Al Williams writes that International Reply Coupons (IRCs) are nearing their end as the Universal Postal Union prepares to phase them out by December 31, 2026. Once essential for radio hobbyists and international mailers, these coupons allowed individuals to pay postage in one country that could be exchanged for local stamps in another, but modern digital communication has rendered such physical vouchers nearly obsolete.
- Radio enthusiasts used the system primarily to receive QSL cards from foreign stations without requiring senders to cover international shipping costs.
- The Universal Postal Union consists of an association of post offices across 192 countries.
- Charles Ponzi's original scheme involved exploiting price discrepancies for these coupons between different nations.
- Radio enthusiasts used the system primarily to receive QSL cards from foreign stations without requiring senders to cover international shipping costs.
- The Universal Postal Union consists of an association of post offices across 192 countries.
- Charles Ponzi's original scheme involved exploiting price discrepancies for these coupons between different nations.
This article details a fascinating project where a researcher successfully used signals from the NISAR radar-imaging satellite to create a passive radar system. By utilizing the satellite's L-band chirp signal, reflected off the landscape, and comparing it to a direct signal, a topographical image could be generated. The setup involved using GNSS antennas and an SDR (Software Defined Radio) with a Raspberry Pi to record and process the signals. While not producing high-resolution images, the experiment successfully demonstrated the feasibility of using satellite signals for passive radar, even with relatively simple and inexpensive equipment.
The article discusses the challenges faced by hobbyists when building antennas like Yagi and WiFi cantennas, emphasizing the importance of antenna size and tuning to the target frequency for optimal signal performance. It references a webinar by Dr. Jonathan Chisum, highlighting the practical insights beyond textbook theory that can improve antenna design.
The article discusses how ham radio has evolved in the internet age with modern technology, globalization, and digital modes transforming the hobby. It covers advancements in radio equipment, digital modes, computer logging, and the changing perspectives within the ham radio community.
An open-source device, kv4p HT, connects to an Android smartphone and turns it into a radio transceiver for about $35. It uses an ESP32 and transmits one watt, featuring APRS and scanning capabilities. The PCB is simple and affordable with a 3D-printed case.
A simple explanation of waveguides, transmission lines, and related topics using real-world examples and minimal math.
