As per the previous post, we recently received a sample of the TCXO modified dongle by Nobu Saitou. Nobu was kind enough to send over two samples, so we’ve decided to give one away to a lucky reader.
To go into the draw simply comment on this post with what you’ve been doing (or have been dreaming about doing) with software defined radio recently. Be sure to include your email in the commenting system so I can get in touch with you if you are the winner (your email address is kept private and only I can see it). The winner will be randomly selected on the 23rd of December 12pm GMT, and the prize sent out after Christmas. Please one entry per person.
Update: Thanks to all that entered. The competition has now ended and the winner has been notified. It has been very interesting to hear about all the amazing SDR projects by the RTL-SDR community. I would urge everyone to read through the comments to see what interesting things people are doing. Feel free to continue commenting about your projects even though the competition has finished.
A few days ago we had a post about a modified RTL-SDR dongle for sale which has the low quality 28.8 MHz oscillator replaced with a high quality 28.8 MHz temperature controlled oscillator.
Nobu Saitou, the creator of these dongles has sent us a sample to review. On the inside of the dongle the 28.8 MHz crystal has been removed, and replaced with a 28.8 MHz temperature controlled oscillator. The desoldering of the old oscillator and soldering of the new TCXO appears to be neatly and professionally done.
TCXO RTL-SDR Dongle Photo
After plugging in the dongle and firing up SDR#, we tuned to a known trunking control channel at 152.850 MHz and measured the frequency offset. It turns out that with the TCXO no frequency correction was required at all. I believe that from Nobu’s blog post, this oscillator can have a max deviation of +-2 PPM, which is incredibly small.
TCXO Dongle with Zero PPM correction required
We compared this result to a standard dongle with the original oscillator and found the frequency offset required to be 44 PPM.
Standard Dongle Frequency Offset
As the dongle heats up from use, the oscillator will experience thermal drift, causing the frequency offset to change. The TCXO should be immune to this problem due to it’s temperature compensation circuitry. To test the temperature compensation, we cooled both a TCXO dongle and a standard dongle down in a refrigerator first to simulate cool climate conditions. We then measured the change in PPM offset after 30 minutes of dongle operation. As expected, the TCXO had almost zero drift after 30 minutes (<<1 PPM), whereas the standard dongle had a drift of about 6-7 PPM (approx. 1 KHz drift).
TCXO Oscillator: Frequency drift after 30 minutesStandard Oscillator: Frequency drift after 30 minutes
The results of this simple test show that the TCXO used in these modified dongles is an accurate and stable frequency source as was expected. If you want one of these dongles they are for sale at the creators Amazon Store (direct link to TCXO product here). Currently it seems that Saitou’s products cannot be sent abroad outside of Japan, but he recommends this agent service for ordering internationally.
Edit: The TCXO can now be bought internationally from 1090mhz.com
Recently this year, Akos from the SDR for Mariners blog has put out a bunch of RTL-SDR tutorials aimed at complete beginners – that is people without any radio knowledge at all.
Hands-on guide to hear to world using the 10-dollar RTL stick. Easy-to understand text covers software installation, antennas, noise reduction, guides from shortwave to airplane information reception – and many more. Diagrams and photos help the beginner, common tools and materials used: no soldering or expensive gear used. Useless tales, anecdotes, complicated theoretical explanations left out: only relevant information included.
If you ever had problems setting up the RTL stick, wish to significantly improve your reception or simply want to hear airplanes talk to tower, receive AIS information on a yacht or track airplanes, this book is for you.
One of his recommendations is to try oil cooling the dongle. This involves completely immersing the dongle in sunflower or vegetable oil. Since oil is not electrically conductive, it will not short the circuits, and the oil will help to dissipate the heat buildup generated by the dongle. Some of his other recommendations involve drilling extra holes in the dongle casing, and adding fan cooling.
After checking for local causes of interference and finding nothing, they decided that the interferer must be coming from further away. To find the location of the jamming signal they did some radio direction finding. This involved driving around with Yagi and magnetic loop antennas and RTL-SDR and USRP N200 SDRs and then measuring the signal strength at various points.
For the software they used a custom GNURadio block which calculated the power spectra using the FFTW C library, and averaged the results to disk. They then post processed the data to calculated the RFI power, and correlated the data with GPS coordinates recorded on his phone.
After all the data was processed, they discovered that the interference originated from an FM radio tower which had a faulty FSK telemetry link. They notified the engineer responsible who then replaced the link and the interference disappeared.
The popular RTL-SDR ADS-B decoder RTL1090 requires the rtlsdr.dll and libusb.dll files to be manually downloaded and then placed into the RTL1090 folder. However, now the author of RTL1090 has created an automatic installer which will download and install all the required files automatically.
This internet based utility helps you with setting up a complete RTL1090 installation with almost no manual intervention. It automatically downloads the relevant files as rtlsdr.dll, zadig.exe and helps to configure zadig with a built in tutorial.
The installer is called the IMU (Installer and Maintenance Utility) and can be download from the RTL1090 website at rtl1090.web99.de.
The American Radio Relay League (ARRL) a.k.a The American National Association for Amateur Radio has put online a freely available ADS-B tutorial featured in their monthly QST magazine, written by Robert Nichols, W9RAN. The tutorial focuses on using an R820T RTL-SDR dongle to receive ADS-B signals, and then using computer software to decode the signals and create a virtual aircraft radar.
ADS-B is a protocol used by most modern aircraft to broadcast their position and altitude which is determined via GPS. ADS-B is intended to supplement and eventually replace traditional radar.
In this ADS-B tutorial, they show how to create a weatherproofed 1090 MHz collinear antenna from RG-6/U coax and PVC pipe and how to use the ADSB# and virtual radar server software to decode and visualize aircraft positions, like a radar.
