Instructions for Building a Portable Double Cross Antenna: Great for NOAA/Meteor Weather Satellites

Over on Reddit user merg_flerg has uploaded an imgur post that carefully details a step by step guide for building a double cross antenna. A double cross antenna is great for reception of satellites like NOAA and Meteor since it has a sky oriented radiation pattern with very few nulls. This means that it can receive satellite signals coming from the sky well. Alternative antennas for NOAA/Meteor include turnstiles and QFH antennas, although the double cross antenna seems to have the least nulls, meaning that the signal is less likely to fade in and out as the satellite moves across the sky.

merg_flerg’s design is also modified from the standard design slightly, allowing it to become easily disassembled and carried within a backpack. At the end of his tutorial he writes that he gets much better reception with his double cross antenna than he does with his QFH.

In the post he demonstrates the final constructed antenna decoding a NOAA APT weather satellite image with an RTL-SDR and the WXtoIMG software. See our tutorial for information on decoding NOAA weather satellite images.

The finished double cross antenna connected to a PC running an RTL-SDR and WXtoIMG.
The finished double cross antenna connected to a PC running an RTL-SDR and WXtoIMG.
Tweet16
Share
Reddit
Vote
Email
16 Shares

50 Units of a $199 Nuand bladeRF x40 for Sale: 1-Day Only

Nuand is the company responsible for the bladeRF software defined radio. The bladeRF x40 is a SDR that usually costs $420. It uses a LimeMicro LMS6002D chip, which has a 12-bit ADC and a tuning range of 300MHz – 3.8GHz.

For one day only they have released a special price for the bladeRF x40 of $199 USD, for the first 50 customers only. At the time of this post the deal still seems to be active, and the coupon code of “MHZ” is still working. Of note is that the recently successfully crowdfunded LimeSDR uses the newer and better LimeMicro LMS7002M chip, so Nuand may be testing the waters for a lower price point on their bladeRF. However, one thing to note is that the bladeRF is proven hardware with active software applications, whereas the LimeSDR is not yet proven. 

Nuand also recently released an update which saw the source released for an ADS-B decoder that can be run on the bladeRF’s onboard FPGA, and also an update which allows the bladeRF to display up to 124 MHz of bandwidth at any one time. The large bandwidth display appears to work in a similar way to rtl_power or SpectrumSpy for the Airspy, by quickly switching between multiple chunks of frequency. The difference is that the bladeRF can do this by using onboard HDL accelerators which allow it retune extremely fast at several thousand times a second.

bladeRF displaying 96 MHz.
bladeRF displaying 96 MHz.
Tweet
Share
Reddit
Vote
Email

Building a Quad RTL-SDR Receiver for Radio Astronomy

Amateur radio astronomer Peter W East has recently uploaded a new document to his website. The document details how he built a quad RTL-SDR based receiver for his radio astronomy experiments in interferometry and wide-band pulsar detection (pdf – NOTE: Link Removed. Please see his website for a direct link to the pdf “Quad RTL Receiver for Pulsar Detection”. High traffic from this post and elsewhere has made the document go offline several times). Interferometry is a technique which uses multiple smaller radio dishes spaced some distance apart to essentially get the same resolution a much larger dish. Pulsars are rapidly rotating neutron stars which emit radio waves, and the strongest ones can be observed by amateur radio telescopes and a receiver like the RTL-SDR.

The Quad receiver has four RTL-SDR’s all driven by a single TCXO, mounted inside an aluminum case with fans for air cooling. He also uses a 74HC04 hex inverter to act as a buffer for the 0.5 PPM TCXO that he uses. This ensures that the TCXO signal is strong enough to drive all four RTL-SDRs.

The Quad RTL-SDR with air cooling.
The Quad RTL-SDR with air cooling.

Whilst all the clocks are all synced to a single master clock, synchronisation between the RTL-SDR’s is still difficult to achieve because of jitter introduced by the operating system. To solve this he introduces a noise source and a switch. By switching the noise source on and off, correlation of the signal data can be achieved in post processing.

Noise Source and Switch Calibration Unit.
Noise Source and Switch Calibration Unit.
How correlation with the pulsed noise source works.
How correlation with the pulsed noise source works.

In the document Peter shows in detail how the system is constructed, and how it all works, as well as showing some interferometry results. The system uses custom software that he developed and this is all explained in the document as well.

Tweet17
Share
Reddit
Vote
Email
17 Shares

Final Hours for LimeSDR CrowdFunding

The LimeSDR crowdfunding campaign is now in it’s final few hours (22 hours left at the time of this post), and funding is up to 95% or 473k out of its 500k goal. After a few unsure days it looks like the goal will be reached just in time. The LimeSDR is a RX/TX capable SDR with a 100 kHz – 3.8 GHz frequency range, 12-bit ADC and 61.44 MHz bandwidth. We’re not affiliated with LimeSDR in any way, but we think it is shaping up to be a much better version of the RX/TX experimenter radios that are on the market now, such as the HackRF and bladeRF. For a price lower than the HackRF you get a much better ADC, a larger bandwidth and full duplex TX/RX capabilities. The LimeSDR capabilities appear to be close to the Ettus Research B210, which usually sells for over $1000 USD. Also, one of the drawbacks of radios like the HackRF and bladeRF was the lack of decent ready to go software apps. LimeSDR have made promises to focus hard on developing a software “app” store for the device meaning that application software will be able to be downloaded very easily, not to mention that all their software and hardware is fully open source.

During the crowdfunding campaign the LimeSDR is available for an early bird price of $249 USD. After the campaign the price will be raised to $289 USD for preorders, and $299 USD once the device actually begins shipping.

In a recent update they show the LimeSDR being used to receive GPS satellites and decode the data in GNU Octave and also mention that the app store development will begin once crowdfunding is successful.

The LimeSDR with four antennas attached.
The LimeSDR with four antennas attached.
LimeSDR Goal Almost Reached.
LimeSDR Goal Almost Reached.

Tweet19
Share
Reddit
Vote
Email
19 Shares

Using the SUP-2400 Downconverter with an LNA and RTL-SDR to Receive 2.4 GHz Video

Earlier in June YouTube user T3CHNOTURK posted a video demonstrating him receiving signals above the maximum 1.7 GHz range of the RTL-SDR by using a modified SUP-2400 downconverter. Back in April it was discovered by KD0CQ that a $5 DirecTV SUP-2400 circuit could be modified and turned into a downconverter for use with the RTL-SDR.

Now T3CHNOTURK has uploaded a new video showing more demonstrations of the RTL-SDR + SUP-2400 combo in action. This time he adds a PGA-103 based LNA to boost the signal strength, which gives him better effective range. In the video he shows reception of a wireless keyboard once again, and then goes on to show him receiving 2.4 GHz analog PAL video using the RTL-SDR program TVSharp. The picture is not particularly clear, but it is a decent demonstration.

RTLSDR, TVsharp 2.4 Ghz video receiver moded SUP-2400 & pga-103 LNA

Tweet
Share
Reddit
Vote
Email

Remote Spectrum Monitoring Drone with OpenWebRX, Raspberry Pi and an RTL-SDR

Recently Zoltan of rfsparkling.com wrote in to us to show us how he combined efforts with András (programmer of the OpenWebRX software) to create a proof of concept remote spectrum monitoring drone. The drone uses an RTL-SDR connected to a Raspberry Pi, and the Raspberry Pi runs an OpenWebRX server which broadcasts the radio data via 4G mobile internet. The full connection flow chart goes as follows:

[Drone] Antenna –> RTL-SDR –> RPi 2 –> OpenWebRX Server –> 4G mobile net –> … Internet … [Notebook] –> 4G mobile net –> Browser with OpenWebRX client

Zoltan writes that some possible applications include emergency communications, ham radio, 3D spectrum mapping, etc. In the future he also hopes to add TX capabilities, so that the drone can also work a a makeshift transceiver tower. The biggest limitation that Zoltan noted is the flight time of only about 10 minutes. However, a solution he suggests for future experiments is using wire powered drones.

In previous posts we showed Hak5’s remote RTL-SDR ADS-B drone. Their results were not particularly great, however Zoltan and András’ results seem to be much better.

The video below shows an example of Zoltan and András’ drone experiments.

Remote Spectrum Analyzer Drone With OpenWebRX using RTL-SDR and Raspberry Pi

Tweet11
Share
Reddit
Vote
Email
11 Shares

SDRplay Releases SDRuno: Free SDR Software for the RSP

The SDRplay is a $149 USD RX only software defined radio with a 12-bit ADC and up to 8 MHz of bandwidth that can tune from 10 kHz – 2 GHz. We consider it and it’s competitors the Airspy R2/Mini to be the best next step up from an RTL-SDR. See our previous post for a review comparing the Airspy and RSP.

One of the main drawbacks of the RSP has been that it does not have any official software associated with it. The closest competitor, the Airspy has the free official SDR# software, but the RSP relied only on third party programs like HDSDR and SDR-Console.

That is set to change today as SDRplay have announced the release of their SDRuno software, a free general purpose software defined radio program for the RSP. SDRuno is a customized version of the Studio1 software which SDRplay acquired the rights to last April. The full press release is quoted below:

SDRplay is pleased to announce the official release of SDRuno for the RSP. SDRuno is the new name for the RSP compatible version of Studio1, the rights to which we obtained and announced on 28th April. SDRuno contains native support for the SDRplay RSP and no extra plugins are required. Third party hardware can also be supported via the ExtIO interface, but with reduced functionality.

SDRuno provides a rugged and flexible, high performance SDR receiver capability and boasts some excellent features:

  • Multiple ‘Virtual Receivers’ which allow for simultaneous reception and demodulation of different types of signals within the same receiver bandwidth.
  • A selectivity filter with an ultimate rejection greater than 140 dB.
  • A unique distortion-free double stage AGC with fully adjustable parameters.
  • Multiple notch filters with BW adjustable down to 1 Hz, Notch Lock feature.
  • A unique synchronous AM mode with selectable/adjustable sidebands, dedicated PLL input filter, and selectable PLL time constants.
  • SNR (stereo noise reduction), featuring a proprietary noise reduction algorithm for stereo broadcast.
  • AFC for FM signals.
  • Calibration for receiver frequency errors.

Over time, we plan to add many more features to SDRuno to enhance the user’s experience of this very powerful piece of software. This software runs on Windows and we don’t yet know how easy it will be to migrate it to other platforms but this is something we will be investigating.

SDRuno will be made freely available to all current and future users of the RSP – to download a copy – simply go to http://www.sdrplay.com/windows.html

Our support for SDRuno in no way lessens our commitment to support HDSDR, SDR Console, Cubic SDR or ANY other software solution where the authors are willing to work with us. We fully recognise that many people have strong preferences for particular pieces of software and we do not want to do anything to undermine the options that people have to use their favoured software packages. Indeed, our view is quite the opposite. Our objective remains aim to have our hardware platforms support any and every SDR package out there. This of course may not be possible, but it is our philosophy and part of the ethos of our company.

About Studio 1:

Studio1 was developed in Italy by SDR Applications S.a.s. and has hundreds of happy customers around the world.

Studio 1 is known for its user friendly stylish GUI, CPU efficiency and advanced DSP capabilities, including features not available on other SDR software packages.

www.sdrapplications.it

About SDRplay:

SDRplay limited is a UK company and consists of a small group of engineers with strong connections to the UK Wireless semiconductor industry. SDRplay announced its first product, the RSP1 in August 2014

www.sdrplay.com

Email: [email protected]

The software can be downloaded at http://www.sdrplay.com/windows.html. SDRuno comes with a full manual (pdf) and SDRplay fans and beta testers of SDRuno have also released a free SDRuno cookbook guide (pdf). From the cookbook it appears that SDRuno is also compatible with any SDR that supports ExtIO modules, like the RTL-SDR, although as noted in the press release functionality for other radios may be reduced. We look forward to being able to test the software out, and post a review within the next few days.

sdruno_announcement

Tweet19
Share
Reddit2
Vote
Email
21 Shares

LimeSDR CrowdFunding Closing in Four Days: 80% Funded

The LimeSDR is a new transmit capable software defined radio with a 100 kHz – 3.8 GHz frequency range, 12-bit ADC and 61.44 MHz bandwidth which is currently seeking crowdfunding. At the time of this post there is about four days left to reach the $500k goal, and it is only 80% funded. To try and reach their funding goal they have released another batch of discounted units which cost only $249 USD. After the crowd funding campaign the price will rise to $289/$299 USD. If the LimeSDR is not funded in time, they write that the project will unfortunately be put on hold and it’s future may be uncertain. We believe that this product is shaping up to be a very good TX/RX capable SDR, like the HackRF and bladeRF, but much better overall and for the same or even lower price.

Recently they also released some new updates that show off some LimeSDR features. In a post previously featured on our blog beta tester Alexandru showed how he was able to get the LimeSDR to transmit DVB-S2 HDTV. In later updates they showed how the LimeSDR can be used to:

The LimeSDR Board
The LimeSDR Board
Tweet21
Share
Reddit
Vote
Email
21 Shares