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The KiwiSDR Backdoor Situation

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.

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.

The KiwiSDR
The KiwiSDR

SuperSDR: A KiwiSDR + CAT Client for Ham Radio

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.

Comparing the KiwiSDR Against the RaspberrySDR Clone

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.

KiwiSDR Clones

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.

KA7OEI's image of the RaspberrySDR

Comparison

Over on his blog KA7OEI has written up a comprehensive comparison between the KiwiSDR and RaspberrySDR. KA7OEI notes RaspberrySDR powers up and works with it's full 62 MHz bandwidth as expected. Measurements for sensitivity, dynamic range, image rejection are about the same.

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.

There has also been some discussion over on the WSPRDaemon forums here.

Ethics + Official Future Software Development

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.

The KiwiSDR
The Original KiwiSDR

KiwiSDR Portal SDR.HU Now Requires a Ham Licence + OpenWebRX Development Discontinued

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."

Fortunately, over on his SWLing.com blog, Thomas has noted that there are still other KiwiSDR directories available such as https://ve3sun.com/KiwiSDR, http://kiwisdr.com/public and http://rx.linkfanel.net.

SDR.HU Requires a Login Now
SDR.HU Requires a Login Now

KiwiSDR Now Supports DRM Decoding

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.

KiwiSDR Decoding DRM
KiwiSDR Decoding DRM

KiwiSDR Conference Talks: KiwiSDR and it’s GPSDO, TDoA Geo-Location and GNURadio Sources

Thank you to John ZL/KF6VO (creator of the KiwiSDR) for submitting some interesting KiwiSDR related conference talks that might be of interest to some readers. If you were unaware 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 or by signal strength and location on this website. One of the most interesting KiwiSDR features is it's TDoA capabilities, which allow users to geographically locate HF transmitters.

Introduction to the KiwiSDR and Bodnar GPSDO

Rob Robinett, AI6VN, gave a talk at the HamSCI Workshop 2019 (USA) “Introduction to the KiwiSDR and Bodnar GPSDO”. In addition to Kiwi basics he shows a live demo of the performance advantages in using an external GPSDO as the Kiwi ADC clock. A line-of-sight measurement of frequency/time station WWV in Colorado using the Kiwi’s internal GPS-compensated crystal oscillator (XO) is compared against using an external Bodnar GPSDO. The Kiwi’s IQ display extension shows the frequency/phase difference between the ADC clock, internal or external, and WWV. Rob also discusses the publicly available (kphsdr.com:8074) eight Kiwi installation he made at coastal radio station KPH north of San Francisco. 

KiwiSDR as a new GNURadio source and TDoA geo-location

Christoph Mayer, DL1CH, is the author of the Kiwi’s TDoA algorithm. His talk “KiwiSDR as a new GNURadio source and TDoA geo-location” was given at the Software Defined Radio Academy (SDRA) as part of HAM Radio 2019 in Friedrichshafen, Germany. He includes a very technical description of the TDoA process used by the Kiwi including a live demo of direction finding a 16 MHz over-the-horizon-radar (OTHR) signal from Cypress.

Comparing the Airspy HF+ And KiwiSDR on Shortwave Radio

The Airspy HF+ and the KiwiSDR are two HF specialty SDR radios. The HF+ advertises excellent dynamic range and sensitivity, whilst the KiwiSDR has it's strength in it's internet connectivity and 30 MHz wide live bandwidth.

Over on YouTube icholakov has uploaded a video comparing the two SDRs on daytime medium wave and shortwave reception with a W6LVP amplified magnetic loop antenna. It is expected that the two SDRs should be quite similar in easy receiving conditions, but the Airspy HF+ should shine in challenging conditions with strong blocking signals and weak signals being received at the same time. The Airspy HF+ should also be a bit more sensitive in all conditions. It's not clear if there were any strong blocking signals in the tests, but the results appear to confirm the sensitivity expectations.

Understanding Direction Finding on the KiwiSDR

Earlier this month we posted about the KiwiSDR direction finding update, which now allows anyone with internet access to utilize public KiwiSDR's for the purpose of pinpointing the physical location of a transmitter that transmits at a frequency below 30 MHz.

A few people have had trouble understanding how to use the direction finding feature, so KiwiSDR fan Nils Schiffhauer (DK8OK) has written up a KiwiSDR direction finding usage guide. Nils' guide explains the basic technical ideas behind the TDoA (Time Difference of Arrival) direction finding technique used, and highlights some important considerations to take into account in order to get the best results. For example he discusses best practices on how to choose receiver locations, how many receivers to choose, and how to properly take into account the time delaying effects of ionospheric propagation with HF signals.

Finally at the end of the document he shows multiple case studies on HF signals that he's managed to locate using the discussed best practices. Looking through these examples should help make it clear on how receiver locations should be chosen.

DK8OK Locates Radio France at 15320 kHz
DK8OK Locates Radio France at 15320 kHz