145 MHz Band Overview

The 145 MHz frequency sits within the 2-meter VHF band, one of the most widely used and versatile bands in the radio spectrum. While globally allocated for amateur radio (ham radio) in most regions, its adjacent frequencies are also used for land mobile, public safety, and aeronautical telemetry. This band is known for its excellent propagation in urban, suburban, and rural settings, offering a reliable mix of range and signal penetration.

Table of Contents

📶 Frequency Range

Center frequency: 145.000 MHz
Common usage range: 144.000 – 146.000 MHz (may extend to 148 MHz in some regions)
Band classification: VHF (Very High Frequency)
ITU Allocation: Secondary / primary allocation depending on region and country

🌍 Regional Use Breakdown

🌐 Region	Frequency Allocation	Primary Use	Licensing
🌍 Region 1 (Europe, Africa, Russia)	144 – 146 MHz	Amateur Radio	Licensed (Amateur Service)
🌎 Region 2 (Americas)	144 – 148 MHz	Amateur Radio	Licensed (Amateur Service)
🌏 Region 3 (Asia-Pacific)	144 – 146 MHz (some up to 148 MHz)	Amateur Radio	Licensed (Amateur Service)

🟢 Harmonized use: The 145 MHz band is harmonized for amateur use across all three ITU regions.

📱 Applications and Use Cases

Application	Description
Amateur Radio Voice Comms	FM simplex, repeater operation (often at 145.000 MHz or nearby)
Emergency Communication	Used by ARES, RACES, and other public emergency groups worldwide
Packet Radio / APRS	Data transmission and GPS location updates for tracking
Satellite Downlinks	Some amateur satellites (OSCARs) use 145 MHz for telemetry or downlinks
Fox Hunting / T-Hunts	Used for radio direction finding competitions and field training
Balloon Telemetry	Weather and amateur high-altitude balloons transmit beacon data on 145 MHz

🔐 Licensing & Access

Restricted to licensed amateur radio operators
Power levels, permissible modes, and channel spacing vary by country
Usage monitored and enforced by national spectrum regulators:
- FCC (USA)
- Ofcom (UK)
- ANFR (France)
- ACMA (Australia)
- TRAI (India)

⚡ Power and Modulation

Parameter	Typical Value
Max Power (ERP)	~50 W (handheld), ~1.5 kW (base station, where permitted)
Common Modes	FM, SSB, CW, AM, Packet, PSK31, FT8, RTTY, SSTV
Bandwidth	12.5–25 kHz (FM), narrowband digital = <6.25 kHz
Channel Spacing	Often 12.5 kHz or 25 kHz depending on local conventions

📊 Regulatory Insights

Region 1: CEPT recommends 145.000 MHz as a simplex calling frequency; repeater outputs are typically around 145.600–145.800 MHz
Region 2: Repeater outputs often range from 145.110–145.490 MHz
Region 3: National variations exist, with harmonization in major metro areas

Spectrum protection note: 145 MHz is protected against high-power adjacent band emissions due to its importance in disaster response.

📡 Adjacent Band Use

Band	Frequency Range	Use
138–144 MHz	Land mobile / military / telemetry
144–146 MHz	Amateur radio (core use)
146–148 MHz	Additional amateur allocation (Region 2 only)
148–150.05 MHz	Government / telemetry / tracking
150–174 MHz	Public safety, business, maritime, weather services

🛰️ Spectrum Sharing & Interference Risks

Generally exclusive to amateurs, but…
- Adjacent commercial/government systems may cause noise floor elevation
- Urban areas often have strong RF noise from other VHF users
- Careful filtering and bandpass design advised in high-density deployments

📚 Historical Context

Introduced for amateur radio use in the 1940s–50s
Became a key band during the Cold War for civil defense and experimental work
Played a major role in the development of repeater networks
Continues to serve as a primary communication method during natural disasters and infrastructure outages

📝 Notes for Engineers

145 MHz propagation combines ground wave and tropospheric ducting
Ideal for line-of-sight communication (30–100 km) with handheld or mobile setups
Enhanced range possible during temperature inversions or sporadic E events
Easily integrated into antenna arrays for direction finding or APRS systems
Equipment availability: widely supported by multiband radios and SDRs (RTL-SDR, HackRF, etc.)

🔗 Related Technologies

SDR (Software Defined Radios)
APRS (Automatic Packet Reporting System)
Repeater networks (linked via RF or internet)
Space-based amateur payloads (CubeSats, balloons)
Mesh and analog-to-digital bridging systems

🔍 Summary

Attribute	Value/Details
Center Frequency	145 MHz
ITU Region Use	All three (1, 2, 3)
Primary Use	Amateur radio
License Required?	Yes (Amateur Service license)
Typical Power	5 W (handheld) to 1.5 kW (base)
Modulation Types	FM, SSB, digital modes (PSK, FT8, etc.)
Harmonized?	Mostly harmonized globally
Key Benefit	Reliable mid-range communication with low-cost gear