PSRA Level 1 Exam flashcards

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

Wavelength formula

Wavelength in meters equals 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

FSPL in dB equals 32.44 plus 20log10 of distance in km plus 20log10 of frequency in MHz. Loss increases 6 dB per doubling of distance or frequency.

ERP versus EIRP

ERP references a half-wave dipole and equals transmitter power plus antenna gain in dBd minus feedline loss. EIRP references an isotropic radiator and equals ERP plus 2.15 dB.

Noise floor calculation

Thermal noise in dBm equals -174 plus 10log10 of bandwidth in Hz plus receiver noise figure. A 12.5 kHz receiver with a 5 dB noise figure has a floor near -126 dBm.

P25 Phase 2 modulation

Phase 2 uses H-DQPSK at 6000 symbols per second, placing two voice slots in a 12.5 kHz carrier, equivalent to 6.25 kHz per voice path.

Decibel reference rules

Plus 3 dB doubles power, plus 10 dB is ten times power, and plus 6 dB doubles voltage or field strength. Zero dBm equals 1 mW.

Trunking control channel

A trunked system uses a dedicated control channel to carry registration, affiliation, and call grants. Loss of that channel forces radios into site search or failsoft.

Simulcast timing requirement

Simulcast sites transmit identical signals on the same frequency, so launch timing must be held within a few microseconds. Excess offset causes overlap distortion at site boundaries.

Failsoft operation

When a trunked site controller is unavailable, radios revert to conventional operation on preprogrammed failsoft frequencies, preserving local voice but losing trunking features.

Erlang and grade of service

Busy-hour traffic in Erlangs drives the number of traffic channels needed to meet a blocking target, commonly one to two percent for public safety systems.

Voting receiver system

Multiple receivers at different sites feed a comparator that selects the best-quality audio for transmission. Voting differs from simulcast, which transmits simultaneously from multiple sites.

NIFOG purpose

The National Interoperability Field Operations Guide lists nationwide interoperability channels such as VCALL, VTAC, UCALL, and UTAC, with eligibility and usage restrictions for each.

Interoperability Continuum lanes

The SAFECOM Interoperability Continuum has five lanes: governance, standard operating procedures, technology, training and exercises, and usage, all advanced together.

P25 ISSI and CSSI

The Inter-Sub System Interface links separate P25 systems for roaming and shared talkgroups. The Console Sub System Interface connects dispatch consoles to a system.

Tactical Interoperable Communications Plan

A TICP documents a region's shared interoperability channels, gateway resources, governance, and activation procedures, and is validated through exercises rather than filed only.

Fresnel zone radius

First Fresnel zone radius in meters equals 17.32 times the square root of d1 times d2 divided by frequency in GHz times total distance in km.

Coverage reliability statement

A coverage prediction must state location and reliability probability, such as 90 percent at 90 percent. A 50 percent contour describes a different design than an in-building design.

In-building penetration loss

Concrete and metal construction can add 15 to 30 dB of loss beyond outdoor design levels, so in-building coverage requires additional margin or a distributed antenna system.

Co-site desensitization

Co-located transmitters raise the receiver noise floor through transmitter noise and intermodulation products, reducing effective sensitivity even when signal strength appears adequate.

Electrical downtilt

Electrical downtilt shifts the antenna pattern downward without physically moving the antenna, letting coverage footprint be adjusted remotely and precisely.

Part 90 public safety rules

FCC Part 90 governs public safety land mobile radio, defining eligibility, authorized frequencies, emission designators, power limits, and geographic service areas on each license.

Emission designator meaning

An emission designator encodes necessary bandwidth, modulation type, and information content. For example, 11K2F3E describes 12.5 kHz analog frequency-modulated voice.

Frequency coordination prerequisite

Public safety frequency coordination is performed by certified coordinators before the FCC application is filed. Coordination is a required prerequisite, not an optional courtesy.

License modification requirement

Changing frequency, power, antenna height, or location beyond authorized parameters requires a license modification before operation. Operating first is noncompliance.

RF exposure evaluation

FCC OET Bulletin 65 methods evaluate controlled and uncontrolled environments against frequency-dependent limits, accounting for transmitter power, antenna gain, and distance.

RSSI versus BER diagnosis

Strong RSSI with high bit error rate indicates interference or simulcast distortion rather than weak signal, so coverage fixes will not resolve the fault.

Simulcast delay spread

Simulcast distortion is diagnosed by measuring timing offsets between sites. When offset exceeds the equalizer's correction range, audio becomes distorted at site boundaries.

Key performance indicators

Public safety radio KPIs include channel busy percentage, access delay, call setup time, dropped call rate, and site availability, each measured over defined windows.

P25 link versus end-to-end encryption

Link layer encryption protects only the air interface. End-to-end encryption protects content through the infrastructure and requires matching keys at both endpoints.

Key management facility role

The KMF generates, stores, and distributes keys to radios and infrastructure. A key mismatch appears as garbled audio or denied access, not as a coverage problem.

COML responsibilities

The Communications Unit Leader manages incident communications within the Logistics Section under ICS, preparing the ICS 205 plan and coordinating channels, equipment, and personnel.

ICS Form 205

The Incident Radio Communications Plan assigns channels, functions, and talkgroups by operational period and is distributed to all users as part of the incident action plan.

FirstNet role

FirstNet provides public safety broadband data services. Mission-critical push-to-talk over broadband complements LMR but does not replace LMR coverage or its interoperability model.

LMR-broadband gateway limits

Gateways bridging LMR and broadband introduce latency and transcoding, and may lose encryption and data features, so these degradations must be documented before use.