Category: RTL-SDR

A Cooking Pot L-Band Antenna

Over on YouTube Adam 9A4QV has uploaded a video showing us his home made cooking pot L-band antenna. The antenna consists of a large aluminum cooking pot which acts as a reflector and a cross-dipole inside the pot acting as the antenna.

The antenna is placed at a height of exactly 1/4 wavelength from the base of the pot, and the cross dipole wire lengths are 0.52 and 0.42 wavelengths long. They are different wavelengths as this achieves circular polarization. Adam writes that the gain should be about 4 – 5 dB’s better than a patch antenna.

The first video shows the performance of the antenna in SDR# when receiving the Outernet and Inmarsat/Alphasat L-band satellite signals indoors. Together with an LNA4ALL and RTL-SDR, Adam gets about 8 dB on the Outernet signal and 24 dB on AERO.

Cooking pot L band antenna

L band cooking pot antenna

Windows Version of the Fully Exposed RTL-SDR Driver now Available

Last week we posted about Milen Rangelov’s (gat3way) new RTL-SDR driver which has exposed filter and gain settings for the R820T/2 chip. This should let you tweak for optimal reception much better. Previously the driver was only available for Linux, however, now over on SourceForge user randaller has ported this driver to Windows.

To use the driver in SDR# simply unzip all the files into the SDR# folder, then while using the dongle in SDR# open the librtlsdr_wincontrol.exe file to open the control interface. The interface also has the ability to directly write values to a register, which together with the newly released register datasheet, can be useful for experimenting with the R820T2 chip.

The description reads:

Unpack all files to SDRSharp folder, start SDR# playback, then run controller exe file.
Do not forget to allow software to use UDP/32323 port in your firewall.

You may use this rtlsdr.dll with osmocom or other software, of course.
It is fully compatible to original one.

There are UDP server on 32323 port inside of rtlsdr.dll. It accepts and answers \n-terminated strings and accept two easy commands: get and set register. Examples:
g 5\n – will return value of R5
s 7 10 15\n – will set four lowest bits (mask 0x0f) of R7 with value 10
s 12 174 255\n – will write complete byte to R12
All values should be decimal.
You may use this feature to develop own gui controller with beauty knobs.

 

The driver GUI.
The driver GUI.

Wireless Analysis of 868 MHz Traffic with an RTL-SDR and the Traffic Detective Software

The Fraunhofer Institute for Integrated Circuits IIS has developed an Android app that allows you to analyze wireless traffic at 868 MHz using an RTL-SDR dongle. In Europe, many wireless IOT, metering and home automation radio standards operate in the 868 MHz band including ZigBee, M-Bus, KNX RF, EnOcean Radio Protocol and s-net.

The software can automatically detect and recognize the wireless protocol being received. It can then be used to catalog what protocols are operating in a network, what frequency they are on and how active they are. That information can then be used for frequency and spectrum planning for new network setups. It can also be used for error diagnosis, intrusion detection and detection of interference.

The Traffic Detective Tool
The Traffic Detective Tool

The promotional pamphlet (pdf) reads:

Numerous applications like smart metering, home automation, building automation, demand side management, ambient assisted living and industrial automation require reliable and cost effective technologies for wireless data transmission. For this purpose the license-free European 868 MHz Short Range Device (SRD) frequency band is prevalently used. Many different and incompatible communication standards and RF-protocols simultaneously occupy this part of the frequency spectrum. Possible negative effects could be interferences, over-occupancy, data collisions and as a result data loss. Special attention must be paid whenever wireless sensor networks are planned or operated. Therefore, network specialists need powerful and flexible tools that provide insights into the wireless data traffic for network planning, operation, fault detection and error diagnosis. The Traffic Detective is such a tool which is easy to use and does not need any knowledge of the different network protocols.

The 868 MHz Traffic Detective is a software-based solution with a user-friendly graphical user interface for monitoring wireless data traffic. A cost-effective and commercially available DVBT USB stick based on a Realtek RTL2832U receiver chip can be used as an analog frontend. In addition to a PC-based implementation, the monitoring software is also available as an app for Android-based mobile devices.

The researchers behind the software have also released an academic paper describing the technology used in the system.

Unfortunately it seems that the app is not actually available for public download yet as we could not see any download links, or find it on Google Play. If you are interested in the app your best bet may be to contact the researchers by email directly.

Review of the ThumbNet N3

Back when it was released in November we posted an initial unboxing and initial first impressions review of the ThumbNet N3 RTL-SDR dongle. In this post we continue that review and post a few more in depth results.

The ThumbNet N3 is the latest iteration of ThumbNet redesigned RTL-SDR dongles. It’s main features include a shielded PCB, metal enclosure, F-type connector, Mini-USB connector, all linear power supplies and an external power mode. It is designed specifically to be used in the ThumbNet system, but because they need to order the units in bulk they sell the excess off to other users too on their new site Nongles.com. The N3’s list of features is shown below.

  • Full backward compatibility with existing RTL-SDR dongles and software
  • High stability TCXO (+/-0.5ppm) (ensuring rock-solid stability from start-up and over a wide range of temperatures)
  • Standard R820T2 + RTL2832U (plus 24C02 EEPROM) chipset
  • Improved/enhanced decoupling. (Common-mode choke on USB port)
  • Low-noise, linear only power regulation (separate 1.2v and 3.3v regulators)
  • External DC (+5v, 450mA) supply connector
  • Mini-USB connection (allows easy separation of the RF unit from the noisy PC)
  • F type RF connector (very common and compatible with existing ThumbNet tracking stations)
  • Large (6x4cm) contiguous ground-plane (for better thermal dissipation)
  • Static drain-away resistor on the RF input (1K to ground)
  • All unnecessary parts (IR receiver, high-current LED etc.) eliminated to reduce parts count and noise
  • Circuit board can be mounted into a common 1455 case

ThumbNet/ThumbSat is a company that hopes to help experimenters get mini satellites into orbit starting from $20k USD. The ThumbNet project aims to provide hundreds of schools and educational institutions with RTL-SDR based satellite receivers in the hope that they will use them as an educational resource, and at the same time help set up a worldwide monitoring network, so that the live data from the launched satellites is always available to the satellite experimenters.

The ThumbNet N3
The ThumbNet N3

Click Continue for the rest of the review

Continue reading →

Receiving CB Radio with an RTL-SDR Dongle

Back in July we posted a story by Mario Fillipi (N2HUN) who wrote an article about using the RTL-SDR to receive CB radio, and how while the CB radio heyday is over, there are still opportunities for good listening available today.

Recently Mario has posted a new article on swling.com where he discusses his CB radio listening hobby further. To listen to the CB band at 26.965 – 27.405 MHz he uses an RTL-SDR dongle together with a ham-it-up upconverter. While an upconverter is not required since most RTL-SDR dongles typically tune down to 24-25 MHz, he finds that using one helps because it can help block out interference from the strong broadcast FM band.  We note that you could also use one of our BCFM Block filters for the same purpose.

Mario notes that recently he noticed the CB band was open during the night. Usually the frequencies that CB radio uses propagate best during the daytime, and poorly at night. But on some occasions it can open up at night as well. He writes that on some occasions during a winters night during a snowstorm he has been able to receive the world on CB, from Europe, the Caribbean and Australia.

CB Band Voice in SDR# with an RTL-SDR and Ham-it-up Upconverter
CB Band Voice in SDR# with an RTL-SDR and Ham-it-up Upconverter

New Linux RTL-SDR Driver with Fully Exposed Controls

A new Linux based driver for the RTL-SDR has been released by Milen Rangelov (aka gat3way) which exposes all the adjustable settings on the R820T/2 tuner chips. This exposes adjustable sliders for settings like preselection, IF and notch filters and the multiple gain stages on the R820T/2. In the standard drivers the filters and gain settings are mostly set automatically, but manually adjusting them could yield better results. The filters are not very strong, but they could be used to help block out an interfering signal, increasing the dynamic range of the RTL-SDR.

Over on his post at r/rtlsdr Milen wrote the following about his driver:

The idea in brief is to modify the librtlsdr code so that an unix domain socket server receives i2c register set/get commands and executes them. It only works for r820t tuners. This modified rtlsdr library is then dynamically preloaded by means of LD_PRELOAD and used by the SDR software. This is actually what happens when you call r820tweak <program>. This way, no modifications to both gr-osmosdr source and the SDR program are required, instead of waiting for them to implement those controls, we kind of have a separate program that tweaks them.

The GUI program is a simple wxpython client, it currently exposes the following settings:

LNA, Mixer, VGA gain stages – the 3 variable gain stages

LPF/HPF filter cutoff – these control the “width” of the r820t2 lowpass/highpass filters, those filters are relatively sharp and this in turn is very useful to increase the dynamic range by fitlering out strong signals “close” to the weak signal you are hunting. Those are among the nicest features to play with, together with the gain stages.

LPNF cutoff – apparently there is also a low pass notch filter, however this doesn’t work as I expected. Anyway, still useful as a kind of variable attenuator.

Filter bandwidth – there is a bandpass filter which isn’t quite “sharp” at all, centered at the center frequency. Kind of additional filter, easier to manipulate than the rest of them, but not that powerful. May provide some extra dynamic range. Behaves kind of weird when gqrx decimation is used.

As far as the gain stages are concerned – the LNA gain is the first stage and thus the most important – it determines the SNR. Mixer gain is less important (unless the signal is too weak). The VGA gain should be almost always set to zero as it doesn’t contribute to the SNR at all while keeping the dongle warmer and so more thermal noise.

In the R820T2 i2c register specs there are some other interesting features, currently unexposed. One of them is the band selection filter (lo/med/high) which apparently is even used in the librtlsdr driver. I found changing that has absolutely no effect for me unfortunately. It might have provided opportunities for better reception around the “verge” where the librtlsdr driver switches them (approx. at 310MHz and 588MHz). But switching them has absolutely no effect.

The new fully adjustable driver by gat3way.
The new fully adjustable driver by gat3way running in GQRX.

RTL-SDR.com V3 Stock Availability and Holiday Shipping Times

This is just an update post for those wishing to purchase or are waiting on delivery for items from our store at www.rtl-sdr.com/store.

Amazon USA

The RTL-SDR.com V3 has proven to be more popular than we anticipated and Amazon ran out of stock a few weeks ago. New stock should be arriving at the Amazon warehouses early next week, but we don’t know how long Amazon will take to process the stock and put it back on the shelves. It should hopefully be ready in under a week.

International

For international orders from our Chinese warehouse, please be aware that international shipping is quite slow at the moment, due to the peak season parcel rush. The international mail system struggles to cope with mail at this time of the year due to a vast increase in Christmas parcel volume. Delivery times are still typically under 4 weeks but for some parcels, and to some countries we can expect shipping times of up to 6 weeks or longer. 

Some people have noted that parcels ordered after a previous order have arrived earlier. We use the same postal system as everyone else (there’s only really one international air mail system!), but what can happen is that on some days the parcels may get a direct flight, and on other days they may get an indirect flight. Those indirect ones can end up taking much longer. Also planes can break down, parcels can miss a connecting flight or security can hold a container of many parcels for days just because they saw one suspicious parcel inside. Thus international parcel delivery times have a very large scattering, ranging from less than a week to six weeks or more. We thank you for your patience if your parcel happens to end up on the slower end of the scale. But if your parcel does end up taking over 6 weeks please let us know as we may be able to open a lost parcel investigation. If your parcel is lost it will be resent or refunded on your preference.

If you are tracking a parcel we recommend 17track.net, aftership.com and track-chinapost.com. Try all three as sometimes one has more up to date tracking than another. Please note that we’ve found that around this time postal workers will often not bother to scan the tracking label on parcels, since they are rushing so much. This can cause a lack of tracking updates for a while. Also if there are queues for customs checks in your local country the parcel can wait around in the container without a scan for a long time, until customs gets to it.

We have several shipping methods available. China Post/Swiss Post/HK Post are about the same speed once they leave. But generally Swiss/HK post are faster to leave China. China Post parcels can sometimes take a few extra days to pass through security. Some countries which support it, will automatically be upgraded to EMS ePacket priority mail. We also have some new special methods for some countries which are still air mail, but use a faster more direct flight to the destination. Of course the more expensive express mail services like DHL/UPS/Aramex are also available, but even they have about a 1 week shipping delay at the moment.

However, despite these shipping time uncertainties, the majority of parcels still seem to be making it through the postal system in a timely manner. Thanks to everyone for supporting the RTL-SDR.com blog!

R820T2 Register Description Data Sheet Now Available

Recently Luigi Tarenga wanted to do some work on developing RTL-SDR drivers, so he emailed Rafael Micro requesting some additional documentation about the chip. Usually previous requests to Rafael Micro for such information seem to have gone unanswered, but this time it seems they have decided to publicly released the Register description document for the R820T2 chip.

Previously the R820T datasheet was leaked/released to the public, but the information in the datasheet did not help much with driver development. This register description document describes the function and configuration bits for the registers on the chip, and may be useful for people wanting to develop better drivers for the RTL-SDR.

We have uploaded a copy on our server here.

Description of some of the registers in the R820T2 chip.
Description of some of the registers in the R820T2 chip.