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Low Noise Amplifier

Dominique, HB9BBD has put a lot of effort in building a "super" low noise amplifier. The result is a fine "state of art" pré-amplifier with a noise figure of around 0,2 dB !!! A lot of discussion has been going on on how measuring the noise figure of a pré-amplifier. Dominique has a HP 8973B noise figure meter with a (low ENR) N4000A noise source. Results have  been compared my 8970B and HP346A (low ENR) noise source showing similar results. In EME pré-amps return loss is not very important. Matching of the high impedance PHEMT fet to a 50 ohm input is very difficult, when you want to keep the losses to a minimum. Dominique has some interesting reading material on his webpage.  Measurements on LNA's with not ideal input match are tricky, and results should be analyzed very careful.

For detailed information on this fine state of art equipment : http://www.hb9bbd.ch/article.php3?key=26

Switching the LNA away from the feedhorn is very important during TX. This is how it has been done at our station:

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Following pictures have been taken by Dominique, HB9BBD. You will be amazed about the quality and finish of this Swiss made product. Not only their watches are gorgious. inside_pream.jpg.jpg (212031 bytes)   Click on pictures to enlarge

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On the Agilent website you find a lot of information in regards of noise figure measurements. The discussion of noise figure measurement uncertainty is also discussed, and this excel sheet gives you a good idea between the relation of noise figure measurement and input match. Go also to this Agilent webpage for further data. 






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