GROL flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Element 1 pass mark

Of the 24 questions on FCC Element 1, basic radio law and operating practice, 18 correct answers, 75 percent, are required to pass.

GROL license term

Commercial radio operator licenses are issued for the lifetime of the holder; they do not expire or need renewal, but the FCC may revoke, suspend, or modify them.

FCC Part 80

The FCC rules governing ship radio stations, covering station licensing, authorized frequencies, watch requirements, and distress and safety operating procedures for vessels.

ITU Radio Regulations

The international treaty text that assigns radio frequency bands and sets operating procedures; FCC Part 2 implements these allocations for stations in the United States.

MAYDAY

Spoken three times, the international radiotelephone distress signal, followed by the vessel name, position, nature of distress, assistance required, and persons aboard.

VHF channel 16

156.800 MHz, the international radiotelephone distress, safety, and calling channel, monitored by ships and coast stations and used to initiate contact.

PAN PAN

Spoken three times, the urgency signal used when a station has a very important message about the safety of a vessel or person but no immediate danger exists.

2182 kHz silence periods

Three minutes of radio silence begin at H+00 and H+30 each hour on 2182 kHz, reserved for distress calls and the stations answering them.

Ohm's law

Voltage equals current multiplied by resistance (V = IR); power equals voltage times current, or current squared times resistance.

Series resonance

The condition in which inductive and capacitive reactance are equal, at f = 1/(2π√LC); the circuit then presents minimum, purely resistive impedance.

Decibel

Ten times the base-10 logarithm of a power ratio, or 20 log of a voltage ratio in equal impedance; adding 3 dB doubles power.

Transistor beta

The ratio of collector current to base current in a bipolar transistor, showing how a small base current controls a much larger collector current.

Class C amplifier

An amplifier conducting for less than 180 degrees of the cycle, giving high efficiency; used in RF output stages with a tuned circuit to restore the waveform.

Full-wave ripple frequency

With full-wave or bridge rectification the ripple frequency is twice the AC line frequency, so a 60 Hz supply produces 120 Hz ripple.

Oscillator feedback requirement

An oscillator requires positive feedback with a loop gain of at least one and a total loop phase shift of zero or 360 degrees.

Colpitts oscillator

An oscillator that uses a tapped capacitive divider across the tuned circuit to supply feedback; the Hartley version uses a tapped inductor instead.

J3E emission

Single-sideband, suppressed-carrier telephony; it occupies about 3 kHz and is the standard emission for HF ship radiotelephone service.

A3E emission

Amplitude modulation with double sideband and full carrier telephony; bandwidth equals twice the highest modulating frequency, about 6 kHz for voice.

AM modulation index

m = (Emax − Emin)/(Emax + Emin); total power becomes Pc(1 + m²/2), and 100 percent modulation occurs when m equals one.

Carson's rule

An approximation of FM bandwidth as twice the sum of peak deviation and the highest modulating frequency: BW = 2(Δf + fm).

Half-wave dipole length

Length in feet equals 468 divided by the frequency in MHz; a resonant center-fed dipole presents about 73 ohms in free space.

VSWR definition

The ratio of maximum to minimum voltage on a transmission line: VSWR = (1+|Γ|)/(1−|Γ|), where Γ is the reflection coefficient; 1:1 is a perfect match.

Velocity factor

The ratio of propagation speed on a line to the speed of light; physical length equals electrical length times this factor, about 0.66 for solid polyethylene coax.

dBd versus dBi

Antenna gain referenced to a half-wave dipole (dBd) is 2.15 dB less than the same gain referenced to an isotropic radiator (dBi).

Maximum usable frequency

The highest frequency the ionosphere reflects between two points at a given time, roughly critical frequency divided by the cosine of the incidence angle.

Radio horizon

Line-of-sight distance is about 1.23 times the square root of antenna height in feet, expressed in nautical miles; in kilometers use 4.12 times the root in meters.

D layer absorption

The lowest ionospheric layer absorbs HF energy during daylight, so higher frequencies work better by day and lower frequencies by night.

Image frequency

An unwanted signal that also converts to the intermediate frequency; it lies 2 × IF from the desired signal and is attenuated by preselectors or a tuned RF stage.

Automatic gain control

A circuit that derives a DC voltage from the received signal to reduce RF and IF gain on strong signals, keeping audio output nearly constant.

Splatter interference

Adjacent-channel interference caused by overmodulation or nonlinear amplification, which generates sidebands extending beyond the assigned emission bandwidth.

X-band marine radar

Radar operating at 9.3 to 9.5 GHz, about 3 cm wavelength, giving narrow beamwidth and high resolution for short-range navigation and collision avoidance.

SART

A search and rescue transponder that transmits on 9 GHz in response to radar pulses, showing a line of twelve dots on the rescuing vessel's radar display.