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Showing posts from September, 2023

Weather Satellite VHF LNA

Minikits in Australia ( ) 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 a

ADS-B Patch Antenna on RF Controlled Impedance PCB

In a moment of boredom/inspiration, I thought about making a patch antenna for my ADS-B aircraft tracking system, which is part of ADS-B Exchange .  One can make one-off patch antennas from garden variety glass/epoxy FR4 board, but the result will have relatively high loss and it will not be repeatable.  In order to simply order high quality batches of antennas from any PCB factory, one needs to use low loss, controlled impedance board stock . With this antenna, the ADS-B receiver simply sits on my window sill and picks up aircraft 200 km away. Cut Corners The design is a typical rectangular patch antenna, with circular polarization.  A circular polarized antenna allows more mounting options for a conformal antenna. Slots The side slots in this design increases the bandwidth, but it also reduces the operating frequency, so slots can be used to tune a patch antenna design. Board Type There are a variety of RF boards made by various manufacturers ( Rogers , Isola , Panasonic ... ) and