Tagged: HF

Tech Minds: Review of the KiwiSDR 2

Earlier this year the KiwiSDR 2 became available for purchase and began shipping out to customers. The KiwiSDR 2 is an upgraded version of the original KiwiSDR with the main upgrades being an enhanced RF front end and the addition of a digital attenuator.

Over on the Tech Minds YouTube channel, Matt received his KiwiSDR 2 and uploaded a review and demonstration of the product. In the video, Matt shows the external ports of the KiwiSDR and discusses the differences between the KiwiSDR 2 and the original version. Matt goes on to show how to set up the KiwiSDR 2 and shows it receiving through it's web-based receiving software.

KiwiSDR is 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. Other than the specifications, the main interesting feature about the KiwiSDR is that it is designed to be operated entirely as an online web-based SDR which is accessed over a network connection. Owners can optionally share their KiwiSDRs online with anyone who wants to access it, which also allows for interesting distributed applications, such as TDoA direction finding, which allows users to pinpoint the location of unknown HF transmissions such as numbers stations.

KiwiSDR 2 - A Standalone Software Defined HF Radio Receiver

Tech Minds: Testing a High Impedance Amplifier for Software Defined Radio

Antenna impedance matching is important for antennas and software defined radios as impedance mismatches can result in poor reception. For transmitting SDR's the situation is more dire because impedance mismatches can actually damage the transmitting hardware or at least cause high power efficiency losses.

Over on his YouTube channel Tech Minds has uploaded a video where he tests out a battery powered HF high impedance amplifier for software defined radios. The amplifier is designed to be used with long wire antennas on the HF bands as these antennas typically have high impedances which don't match the 50 Ohm impedance that most SDRs expect to see. This device is an amplified alternative to using a passive unun.

The results in his video show that the signal to noise ratio is indeed boosted when the impedance matching amplifier is used. Later the device is opened to show the battery, charging management chip and amplifier chip.

High Impedance Amplifier for Software Defined Radio

Testing the ATS25 Max-Decoder Receiver

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.

Alter ATS25 umbauen zum max Decoder Teil 1 Die Hardware

Building an OpenWebRX Server with an RTL-SDR Blog V3 for HF Monitoring

Thank you to Ramadhan (YD1RUH) who has put together a brief set of commands showing how to quickly get setup with OpenWebRX and an RTL-SDR Blog V3. OpenWebRX is a web based SDR program that allows users to use their SDR over a network or internet connector. It is compatible with several SDRs including the RTL-SDR.

 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.

The SDRSharp ListenInfo Plugin

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.

SDR# ListenInfo Plugin
SDR# ListenInfo Plugin

A Broad Overview About HF on the RTL-SDR Blog V3

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)

Video on Receiving HF Signals with the RTL-SDR Blog V3

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.

HF Ham Radio with RTL-SDR Made EASY!

Frugal Radio: Testing a Loop on Ground Antenna with an Airspy HF+ Discovery

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