticals are simply a piece of wire or aluminum tubing mounted vertically, but others, such as those designed for [[mobile antenna|mobile]] use, are significantly more complex.

== 1/4 wave Vertical ==

A quarter wave vertical is electrically equivalent to one half of a center fed dipole that is oriented vertically rather than horizontally. The other half of the dipole is in effect a reflection in the ground-plane of the vertical element.

[[Image:Quarter_vert.jpg | 400px]]

The ground-plane need not actually constructed of solid material. Just as effective is four radials or "arms" at right angles to each other.

For best results the radials may be perpendicular to the vertical element or angled downwards at about 45 degrees.

== 5/8 Wave Vertical ==

== 1/2 Wave Vertical ==
A half wave vertical is electrically equivalent to one half of a center fed dipole that is oriented vertically rather than horizontally. The other half of the dipole is in effect a reflection in the ground-plane of the vertical element.

==Slim-Jim and J-Pole antennas==

[[Image:Slimjim_jpole_pix.jpg | 600px]]

===Indicative dimensions for Slim-Jim and J-Pole antennas===

* Note that the Slim-Jim only uses dimensions A, D, F and C

[[Image:Slimjim_jpole_meas.jpg | 700px]]

== Importance of Ground ==

=== Ground Radials ===

=== Elevated Ground Plane ===

== Efficiency ==

Refer to KE4UYP's [[Vertical Antenna efficiency]] article for more discussion.

== Loaded Verticals ==

Antenna loading is the practice of shortening antennas to less than the length that [[resonance]] would normally require, then adding [[reactance|reactive elements]] to bring them back to resonance. They are very useful when the space a full-size antenna would require is not available. All verticals designed for mobile use must use some type of loading.

See [[antenna loading]] for a detailed discussion.

== Phased Vertical Arrays ==

{{antennas}}

Vertical antenna

2010-08-05T00:01:30Z

KJ6EUO: /* 1/2 Wave Vertical */

Related wiki pages: [[Antennas]], [[Propagation]], [[Feedlines]]

Vertical antennas, often simply known to amateurs as "verticals," are [[antennas]] in which the [[driven element]] is vertical. Most common verticals are simply a piece of wire or aluminum tubing mounted vertically, but others, such as those designed for [[mobile antenna|mobile]] use, are significantly more complex.

== 1/4 wave Vertical ==

A quarter wave vertical is electrically equivalent to one half of a centre fed dipole that is oriented vertically rather than horizontally. The other half of the dipole is in effect a reflection in the groundplane of the vertical element.

[[Image:Quarter_vert.jpg | 400px]]

The groundplane need not actually constructed of solid material. Just as effective is four radials or "arms" at right angles to each other.

For best results the radials may be perpendicular to the vertical element or angled downwards at about 45 degrees.

== 5/8 Wave Vertical ==

== 1/2 Wave Vertical ==
A half wave vertical is electrically equivalent to one half of a center fed dipole that is oriented vertically rather than horizontally. The other half of the dipole is in effect a reflection in the ground-plane of the vertical element.

==Slim-Jim and J-Pole antennas==

[[Image:Slimjim_jpole_pix.jpg | 600px]]

===Indicative dimensions for Slim-Jim and J-Pole antennas===

* Note that the Slim-Jim only uses dimensions A, D, F and C

[[Image:Slimjim_jpole_meas.jpg | 700px]]

== Importance of Ground ==

=== Ground Radials ===

=== Elevated Ground Plane ===

== Efficiency ==

Refer to KE4UYP's [[Vertical Antenna efficiency]] article for more discussion.

== Loaded Verticals ==

Antenna loading is the practice of shortening antennas to less than the length that [[resonance]] would normally require, then adding [[reactance|reactive elements]] to bring them back to resonance. They are very useful when the space a full-size antenna would require is not available. All verticals designed for mobile use must use some type of loading.

See [[antenna loading]] for a detailed discussion.

== Phased Vertical Arrays ==

{{antennas}}

Random Wire Antenna

2010-08-04T23:33:09Z

KJ6EUO:

A "Random Wire" antenna is an end-fed antenna that is operated against ground or an artificial ground system - much like a vertical antenna. The "Random Wire" must normally be coupled to the transmitter by an [[Impedance_matching|ATU]] (except if it happens to be in resonance on some amateur band).

A popular length is 7m. This does not provide excessive impedances for the ATU to tune out for bands between 80 and 10m.

Jack Clarke VE3EED adds that for optimum performance, "random length" antennas should not be multiples of half wavelengths in the intended bands. The following table reproduced with permission from his [http://www.jackclarke.net/hamdnld.htm website] details half wave lengths that should be avoided.

<table border="1" cellpadding="6" cellspacing="0" width="58%">
<tr>

<td width="20%" align="center">Frequency
MHz</td>
<td width="20%" align="center">1/2
Wave</td>
<td width="20%" align="center">2nd
Multiple</td>
<td width="20%" align="center">3rd
Multiple</td>
<td width="20%" align="center">4th
Multiple</td>
</tr>

<tr>
<td width="20%" align="right">1.9</td>
<td width="20%" align="right">246</td>
<td width="20%" align="right">492</td>
<td width="20%" align="right">738</td>
<td width="20%" align="right">984</td>

</tr>
<tr>
<td width="20%" align="right">3.8</td>
<td width="20%" align="right">123</td>
<td width="20%" align="right">246</td>
<td width="20%" align="right">369</td>
<td width="20%" align="right">492</td>

</tr>
<tr>
<td width="20%" align="right">7.2</td>
<td width="20%" align="right">65</td>
<td width="20%" align="right">130</td>
<td width="20%" align="right">195</td>
<td width="20%" align="right">260</td>

</tr>
<tr>
<td width="20%" align="right">10.1</td>
<td width="20%" align="right">46</td>
<td width="20%" align="right">92</td>
<td width="20%" align="right">138</td>
<td width="20%" align="right">184</td>

</tr>
<tr>
<td width="20%" align="right">14.2</td>
<td width="20%" align="right">33</td>
<td width="20%" align="right">66</td>
<td width="20%" align="right">99</td>
<td width="20%" align="right">132</td>

</tr>
<tr>
<td width="20%" align="right">18.1</td>
<td width="20%" align="right">26</td>
<td width="20%" align="right">52</td>
<td width="20%" align="right">78</td>
<td width="20%" align="right">104</td>

</tr>
<tr>
<td width="20%" align="right">21.3</td>
<td width="20%" align="right">22</td>
<td width="20%" align="right">44</td>
<td width="20%" align="right">66</td>
<td width="20%" align="right">88</td>

</tr>
<tr>
<td width="20%" align="right">24.9</td>
<td width="20%" align="right">19</td>
<td width="20%" align="right">38</td>
<td width="20%" align="right">57</td>
<td width="20%" align="right">76</td>

</tr>
<tr>
<td width="20%" align="right">28.5</td>
<td width="20%" align="right">16</td>
<td width="20%" align="right">32</td>
<td width="20%" align="right">48</td>
<td width="20%" align="right">64</td>

</tr>
</table>

Further calculations by Jack led him to produce the following list of "preferred" list of antenna lengths, to avoid half wavelengths and their multiples (measurements in feet):

29 35.5 41 58 71 84 107 119 148 203 347 407 423

== Advantages and Uses ==

== Basic Construction ==
The basic design of a random length wire Antenna consists of a driven wire of a length that does not correspond to the wavelength of the intended Band and a grounded plane of conductive material such as steel. It differs physically from a Vertical in that ???.

{{antennas}}