1:49 UNUN is a type of transformer that can be used to match an end fed half wave antenna to a 50 ohm coaxial cable. It is made from two stacked FT240-43 cores.
DIY
“DIY” on DXR Electronics Bits is where practical ham radio projects come to life. Here you’ll find buildable circuits, antennas, receivers, preamps, audio tools, and experimental rigs designed for real‑world shack and field use. From compact HF antennas for small spaces to regenerative receivers, QRP transmitters, and uBITX add‑ons, each article focuses on parts you can actually source and solder on the bench.
Ten Minute QRP Transmitter
Build a functional “Ten-Minute” QRP Transmitter with this simple DIY guide. Featuring a minimal component count and a crystal oscillator, this ultra-fast build is perfect for beginners and ham radio emergency kits.
Circuits – Sovina2 40M Class E Transmitter
This is a Class E Transmitter designed for the 40-meter amateur radio band, capable of producing approximately 4.6W output power at 80% efficiency. Class E Transmitter Power Supply 11.5V DC supply (Vcc) powers the circuit 470µF electrolytic capacitor provides power supply filtering and decoupling Input Stage 1M input resistor provides high impedance input matching 10µH […]
VK4FUQ Optimized sloper antenna for 3.5Mhz
VK4FUQ’s optimised sloper antenna for 3.5MHz. Radiator and counterpoise radial are both one-quarter-wave in length (length in metres = 71.37/(frequency in MHz) or in feet 234/MHz). The radial should be at least 5ft (preferably about 8ft) above ground and immediately underneath the radiator. Good quality insulators are need at the top of the preferably non-conductive […]
Half Rhombic antenna with counterpoise
The inverted rhombic antenna boasts a distinctive half-rhombic configuration. Its directivity focuses toward the terminated end, enhancing signal precision. Developed by Bruce, it demands a non-conductive mast for optimal performance. This design delivers significant gain across the 50 to 70MHz bands. A non-inductive terminating resistor is essential, tailored to the RF power delivered. For SSB […]
Terminated End Fed Vee Antenna (TEFV)
Terminated End Fed V Antenna (TEFV) – It Is a travelling wave antenna, which has a constant current distribution along its length.
Circuits – Simple Crystal Tester
Simple Crystal tester – The idea for this crystal tester circuit sprung out of the need of testing a large number of oscillator crystals lying unused in a big hobby box. testing the crystals one by one without the appropriate device would have been very slow and a time consuming task. Commercial crystal testers are […]
Circuits – 40M tag QRP Transmitter
Here is another qrp cw transmitter pulled out from SPRAT back issues, which is simple to build with commonly available components from every one shack. We can subsititute 2N2222 for BC108 and BD139 for BD 131.
Antenna – Rockloop HF Antenna for 10,15,20 metre ham bands
Rockloop HF antenna for 10,15,20 metre ham bands The Rockloop HF Antenna ‘s a tuned loop antenna measuring 33 feet square (10m x 10m) designed for 15m, 20m, and 30m bands.This rock loop antenna tunes to 15 meter band with 15 to 20pf,20 meters with about 30pf, and 30 meters with about 60pf, much suitable […]
Circuit – FM Bandstop Filter for RTL SDR
FM Bandstop Filter for RTL SDR The given FM band stop filter is nothing more than a simple Band stop filter for the frequency range of 88-108Mhz. FM Broadcast transmitters transmit at high power and can cause overloading and intermodulation problems on simple receivers like RTL-SDR due to its wide open front end. The said […]