M - Mike - dah-dah
M.
Shorthand notation for multiply by 1,000,000 or Mega.
m.
Shorthand notation for divide by 1,000 or milli.
mA.
milliAmp. See: Ampere.
Magnetic Loop / Magnetic Loop Antennas.
Have a small antenna size compared to other antennas for the same wavelength. The antenna is typically smaller than quarter wavelength of the intended frequency of operation. Antennas for shortwave communication are normally very large sometimes covering hundreds of feet or meters in length. The advantage of the magnetic loop is that with its small size it maintains very high efficiency levels.
Magnetic Field Strength.
This is the field resulting from the currents on a radiating element. Magnetic field strength is expressed in amperes per meter (A/m).
Magnetic Mount / Mag-Mount.
A mobile antenna with a magnetic base that permits quick installation and removal from a motor vehicle.
Magnetizing Current.
A small current that flows in a transformer primary winding, even with no load connected to the secondary.
mAh.
Maidenhead Locator System.
A scheme used by amateur radio operators for identifying positions on the Earth. It was proposed by the British radio amateur Dr. John Morris (G4ANB), and later adopted by a group of VHF managers, meeting in Maidenhead, England in 1980. The Maidenhead Locator System supplants the older QRA locator system with one that is usable outside of Europe. Maidenhead locators are also commonly referred to as grid locators or grid squares, despite having a non-square shape on almost any cartographic projection.
Main Lobe.
The direction of maximum radiated field strength from an antenna. Also called major lobe.
Major Lobe.
Make-Before-Break.
A switch that is configured to keep the first set of contacts closed while engaging (closing) the new contacts. This causes the momentary connection of both the old and new signal paths. Applies to mechanical systems (e.g. that use relays or manual switches) and to solid-state analog multiplexers and switches.
Malicious (Harmful) Interference.
Intentional, deliberate obstruction of radio transmissions. If an amateur station is found to be causing malicious interference it could be closed down, the equipment siezed and the operator prosecuted and fined and/or imprisioned.
Maximum Average Forward Current.
The highest average forward current that can flow through a diode for a given junction temperature.
Maximum Permissible Exposure Limits (MPE).
The electric field strength, magnetic field strength and plane-wave equivalent power density associated with a radiated electromagnetic wave to which a person may be exposed without harmful effect, and with an acceptable safety factor.
Maximum Useable Frequency (MUF).
The highest-frequency radio signal that will reach a particular destination using sky-wave propagation, or skip. The MUF may vary for radio signals sent to different destinations.
MAYDAY .
From the French m'aidez (help me), MAYDAY is used when calling for emergency assistance in voice modes.
Medium Frequency (MF).
The portion of the radio spectrum from 300 kHz to 3,000 kHz or 300,000 to 3,000,000 cycles per second. One Amateur band can be found in this region of the spectrum:
| ITU Region 1 (Including UK) |
|---|
| Band | Frequency Range |
|---|
| 160 meter | 1.81 - 2.000 MHz |
The Medium Frequency, or Mediumwave Band is where the AM broadcast band is found: 530 kHz to 1610 kHz (1710 kHz in North America).
See also: EHF. HF, LF, SHF, UHF, VHF.
Mega.
The metric prefix for 106, or times 1,000,000.
Megahertz (MHz).
A unit of frequency measurement equal to 1,000,000 cycles per second Hertz.
Memory bank.
A set of memory channels organized into a group.
Memory Effect.
Rechargeable Ni-Cd cells may be consistently getting less capacity as a result of repeated non-full charged/discharged cycles. It is called this because rechargeable batteries lose capacity as if they are "memorising" the wrong full capacity level at less than full charge. Ni-MH cells do not suffer from memory effect as much Ni-Cd and Li-Ion cells are free from this effect.
Meteor Scatter / Meteor Burst Communications (MS / MBC).
A radio propagation mode that exploits the ionized trails of meteors during atmospheric entry to establish brief communications paths between radio stations up to 2200 kilometers (1400 miles) apart. It is also referred to as Meteor Scatter Communications in some documents.
Metric Prefixes.
A series of terms used in the metric system of measurement. We use metric prefixes to describe a quantity as compared to a basic unit. The metric prefixes indicate multiples of 10.
Metric System.
A system of measurement developed by scientists and used in most countries of the world. This system uses a set of prefixes that are multiples of 10 to indicate quantities larger or smaller than the basic unit.
MF.
MIC.
micro (μ).
The metric prefix for 10-6, or divide by 1,000,000.
Microphone.
A device that converts sound waves into electrical energy.
Microwave.
The region of the radio spectrum above 1 giga hertz (GHz).
milli.
The metric prefix for 10-3, or divide by 1000.
Mixer.
A circuit that takes two or more input signals, and produces an output that includes the sum and difference of those signal frequencies.
Mobile.
An amateur radio station designed to be mounted in a vehicle. An amateur radio station installed in a vehicle. A mobile station can be used while in motion. A push-to-talk (PTT) switch usually activates the transmitter.
See also: Hints & Tips for mobile fitting, Legal standpoint and Portable.
Modem.
Short for modulator/demodulator. A modem modulates a radio signal to transmit data and demodulates a received signal to recover transmitted data.
Modes.
1. The older meaning of "mode" refers to the type of signal (modulation) that a transmitter sends. Examples of this meaning include AM, FM, SSB or CW..
2. In our modern age with many ways to encode a signal, the word "mode" also may refer to the type of encoding used to send the signal such as Packet, Pactor, Slow Scan TV, RTTY or Fast Scan TV.
Modulate / Modulation / Modulated.
To vary the amplitude, frequency, or phase of a radio-frequency signal. The process of varying an RF carrier in some way (the amplitude or the frequency for example) to add an information signal to be transmitted, the result is a Modulated signal.
Modulation Index.
The ratio between the maximum carrier frequency deviation and the audio modulating frequency at a given instant in an FM transmitter.
Monitor Mode.
One type of packet radio receiving mode. In monitor mode, everything transmitted on a packet frequency is displayed by the monitoring TNC. This occurs whether or not the transmissions are addressed to the monitoring station.
Monitor Oscilloscope.
An oscilloscope connected to an amateur transmitter and used to observe the shape of the transmitted signal waveform.
Morse Code.
Originally a code developed by Samual Morse. It consists of a series of dots and dashes to make up the letters, numbers and punctuation. In radio terms it is achieved by the switching on and off of the carrier wave.Each page of this glossary is headed with the letter for the page, followed by the recognised phonetic alphabet for that letter, followed by the Morse Code for the letter.
See also: CW & Morse Code.
MPE.
MSK.
Minimum Shift Keying. A modulation method similar to FSK in which the shift in Hertz is equal to half the signaling rate in BPS.
See also: AFSK, FSK, PSK.
MUF.
Multimeter.
An electronic test instrument used to measure current, voltage and resistance in a circuit. Describes all meters capable of making these measurements, such as the volt-ohm-milliammeter (VOM), vacuum-tube voltmeter (VTVM) and field-effect transistor VOM (FET VOM).
Multimode Transceiver.
A transceiver capable of SSB, CW and FM, and possibly AM, operation.
Multiplex / Multiplexed / Multiplexing .
Multiple analog message signals or digital data streams are combined into one signal. In communications, the multiplexed signal is transmitted over a communication channel. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred. A reverse process, known as demultiplexing, can extract the original channels on the receiver side.
mV .
milliVolt. See: Volt.