OH2NLT HF FET amplifier

Experiments started 31.01.2004

Page updated 19.12.2005



The project

This project is not yet ready. I have just put here few pictures to show current status.

My aim is to make mobile 1,8 to 28 MHz 100W HF amplifier operating with 12 to 14V power source. Amplifier is going to be used with Yaesu FT817 all mode QRP transceiver, Amplifier control is going to be fully integrated with transceiver controls. Currently I am experimenting with Philips BLF177 HF/VHF power MOS FETs.


PA Board prototype

Philips BLF177 transistors

Amplifier controller top view and bottom view

Amplifier is going to be build in old modem housing. Possible module layout.


New interesting / promising transistors. BLF548

Measurement setup for BLF548

High RF currents are too much for by pass capacitors

Same catastrophe happened also earlier with BLF177 transistors when testing low impedance phase reversing transformer.


For DC transceiver project amplifiers with Mitsubishi RD70HVF1 and RD15HVF1 FETs have been successfully constructed. 10 50W power level is easier to achieve with 12-14V power supply. Higher power levels means lower Drain impedance which is much more difficult to handle.


Countless number of transformers has been measured to find out right construction. Here are few examples measured with OH7SV.

Many different alternative constructions has also been build and tested. Few examples here.


Maybe some day all this will be ready.