Antenna

My new favorite HF antenna is the 1/4 Wave HF Vertical DX Antenna with 2 Elevated Radials. It is NOT the most portable antenna (an EFHW wins there) but it is the easiest HF antenna to construct! It is easier to construct, install, and tune than even the basic dipole antenna! It takes less than 15 minutes to build and get on the air with this HF DX antenna! No impedance transformer is required. After trimming, the antenna can directly feed 50 Ω coax. A 1:1 common-mode choke (coax choke works too) at the feedpoint is recommended but NOT absolutely required at low power levels. ...

I recently worked on a redesign of the PA0FRI active antenna using high-speed BFR93A, BFR106, and BFR193 transistors. As a fallback in case of issues, we planned to use NXP MMBT2222A,215 transistors. Design 3D render: Schematic: Previous Next     / [pdf] View the PDF file here. Simulation Results ...

The HFDY Active Loop is working extremely well, even from an indoor location in MK68. Design I am currently running the loop at 5V (via a regulated linear power supply), where it consumes slightly less than 65mA. The recommended voltage is 10V, which I plan to switch to soon. Results I am using Airspy HF+ Discovery SDR for this experiment. Future work It would be very interesting to compare this HFDY Active Loop against the PA0FRI Active Antenna. ...

My homebrewed PA0FRI Active Antenna is working well from a very physically constrained location. Design 3D render: Schematic: Results The antenna is connected to an RSP1 Clone SDR running custom FT8 band-hopping software. I am using a SOLID 4-Way 5-2400 MHz RF splitter to connect multiple SDRs to the same active antenna. NB: Plug in 75-ohm dummy loads (terminators) on the unused splitter ports; MX-282 / MX-280 75-ohm loads work fine. ...