The world of amateur radio has been revolutionized by digital modes, with FT8 and FT4 standing out as two of the most popular protocols from the creators of WSJT-X. Both are masterpieces of software engineering designed to facilitate contacts under challenging, weak-signal conditions. However, despite their similarities, they are optimized for different purposes.
The OXO QRP HF transmitter is a simple, low-power CW (continuous wave) transmitter designed by George Burt, GM3OXX. It is a single-band transmitter that can be built to operate on any of the amateur radio bands from 160 to 20 meters. The transmitter is built around a few standard transistors and a crystal oscillator. It is an elementary circuit to build, and can be assembled from a kit or from scratch.
The OXO transmitter is a QRP HF transmitter, which means that it produces a very low output power. This makes it ideal for making short-range contacts with other amateur radio operators. The OXO transmitter can also be used for experimentation and learning about radio electronics.
The TL071 operational amplifier makes an excellent foundation for DIY audio compressor circuits. This single-supply design TL071 Audio Compressor offers reliable dynamic range control for musical instruments and recording applications.
This circuit diagram illustrates an audio compressor for microphone signals. Its primary job is to even out the volume of your voice, making soft sounds louder and loud sounds quieter, resulting in a more consistent and professional audio output. This is incredibly useful for podcasts, voice overs, amateur radio, or any application where microphone levels can fluctuate.
The Automatic Identification System (AIS) is a VHF radio-based collision-avoidance protocol that virtually every commercial, passenger, and large recreational vessel in the world is required to carry. Since 2004, the International Maritime Organization (IMO) has mandated AIS transponders on all ships of 300 GT or more engaged in international voyages, all cargo ships of 500 GT or more on domestic routes, and all passenger ships regardless of size.
Every few seconds — sometimes as often as every two seconds when a vessel is manoeuvring — its AIS transponder transmits a compact digital burst on one of two dedicated VHF channels: 161.975 MHz (Channel 87B) and 162.025 MHz (Channel 88B). That burst contains a rich data payload: MMSI number (a unique vessel ID), ship name, call sign, IMO number, vessel type, dimensions, draught, destination, navigational status, GPS position, course over ground, speed over ground, rate of turn, and more.
Minimalist RF circuits often teach more than complex modern designs. This small DSB transmitter is a good example. The entire DSB transmitter uses only one active semiconductor device together with a pair of diodes and a few tuned circuits.
At first glance the circuit almost looks too simple to work seriously. Yet it does. When connected to a properly matched antenna, the transmitter can establish contacts with ordinary SSB stations surprisingly well. Most operators on the other end will hardly notice that the signal comes from such a basic setup because the carrier is largely suppressed.
The original concept was published by the well-known experimenter JF1OZL and later reproduced by several European homebrew enthusiasts. Its appeal comes from one thing: simplicity.
Want a simple, low-cost antenna that actually performs well on VHF/UHF? The twin-lead J-pole might be exactly what you need.
Built from basic 300-ohm twin-lead, this classic design combines a half-wave radiator with a quarter-wave matching section, giving you efficient performance without radials or complicated tuning networks.
Why it’s so popular among ham operators:
• Easy to build with minimal materials
• Naturally omnidirectional—great for repeaters and local contacts
• Adjustable feed point for low SWR without extra components
• Lightweight and portable—perfect for field setups or emergency kits
Whether you're experimenting with antennas or need a reliable backup for your station, this design delivers solid performance for its simplicity.
Check out the full build guide and dimensions here:
🔗 https://vu3dxr.in/twin-lead-j-pole-antenna-for-vhf-and-uhf-amateur-radio/
Looking to upgrade your VHF/UHF setup without complicated gear? Try building a full-wave loop antenna.
This design uses a loop with a perimeter equal to one wavelength, giving you better efficiency and a more balanced radiation pattern compared to basic antennas.
Why hams love it:
• Lower noise pickup (great for cleaner signals)
• Around 2 dB gain over a dipole
• Works across VHF, UHF, and even FM bands with simple scaling
It’s compact, easy to build, and surprisingly effective for both transmitting and receiving.
If you enjoy DIY radio projects, this guide walks you through dimensions and construction step by step:
🔗 https://vu3dxr.in/full-wave-loop-antenna-for-vhf-uhf-fm-radio-bands/
Want to build an FM transmitter from scratch? 🎙️📡
This simple circuit uses a single 2N2222A transistor and a 9V battery to create a functional FM band broadcaster. A great weekend project for learning about tank circuits and frequency modulation!
Schematic and build guide:
Build your own tiny radio station! 🎙️📡
This Mini FM Radio Transmitter circuit is a great way to learn about oscillators, tank circuits, and RF modulation. Simple components, 9V powered, and easy to tune.
Details and schematic here:
If you’ve been hearing the buzz about Meshtastic but aren't sure how it fits into the Amateur Radio world, this comprehensive guide from VU3DXR is a must-read.
While some dismiss it as just for "preppers," hams worldwide are leveraging LoRa (Long Range) technology to build self-healing, infrastructure-independent mesh networks.
What’s inside the guide: ✅ The Tech: How LoRa achieves incredible range below the noise floor. ✅ The Hardware: A look at the T-Beam, Heltec, and RAK WisBlock. ✅ Meshtastic vs. APRS: Why Meshtastic is winning in areas with low infrastructure (like India). ✅ Ham Compliance: How to stay legal (callsign ID, disabling encryption, and frequency selection).
Whether you're in a disaster-prone area or just love experimenting with digital modes, it's time to see what LoRa can do for your shack.
📖 Read the full guide here:
