A new video showing how to build a V-dipole for weather satellite reception has been uploaded over on the Tech Minds YouTube channel. A V-dipole isa dipole antenna arranged in a 120 degrees "vee" shape, and mounted horizontally. It was first popularized by Adam 9A4QV who realized that such a simple antenna would work well for low earth orbit satellites like the NOAA and Meteor weather sats.
The video shows how to use some steel rods, a plastic pipe and terminal block to build the v-dipole. After building and mounting the antenna in the required North-South orientation he shows how he's using Gpredict with SDR# and WxToImg to decode the NOAA satellite image.
How To Build A V Dipole For Receiving Weather Satellites
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.
73!
Andras, HA7ILM
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.
Also, although Andras has stopped development on OpenWebRX, a fork of the project led by Jakob Ketterl (DD5JFK) is alive and well at github.com/jketterl/openwebrx and openwebrx.de.
Back in March we posted about Othernet's release of their "Bullseye" TCXO ultra stable LNB for receiving QO-100 and other Ku-Band satellites. We have decided to now offer these for sale on our store as well.
They cost US$29.95 with free shipping to most countries. We are currently selling it over on our blog store and on our Aliexpress store. The Aliexpress store uses Aliexpress Standard Shipping which may be better for some countries like Poland, Ukraine, etc. As usual, please expect that there could be shipping delays at the moment due to the ongoing global pandemic. Since the US is not covered by QO-100 we will not be stocking Amazon USA.
QO-100 / Es'hail-2 is a geostationary satellite at at 25.5°E (covering Africa, Europe, the Middle East, India, eastern Brazil and the west half of Russia/Asia) providing broadcasting services. However, as a bonus it has allowed amateur radio operators to use a spare transponder. Uplink is at 2.4 GHz and downlink is at 10.5 GHz. Most SDRs do not tune all the way up to 10.5 GHz, so an LNB (low noise block) is typically used, which contains the feed, an LNA, and a downconverter which converts the 10.5 GHz frequency into a much lower one that can be received by most SDRs.
In order to properly monitor signals on QO-100 an LNB with a Temperature Compensated Oscillator (TCXO) or other stabilization method is required. Most LNBs have non-stabilized crystals which will drift over time with temperature changes. This means that the narrowband signals used on QO-100 can easily drift out of the receive band or cause distorted reception. It is possible to hand modify a standard Ku-band LNB by soldering on a replacement TCXO or hacking in connections to a GPSDO, but the Bullseye LNB is ready to use and cheap.
The Othernet TCXO Ultra Stable LNB for QO-100 and Ku-Band Satellites
The official product details read:
The Bullseye LNB is the world's most precise and stable DTH/consumer Ku-band down converter. Even a VSAT LNBF costing hundreds of dollars more is no match for the performance of the Bullseye 10K LNB. Each unit is calibrated at the factory to within 1 kHz of absolute precision against a GPS-locked spectrum analyzer. Under outdoor conditions, the stability of the LNB is well within 10 kHz of offset. As a bonus feature, the Bullseye 10K provides access to its internal 25 MHz TCXO through the secondary F-connector. This reference output can be used to directly monitor the performance of the TCXO over time.
Features
Bullseye 10 kHz BE01
Universal single output LNB
Frequency stability within 10 kHz in normal outdoor environment
Phase locked loop with 2 PPM TCXO
Factory calibration within 1 kHz utilizing GPS-locked spectrum analyzers
Ultra high precision PLL employing proprietary frequency control system (patent pending)
Digitally controlled carrier offset with optional programmer
25 MHz output reference available on secondary F-connector (red)
Return loss of 8 dB (739 - 1950 MHz) and 10 dB (1100 - 2150 MHz)
Noise figure: 0.5 dB
We note that an external bias tee power injector is required to power the LNB as it requires 11.5V - 14V to operate in vertical polarization and 16V - 19V to operate with horizontal polarization. The bias tee on the RTL-SDR Blog V3 outputs 4.5V so it is not suitable.
Just on the back of yesterday's post about a helical antenna Hydrogen line radio telescope, we have another submission. This telescope is a bit more advanced as it consists of a large motorized horn antenna, with a custom made LNA and filter board connected to an RTL-SDR with GNU Radio DSP processing.
Over on Instructables "diyguypt" has posted a full overview of his creation. The horn antenna is first created out of aluminum sheets, and then the waveguide is cut out of copper wire and installed into the can part of the horn. He then notes that he created two custom LNA+filter boards with the Minicircuits PMA2-43LN+ LNA and the Minicircuits BFCN-1445+ filter. This then connects to the RTL-SDR that is accessed via GNU Radio which creates a visualization spectrograph.
He then shows how he made the rotation system out of a salvaged drill motor and two relays, and how he made the Z-Axis control with a stepper motor. The motors are controlled with an Arduino and a gyroscope module.
"diyguypt"'s Hydrogen Line Horn Antenna connected to an RTL-SDR
Earlier in the month SDRplay released SDRuno V1.4 RC1. This is a beta version that amongst other changes now has the capability to run "plugins". Plugins allow developers to easily create modules that extend the functionality of the SDRUno software. For example right now there is a plugin included with V1.4 RC1 that allows users to listen to DAB audio. Up until recently plugin functionality has only been available in Airspy's SDR# software, so it's good to see SDRuno finally including this feature too.
Over on the Techminds YouTube channel Matthew has uploaded a short video where he tests out the new plugins feature. First he tests out the DAB decoder, noting that the CoreAAC codec needs to be installed first separately. Later he tests the second plugin which is an audio recorder that allows users to record audio to MP3.
Over on YouTube the "Unboxing Tomorrow" channel has uploaded a video explaining how he uses RTL-SDR dongles to monitor various radio channels for storm warnings. He notes how he uses his RTL-SDR to monitor the NOAA national weather service channel as well as the Skywarn channel which is the amateur radio based storm spotting network used in some parts of the USA. He also monitors a P25 trunking network with DSD+ for good measure.
In addition he shows a bit of his setup which includes an RTL-SDR Blog V3 and Raspberry Pi connected to an LCD screen all mounted on a neat rail system made from T-slots.
Thank you to YouTuber M Khanfar for submitting news about his various Windows GNU Radio tutorials that he has been uploading to YouTube. So far he's uploaded tutorials on creating an FM Receiver, Air Band Receiver, AM/NFM Receiver, NFM Receiver with Squelch and Recorder and Spectrum Analyzer with GNU Radio on Windows 10. The tutorials are straight to the point and designed to be followed along with the video. The full list of videos can be found on his YouTube channel, and we have embedded one below.
Build NFM Reciver with Squelch and Recorder Activity GNU RADIO Win10
Thank you to Geoff for submitting his experience with creating a hydrogen line radio telescope out of an easy to build helical antenna, Raspberry Pi, LNA and an RTL-SDR. The Hydrogen Line is an observable increase in RF power at 1420.4058 MHz created by Hydrogen atoms. It is most easily detected by pointing a directional antenna towards the Milky Way as there are many more hydrogen atoms in our own galaxy. This effect can be used to measure the shape and other properties of our own galaxy.
Earlier in the year we uploaded a tutorial showing how to observe the Hydrogen line with a 2.4 GHz WiFi antenna. In Geoff's setup he used a home made Helical antenna instead. This antenna is basically a long tube with a spiral wire element wrapped around the tube. He also shows how he needed to impedance match the antenna with a triangular piece of copper tape. The result is a directional antenna with about 13 dBi gain. To complete his setup he used a NooElec SAWBird H1+ LNA/Filter, an RTL-SDR Blog V3 dongle and a Raspberry Pi.
The results show a clear increase in RF power at the Hydrogen line frequency when the antenna points at the Milky Way, indicating that the setup works as expected. It's good to see a Helical working for this, as it is fairly light weight and could easily be mounted on a motorized mount to scan the entire sky.
A Hydrogen Line Radio Telescope made with a Helical Antenna.
