The LimeSDR can now tune to HF Frequencies

Back in June the LimeSDR completed its $500,000 crowd funding goal. The units are still in production and have not yet shipped, but the software is currently being worked on heavily. In a recent update they have enabled HF reception on the LimeSDR hardware. LimeSDR beta tester Marty Wittrock wrote in to let us know his review of the new update:

Another major step forward for the LimeSDR yesterday…

As a part of the continuing development of the PPAs for Ubuntu and other distros, the LimeSDR is now supported for native HF tuning – – no transverter required. Receive has been functionally tested from 7.0 MHz to 56 MHz and even with the matching networks as they are in the LimeSDR I have (which is not what will be delivered in November – the LimeSDRs the backers will receive in November will have modified matching networks to be more broadband and perform better than what I have right now) the receive quality was very good with my applied HF station antenna (ground mounted vertical for 80m – 6m). I shot two videos yesterday of the LimeSDR operating on the 20m band – one with USB voice and one with CW/RTTY on the contest weekend for RTTY (REAL active). I ran this completely from a USB 3.0 Flash Drive plugged into a Dell 3020 and booted from that Flash Drive to operate the LimeSDR. The Flash Drive is loaded with Ubuntu Xenial (16.04), all the applied support files (SoapySDR, GNURadio, OsmoSDR. etc) and the application GQRX to tune and demodulate the LimeSDR. The setup worked VERY well and the results can be viewed with the two videos provided here:

https://www.youtube.com/watch?v=Z0xIN8AyaFs&feature=youtu.be
https://www.youtube.com/watch?v=mTWA3KRK_Rg&feature=youtu.be

Again, I was impressed with the quality of the direct, native, HF tuning of the recent updates to LimeSuite. Having this functionality in LimeSuite finalizes for receive, but I still need to check out the transmit. It’s my hope that Simon Brown’s SDR Console V3.0 will update with the new HF tuning improvements such that I can use his app on Windows to do a full checkout in receive/transmit with the LimeSDR and hopefully apply it to the WSPR app to have the LimeSDR operate HF digital modes on the HF band and Amateur Radio frequencies to have the first true LimeSDR operation benchmark.

I fully intend to have Flash Drive images available for download once I put the final touches on the Flash Drive I have. This will allow all Hams that want an instant solution for booting Ubuntu and running GQRX for receive to use their LimeSDRs right out of the chute without having to install ANYTHING provided that they have a PC that is decently fast (3.0 GHz, 8GB RAM) and has USB 3.0 ports on the PC. I’m looking for a reliable means to read/write the Flash Image and then take the image and ‘burn’ other USB 3.0 Flash Drives with the image. Once I have that reliably working, I’ll post the image and the Flash Drive app so ANYONE can make their own from a blank 32GB to 128GB Flash Drive.

More to follow on the HF transmit as I have those apps and check that out – – Stay tuned..!

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. It costs $299 USD.

Using an RTL-SDR to Listen to Superhet Radio’s Unintentional Emissions

Recently two students (Léo Poughon and his friend Thomas Daniel) wrote in to let us know about their work with SDR’s for their school project. Their project was to try and repeat the work of “Operation RAFTER” which was a technique use by MI5 in the 60’s to find hidden soviet spy radio equipment. Essentially, all superhet radios (almost any consumer radio is of the superhet design) will emit unintentional emissions from its local oscillator. By tuning to these unintentional emissions, and then emitting your own signal, it is then possible to know what frequency a radio is listening to.

They write the following:

As a french student (sorry for my bad english) in Higher School Preparatory Classes, I (and a friend) had to work with a rtl-sdr dongle for a school project. We tried to do, with the help of amateur radio near Toulouse (F6GUS, his club F5KUG) the same thing as the “RAFTER Operation” (https://en.wikipedia.org/wiki/Operation_RAFTER ) did during the 60′ : hearing at unintentional electromagnetic emissions coming from a widely-used consumer superhet receiver.

So because of its structure, a superheterodyne receiver (i.e. listening at FM broadcast) spreads some unintentional radiations due to the local oscillator upstream the mixer. Anybody with a suitable receiver (for example any rtl-sdr based dongle) can receive these emissions. Because of standards, in most FM radio the local oscillator (that is what the user actually tune) is tuned at the frequency he wants to listen plus 10.7 MHz. So if somebody in the close neighborhood is listening at a broadcast at 100 MHz, you will be able to “receive” its local oscillator at 110.7 MHz. (Please note it may be illegal in some countries to listen at these bands)

What is interesting is to know if a signal you receive at these frequency is actually coming from a radio receiver. During the RAFTER Operation, MI5 broadcast on the band they thought to be heard by soviet spies, and then listened for “the change in the superhet tone” to identify them.

We was able to receive with RTL-SDR the Local Oscillator of a superhet receiver we own.

rafter_1

We can see that the frequency isn’t stable on most of the time (the receiver was tuned to “France Info”, a french public station), but becomes stable sometime (when there is a “blank” between two news) : the frequency of the local oscillator “follows” what the superhet receiver demodulates.

Among other factors, a variation of the supply voltage of the local oscillator can make its frequency slightly shift. So we established experimentally a link between the supply voltage of our radio receiver and what is broadcast via the speaker (because when a speaker is using electrical current, the supply voltage slightly varies).

rafter_2

On the top, the HP voltage, and behind there is the supply voltage. Then, we saw that voltage variations could make the frequency to vary

capture du 2016-04-05

Here we supply the receiver (with a low frequency generator) making the supply voltage slightly varying and plot the frequency of local oscillator with a Python script we made.

Then, listening at the radio receiver local oscillator with GQRX and our RTL-SDR dongle, demodulating it with “narrow FM” demodulation and adapted parameters, we could hear with the PC (and obviously with poorer quality) what the radio receiver was listening at.

With the stock antenna we could hear at our radio only a dozen meters away, but with a homemade very low quality discone antenna we could receive it on another building, 60 meters away of our antenna. The ability to listen more or less the local oscillator broadcast depends also of the shielding of the radio receiver, its price (because a cheap radio will have a bad power supply and so its local oscillator frequency can “follow” what the speaker is telling, allowing us to “listen” at the local oscillator spike) and how you supply it (with the power grid or with batteries).

To conclude, we could (more or less depending on the previously cited parameters) know what a radio receiver in the neighbourhood was listening to using a RTL-SDR.

Modifying the Outernet LNA for Iridium Reception

A few days ago we posted a review on the Outernet LNA which can can be used to help receive their new L-band service signal. Their LNA uses a filter which restricts the frequency range from 1525 – 1559 MHz as this is the range in which the Outernet signals are located.

By default this LNA cannot be used to receive Iridium because the pass band on the default SAW filter does not cover the Irdidium frequency band of 1616 – 1626.5 MHz. Over on Reddit, devnulling decided to experiment with one of these LNA’s and see if he could replace the default SAW filter to enable Iridium reception. In his post he shows how he removes the default SAW filter, and replaces it with a Murata SF2250E SAW filter, which is the same size, but has a center frequency of 1615 MHz and a bandwidth of 20 MHz. Iridium is used for data services like satellite pagers, and with the right tools can be decoded.

We are also curious to see if this LNA could be modified to be used with GOES reception, which occurs at 1692 MHz.

Note: For those who had trouble with obtaining international shipping on these LNA’s the Outernet store now supports USPS international shipping, and NooElec appear to now be selling them on their site directly. Their products can also still be obtained on Amazon for US customers.

Additional Note Regarding the Downconverter: Also, it appears that the Outernet downconverter prototype that we posted about back in May has unfortunately been discontinued indefinitely and will not enter mass production. For now the LNA is the best option for receiving their signal.

Outernet LNA Modified for Iridium Reception
Outernet LNA Modified for Iridium Reception

More videos showing HF reception on the RTL-SDR V3 Dongle

In this video icholakov from our last post continues his testing, and does some more tests on daytime HF reception.

https://www.youtube.com/watch?v=3mugscC8B7U

In his third video he tests night time reception against the SDRplay.

https://www.youtube.com/watch?v=3I-ROZ-2Lc8

In this video YouTube user Michael Jackson tests his RTL-SDR V3 at 8 MHz, with a dipole antenna.

https://www.youtube.com/watch?v=YSLfUFKqOGI

Finally, in this video YouTube user jonny290 tests the V3 dongle on HF reception using CubicSDR.

https://www.youtube.com/watch?v=I7WvFz1XGYY

Receiving GOES LRIT Full Disk Images of the Earth and EMWIN Weather Data with an Airspy

Over on Reddit user devnulling has made a post showing how he was able to use his Airspy SDR to download full disk satellite images of the earth from the GOES satellite. In a separate imgur post he also shows that he was able to receive EMWIN weather data images from the same GOES satellite.

The Geostationary Operational Environmental Satellite (GOES) is a weather satellite placed in geosynchronous orbit (same position in the sky all the time) which is used for weather forecasting, severe storm tracking and meteorology research. It transmits full disk images of the earth on its Low Rate Information Transmission (LRIT) signal, and weather data images and text on its Emergency Managers Weather Information Network (EMWIN) signal. EMWIN is a service for emergency managers that provides weather forecasts, warnings, graphics and other information in real time.

In his post devnulling writes about receiving GOES:

GOES LRIT runs at 1691.0 MHz , EMWIN is at 1692.7 MHz and is broadcasted from GOES-13 and GOES-15. GOES-14 is currently in a backup position to take over in either fails.

FFT/Waterfall of LRIT + EMWIN – http://i.imgur.com/rgSIORv.jpg
http://www.n2yo.com/?s=36411|29155|35491

For the hardware side, it is recommended to use roughly a 1.2m or larger dish, depending upon how far north you are, you may need a 1.8m dish (larger the better). Repurposed FTA or C-band dishes are easy to come by and work well.

I made a 5 turn helical feed with some 12ga copper wire and a piece of copper plate, and used this calculator to design it – https://jcoppens.com/ant/helix/calc.en.php

Picture of my dish/feed setup: http://i.imgur.com/Q1ZBFrs.jpg

I have a short run of coax into the LNA/Filter box. The first LNA is a TriQuint TQP3M9037 which has a very low noise figure (0.3 dB NF and 22 dB gain at 1.7 GHz).

That is ran into a Lorch 1675 MHz filter (150 MHz pass band), then a LNA4ALL and another Lorch before going over a 30ft run of RG-6 to the SDR.

Picture of the LNA/Filter box – http://i.imgur.com/yt7SvFL.jpg

I am using @usa_satcom (twitter.com/usa_satcom, usa-satcom.com)’s LRIT Decoder and that feeds into XRIT2PIC to produce the images and other data streams. By default the decoder only works with the Airspy, but with a custom GNU Radio UDP block, it can be fed with other SDRs like the BladeRF/USRP/SDR Play. A regular R820T(2) RTL probably won’t work because of the higher frequency (rtls tend to not work above 1.5 GHz) and 8 bit ADC. I’m going to try and use the Outernet e4k to see if I can pickup the EMWIN signal in the near future.

EMWIN is broadcasted on 1692.7 MHz, along with being encoded in the LRIT stream at 1691 MHz. The 1692.7 MHz signal is stronger and narrower, so it is easier to pickup. For decoding EMWIN I used @usa_satcom’s EMWIN decoder that piped data into WxEmwin/MessageClient/Weather Message Server from http://weathermessage.com.

LRIT will contain the full disk images from GOES-15, and relayed images from GOES-13 and Himawari-8. It will also included zoomed in pictures of the USA, and northern/southern hemispheres. The images will be visible light, water vapor and infrared. The full disk images are transmitted every 3 hours, with the other images more often. EMWIN will contain other weather data, text, charts, and reports.

Full disk GOES-15 – http://i.imgur.com/tWlmNMW.jpg

Charts / images from EMWIN – http://imgur.com/a/tsn1K

Text data – http://pastebin.com/raw/ULJmSSTP

Zoomed in west coast USA LRIT – http://i.imgur.com/rzfB0SV.jpg

Northern Hemisphere LRIT – http://i.imgur.com/5tKtPmn.jpg

Himawari-8 LRIT – http://i.imgur.com/sVzikys.jpg

Himawari-8 LRIT – http://i.imgur.com/LBvpTD1.jpg

It seems as though it may be possible to receive LRIT and EMWIN signals with an RTL-SDR since the signals are at 1690 MHz, which should be covered by cooled R820T2 and E4000 dongles. The only hardware requirements would be a 1m+ dish, 1690 MHz L-band feed, and an LNA + filter.

In 2017 these satellites are due to be replaced by new ones that will use a HRIT signal, which will be about 1 MHz. New software to decode this signal will be required then, but we assume the same hardware could still be used as the frequency is not due to change significantly.

Please note that the decoding software is only available by directly contacting usa-satcom, and devnulling writes that you must have the proper equipment and be able to show that you can receive the signal first before attempting to contact him.

GOES Full Disk Image
GOES Full Disk Image
One of several received EMWIN images
One of several received EMWIN images

A Preliminary Review of the HF Mode on Our V3 Dongles

Over on YouTube user icholakov shows a video where he compares our new RTL-SDR V3 dongles with direct sampling against an SDRplay and Icom 7100. The video shows reception at various HF frequencies on AM shortwave, time signals and SSB signals during day time reception. The performance seems to be fairly decent, but of course not as good as the more expensive SDRplay or Icom receivers.

This was originally posted on swling.com.

https://www.youtube.com/watch?v=BKAdtJA9s3w

A New LabVIEW interface for RTL-SDR Dongles

Today LabVIEW and RTL-SDR user Albert Lederer wrote in to let us know that he’s created a new LabVIEW interface for the RTL-SDR. LabVIEW is a visual programming language which is used commonly by engineers and scientists to quickly build applications for things like product testing, system monitoring, instrument control etc.

Currently there is already a LabVIEW interface for the RTL-SDR available called sdrLab. However sdrLab uses rtl_tcp for communication which can cause poor responsiveness and issues with corporate firewalls. Albert’s solution is instead a wrapper for rtlsdr.dll which allows LabVIEW to gain direct access to the RTL-SDR.

On his post Albert has created a write up that explains how his driver works, and how it can be used with LabVIEW. Keep an eye on Alberts future posts, as he writes that he intends to post a part two, where he will show how to attach an RTL-SDR to an NI myRIO.

An FFT in LabVIEW
An FFT in LabVIEW

Review: Outernet LNA and Patch Antenna

Recently we posted news that Outernet had released their 1.5 GHz LNA, Patch Antenna and E4000 Elonics RTL-SDR + E4000/LNA Bundle. When used together, the products can be used to receive the Outernet L-band satellite signal, as well as other decodable L-band satellite signals like AERO and Inmarsat STD-C EGC. Outernet is a new satellite service that aims to be a free “library in the sky”. They continuously broadcast services such as news, weather, videos and other files from satellites.

EDIT: For international buyers the Outernet store has now started selling these products at http://store.outernet.is.

A few days ago we received the LNA and patch antenna for review. The patch antenna is similar to the one we received a while ago when writing our STD-C EGC tutorial, although this one is now slightly larger. It is roughly 12 x 12 cm in size, 100g heavy and comes with about 13 cm of high quality RG316 coax cable with a right angled SMA male connector on the end. The coax cable is clamped on the back for effective strain relief.

The Outernet patch antenna and LNA
The Outernet patch antenna and LNA

The LNA is manufactured by NooElec for Outernet. It amplifies with 34 dB gain from 1525 – 1559 MHz, with its center frequency at 1542 MHz. It must be powered via a 3 – 5.5V bias tee and draws 25 mA. The package consists of a 5 x 2.5 cm PCB board with one female and one male SMA connector. The components are protected by a shielding can. Inside the shielding can we see a MAX12000 LNA chip along with a TA1405A SAW filter. The MAX12000 (datasheet here) is an LNA designed for GPS applications and has a NF of 1 dB. It has a design where there are two amplifiers embedded within the chip, and it allows you to connect a SAW filter in between them. The TA1405A SAW filter appears to be produced by Golledge (datasheet here), and it has about a 3 dB insertion loss.

The Outernet L-Band LNA
The Outernet L-Band LNA
Inside the Outernet LNA
Inside the Outernet LNA

We tested the patch and LNA together with one of our V3 RTL-SDR Blog dongles, with the bias tee turned on. The LNA was connected directly to the dongle, with no coax in between. The patch antenna was angled to point towards the Inmarsat satellite. A 5 meter USB extension cord was then used to interface with a PC. The images below demonstrate the performance we were able to get.

http://OuternetSignal

Outernet Signal

http://OuternetSignalwith4xDecimation

Outernet Signal with 4x Decimation

http://AERO

AERO

http://STD-CEGC

STD-C EGC

The Outernet team writes that a SNR level of only 2 dB is needed for decoding to work on their signal. With the patch and LNA we were able to get at least 12 dB so this is more than good enough. Other signals such as AERO and STD-C EGC also came in very strongly. Even when not angled at the satellite and placed flat on a table it was able to receive the signal with about 5 dB’s of SNR.

In conclusion the patch and LNA worked very well at receiving the Outernet signal as well as AERO and STD-C EGC. We think these products are great value for money if you are interested in these L-Band signals, and they make it very easy to receive. The only minor problem with the patch antenna is that there is no stand for it, which makes it difficult to mount in a way that faces the satellite. However this issue can easily be fixed with some sellotape and your own mount.

In the future once the Outernet Rpi3 OS and decoder image is released we hope to show a demonstration and tutorial on receiving Outernet data.