If you’re planning on working satellites or doing any sort of RF work where the signal lives down in the dirt, you’re going to need a low-noise amplifier. That’s typically not a problem, as the market is littered with dozens of cheap options that can be delivered in a day or two — you just pay your money and get to work. But is there a case to be made for rolling your own LNA?

[Salil, aka Nuclearrambo] thinks so, and he did a nice job showing us how it’s done. The first step, as always, is to define your specs, which for [Salil] were pretty modest: a low noise figure, moderate gain, and good linearity. He also wanted a bandpass filter for the 2-meter amateur radio band and for weather satellite downlinks, and a bias-tee to power the LNA over the coax feedline. The blog post has a detailed discussion of the electrical design, plus some good tips on PCB design for RF applications. We also found the discussion on bias-tee design helpful, especially for anyone who has ever struggled with the idea that RF and DC can get along together on a single piece of coax. Part 2 concentrates on testing the LNA, mostly using hobbyist-grade test gear like the NanoVNA and tiny SA spectrum analyzer. [Salil]’s tests showed the LNA lived up to the design specs and more, making it more than ready to put to work with an RTL-SDR.

Was this more work than buying an LNA? Absolutely, and probably with the same results. But then again, what’s to learn by just getting a pre-built module in the mail?

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 a list of receivers suitable for Jovian listening, although you can use basically any receiver that covers the right frequency band. If you want to hear what the giant planet sounds like, check out the video, below.

If you are interested in a cheap way to listen to some of our other cosmic neighbors, you might think about converting a satellite dish. Or, you can try something smaller.

[Will] recently tipped us about a 400MHz Low Noise Amplifier (LNA) module he made. His detailed write-up starts by explaining the theory behind an amplifying chain. Assuming a 50 Ohm antenna system receives a -70dBm signal, the total peak to peak voltage would be less than 200uV (.0002 volts). If the first amplifying stage doesn’t consist of an LNA, then the added noise would later be amplified by the other elements of your system.

[Will] then detailed how he picked his LNA on Digikey, mainly by looking for one that had a less than 1dB Noise Figure. His final choice was the Sky65047: a small budget-priced 0.4-3.0GHz low noise amplifier with a theoretical gain of 20dB at 400MHz. He made the PCB you can see in the picture above, removing the soldermask on the signal path in order to lower the permitivity. Because of a few mistakes present in the application note, it took [Will] quite a while to get his platform up and running with a 20dB gain but a 4.5dB NF. He also measured the input return loss using a directional coupler, which ended up being quite close to the datasheet’s 14dB number.