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Weather Satellite VHF LNA

Minikits in Australia (https://www.minikits.com.au/) makes a nifty little low noise RF amplifier for a VHF weather satellite receiver, such as the Meteor satellite on 137 MHz.   Note that SatDump is very much improved now - it is all the software you need to see that it is raining outside, without the stress of looking out the window.

Some careful soldering is required, but it is not difficult to build. When I test an RF circuit, I run it from a 12V sealed battery - my noise free power supply.

Once tuned up carefully with a nylon screwdriver (the little spatula that you get with epoxy glue!), it can provide up to 20 dB gain, but on average over the band, expect about 5 to 10 dB.  With some patience I eventually managed to eek out 7.6 dB at 137 MHz.  This may not sound like a lot, but a radio receiver is more dependent on the Signal to Noise and Distortion Ratio (SINAD), than the actual signal level.


The LNA is a tuned single transistor amplifier with a linear power supply and a bias-T circuit, which is just the job for a weather sat.

 

Also see these: 

 

La Voila!

Herman


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