Brilliant Article on RTL-SDR Dongle Uses

sdr-Mario2Frequent contributor Mario Filippi N2HUN has written a brilliant piece for the latest edition of The Spectrum Monitor entitled RTL-SDR: Your Eye To The Wireless World, February 2016. Here is a brief synopsis:

RTL-SDR Dongle: Your Eye to the Wireless World

By Mario Filippi N2HUN

The RTL-SDR dongle has garnered much popularity over the last several years as an inexpensive and effective broadband receiver for the radio enthusiast. Now Mario shows us how the RTL-SDR can be pressed into serving in other ways: as a rudimentary piece of test equipment to explore those countless wireless devices that power our world and make life convenient. You can use it when restoring vintage radios, doing frequency analysis, antenna analysis and a host of troubleshooting activities you may never have thought of.

I highly recommend buying at least the current issue ($3.00 / PDF Download – what a steal!) or better yet, subscribing for a whole year. Every issue gives far more value than the cost ($2.00/issue at the current subscription rate).

Mario’s article explores things I never would have thought of, and he explains how he uses these inexpensive dongles in place of much more expensive equipment. It is truly amazing what these little wonders can do, and Mario just keeps pushing back the envelope of what is possible.

Thanks Mario for a truly inspiring article – yet again you have given us even more rabbit trails to explore!

Robert Gulley, AK3Q, is the author of this post and a regular contributor to the SWLing Post. Robert also blogs at All Things Radio.

Chris has developed an easy way to run the RTL-SDR dongle on a Mac


Many thanks to Chris Smolinski who writes:

I wanted to run SdrDx, and other SDR apps on my Mac with an RTL SDR Dongle. So I wrote this server app, that makes it appear like a networked SDR.


No need to install any RTL libraries, or compile any code.


Just run the app on your Mac, configure it and your SDR app, and you’re all set.


The app is free, and should work with Mac OS X 10.6 through 10.11.

Chris has kindly allowed me to share his full post here on the SWLing Post below–you can read the original at

Running an RTL SDR USB Dongle On Your Mac The Easy Way With Cocoa RTL Server

I’ve had a few of the RTL radio tuner dongles for a while. These are USB devices that were originally made for use as TV tuners overseas, but it turns out that you can access the I/Q data stream, and turn them into an SDR (Software Defined Radio). They can be tuned roughly over a range of 25 to 1700 MHz, and sometimes even higher, depending on the tuner IC chip inside the particular dongle.RTL-SDR


I previously posted about how to get the RTL dongle working on the Mac here: An SDR for $17 – The R820T USB RTL-SDR DVB-T Dongle and here: An SDR for $17 – The R820T USB RTL-SDR DVB-T Dongle – Part 2. These posts were from 2013, and I did the installation on a Mac running OS X 10.6, using some pre-built libraries.

Fast forward to the present day. I got a new Mac running OS X 10.11 El Capitan, and I wanted to be able to use the RTL dongles with my favorite SDR software on the Mac,SdrDx. Enter Cocoa RTL Server.

Cocoa RTL Server is a stand alone app that interfaces with an RTL dongle. It does not require you to build or install any drivers or libraries. It just works. It’s based off of an open source app called SoftShell, that I heavily extended. Cocoa RTL Server also acts like a networked SDR, following the RF Space protocol. That means it works with SdrDx, as well as any other SDR app on the Mac that supports RF Space SDRs like the netSDR. You can download a copy of the app from the Cocoa RTL Server page. Source code is included, however I am not offering any support for the project or final app.

Here’s a screenshot of the app running:


Getting up and running is easy:

1. Plug in your RTL device
2. Run CocoaRTLServer 2.0
3. Select the device from the popup menu (usually it is already selected)
4. Change the rtl_tcp or tx_tcp port values if needed
5. Click Open
6. Configure your SDR app (set the correct TCP port) and run it

I’ve run it under Mac OS X 10.6, 10.10 and 10.11, It should run under 10.7-10.9 as well.

Using SdrDx, I can tune a large portion of the FM broadcast band, click to view full size:



In this case I am tuned to 97.9 MHz. To the left of the signal meter, you can see it has decoded the station ID from the RDS data. Yes, SdrDx decodes RDS.

If you look at the lower right corner, you see the scope display of the demodulated FM audio. There are markers for the portions of interest:
You can see the main audio above the green marker to the left.
The stereo pilot at 19 kHz (red marker).
The stereo subcarrier (aquamarine)
The RDS data (orange)
The 67 kHz SCA subcarrier (purple)
The 92 kHz SCA subcarrier (yellow)

Cocoa RTL Server also includes a server that emulates rtl_tcp, so it works withCocoa1090 which decodes aircraft transponders that transmit on 1090 MHz. It should also work with any other app that gets data from rtl_tcp. Here’s a screenshot of Cocoa1090 running:


Thanks so much for developing this app, Chris!

I think I might go ahead and pull the trigger on an RTL-SDR as it would be great to run one on my Mac. I think your app will make the process much easier.

Readers: make sure you check out Chris’ blog



SDRplay shipping the RSP in quantities of 1,000 a month

SDPlay-RSPThis article from Electronics Weekly just popped up in my news feed:

SDRplay of Wakefield, the 18-month-old software defined radio specialist, is now shipping its $149 software defined radio (SDR) receiver in quantities of 1,000 a month

Inspired by the SDR capabilities that even a simple 8-bit TV dongle can perform, SDRplay had the idea of partnering with Mirics to take their 12-bit wideband broadcast chipset and to re-purpose it for the hobbyist market.

At the moment, the hobbyist market for SDR radios tends to be dominated by radio amateurs and ‘short-wave listeners’ and SDRplay’s initial product, the ‘Radio Spectrum Processor’ (RSP) has been well received – winning Ham Radio Science’s RSP ‘Best Bang for the Buck’ rating.

Continue reading at Electronics Weely’s website…

I’m quite proud of the folks at SDRplay as their RSP is truly one of the best receiver values on the market right now.

After (apprehensively) agreeing to review the SDRplay RSP last year, I was simply blown away by this little $149 receiver’s performance. Click here to read the review. Later, I couldn’t bring myself to return the RSP on loan for the review–so I purchased it instead.

I’m glad I bit the bullet!

In fact, last year, at the SWLing Post DXpedition, my buddy, Mark Fahey–who traveled all the way from Australia–forgot to bring the appropriate power adapter for his WinRadio Excalibur, so I let him use mine. I had planned to run the WinRadio Excalibur and Elad FDM-S2 simultaneously on my PC so that I could record spectrum in two different parts of the band at the same time.

Fortunately, I brought the SDRplay RSP, so it took the Excalibur’s place and ran alongside the FDM-S2. It worked amazingly well!

(I should note here that I also believe the FDM-S2 is a great value–at $519 US, it holds its own against receivers that cost upwards of $1,000.)

Shortly after I published my RSP review, I invited SDRplay to become a sponsor of the SWLing Post. I’m happy they accepted. Sponsorship on the SWLing Post is only open to retailers and manufacturers who produce quality goods; those who are well-known in the industry and, often, ones with which I have direct experience. I think SDRplay is a great fit.

So, Kudos to Jon Hudson and his team at SDRplay! I’m very happy to hear how popular the RSP has become.

If you’re an RSP owner, or plan to be soon, make sure you check out the official SDRplay forum and the SDRplay Facebook group: both excellent resources backed by active SDR enthusiasts!

New improved API for the SDRplay RSP

The SDRplay RSP software defined radio

The SDRplay RSP software defined radio

Many thanks to Jon Hudson with SDRplay, who shares the following announcement:

We are pleased to announce release 1.8.0 of the API for the RSP. This is a major upgrade to the API with new features and an improved gain map which should result in improved performance over a key portion of the gain control range. Currently this API is available for Windows only, but versions for Linux and Mac OS and Android will follow shortly.

The API now incorporates automatic post tuner DC offset correction and I/Q compensation. This will almost completely eliminate the DC centre spike that was previously present in zero IF mode and also correct for amplitude and phase errors in the I/Q signal paths that can lead to in-band images when strong signals are present.

There is a new gain map for the RSP which should help improve the receiver noise floor for gain reduction settings in the range of 59-78 dB. To achieve this, the IF gain control range has been increased from 59 to 78 dB. In addition, the user can now turn the LNA on or off at any point within the IF gain control range. This means that the LNA can remain on for gain reduction settings of up to 78 dB, whereas previously the maximum gain reduction that could be attained whilst the LNA was on was only 59 dB. Being able to leave the LNA on will result in improvements in the receiver noise performance for gain reductions in the range of 59 to 78 dB. The upper 19 dB of the IF gain control range have now been disabled. In practice this part of the gain control range was useless as trying to operate within this region always lead to receiver overload even when signals were very weak.

To fully exploit the features of this new API release, we have also issued release 3.5 of the ExtIO plugin. This plugin will work with HDSDR, SDR sharp (releases 1361 or earlier) and Studio 1. Automatic I/Q compensation and DC offset correction will work with later versions of SDR sharp, but we will need to update the native plugin for users of these later versions to be access the new gain map.

Similarly, users of SDR Console will gain the benefit of automatic DC offset compensation and I/Q correction, but will not yet be able to access the new gain map. We hope that a version of SDR console that unlocks this feature will become available in the near future.

Until a new release of SDR-Console is available, you can copy the API into the SDR-Console installation directory…

from C:\Program Files\MiricsSDR\API\x64\mir_sdr_api.dll to C:\Program Files\\mir_sdr_api.dll

The API installer has also contains an extra certificate to be more user friendly for Windows XP, Vista and Windows 7 users.

The new API and ExtIO plugin can be downloaded from our website at:

Many thanks for sharing this, John!  I’ll update my RSP today.

Click here to read the SWLing Post review of the SDRplay RSP.

How to use the SDRPlay RSP as a panadapter


In this post, I will show you how to use an SDR as a panadapter for a commercial communications receiver. I’m using an Icom R72 and a SDRPlay RSP, but you can do it with nearly all receivers and SDRs.

The Icom R72 is a double conversion HF (0-30 MHz) communications receiver.

A panadapter lets you see the spectrum of your receiver (it gives you a broader, higher-level picture of what’s around your tuned frequency). After using it, you’ll wonder how you’ve been using your receiver without a spectrum display! :)

Almost all the radios we use are of superhetrodyne type. To connect a SDR to the radio, you should first find its 1st IF mixer output (if it has more than one Intermediate Frequency stage).

To find it, the best way is to consult the service manual. The first IF of Icom R72 is 70.4500 MHz, so we can use RTL-SDR dongles too.

Here’s a part of R72’s schematics, extracted from its service manual:


Look at the R82 resistor; it’s located at the output of first IF stage, so I soldered a connector to its pins (its other pin is connected to the ground)

Between the R82 resistor and the output, we’ve added a series 470-ohm resistor (to prevent loading the IF stage)


Click to enlarge.

The other side of this connector is connected to the antenna input of my SDRPlay RSP.

Now I can view my spectrum on a PC.

Here’s a screenshot of CubicSDR on Mac OS X (you can use other apps like HDSDR, SDR Console, etc.):


Although this post was about the SDRPlay RSP and Icom R72, this procedure can be done for almost any combination of receivers and SDRs provided that your SDR covers the frequency of first IF stage.

Also, don’t forget that you should tune the SDR to the frequency of IF–in this case: 70.4500 MHz.

Mehdi Asgari, the author of this post, is a regular contributor to the SWLing Post. Mehdi lives in Tehran and is an active member of the EP2C amateur radio club.

Now Online: A New WebSDR in Iran


SWLing Post contributor, Mehdi, has informed me that his ham radio club (EP2C) has just put a WebSDR online in Iran–perhaps the first in this part of the world. Mehdi notes some of the details about the receiver:

[The WebSDR is] installed and operated by our amateur club: EP2C (

[Perhaps] the first WebSDR in the Middle East (the nearest one I know of is located at Armenia). We have a dipole antenna and an AVALA SDR receiver (going to be replaced by a SoftRock).

For the moment, it just covers 20 meter band, but we may increase the coverage to 30 and 40 meters too.

The server and antenna are all in EP2C club’s office (Karaj/Iran). Iran’s timezone is GMT+03:30.

Because of our bandwidth limitations, the total number of simultaneous users is limited to 10 (will try to increase it in the future).

Our WebSDR address:

Thank you for the announcement, Mehdi! I’ve been listening to the EP2C WebSDR this morning–it’s been working flawlessly.

Please keep up informed as you improve and upgrade the EP2C WebSDR!

Click here to use to the EP2C WebSDR online.

HDTV via an SDRplay RSP


Check this out: a tutorial on decoding ATSC HDTV via the SDRPlay RSP software defined receiver.


One of the main reasons I got the SDRPlay RSP was its wide bandwidth. It can show up to 8 MHz of spectrum at once. I figured it should be able to watch TV. Turns out it can, but it’s only designed to receive DVB-T.

Unfortunately, they only use that in Europe and a few other places. In North America we use ATSC.

In this article I will show how to use it to watch ATSC.

Click here to read the full tutorial…

This is one of the things I love about SDRs: in many ways, their applications are only limited by your imagination.

Click here to read our review of the SDRplay RSP.