Making a 20dB Low Noise Amplifier for a 400MHz radio

[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.

Automatic Antenna Tuner

Automatic Antenna Tuner

To get the best power transfer into an antenna, tuning is required. This process uses a load to match the transmission line to the antenna, which controls the standing wave ratio (SWR).

[k3ng] built his own automatic antenna tuner. First, it measures the SWR of the line by using a tandem match coupler. This device allows the forward and reflected signals on the line to be extracted. They are buffered and fed into an Arduino for sampling. Using this data, the device can calculate the SWR. The RF signal is also divided and sampled to measure frequency.

To automate tuning, an Arduino switches a bank of capacitors and inductors in and out of the circuit. By varying the load, it can find the ideal matching for the given antenna and frequency. Once it does, the settings are stored in EEPROM so that they can be recalled later.

After the break, check out a video of the tuner clicking its relays and matching a load.

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Cleaning Slides with Plasma

Plasma Cleaner

[Ben Krasnow] hacked together a method of cleaning sides using plasma. His setup uses a mechanical vacuum pump to evacuate a bell jar. This bell jar is wrapped with a copper coil, which is connected to an RF transmitter. By transmitting RF into the coil, plasma is created inside the bell jar.

Plasma cleaning is used extensively in the semiconductor industry. Depending on the gas used, it can have different cleaning effects. For example, an oxygen rich environment is very effective at breaking down organic bonds and removing hydrocarbons. It is used after manual cleaning to ensure that all impurities in the solvents used for cleaning are fully removed. According to [Ben], it’s possible to get a surface atomically clean using this process, and even remove the substrate if the energy levels are too high.

These machines are usually expensive and specialized, but [Ben] managed to cook one up on his bench. After the break, check out a video walk through of [Ben]’s plasma cleaner

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Android and Arduino RF Outlet Selector

ardAndRFoutlets

Cyber Monday may be behind us, but there are always some hackable, inexpensive electronics to be had. [Stephen’s] wireless Android/Arduino outlet hack may be the perfect holiday project on the cheap, especially considering you can once again snag the right remote controlled outlets from Home Depot. This project is similar to other remote control outlet builds we’ve seen here, but for around $6 per outlet: a tough price to beat.

[Stephen] Frankenstein’d an inexpensive RF device from Amazon into his build, hooking the Arduino up to the 4 pins on the transmitter. The first step was to reverse engineer the communication for the outlet, which was accomplished through some down and dirty Arduino logic analyzing. The final circuit included a standard Arduino Ethernet shield, which [Stephen] hooked up to his router and configured to run as a web server. Most of the code was borrowed from the RC-Switch outlet project, but the protocols from that build are based on US standards and did not quite fit [Stephen’s] needs, so he turned to a similar Instructables project to work out the finer details.

Stick around after the break for a quick video demonstration, then check out another wireless outlet hack for inspiration.

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Xbox 360 light right and RF module connected to Raspberry Pi

rpi-connected-to-xbox-lightring

If you want to mess around with your Xbox 360 controllers on a computer Microsoft would be happy to sell you a USB dongle to do so. But [Tino] went a different route. The board that drives the Xbox 360’s status light ring also includes the RF module that wirelessly connects the controllers. He wired this up to his Raspberry Pi using the GPIO header.

The module connects via an internal cable and is treated much like a USB device by the Xbox motherboard. The problem is that it won’t actually handle the 5V rail found on a USB connector; it wants 3.3V. But this is no problem for the RPi’s pin header. Once a few connections have been made the lights are controlled via SPI I2C and [Tino] posted some example code up on Github to work with the RF module. He plans to post a follow-up that interfaces the module with a simple microcontroller rather than an RPi board. If you can’t wait for that we’re sure you can figure out the details you need by digging through his example code.

Electric Imp as an Internet to RF gateway

a-little-automation-with-the-electric-imp

This project is a study in connecting several different families of hobby electronic hardware. The image above shows the Electric Imp side of things. It bridges its Internet connection with the RF connections of the rest of the project.

The Imp is a peculiar (intriguing?) piece of hardware. Take a look at [Brian Benchoff’s] hand’s on experience with the SD form factor hardware which is not an SD card at all. It’s an embedded system which uses light programming and a cloud-based software setup to bring wireless Internet to your projects.

In this case [Stanley Seow] started wondering if he needed multiple Imps to connect different parts of his setup. A bit of head scratching led him to the use of nRF24L01 modules which are cheap and easy to use Radio Frequency transceiver boards. He took a partially finished driver project and brought it home to play nicely with the Imp. Now he can use the system to communicate with other components which will eventually be used for home automation. Right now his proof of concept issues wireless commands to an Arduino driving a strip of LEDs.

Remote control command center includes RF and IR functions

all-in-one-remote-relay-includes-RF

We’re still not quite sure what to call these projects, but as we’ve said before, it’s a pleasure to see what people are doing to use one remote control to rule them all. The project being developed by [Kalle Löfgren] seeks to simplify the remote controlled items in his home by combining all control into one smart phone app. The linchpin of the system is this command center which lets a smart phone send IR and RF commands to various devices (translated).

We’ve seen this done with pretty beefy microcontrollers, like this project that uses a PIC32. But the communications going on between the smartphone and the base station are very simple, as are the remote control commands which are being relayed. So we’re not surprised to find that this setup just uses an ATmega88, IR LED, Bluetooth Module, and RF module. There is no connection to a computer (the USB simply provides power via a cellphone charger). If you’re interested in how [Kalle] sniffed the protocol for each remote he wrote two other articles which you can find in the write-up linked above.