Ladder Line.
An open wire transmission line typically 300 or 450 Ohms.
LCD.
See: Liquid Crystal Display.
Lead Acid.
The oldest type of rechargeable battery. Their ability to supply high surge currents means that the cells maintain a relatively large power-to-weight ratio. This, along with their low cost, makes them ideal for use in cars, as they can provide the high current required by automobile starter motors. They are also used as standby power sources for telecommunications facilities, generating stations, and computer data centers.
See also: Valve Regulated Lead Acid, Rechargable Battery Information page.
LED.
See: Light Emitting Diode.
LEO.
See: Low Earth Orbit
LF.
See: Low Frequency.
Licence / Radio Licence.
The document demonstrating that permission has been granted to the named holder for operation of an amateur radio station.
Light Emitting Diode (LED).
A semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction of the P-N junction. This effect is a form of electroluminescence. LEDs are small extended sources with extra optics added to the chip, which make it easier to see. The color of the emitted light depends on the composition and condition of the semiconducting material used and can be infrared, visible or near-ultraviolet.
Lightning Protection.
There are several ways to help prevent lightning damage to your equipment (and your house), among them unplugging equipment, disconnecting antenna feed lines and using a lightning arrestor.
Li-Ion.
See: Lithium-Ion.
Limiter.
A stage of an FM receiver that makes the receiver less sensitive to amplitude variations and pulse noise.
Line-of-Sight Propagation.
The term used to describe VHF and UHF propagation in a straight line directly from one station to another.
Linear Amplifier.
An electronic circuit whose output is proportional to its input, but capable of delivering more power into a load. The term usually refers to a type of RF power amplifier.
Link / Linking.
1. Some repeater systems have the capability to interconnect receivers and transmitters on more than one band. A n area with a 2-meter repeater, for example, may have a repeater on the 70-cm band as well. The repeaters can be tied together (ie, all signals received on 2 meters or 70-cms are simultaneously retransmitted on 2 meters and 70-cms, and vice versa). When the repeaters are in this state, they are said to be "linked." In this operating mode, users on one band can't readily tell what band other users are operating on because the repeater equipment automatically carries the incoming signals across both bands. Such repeaters may be linked or unlinked by remote control, by users or by a designated control operator, and may have coded courtesy tones that indicate the status of the links. Complex systems may provide links to operators on 29, 50, 144, 430 and 1240 MHz.
2. Also, now, refers to the more common Internet Radio Linking Project links.
Link Budget.
The system of calculating gains and losses of a signal from a transmitter to a receiver through some medium (free space, coax cable etc).
See: Link Budget on the deciBels page.
Liquid Crystal Display (LCD).
A thin, flat display device made up of any number of color or monochrome pixels arrayed in front of a light source or reflector. It uses very small amounts of electrical power and is, therefore, suitable for use in battery powered electronic devices.
Lithium-Ion (Li-Ion).
A type of rechargeable battery commonly used in consumer electronics. They are currently one of the most popular types of battery for portable electronics, with one of the best energy-to-weight ratios, no memory effect and a slow loss of charge when not in use. They can be dangerous if mistreated, however, and unless care is taken their lifespan may be reduced. A more advanced lithium-ion battery design is the lithium polymer cell.
See also: Rechargable Battery Information page.
LO.
See: Local Oscillator.
Local Oscillator (LO).
A receiver circuit that generates a stable, pure signal used to mix with the received RF to produce a signal at the receiver's Intermediate Frequency.
Long-Path Communication / Contact.
Communication made by pointing beam antennas in the directions indicated by the longer Great Circle path between the stations. To work each other by long-path, an amateur in Hawaii would point his antenna west and an amateur in Florida would aim east.
Long Wire Antenna.
See: Random-Length Wire Antenna.
Low Earth Orbit (LEO).
Any orbit around the earth substantially below the geostationary satellite orbit, generally within several hundred km above the earth's surface and usually inclied to the equatorial plane.
Lower Sideband (LSB).
The common single-sideband operating mode on the 40, 80 and 160-meter amateur bands.
Low Frequency (LF).
The portion of the radio spectrum from 30 kHz to 300 kHz. or 30,000 to 300,000 cycles per second. One Amateur band can be found in this region of the spectrum:
| ITU Region 1 (Including UK) | |
|---|---|
| Band | Frequency Range |
| 136 kHz | 135.700-137.800 kHz |