Similarly, the ideal 2m antenna for an HT would be approximately 0.5m with you holding the radio for the other half of the antenna, although you can also get a 1m antenna ("half wave") that will work somewhat better, as this is an end fed dipole instead of a monopole, and doesn't rely on you holding the radio to make ...
Most commercially available antennas come in length equivalent from 1/4 to 5/8's of a full wavelength. This means that if you want to run a 2m rig (144'ish Mhz),a half wavelength antenna would be 3.3” long, and 3.3 ft is very manageable for vehiclular operations.
Ideally, the antenna length should be equivalent to the wavelength of a signal. However, this is often not practical given the very long wavelength of LPWAN signals. As a rule of thumb, antenna size of ½ or ¼ wavelength will produce good results.
2 METER 5/8 WAVE ANTENNA
The over all length is 48.2" (122.4cm).
Since the UHF band covers a much larger range of frequencies than VHF, 1/4-wave antennas can range anywhere from 3 to 6 inches (7-15 cm) in length, so using the proper length antenna is somewhat more important. For a system operating at 500 MHz, a 1/4-wave antenna should be about 6 inches (15 cm).
The length of the antenna is inversely proportional to the frequency and directly proportional to the wavelength. The higher the frequency and the shorter the wavelength, the shorter the antenna can be made.
Antenna length formula
Fortunately, there is a simple formula for this. To calculate the effective length of the antenna , the formula λ= v/ f must be used .
In particular, the 2m band extends from 144 MHz to 148 MHz. The FCC Rules say that any mode (FM, AM, SSB, CW, etc.) can be used on the band from 144.100 to 148.000 MHz.
The ideal size of an antenna relies on the wavelength of the signal to be broadcasted or received, it's given because of the one-fourth of the wavelength value. So, the scale of the antenna mustn't be of any length. Therefore, Antennas must not exceed a certain length.
If the antenna is too short, capacitive reactance is present. If it is too long, inductive reactance will be present.
The direction of the field can be determined using the right hand thumb rule. The thumb is pointed in the direction of the current and the fingers of the right hand wrapped into a loose fist. The fingers point in the direction of the magnetic field.
A good long-range antenna may have a maximum range several times greater than a short-range antenna. That's because long-range antennas are designed to pick up weak signals, and their shape and structure let them pick up even faint signals as long as they have a direct line of sight to the tower.
The distance between the two diversity antennas should be at least one quarter of a wavelength, and the distance between them will affect the signal.
Thus, the popular quarter-wave antenna often used for AM might be 246 feet high, and the FM antenna elements would be only around three or six feet long, depending on the antenna design.
A height of 120 feet or even higher will provide even more advantages for long-distance communications. To a distant receiving station, a transmitting antenna at 120 feet will provide the effect of approximately 8 to 10 times more transmitting power than the same antenna at 35 feet.
According to Wikipedia, "The 2 meter amateur radio band is a portion of the VHF (very high frequency) Spectrum, comprising of frequencies stretching from 144.000 MHz to 148.000 MHz." These communications are generally FM or frequency modulated transmissions although some operators do operate using SSB (single sideband) ...
Channel Spacing: 15 kHz or 20 kHz
A big issue for the 2-meter band is that some areas have adopted a 15-kHz channel spacing while others use a 20-kHz channel spacing.
Reception distance
VHF radio waves usually do not travel far beyond the visual horizon, so reception distances for FM stations are typically limited to 30–40 miles (50–60 km).
The length of the antenna is inversely proportional with the frequency of the transmitted signal. It means the higher the frequency the shorter the antenna, or the lower the frequency the longer the antenna.
The resonant frequency decreases with increasing antenna physical length, lm. Further evident in Fig. 5.7 is that longer physical antenna lengths lm shift the antenna resonant frequency to lower frequencies, while shorter lm shift the resonant frequency to higher frequencies.
Constructing a dipole for 160 meters with a length of approximately 254 feet and a height of 50 feet or higher will produce a low angle of radiation. This antenna configuration produces a high angle of radiation, consists of a loading coil in each leg resulting in narrow bandwidth, and is only 18 feet at its apex.
An ideal antenna called an isotropic source radiates spherically or equally well in all directions. In a dipole, the radiation pattern is shaped like a doughnut. Looking down on the antenna, you will see a radiation pattern shaped like a figure 8 (Fig. 2b).
Parabolic antennas are the most efficient type of directional antennas because they have small side lobes, sharp radiation angles, and a large front-back ratio. They can serve as a primary mirror for all the frequencies of WiFi signal with a small irradiation loss.