Contact: info@pavlin.si
Archive for the ‘HF’ Category.
This is complete project for 1×6 antenna switch. It was bult in more than 50 pieces around the world and performs really good. Even big guns use it for their systems. The project was designed with help from other OMs (S55O, S59MA, S50LD, S51CT, S51ZJ, SM2WMV/SJ2W and others).
6×1 antenna switch
Low noise amplifiers are very useful. I built one with single BFG425W transistor with adjustable bias current. The schematic diagram is very simple:
LNA schematic diagram
and the PCB is 20x24mm:
LNA PCB
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
I will briefly describe this quick and simple project and I hope readers would enjoy it.
I designed dedicated PCB for the CW keyer. The project is very similar to the version made on prototyping board.
Here are the updates:
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.
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:
