Many thanks to SWLing Post contributor, Tudor Vedeanu, who has kindly shared details about his portable Raspberry Pi system which now can run the AirSpy HF+ SDR.
Tudor writes:
I bought the RPi to use it as a Spyserver for my Airspy HF+ SDR.
My main radio listening location is a small house located on a hill outside the city and there is no power grid there (it’s a radio heaven!), so everything has to run on batteries and consume as little power as possible.
My first tests showed that the Raspberry Pi works very well as a Spyserver: the CPU usage stays below 40% and the power consumption is low enough to allow it to run for several hours on a regular USB power bank. If I add a 4G internet connection there I could leave the Spyserver running and connect to it remotely from home.
Then I wondered if the Raspberry Pi would be powerful enough to run a SDR client app. All I needed was a portable screen so I bought the official 7” touchscreen for the RPi.
I installed Gqrx, which offers support for the Airspy HF+. I’m happy to say it works better than I expected, even though Gqrx wasn’t designed to work on such a small screen. The CPU usage is higher than in Spyserver mode (70-80%) but the performance is good. Using a 13000 mAh power bank I get about 3.5 hours of radio listening.
I made a video showing how it works:
Click here to view on YouTube.
This is fantastic, Tudor. Thanks for taking the time to put together a video for us. I’ve just ordered the latest Raspberry Pi 3 (Model B+). It has slightly more horsepower than the previous Pi3. Tudor, you’ve inspired me to grab the 7″ touch display as well and try my hand at running the AirSpy HF+ portable.
I’m not sure if the Raspberry Pi 3 will be able to record spectrum without hiccups, but it’s certainly worth a try.
As you tweak your system, please keep us in the loop!
Has anyone tried console cilent with RPi? similar to airspy-fmradion
I would think this might work better ?
Did you manage ro get your SDRplay radios working with GQRX? If so, how was the refresh rate on the 7″ touchscreen?
The RPi3 software from SDRplay appears to offer a very slow refresh rate and furthermore requires fan cooling of the RPi to prevent it from throttling back. For me that’s a severe limitation for portable use.
I made an upgrade to my Raspberry Pi radio setup. I added a nice case for the RPi and the touchscreen, and a new power source (12 V AGM battery + DC/DC converter) which should last for many hours. Sound is output through an Eton Satellit radio which has a very useful line in function. Here is a short video: https://youtu.be/EPUU_qigTRQ
How’d you get the gqrx app to fit fully on the 7″ screen. I can’t get the app to shrink enough and the control side is off to the right . I’ve got the same hw as yours.
Make sure you’re using the latest version of Gqrx. There was a bug in a recent version which made impossible to resize the window below a certain width.
Perfect thank-you sir, nice work.
I tried something similar a few years ago. I was attempting to make a portable system with a 5 inch LCD but realized that SDR Sharp or GQRX was designed for large screen. Could not easily see the writing on the GUI. I wish they would make a small screen version of these excellent GUIs’ with larger font and specifically for the popular screen sizes like 3.5″, 4.3″, 5″ and 7″.
Is this over the air radio listening or is this an IOT (internet of things) net connected device? I am confused.
It’s over the air radio. No internet.
Thomas and Tudor:
I’m wondering if all of this will fit ok in the 512 MB RAM of the new 3B+…the original 3B has 1 GB of RAM. @Tudor, can you comment on the memory utilization? (Perhaps the output of the free command?)
Thanks.
The raspberry pi 3B and 3B+ both have 1gb of ram, so anything that works on one will work on the other. However, the 3B+’s faster processor will require a bit more power, so it will last for less on a battery barring certain ways of dealing with processor load.
Thank you Thomas! There were three challenges that I faced when I first tried this setup:
1. Finding a battery which can supply 5.1V at a current of at least 1.5A. My USB power bank is rated 2A and theoretically it should work just fine. However, when I use it to power the the RPi, the system displays the low voltage warning continuously on the screen. That means the actual voltage supplied to the computer falls below 4.65V.
2. Finding a good micro USB cable to connect the battery to the RPi with minimum voltage drop. Most cables have thin wires inside which are only good for data and low DC current. At 1-2 A, the voltage drop across the cable can be significant. For powering the RPi, the screen and a SDR you need a cable rated for 2A.
3. Reducing or eliminating the noise coming from the RPi through the USB data bus. This depends on the cable used to connect the Airspy HF+ to the RPi. I tried several cables. The worst one was the USB cable which came with the Airspy. I got lots of noise on that one, on 5, 10 and 20 MHz. The best cable was one made by Logitech, supplied with their K811 keyboard. Nevertheless, I had to wrap the cable on a large #31 ferrite ring to get rid of noise completely.
On the Airspy mailing list there is an interesting topic discussing good quality USB cables:
https://airspy.groups.io/g/main/topic/14476245
Those are interesting challenges, Tudor–I had not even considered the fact that the microUSB cable must be able to handle that amperage, but it makes complete sense.
Here in my shack, I also have a 12VDC solar-powered system. Hypothetically, I could run the Raspberry Pi setup from it when grid power is down. I’ve never checked my 12VDC to 5VDC Powerpole plug to see if it creates any RFI.
I noticed that large ferrite ring–good to know that helps defeat the noise.
In terms of portable batteries, I have two LiFePo batteries with a lot of capacity, but then again, I’d need to find a quiet 12 to 5VDC converter with enough amperage.
Thanks again!
Thomas