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Showing posts from August, 2020

RTL-SDR Weather Satellite Preamplifier

I have been playing with the SATNOGS earth observation satellite system for a few years, but since I am still living in the desert, the climate is against outdoor activities, so its been a bit low key. To work on an antenna on the roof, requires a hat, black sunglasses, a wet T-shirt, a wet towel, a litre of water and a big black umbrella and after that I'm broiled for the day... The few times I tried to download a weather picture, it actually worked, despite having seemingly more noise than signal.  An RTL-SDR  or HackRF One receiver really needs to have a low noise RF preamplifier for best results.  There are several solid state, one transistor preamp kits available that one can buy and build in an evening and stick on the antenna cable, but why do something the easy way, if one can do it the hard way? I recently made a 'simple' (!?) power supply for a Magic Eye cathode ray tube VU meter and the same power supply circuit can be used for a one valve RF receive amplifier

GI-7b Microwave Triode

I recently obtained an ancient Rusky GI-7b microwave C-band triode.  Packed in an innocent looking styrofoam container (I didn't know they had styrofoam in the bronze age - maybe that is how they floated the pyramid stones down the Nile!), it is quite a monster: GI-7b Radar Amplifier Triode This is a radar amplifier tube designed to operate while pulsing at up to 9 kV and 3 GHz. To digress a bit, contrary to common perception, there are still lots of microwave electron tubes in use,  for example microwave ovens, radars, medical diagnostic equipment and satellites .  Travelling Wave Tubes are popular in satellite transmitters, because they are very efficient, very rugged and small. TWT amplifiers have been manufactured by the likes of Honeywell, Thales and others for over half a century - the frequency band just keeps going up and they now operate in the Ka band : What I would