Archive for the ‘HF’ Category.

Simple HF amplifier for QRSS beacon

This is 5 minutes soldering project. There is no schematic, just simple circuit, something between “dead bug” and conventional PCB design. I did this in two steps. First attempt was complete failure. Local OM told me that any power mosfet can operate as power amplifier for HF. Ok, maybe not just any. I tested with couple of them including IRFZ24N. Finaly I took “proper”  MOSFET for higher frequency and the circuit worked pretty good:

Simple output stage for QRSS beacon assembled in "mixed" technology

Simple output stage for QRSS beacon assembled in “mixed” technology

I will briefly describe this quick and simple project and I hope readers would enjoy it.

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Mini CW Keyer / QRSS beacon V1.1

I designed dedicated PCB for the CW keyer. The project is very similar to the version made on prototyping board.

keyer pcb

Here are the updates:

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Programmable CW Morse Keyer / beacon

Mini USB dongle with STM32F0xx is suitable many for simple, mini projects. I attached speaker to Timer14 PWM output (Pin PA6) and LED (or optocoupler connected to PTT) to GPIO pin PA0:


The provided software is based on USB Virtual Com Port (VCP) device. The setup is done with command line interface using terminal from any PC. The setup is stored in the internal flash and PC is not required for normal operation. The mini beacon keyer can be used when powered with 5V.

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Simple small QRO for HF

I followed the ARRL Homberw challenge 50 watt aplifier entry. It is low cost, simple HF linear amplifier designed and built by the author as an entry in the ARRL’s 2009 Homebrew Challenge contest.  The requirements of the amplifier were: 40 meter band 50 watt output amplifier intended for use with a QRP transmitter as driver (less than 5W), constructed at a total material cost of not  over $125.00.

I redesigned author original design an put it on the double sided PCB with additional output banpass filters. I started with first prototype:


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