432MHz Low Noise Preamp with FHX35LG
(design JH0WJF)

Presenting you another preamplifier design, made by Noriyuki (JH0WJF). The advantages of this designs are:

  • cheap HEMT FET Transistor
  • easy to build
  • fits in pre made tinplate housing
  • no expensive PCB needed
  • good performance
Schematic of 432MHz low noise preamp

You can use either self made housing from brass or copper sheet metal, or buy a pre made tinplate housing. The dimension is 111 x 55 x 30 mm. The cavity is made by 100x6 mm copper or brass pipe (for better performance [0.01db ??] you can put some silver on it).

Preamp made by Noriyuki (JH0WJF) Preamp made by Frank (DL5LF)

Alignment
Set the draincurrent of the FET to 10mA, by adjusting the 150 ohm source trimmer. Then tune the HQ-trimm Cīs alternative to best NF. If you do not have a NF-meter, take the signal of a weak beacon and tune for best signal-to-noise (I did so and got 0.6 dB, measured later).
You may use GaasFet MGF1302 with not so good NF performance. Therefor the two 1N4148 must be left out.



Look also for another easy design at Christophs (DF9CY) Page.

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