Thank you to Jason for writing in and letting us know that OpenWebRX Version 1.1.0 has been released on August 03. OpenWebRX is an open source program that allows users to make RTL-SDRs, KiwiSDRs and other SDRs accessible over the internet via a web browser. It is is currently available as a Raspberry Pi SD card image, in the Debian + Ubuntu repositories, as a docker image, or for manual installation.
The latest version adds an AMBE voice data decoder, new decoders and metadata displays for NXDN and D-Star, and crisper SVG graphics.
Since we last posted about OpenWebRX updates in early 2020, there has also been support added for the Perseus-SDR, RadioBerry 2, Hermes HPSDR, Funcube Dongle Pro+ software defined radios. New decoders and support for external decoders such as JS8Call, FreeDV, Wideband FM, DREAM DRM, FST4, FST4W, Q65 and M17 digital voice have been added.
There is also now a site called Receiverbook.de that aggregates a list of publicly available OpenWebRX receivers.
Since it's announcement in early 2016 we've posted many times about the KiwiSDR, a 14-bit wideband RX only HF software defined radio created by John Seamons (ZL/KF6VO). The KiwiSDR has up to 32 MHz of bandwidth, so it can receive the entire 10 kHz - 30 MHz VLF/LF/MW/HF spectrum all at once.
Compared to most other SDRs the KiwiSDR is a little different as it is designed to be used as a public web based SDR, meaning that KiwiSDR owners can optionally share their KiwiSDR online with anyone who wants to connect to it. The public functionality allows for some interesting distributed applications, such as TDoA direction finding, which allows users to pinpoint the location of unknown HF transmissions such as numbers stations.
In order to implement this online capability, the KiwiSDR runs custom open source software on a Beaglebone single board computer which connects to your home network. Recently there has been vocal concern about a security flaw in the software which could allow hackers to access the KiwiSDR. The flaw stems from the fact that the KiwiSDR has 'backdoor' remote admin access that allows the KiwiSDR creator to log in to the device and troubleshoot or make configuration changes if required. This backdoor has been public knowledge in the KiwiSDR forums since 2017, although not advertised and explicit consent to have it active and used was not required.
The intent of the backdoor is of course not malicious, instead rather intended as an easy way to help the creator help customers with configuration problems. However, as KiwiSDR owner Mark Jessop notes, the KiwiSDR operates in HTTP only, sending the admin master password in the clear. And as KiwiSDR owner and security researcher @xssfox demonstrates, the admin page gives full root console access to the Beaglebone. These flaws could allow a malicious party to take over the Beaglebone, install any software and perhaps work their way onto other networked devices. Another tweet from xssfox implies that the password hashes are crackable, allowing the main admin password to be easily revealed.
Quick video showing how the backdoor on the kiwisdr works.
I've also tested that touch /root/kiwi.config/opt.no_console mitigates the issue
Creator John Seamons has already released a patch to disable the admin access, and as of the time of this article 540 out of 600 public KiwiSDRs have already been auto-updated. Owners of KiwiSDR clones should seek out updates from the cloner.
It is clear that the KiwiSDR is a passion project from John who has dedicated much of his time and energy to consistently improving the technical RF engineering side of the device and software. However we live in an age where malicious hacking of devices is becoming more common, so anyone releasing products and software that network with the internet should be reminded that they have a responsibility to also dedicate time to ensuring security.
John has reached out to us in advance and noted that he currently cannot yet comment publicly on this topic due to legal advice.
Thank you to Marco (IS0KYB) for informing us about the release of his new software called "SuperSDR". SuperSDR allows you to easily synchronize frequency tuning with a remote KiwiSDR via a CAT connection to a standard ham radio. The KiwiSDR is a 14-bit wideband RX only HF SDR which has up to 32 MHz of bandwidth, so it can receive the entire 10 kHz - 30 MHz spectrum all at once.
It allows to use a remote KiwiSDR along with a local (or even remote) standard radio in sync. It works on Linux, Windows and MacOSX.
The main purpose is to have an interactive panadapter that is not forcibly tied to our local antenna, but allows one to try any combination of CAT radio / SDR. I'd like to implement a remote KiwiSDR selection interface to choose the best SDR for the purpose.
I'm still developing it, and it is not complete feature-wise, but it is ready to be used.
Somebody asked me if it would be possible to integrate a RTL-SDR into it and I plan to do that using the old PEPYSCOPE project code [covered in a previous post].
The video below shows a slightly older version of SuperSDR in action.
The KiwiSDR is a 14-bit wideband RX only HF SDR which has up to 32 MHz of bandwidth, so it can receive the entire 10 kHz - 30 MHz spectrum all at once. Notably, the KiwiSDR does not connect to a PC directly, rather it is a cape (add on board) for the Beaglebone single board computing platform which similar to a Raspberry Pi. With most of the DSP processing done on the KiwiSDR's onboard FPGA, the Beaglebone serves a custom OpenWebRX browser interface which can be accessed over a network connection from anywhere in the world. If you're interested our initial KiwiSDR review from 2017 is here.
Over the years the KiwiSDR has brought some very interesting software developments out such as several new demodulators. However, our favourite is the TDoA feature, which allows users to leverage multiple public KiwiSDRs to locate the source of an HF transmission with remarkable accuracy.
This year we've seen a number of cloned SDRs come out on the market, with almost all using LTC2208 ADC chips that have most likely been recycled from discarded equipment. One of those clones is the RaspberrySDR, which is a clone of the KiwiSDR.
The RaspberrySDR is not a direct clone however, as it brings some improvements. The biggest change is that the LTC2208 chip has a 16-bit ADC, and can provide up to 62 MHz of real time bandwidth. Also instead of a Beaglebone single board computer, a Raspberry Pi 3B+ is used instead. At the time of this post the RaspberrySDR retails for roughly $70 less than the KiwiSDR.
However, there are some issues such as inconsistent RF level calibration, a broken s-meter at high SNR levels, "motorboating" on strong narrowband signals, and a broken firmware update button. Also interestingly, KA7OEI's tests show no improvement to the dynamic range. With two extra bits of ADC resolution on the RaspberrySDR we would have expected an improvement. Most of these issues are probably firmware bugs which could be fixed, but the dynamic range issue could be related to less care taken in the hardware design.
As the KiwiSDR source code is open source, it could be considered fair game to fork the code and make use of it in a derivative product. However, at the same time we should remember that the KiwiSDR developers have been working on this code and providing constant updates ever since the release. No funds from the clones will go to them and the success of a clone could spell the end of motivation for future software developments. In addition as KA7OEI notes, the code used on the RaspberrySDR seems to be somewhat obscured, and unlike the KiwiSDR, no open source schematic has been released. Any official long term support of the RaspberrySDR seems unlikely too.
John Seamons (ZL/KF6VO), the leader of the KiwiSDR project has announced that despite the clones KiwiSDR development will remain 100% open source with any future updates also being available to the cloners should they choose to implement them. He also mentioned to us that the clones will also be able to contribute to the TDoA service and can be listed on the KiwiSDR directory. However, the reverse proxy feature will be limited only for official products.
This weeks video on the TechMinds channel explores the various online web SDRs that are available to access for free. Accessing these online SDRs does not require any hardware apart from a PC and internet connection, although of course you are then receiving signals from a different location to yourself.
In the video he shows how to access the SDR# Spy Server Network which mostly consists of Airpsy and RTL-SDR units, the SDR-Console V3 Server network which consists of a wide array of different SDRs, the browser based WebSDR network which is mostly soundcard based SDRs but also RTL-SDR and other SDRs, and finally the KiwiSDR network which is made up of KiwiSDRs.
Using Software Defined Radio Without SDR Hardware - WebSDR
OpenWebRX was first developed by Andras Retzler and is and open source program that allows users to make RTL-SDRs, KiwiSDRs and other SDRs accessible over the internet via a web browser. Recently the OpenWebRX public directory at SDR.hu, also run by Andras, has been closed. In the past we've posted about Andras' decision to move on from OpenWebRX and how sdr.hu went from public access to requiring an amateur radio callsign to access. Now Andras has decided to take the final step and close sdr.hu for good. The sdr.hu website now reads:
The SDR.hu project has been finished
I'd like to say a big thanks to everyone who joined my journey with this project!
I hope you had a good time listening on the site, and learnt some things about SDR. The purpose of this site was to provide a technological demonstration for amateur radio operators about Software Defined Radio, and I hope this goal has been reached. As this website was a one-person hobby project, with my tasks and responsibilities growing, and my focus moving to other projects at which I hope to make a greater positive impact, I'm unable to further develop SDR.hu and protect it from abuse.
Furthermore, I think this site has some good alternatives now. Nevertheless, in my opinion amateur radio receivers should be shared with strict access control in the future.
If you have more questions, feel free to consult the FAQ.
We want to note that although KiwiSDR makes use of OpenWebRX, the KiwiSDR project is not affected by this closure as they use a custom fork of OpenWebRX, and there is an official KiwiSDR directory at kiwisdr.com/public, a map version at map.kiwisdr.com, and an SNR score directory at snr.kiwisdr.com. Unfortunately the one major drawback is that these directories do not list public RTL-SDRs or other SDRs running OpenWebRX as only sdr.hu did that.
The KiwiSDR is a US$299 HF SDR that can monitor the entire 0 - 30 MHz band at once. It is designed to be web-based and shared, meaning that the KiwiSDR owner, or anyone that they've given access to can tune and listen to it via a web browser over the internet.
OpenWebRX is code originally created by András Retzler and a modified version runs on the KiwiSDR devices. This code is what allows them to be accessed online by a browser and was popularized by it's use in the KiwiSDR. The original code can also be used by other compatible SDRs such as the RTL-SDR.
Recently András released news that he is discontinuing work on OpenWebRX due to interest in other projects, but it will remain on GitHub as open source code. András also notes that the security of OpenWebRX will soon be in question as it utilizes Python 2, which has been designated end of life on January 1 2020. In addition, if you've been following OpenWebRX since the beginning, you'll know that in the past OpenWebRX was involved in an legal/ethical issue over open source licencing with KiwiSDR. Although the problems with KiwiSDR were resolved amicably, Andras also references his frustrations with similar situations to do with his code being forked again and again.
We note that maintenance and development of the KiwiSDR OpenWebRX code will continue as they are considered separate projects. Due to some confusion, we importantly reiterate that the KiwiSDR product is unaffected by OpenWebRX being discontinued. Although KiwiSDR is based on OpenWebRX they use their own custom branch of the software that is maintained by the KiwiSDR owners and not by András.
András also runs the popular sdr.hu OpenWebRX/KiwiSDR directory, which was/is considered the main directory for finding and accessing public KiwiSDR and other SDR devices running OpenWebRX. Recently the directory was restricted, and now can only be accessed by those with a ham radio callsign. It is unclear why this decision was made as sdr.hu was very popular with shortwave listeners and radio newbies who are typically not hams. But the sdr.hu FAQ notes "The purpose of the site is to serve amateur radio. I decided to restrict access to the receiver list in order to protect the site and its purpose in the long term."
KiwiSDR have recently implemented DRM decoding into their OpenWebRX implementation. Digital Radio Mondiale (DRM) is a type of digital shortwave radio signal that is used by some international shortwave radio broadcasters. It provides superior audio quality compared to AM stations thanks to digital audio encoding.
The KiwiSDR is a US$299 HF SDR that can monitor the entire 0 - 30 MHz band at once. It is designed to be web-based and shared, meaning that the KiwiSDR owner, or anyone that they've given access to can tune and listen to it via a web browser over the internet. Many public KiwiSDRs can be found and browsed from the list at sdr.hu.
The new DRM implementation is based on DREAM 2.1.1 which is an opensource DRM decoder that can be used with any HF capable SDR. Due to computational limits of the BeagleBone singleboard computer which the KiwiSDR runs on, only one DRM channel can be decoded at any one time, restricting this capability to only one user at a time. However, if the KiwiSDR is running on the newer BeagleBone AI, it can support up to four DRM channels. KiwiSDR write that work is still ongoing to improve the code, so this situation may improve in the future.