PSRA Level 1 Exam cheat sheet

Wavelength in meters = 300 divided by frequency in MHz; a 150 MHz signal has a 2 m wavelength, and a 700 MHz signal about 0.43 m.

Free-space path loss in dB = 32.44 + 20log10(d_km) + 20log10(f_MHz); loss rises 6 dB per doubling of distance or frequency.

ERP = transmitter power in dBm plus antenna gain in dBd minus feedline loss in dB; EIRP = ERP + 2.15 dB.

Receiver sensitivity is the minimum signal producing acceptable output; noise floor in dBm = -174 + 10log10(BW in Hz) + noise figure, before any interference margin.

FM deviation, occupied bandwidth, and channel spacing are distinct: a 12.5 kHz channel typically uses 2.5 kHz deviation, while 25 kHz channels use 5 kHz.

P25 Phase 1 uses C4FM at 4800 symbols/s in 12.5 kHz; Phase 2 uses H-DQPSK at 6000 symbols/s in 6.25 kHz-equivalent slots.

Decibel rules: +3 dB doubles power, +10 dB is ten times power, +6 dB doubles voltage or field strength, and 0 dBm equals 1 mW.

Duty cycle reduces average power: a 50% duty cycle lowers average power by 3 dB relative to key-down continuous transmission.

FirstNet and the public safety broadband network provide data services; mission-critical push-to-talk over broadband is complementary to LMR, not a drop-in replacement for coverage.

P25 Phase 2 and 6.25 kHz efficiency support spectrum migration; the transition plan should describe subscriber, infrastructure, and encryption impacts.

LTE and 5G network slicing and priority services address public safety data, but voice interoperability across agencies still depends on LMR or gateways.

Interoperability gateways bridge LMR and broadband; latency, transcoding, and loss of features such as encryption must be assessed.

Location services and indoor coverage improvements use small cells and distributed antenna systems; design must account for in-building penetration loss.

Modernization planning includes end-of-life analysis for infrastructure and subscriber equipment, funding cycles, and backward compatibility during transition.

Standards evolution includes P25 ISSI and CSSI updates and broadband standards; procurement should reference specific interface standards.

Spectrum policy changes, including reallocation and repacking, require license modification and equipment retuning planning before deadlines.