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The output (plate) impedance of the diode vacuum tube rectifiers in the power supply is high, so the increasing impedance of the filter capacitors at low frequencies can mean that low frequency swings in the current drawn by output stages can cause voltage swings in the power supply voltage which feed back to earlier stages, [2] [6] [4] making ...
In amateur radio, QRP operation refers to transmitting at reduced power while attempting to maximize one's effective range. QRP operation is a specialized pursuit within the hobby that was first popularized in the early 1920s. QRP operators limit their transmitted RF output power to 5 W or less regardless of mode (Some call 10 W on Phone QRP) . [1]
The main disadvantage is normally the power supply available. As normal mains grid power is unavailable, the /P operator may have to resort to batteries, portable generators, solar panels. [3] and wind turbines. Operating amateur radio at sea is known as 'maritime mobile', as is signified by the suffix '/MM' on the call.
The power supply voltage changes will appear in the input stage as positive feedback. An example is a transistor radio which plays well with a fresh battery, but squeals or "motorboats" when the battery is old. In audio systems, if a microphone is placed close to a loudspeaker, parasitic oscillations may occur.
In battery-powered equipment, a battery eliminator circuit (BEC) is an electronic voltage regulator used to power a subsystem at a different voltage without the need for a supplemental battery. BECs are commonly used in radio-controlled models , which need separate voltages to power the motor and the RC equipment.
Amateur radio repeaters may even use commercially packaged repeater systems that have been adjusted to operate within amateur radio frequency bands, but more often amateur repeaters are assembled from receivers, transmitters, controllers, power supplies, antennas, and other components, from various sources.
The program is designed for sending and receiving low-power transmissions to test propagation paths on the MF and HF bands. WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. Transmissions carry a station's callsign, Maidenhead grid locator, and transmitter power in dBm.
An amateur radio license is valid only in the country where it is issued or in another country that has a reciprocal licensing agreement with the issuing country. [42] [43] In some countries, an amateur radio license is necessary in order to purchase or possess amateur radio equipment. [44]