GROL case studies
GROL · Put your knowledge to work in context.
The General Radiotelephone Operator License (GROL) is a commercial operator license issued by the U.S. Federal Communications Commission. The GROL case studies are 5 cases and about 3,545 words.
1Distress Alerting from a Sinking Yacht Offshore
A 60-foot sailing yacht with four persons aboard is 60 nautical miles east of Cape Hatteras at 0230 local time. She has just been holed by a submerged container and is taking on water faster than the manual pumps can handle; the engine will not start.
772 words, about 4 min2A Clean SWR Reading That Hides a Bad Antenna
A 25 W VHF marine transceiver on 156.800 MHz feeds a masthead antenna rated 3 dBd through 35 m of RG-58C/U coaxial cable; the cable's published attenuation at 150 MHz is 0.20 dB per metre. At the radio end the technician measures 25 W forward and 0.2 W reflected, and computes a healthy 1.2:1.
681 words, about 3 min3Series-Regulator Supply Overheating at Full Load
A shore station's 13.8 V, 25 A linear supply uses an 18 V RMS transformer secondary, a bridge rectifier, a 40,000 µF filter capacitor, and four parallel pass transistors bolted to one unfanned heatsink of 1.1 °C/W in a 45 °C radio room. It powers a 100 W PEP HF transceiver drawing about 8 A average and 20 A on voice peaks.
732 words, about 4 min4Deviation Creep and Adjacent-Channel Splatter
A technician services a 25 W VHF FM marine radiotelephone operating on 156.800 MHz in 25 kHz channels. To "make it sound louder" he turns up the microphone gain trimmer, and peak deviation rises from 5 kHz to about 9 kHz on voice peaks.
672 words, about 3 min5Second-Trace Echo or Close Target?
An X-band radar on 9410 MHz with a 4-foot slotted-waveguide antenna mounted 40 m above the water is operating in a coastal area where a strong surface duct has formed. In short-pulse mode the set uses a 2000 Hz PRF.
688 words, about 3 min