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Red Pitaya’s SDR Transceiver

It is becoming fashionable. After the Apple computer there came the Raspberry and Banana Pi and now the Red Pitaya.

The pitaja (also known as pitahaja or dragon fruit) is the fruit of various types of cacti, in particular the genera Hylocereus and Selenicereus. These plants occur naturally in Mexico, Central America and South America. They are also cultivated in South-East Asia in countries such as Indonesia, Malaysia, Vietnam, Thailand and the south-east of China and Taiwan.

There are three types of pitaya that are grown commercially for their fruit:
• Hylocereus undatus with white flesh and a pink-red skin
• Hylocereus polyrhizus with red flesh and a pink-red skin
• Selenicereus megalanthus with white flesh and a yellow skin

The pitayas with the pink skin have relatively little flavor, this is because the fruit is generally harvested too early in the country of origin and the fruit does not continue to ripen, unlike bananas for example. In contrast, the yellow pitaya from Colombia always tastes sweet, the taste does somewhat resemble that of kiwifruit. The pitayas can be cut in half and the flesh removed with a spoon, it is also possible to peel it before eating. The seeds can be eaten too. Many actually appreciate the seeds when consuming the fruit.

Source: Wikipedia.

The Red Pitaya
The Pitaya that is the subject of this blog is, however, something completely different. Not edible, but measurable.

Red Pitaya is an open source project developed around a re-configurable measurement instrument the size of a credit card. It can replace many expensive laboratory measurement and control instruments.
The users can start using the applications available within the ‘Bazaar’ free of charge marketplace. This can be achieved with a single click. At the same time they can view and modify the published source code in order to develop new applications and share their results with the community.
The Red Pitaya unit is a network attached device based on Linux operating system. It includes Radio Frequency signal acquisition and generation technologies, FPGA, Digital Signal Processing and CPU processing. Red Pitaya enables everyone to start using technologies, which were previously available only to advanced research laboratories and industry.


Why Red Pitaya?
Now with that knowledge we’re are already a long way in the right direction. But why is the Red Pitaya now considered so ‘hot’ by various amateur radio enthusiasts in the Netherlands? I think a number of developments are responsible for that:

• There has been a lot of activity in the open-source world to make the Red Pitaya measurement platform also suitable for SDR (Software Defined Radio). With thanks to Pavel Demin.
• The Red Pitaya has been halved in price. According to the January 2015 brochure from Reichelt, at that time the board cost twice as much as what it costs now (end of 2015).
• Heated debates on 3630 kHz about the various SDR solutions (FlexRadio (old and new), ANAN, HackRF, ELAD, ZEUS etc.).
And there are probably even more reasons. However, my interest was triggered because Onno, PA0ONO was already operational with a Red Pitaya transceiver and then, well, as an SDR man I did not want to be left behind. As one of the first users of the FLEX-1500 in the Netherlands and the promoter since 2006 of the various SDR receivers, I was keen to take a closer look at the Red Pitaya. Because I know from experience that Reichelt are very quick to deliver, I therefore ordered the Red Pitaya from them, and it was delivered by UPS within 2 days. Including the enclosure.

Unpacking Red Pitaya
I was actually planning to spend the next few weeks quietly experimenting with my new toy and to try various things. But as usual, enthusiasm got the better of me and so full-speed ahead. Embracing simplicity, here is a summary of what you need to do.

NB: These are instructions of how to install a fully fledged transceiver straight away. There are also other other solutions available for receive-only, using the programs SDR# or HDSDR.
• Make sure that you have a USB power supply (5 Volts, 2 A) with micro USB connector
• Buy a micro SD cart with at least 4 GB capacity
• Go to this website:
• Download the Image and copy it to the SD card using Win32 Disk Image
• Follow the subsequent instructions on the quick-start website.

Once you have completed all this and have entered the MAC address you will, if all is well, see the page shown below in your browser:
(perhaps you still have to register and log in at the Red website)

You now click on ‘start’ and a connection is established with your Red Pitaya. You therefore do not have to enter the IP address, but you will see that IP address does appear in the URL field of your browser. It is useful to remember that because you can then ‘surf’ directly to the Red Pitaya without the intermediate step of the Red website with logging in etc.

With this you arrive at the home page, you could call it the main menu, of your Red Pitaya.

Installing SDR transceiver
The next step is to download the SDR Transceiver application and to install it. Click on “Get more applications” and search for:

Now click on “Install” to install the application on your Red Pitaya. Surf back to the home page of your Red Pitaya and now select the installed “SDR transceiver compatible with HPSDR” application, which will configure the Red Pitaya so that it will communicate with an HPSDR program on your computer. Don’t forget to click “Run”.

You will now see this screen in your browser. You will have to keep this screen open so that the application on the Red Pitaya continues to run!!

My hobby computer still runs MS (Windows 10) and I therefore downloaded PowerSDR mRX PS. You can find the link on the page of the Red Pitaya as is shown above. The installation is very easy and the only thing you need to do is enter the correct IP address of your Red Pitaya at “Setup > General > Hardware Config”. Subsequently click on POWER and you are operational.

Oh yes, it is very handy to connect an antenna to IN 1 and a dummy load to OUT 1!!

OpenHPSDR has a strong resemblance to the FlexRadio PowerSDR, which I used to use with the FLEX-1500, so immediately familiar and easy to use. The options are endless, including a complete second receiver. The version of OpenHPSDR that I use is 3.3.6 from 16 November 2015. (It is however a little untidy in that some menu screens have the FlexRadio logo!)
Transmitting is possible too, but you only have about 10dBm (10 mW) available. So a final power stage with sensitive input and good filtering is useful. Incidentally, the initial transmission tests went very well, with nice audio. You need to connect the microphone to the PC. So there are a few differences compared to the FLEX-1500, but otherwise really the same SDR concept.

Red Pitaya vs Raspberry Pi
Now that I have mentioned the SDR concept, I will briefly return to one of the arguments of why the Red Pitaya is so ‘hot’: The discussions on 80 meters and the comparison between the various SDR equipment / solutions. In my opinion this is a comparison between apples and oranges, to continue the fruit theme. For example, when you compare an Apple with a Raspberry Pi: they are both suitable for use as a computer, but there are nevertheless differences in specifications, price and capabilities.

Red Pitaya vs FLEX-600
The same is true between, for example, a FLEX-6000 series transceiver and a Red Pitaya. Both can serve as transceiver for the ham radio enthusiast, but there is an important difference when considering the ‘out of the box’ experience. The FLEX is ready to be used, but you have to bring the Red Pitaya to life yourself and then build the necessary additional hardware before you have a complete transceiver sitting on your shelf. And then I haven’t even mentioned the technical differences yet. The FLEX-6000 series uses developments where fast hardware is used to already start processing signals at the RF signal stage. A fantastic technical advancement which gives us radio amateurs the ability to perform professional signal processing in amateur transceivers now and in the future. The PC is then only used to control the operation and not for any signal processing, which is still the case for the Red Pitaya / OpenHPSDR combination.
Nevertheless I do find the Red Pitaya very interesting, all the more because it offers the opportunity for do-it-yourself and it is perhaps also more compatible with the hobby budget. For € 235 you will have a measuring platform that you can also use as an SDR transceiver. In particular this multi-purpose use appeals to me and there is no need to be afraid to experiment with the software. If you are going to use it exclusively as a transceiver then, as already mentioned, you will need a final power stage with low-pass filter and it would also be useful to build everything, including cooling, into an enclosure. You will then have quickly spent € 550, nearly the price of a FLEX-1500. .

On request; a video where I demonstrate OpenHPSDR. After starting the Red Pitaya by loading the URL in the browser I start OpenHPSDR and scan through the lower bands. I also demonstrate the use of the second receiver. Receiver 1 is connected to a ALA1530+ loop and receiver 2 to the G5RV.
Finally a few useful links to get started with the Red Pitaya SDR transceiver:


about SDR concepts:

and about the OpenHPSDR project:

Who is Johan van Dijk?

Johan van Dijk is a HAM operator since 1975 and licensed with callsign PA3ANG. Born in 1958 so 57 year old. Studied Electronics and worked for many years with Ericsson. Nowadays I’m a IT Business Consultant. You also can find him on Linkedin.

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