VK4DD Ham Radio

Brisbane, Australia

Aug 29th
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HF/50 MHz Solid State PA PCB

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The HF / 50 MHz 2x BLF177 SOLID STATE Amplifier

This amplifier is based on 2 x BLF177, a very rugged Fet which has become, in a very short time, one of our most popular products. The fets are rated 150W each, but Harris, a commercial amplifier producer uses 2 of them to make 500W!

The PCB is a high quality 1.6mm board made from the very best FR4 material. Excellent industrial quality boards.

This Amplifier development board retails for US$ 25 while stocks last!


This HF/50MHz PA is based on a Philips application note. Click here to download the Philips / NXP application note.

It describes how 2 x BLF177 can be used to make 300W + out. In the application note you can see that even Philips gets 400W out of the linear amplifier.

Harris a builder of commercial RF gear uses the 2 x BLF177 in a commercial product and pushes them even to 500W in class C.

In order to keep inter-modulation products down I would not recommend to go beyond the 350W. If you want more power, than simply combine 2 boards. There are broadband 50 Ohm combining solutions available for a reasonable price.

The application note shows that the amp runs up to 40 MHz, but with other ferrite it will run up to 50 MHz.

I made a few changes to the original circuit board in the application note.

Each Fet has now its own bias trimmer resistor. This allows you to use also not matched pairs.

I have added a hole in the PCB for a temperature sensor close to the Fets. with this you can cut out he amplifier if the heat sink gets to hot.

Other than that, I hope you will enjoy building this amp as much as I will.


More info on this product can be found here LINK to VK4DD forum for BLF177PA .

73 Ron

For me amateur radio is more than plug and play equipment.

Made in Queensland, the amplifier state of Australia.