V - Victor - di-di-di-dah
V.
Valve Regulated Lead Acid (VRLA).
Used to be called Sealed Lead Acid (SLA) but was considered misleading as the cells were not sealed but vented. Unlike a traditional wet-cell lead-acid battery, these batteries do not need to be kept upright (though they cannot be charged inverted), they virtually eliminate the electrolyte evaporation, spillage (and subsequent corrosion issues) common to the wet-cell battery, and boast greater resistance to extreme temperatures, shock, and vibration. As a result, they are primarily used in automobiles, boats, aircraft, and other motorized vehicles. They are not completely sealed; the valve regulation system allows for gas to be expelled. Chemically they are the same as wet (non sealed) batteries except that the antimony in the lead plates is replaced by calcium. This preserves the mechanical characteristics but renders the construction far less prone to gassing. The battery type is often referred to as a Lead-Calcium battery.Care must be taken to prevent short circuits and rapid charging. Charging with a constant voltage can cause a rapid initial current, so therefore it is suggested to begin with a constant current, using constant voltage only for the final portion of the charging.
See also: Rechargable Battery Information page.
Varactor Diode.
A diode that varies its capacitance when a varying voltage is applied.
Variable Capacitor.
A capacitor that can have its value changed within a certain range.
Schematic symbol: 
Variable Frequency Oscillator (VFO).
An oscillator used in receivers and transmitters. The frequency is set by a tuned circuit using capacitors and inductors. The frequency can be changed by adjusting the components in the tuned circuit.
Variable Resistor (VR).
A resistor whose value can be adjusted over a certain range, without removing it from a circuit.
Schematic symbol: 
VCO .
Velocity Factor.
The speed at which an electrical signal (e.g. radio) passes through a medium. Expressed as a percentage, it is the ratio of a signal's transmission speed compared to the speed of light in vacuum. Transmission in a vacuum would have a VF of 100. VF equals the reciprocal of the square root of the dielectric constant of the material through which that signal passes.
Vertical Antenna.
A common amateur antenna, often made of metal tubing. The radiating element is vertical. There are usually four or more radial elements parallel to or on the ground.
Vertical Polarisation.
Where the direction of the radio wave oscillates up and down, perpendicular to the surface of the Earth.
Vertically Polarized Wave.
A radio wave that has its electric lines of force perpendicular to the surface of the Earth.
Very High Frequency (VHF).
The portion of the radio spectrum from 30 MHz to 300 MHz or 30,000,000 to 300,000,000 cycles per second. Three Amateur bands can be found in this region of the spectrum:
| ITU Region 1 (Including UK)
|
|---|
| Band | Frequency Range
|
|---|
| 6 meter | 50.000 - 52.000 MHz
|
| 4 meter | 70.000 - 70.500 MHz
|
| 2 meter | 144.000 - 146.000 MHz
|
VHF is where the FM broadcast band is found: 88 to 108 MHz.VHF signals depend largely on line of sight for communication since VHF and higher frequencies are not normally reflected by the Ionosphere. However by using Amateur Satellites or repeaters or because of interesting weather conditions or other means; VHF signals may travel longer distances than the normal line of sight suggests.
See also: EHF, HF, LF, MF, SHF, UHF.
Very Low Frequency (VLF).
The portion of the radio spectrum from 10 kHz to 30 kHz or 10,000 to 30,000 cycles per second. No Amateur bands currently exist in this region of the Radio spectrum in the UK (2007).
VFO.
VHF.
Visible Horizon.
The most distant point one can see by line of sight.
VLF.
Voice.
Any of the several methods used by amateurs to transmit speech.
Voice Communications (Telephony).
Quite simply talking over the airwaves. Radio Amateurs can use several voice modes, including FM and SSB.
Voice Operated Transmit (VOX).
VOX or Voice Operated eXchange, as it should properly be called, is a switch that operates when sound over a certain level is detected. It is usually used to turn on a transmitter when someone speaks and turn it off when they stop speaking. It is used instead of a push-to-talk button on transmitters. The circuitry usually includes a delay that leaves the circuit activated for a short time after the sound stops so keeping the circuit from turning off during short pauses in speech, i.e. a taking of breath. VOX can be of great use on SSB as, if set correctly, the receiver will switch back on when you take a breath, so giving a chance for comment or another operator to 'break in'.
Voice Over Internet Protocol (VoIP).
The routing of voice conversations over the Internet or through any other Internet Protocol based network. Amateur radio has adopted VoIP by linking repeaters, gateways and users with Echolink, IRLP, D-STAR and EQSO. Echolink and IRLP are programs/systems based upon the Speak Freely VoIP open source software. In fact, Echolink allows users to connect to repeaters via their computer (over the Internet) rather than by using a radio. By using VoIP Amateur Radio operators are able to create large repeater networks with repeaters all over the world where operators can access the system with actual ham radios. Amateur Radio operators using radios are able to tune to repeaters with VoIP capabilities and use DTMF buttons to command the repeater to connect to various other repeaters, thus allowing them to talk to people all around the world, even with 'line of sight' VHF and UHF radios.
See also: Digital Modes page.
VoIP.
Volt / Voltage (V).
The basic unit of electrical pressure or Electro Magnetic Force (EMF).
'V' can be used in conjunction with any of the standard multipliers or dividers to give larger or smaller amounts: Microvolt (μV), 1/1000000 (millionth) of a volt, Millivolt (mV), 1/1000 (thousandth) of a volt, Kilovolt (kV), 1000 Volts, Megavolt (MV), 1000000 Volts being the most common.
Voltage Controlled Oscillator (VCO).
A radio frequency oscillator used in receivers and transmitters, usually tuned by applying a variable voltage to a varactor diode in a PLL or frequency synthesizer.
Voltmeter.
A test instrument used to measure voltage.
VOX.
VR.
VSWR.