PG103 Preamp with filter for 144 MHz.

Leo ON6LEO needed a preamp as a second stage. I needed a preamp for 432 MHz and also one as a broadband measurement preamp. The PGA103 looked like a nice device. Simple to set up and low noise figure and enough gain.

I used several articles on the web.

First application sheet about stability from Mini Circuits HERE

And the article from W1GHZ found HERE

Schematic of the Preamp, designed with all possible variations. I build 4 units, two of them with the stabilization circuit, two units without it. No instabilities observed at all. Only very little variations in noise figure. Hard to say if it comes from the stabilization circuit.


The inductor feeding the MMIC L2 is NOT 1uH This is a 6 or 7 turn on a 5mm drill Adjusted to PCB length (15mm abt)

The filter was designed with ELSIE by TONNE software. And consists of a bandpass- and a highpass filter

The plot in ELSIE looked like this:

The filter was build on a piece of copper clad PCB. Adjusting is done by bending / stretching the inductors and a 22 pF trimmer

Loss is about 1dB but that is not so important for a second stage preamp.