O - Oscar - dah-dah-dah
Odd Split.
An unconventional frequency separation between input and output frequencies of a repeater.
Ofcom.
The body responsable for Amateur Radio Licences in the UK.
Offset.
1: The 300 to 1000-Hz difference in CW transmitting and receiving frequencies in a transceiver.
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2: For a repeater, offset refers to the difference between its transmitting (output) and receiving (input) frequencies.
Offset Frequency.
See: Offset section 2.
Ohm.
The basic unit of electrical resistance, used to describe the amount of opposition to current.
Symbol: Ω Omega. Named after Georg Simon Ohm (short history).
Ohm's Law.
A basic law of electronics. Ohm's Law gives a relationship between voltage (V), current (I), resistance (R) and power (P or W). The basic calculations are: (V = I×R), (W=I×V), (I=V÷R), (R=V÷I).
See also: Ohm's Law page.
Open Circuit.
An
electrical circuit that does not have a complete path, so current can't flow through the circuit.
Open Repeater.
A repeater that can be used by all hams who have a license that authorises operation on the repeater frequencies.
OSC.
OSCAR.
The acronym for Orbital Satellite Carrying Amateur Radio. OSCAR series satellites use amateur radio frequencies to communicate with earth. They are conceived, designed, and built by amateur radio operators under the general direction of national organisations such as AMSAT.
Oscillator.
An electric circuit that generates a frequency.
Oscilloscope.
An electronic test instrument used to observe wave forms and voltages on a cathode-ray tube.
Output Frequency.
A repeater's transmitting frequency. To use a repeater, transmit on the input frequency and receive on the output frequency.
See also: Duplex Operation.
Output Impedance.
The opposition exhibited by a circuits output terminals to the flow of an alternating current (AC) of a particular frequency as a result of resistance, inductance and capacitance. For example, a preamplifier with 100 ohm output impedance means the output voltage signal appears to be in series with a 100 ohm resistor.
Over.
1. The period of a persons speech when using telephony.
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2. Formally, the word used to indicate the end of a voice transmission and invite a reply.