Category Archives: LNA

Everything You Didn’t Know You Were Missing About Bias Tees

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Do you need a bias tee? If you want to put a DC voltage on top of an RF signal, chances are that you do. But what exactly are bias tees, and how do they work?

If that’s your question, [W2AEW] has an answer for you with this informative video on the basics of bias tees. A bias tee allows a DC bias to be laid over an RF signal, and while that sounds like a simple job, theory and practice often deviate in the RF world. The simplest bias tee would have a capacitor in series with the RF …read more

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Fallen Radiosonde Reborn as Active L-band Antenna

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If your hobby is chasing radiosondes across vast stretches of open country, and if you get good enough at it, you’ll eventually end up with a collection of the telemetry packages that once went up on weather balloons to record the conditions aloft. Once you’ve torn one or two down though, the novelty must wear off, which is where this radiosonde conversion to an active L-band antenna comes from.

As it happens, we recently discussed the details of radiosondes, so if you need a primer on these devices, check that out. But as Australian ham [Mark (VK5QI)] explains, radiosondes are …read more

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Cascade LNAs and Filters for Radioastronomy with an SDR

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It may not be the radio station with all the hits and the best afternoon drive show, but 1420.4058 MHz is the most popular frequency in the universe. That’s the electromagnetic spectral line of hydrogen, and it’s the always on the air. But studying the H-line is a non-trivial task unless you know how to cascade low-noise amplifiers and filters to use an SDR for radio astronomy.

Because the universe is mostly made of hydrogen, H-line emissions are abundant, and their distribution can tell us a lot about the structure of galaxies. The 21-cm emission line is so characteristic and …read more

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Portable Classroom Upgrade: Smaller, Cheaper, Faster

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[Eric] at MkMe Lab has a dream: to build a cheap, portable system that provides the electronic infrastructure needed to educate kids anywhere in the world. He’s been working on the system for quite a while, and has recently managed to shrink the suitcase-sized system down to a cheaper, smaller form-factor.

The last time we discussed [Eric]’s EduCase project was as part of his Hackaday Prize 2016 entry. There was a lot of skepticism from our readers on the goals of the project, but whatever you think of [Eric]’s motivation, the fact remains that the build is pretty cool. The …read more

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Listening to Jupiter on a DIY Radio

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By Jove, he built a radio!

If you want to get started with radio astronomy, Jupiter is one of the easiest celestial objects to hear from Earth. [Vasily Ivanenko] wanted to listen, and decided to build a modular radio receiver for the task. So far he’s written up six of the eight planned blog posts.

The system uses an LNA, a direct conversion receiver block, and provides audio output to a speaker, output to a PC soundcard, and a processed connection for an analog to digital converter. The modules are well-documented and would be moderately challenging to reproduce.

NASA maintains …read more

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