Thank you for Manuel Lausmann for submitting his videos where he tests out and upgrades an ATS25 Max-decoder receiver. The ATS25 Max-decoder is a low cost portable HF receiver which has a large number of decoders built in such as RTTY, Hell, FT8 and FT4. Manuel notes that more decoders are still to come, such as SSTV. The built in decoders make it superior to it's predecessors the x1 and x2.
We note that the ATS25 Max appears to be around US$75 on Aliexpress, but these appear to be Max units without the "-decoder" add on. So if you are looking at purchasing one, please make sure to check that you are getting one with the text "max-decoder".
Manuel also notes that older models of the ATS25 can be retrofitted with a decoder PCB and converted into an ATS25 Max-decoder with a firmware update written by Bernhard Binns.
Note that Manuel's videos below are narrated in German, however the YouTube subtitle auto-translate feature works well enough to understand what is being said. In the first video Manuel demonstrates and reviews the ATS25 Max-Decoder, showing off some of the decoding features.
In the second video Manuel shows how to update an old model ATS25 in to the ATS25 Max by soldering on the decoder board.
ATS25 max-Decoder
Alter ATS25 umbauen zum max Decoder Teil 1 Die Hardware
The installation is based on Ubuntu, and uses docker for the install. He also shows how to set up the OpenWebRX configuration file so that it will use the Q-branch direct sampling mode in RTL-SDR Blog V3 dongles for HF reception.
A demonstration of the result can be seen on Ramadhan's public OpenWebRX page. You can select between the various enabled HF bands in the lower left.
OpenWebRX HF reception running on an RTL-SDR Blog V3 dongle.
SDR# is a popular software defined radio program that is compatible with RTL-SDR, Airspy and several other SDR devices. One feature is the ability for third parties to develop plugins for the software.
One recently released plugin that is gaining popularity is the "ListenInfo" plugin. The ListenInfo plugin uses a publicly available database of shortwave stations to display frequency station info for the LW, MW, SW bands within the SDR# spectrum display.
If you've ever been browsing the shortwave bands and wondered where a station is broadcasting from, and what it's transit power, beam direction and transmit schedule are like, then this will be a very useful plugin for you.
Over on YouTube, Tom the Dilettante has uploaded a video demonstrating how to receive HF signals with an RTL-SDR Blog V3 running in direct sampling mode. This is something already known to most RTL-SDR fans, but on the RTL-SDR V3 we have built in a direct sampling circuit that enables reception below 24 MHz with a simple settings change in software.
In the past and with other dongle brands, enabling direct sampling required hardware mods involving directly soldering a wire antenna to very small pins or pads. Direct sampling is not a high performance mode for HF, but in many situations it can be good enough for casual listening.
In his video Tom demonstrates HF reception with the RTL-SDR Blog V3 and an MLA-30 active loop antenna. This is a cheap loop antenna available on Aliexpress that works very well for the price.
Listen Around the World - No Internet Required (HF & Shortwave on RTL SDR)
Over on YouTube TheSmokinApe has uploaded a video showing how to use the direct sampling mode on RTL-SDR Blog V3 devices to receive HF transmissions, such as the ham bands, short wave and AM broadcast. In the video he shows how to activate direct sampling mode in SDR#, and then goes on to show reception of a few HF signals.
We note that an appropriate HF capable antenna is required to receive HF signals. The multipurpose dipole kits we sell are for VHF/UHF reception only. A simple and low cost HF antenna could just be a long wire running through your house.
The KK5JY Loop on Ground (LoG) antenna is a 15 feet per side square loop designed for reception of HF and lower. It simply consists of an isolation transformer and wire that as the name implies is placed somewhere on the ground in a square loop like shape. It is cheap and easy to build and compact in that it does not take up any usable space.
In his latest video Rob from the Frugal Radio YouTube channel tests out this antenna with his Airspy HF+ Discovery SDR. He uses a bit of wire lying around, and a low cost 9:1 Balun from NooElec as the isolation transformer. With this antenna he was able to pick up signals in the USA and all the way over to Australia from his home in Canada. NDB signals were also receivable.
2022 LoG (Loop on Ground antenna) for SDR radio tested on Airspy HF+ Discovery SDR KK5JY HAM radio
Over on the Techminds YouTube channel, Matt has uploaded his latest video which is a review of the GA-450 portable HF active loop antenna. The antenna costs between US$60-$80 + shipping and is available on Chinese market sites like Aliexpress and Banggood. It's advertised as covering 2.3 - 30 MHz, and uses a very portable and sturdy 20cm stainless steel loop. The active base amplifier is powered via a USB-C connector, and it even has a built in lithium battery for portable field use.
In his review Matt shows the antenna in action, noting that it's performance is quite a lot better than expected for it's small size, but it can't compare to his large half-wave end fed antenna. He notes that it appears to work best from 7 - 21 MHz, but not so well below 7 MHz. Overall he recommends it if you're looking for a small sized loop antenna.
For some time now there has been chatter about the possibility of using WSPR logs to help track the mysterious disappearance of flight MH370. WSPR or the "Weak Signal Propagation Reporter" is a protocol typically used on the HF bands by amateur radio operators. The properties of the protocol allow WSPR signals to be received almost globally despite using low transmit power. Amateur radio operators use it for making contacts, or for checking HF radio propagation conditions. MH370 is a flight that infamously vanished without a trace back in 2014.
The theory proposed by aerospace engineer Richard Godfrey is to use logs of sent and received WSPR transmissions that may have intersected the potential flight path of MH370, and to look for potential reflections or 'scatter' in the signal from the metal aircraft hull. From the reflections an approximate track of the aircraft could be calculated much in the same way that bistatic over the horizon radar systems work.
While it is an exciting theory, it is unfortunately considered by most experts as highly unlikely to yield any suitable results with the main problems being WSPR transmission power too weak to detect reflections from an aircraft, and the effect of the ionosphere too difficult to account for.
Over on his blog Nils Schiffhauer (DK8OK) has posted a thorough critique of the idea, explaining the theory, technical details and difficulties in depth, ultimately coming to the conclusion that the idea is based more in wishful thinking than in fact. Nils summarizes:
Time and again, there are news stories in the professional and popular press about the fact that log data from the WSPR data network can help locate aircraft. In particular, the effort is to determine the actual crash site of flight MH370. This effort essentially amounts to detecting "unusual" level jumps and frequency changes ("drift") in the archived WSPR log data and attributing them to reflections from specific aircraft ("aircraft scatter").
In a blog entry, Nils Schiffhauer, DK8OK, for the first time critically evaluates this theory. On the one hand, this is based on years of observation of aircraft scatter on shortwave as well as an investigation of about 30 Doppler tracks. The results of this complex analysis of more than 10,000 data in one example alone are sobering: The effects of aircraft scatter on the overall signal are almost always well below 0.3 dB.
To prove a correlation between level changes of the overall signal and aircraft scatter seems hardly possible on the basis of the WSPR data material. The reasons are manifold, but lie mainly in shortwave propagation, where level changes of 30 dB within a few seconds are the rule rather than the exception.
However, since the local and temporal state of the ionosphere is not known in previous investigations on the WSPR data material - it is recorded in parallel in professional OTH radar systems and calculated out of the received signal - level jumps can hardly be clearly assigned from the sum signal alone. This finding is supported by further arguments in the blog: https://t1p.de/t5kr
Nils demonstrates aircraft scatter on China Radio International, a 500kW transmitter.
