Th0ma5w has released his rtl_fm_python program which is a modification of rtl_fm. The added feature is an API and web interface which allows interaction with a running instance of rtl_fm. The API and web interface allows you to change the frequency, modulation and gain settings while rtl_fm is running. This may be useful for remote devices running rtl_fm such as a Raspberry Pi.
Over on Reddit user soooooil has posted about his work in building an LNA, including etching the PCB. On his imgur page he shows the design and construction process through images, before showing the final result in SDR#. For the LNA he used a ERA-3SM+ MMIC which has 17-23 dB of gain and a NF of 2.6-2.8 dB. While the noise figure is fairly high for an LNA, it is still likely lower than the RTL-SDRs internal amplifier noise figure which is around <4.5 dB.
The NRF905 is a multiband RF tranceiver IC that uses frequencies in the ISM bands. Fabien le mentec posted about a project where he wanted to remotely monitor his garage door status using a microcontroller and the PTR8000 wireless module which contains the NRF905 chip.
In order to validate that his hardware settings were set correctly and that the NRF905 was transmitting correctly, he used an RTL-SDR and his recently written NRF905 decoder program to check the output frames.
Recently, we posted a similar project involving the NRF24L01+ wireless tranceiver where a decoder for that had been written as well.
Back in November last year we posted about the possibility of an “LNA4HF” low noise amplifier (LNA) for the HF bands being made available for sale. The LNA4HF is now available for purchase.
The LNA4HF is a low noise amplifier with built in low pass filter that runs on a 6-12 V power supply and covers a frequency range of 150khz to 30MHz, with a 18-20 dB gain and 1-2 dB noise figure. It costs 20 Euros. The low pass filter can also be disabled with a small board modification which will allow the amplifier to be useful at up to 2 GHz.
Akos from the SDR for Mariners blog has reviewed the LNA4HF on his latest post. His results show that the low pass filter significantly reduces broadcast FM interference and that the amplifier also increases signal strength by around 20 dB as advertised.
Andy programmer of the RTL1090 ADS-B decoder software, and owner of the 1090Mhz webstore has notified us that the modified TCXO RTL-SDR we reviewed in December is now available for sale to international customers via their webstore.
Previously in December we gave a brief review of the modified temperature controlled oscillator (TCXO) RTL-SDR created by Japanese RTL-SDR modifier Nobu Saitou. In the review the TCXO showed good temperature stability and a very low PPM offset, which may be useful for some applications.
The console based FM decoder for the RTL-SDR, rtl_fm has had a code overhaul which contains improvements and bugfixes. The updated code has been merged into the official rtl-sdr release.
The rtl_fm guide has also been updated to include information on the new options.
The rtl_acars console based ACARS decoder which is based on rtl_fm has been updated by a new author, gat3way on Reddit. The new updates include decoder sensitivity improvements and the following:
- Multiple frequencies scanning is now supported (by providing multiple -f arguments at command line and -l
). Since there is no audio output and it’s hard to determine right squelch level, a squelch debug option (-r) is implemented. Use it to experiment with squelch value, it’s simple: good squelch values flood stdout with “hopping freq!” messages yet avoid too high squelch levels. In general, values between 20-30 work good with my setup (big city, lots of radio interference, NOAA turnstile which gives -3db due to rhcp polarization).
- Aircraft and airline databases now supported (using the acarsdec builtin ones). DBs are text files using simple format, so you may easily update them. I would very much appreciate your help to keep that up-to-date.
- Certain improvements in frequency hopping code as compared to rtl_fm, but don’t expect wonders, it takes time to retune so data loss is not avoidable especially if you provide lots of frequencies to scan or huge ranges.
- A simple Makefile to make it simpler 🙂
In the future gat3way hopes to support the decoding of multiple ACARS channels as well. The updated rtl_acars software can be downloaded from github here.
Linrad is an advanced SDR software program which supports the RTL-SDR. It is not as easy to use as the more popular SDR#, but some people prefer to use it as it has a very high information density GUI. The author of Linrad has uploaded two videos to YouTube that show how to install Linrad on Windows XP and Linux, which may be useful to those wishing to try Linrad out.
