Preparing MP3s for an Evoke 3 Radio

I use an Evoke 3 radio made by Pure to listen to music. It has a very good sound — at least to my cloth ears. One of its features is that it plays MP3s from an SD card. But its firmware is quite old-fashioned perhaps because of technical limitations. It displays the song information but can only understand ID3v1 tags. The world has moved on and ID3v2 tags are now the default for most devices. Also the Evoke displays all files even those which are hidden on computers by having a dot as the first character. This makes the display of the folders and songs messy.

I used to deal with the tagging by using a very good application called kID3 to copy the ID3v2 tags to ID3v1 tags in its GUI. I have recently been reading “The Art of Unix Programming” by Eric Steven Raymond and it prompted me to write a script to do the tagging. I’ve since seen that kID3 can be driven from a CLI so that may be a better way to do the tag copying. 

Kid3 screenshot

I looked for command-line utilities to copy tags and couldn’t find any. But the good folks in the Perl community provide a library called MP3::Tag which allows easy manipulation of MP3 tags — as long as you can write in the Perl language. The library is available on CPAN but I used the MacPorts version. Many moons ago I could write Perl in my sleep so I decided to dust off the necessary neurones and write a Perl script. 

The Perl script ‘’ is not new and exciting but may help as an example for whatever you want to do. The script looks at all the MP3 files in a folder and copies the ID3v2 tags to ID3v1 if they don’t already exist. It will also copy the ID3v1 tags to ID3v2 if they don’t already exist. 

For my purposes I needed some other scripts. I had already written a shell script ‘tidy-mp3s’ to tidy MP3 folders of extraneous files that MacOS leaves lying about for its own purposes but that show on the Evoke 3 cluttering up the display.

I also needed a script to put it all together. ‘mp3s-to-evoke.ksh’ is a script which tags the MP3s in the way that suits the Evoke 3 and then copies them to the Evoke 3.So when I decide to change the songs on the Evoke 3 (it only handles a 2GB disc) I can just call the script in each MP3 folder on my computer and it will get copied to the Evoke 3.


Screen Shot of Evoke script runThe scripts are in this compressed file:

I use Korn shell (ksh) for scripts because that’s what I grew up with. I think the scripts should run under Bash if that’s what you prefer.

So now my Evoke 3 screen is nice and clean.

Evoke 3 Running MP3s

Cebik Moxons in the Attic

I now have both 2m and 70cm Cebik Moxons in the attic separated using a HA8LFK diplexer. After trying out the 70cm aerial it is clear that it needs a preamp to pick up any signals. Partly this is due to the poor coax I’m using and I should replace it with something better. So I’ve added an M-100 preamp powered from a shack PSU through a pair of bias-tees.

I tried bypass the M-100 with a relay but I haven’t been able to source a relay that works well at UHF. Usually the non-connected path is only 20 or 30 dB down on the connected path. This is not safe enough to protect the preamp, so that’s another reason for giving up transmitting for now. I’m pretty sure the aerials will not be good enough for decent transmissions and I would end up being the recipient of pleas from an OM: “I got the Mike, Zero and Yankee, your callsign again again please…”.

The setup looks like this scribble from my lab book:

Scribble form lab book

Unfortunately the M-100 draws 55mA which is 5mA too high for the built-in bias-tee in the SDRplay RSP2. The RSP2 is my receiver of choice at the moment. More on that later.

Cebik Moxons, SDRplay and satellites

There was a pass of the AO-91 satellite over my location today and I listened to the ham radio operators operating through it.

I used my home-built Cebik Moxon aerials which are located in my attic and the nice SDRplay RSP2.

Cebik Moxon in attic

Here’s a screenshot of SDRuno displaying the AO-91 signals for those of you who don’t think the Doppler effect is real.

Doppler on Waterfall

You can easily see the received signal changing frequency as the satellite hurtles past.

This is what it sounds like. 


It was recorded using Audio Hijack Pro from a Microsoft Remote Desktop session of SDRuno on a Dell XP workstation. Apologies for the over-driven audio — I was concentrating on receiving rather than recording.

SDRplay Macs and Linux

The Good News

I bought an SDRplay RSP2 recently and have been enjoying using it a lot. The RSP2 has three antenna connections and covers from 1kHz to 2GHz. It is amazingly good value. SDRplay provide a nice receiver application called SDRuno. The SDRplay website has links to reviews of the RSPs and they must be pleased with them.


The Bad News

My shack is full of computers accumulated over the years. However, as far as Microsoft Windows machines are concerned I only have an ageing Dell Precision 380 running Windows XP and a VirtualBox VM on a Mac Mini running Windows 10. My W10 VM isn’t fast enough for SDRuno and the audio stutters. The XP machine is usable as long as the sample rate is kept low and you decimate a lot.

On Macs and Linux computers SDRplay only provide an API/HW Driver, although they do provide a full image to boot a Raspberry Pi from. The software for Mac and Linux is CubicSDR which just about does the job but does not have all the features of SDRuno. I prefer GQRX  and have managed to get it working on macOS but the Hi-Z antenna connexion only works intermittently. It’s all quite unsatisfactory. It’s frustrating to have such good hardware spoilt by the lack of easy-to-install software. You get sucked into handling a morass of libraries with differing versions and it’s time-consuming if not impossible to find out which versions you need to use.

The Raspberry Pi image works well as long as you connect an HDMI display. I prefer to run my Raspberry Pi through Microsoft Remote Desktop so I don’t have multiple monitors, keyboards and mice on my desk. But with Microsoft Remote Desktop CubicSDR does not display well at all.

I only hope that SDRplay comes out with SDRuno on other platforms other than Windows. 

In Other News…

So I’m currently using the Dell XP computer with SDRuno run through Microsoft Remote Desktop as the best solution for me, even though it isn’t supported. Don’t worry, my insecure Dell XP is only connected to my LAN and is not connected to the Internet.

The blue arrow points to the low sample rate and high decimation needed on the Dell XP.

Screen Shot 2019 05 08 at 15 17 58

But it works well enough, it just doesn’t use the capabilities of the RSP2.

Screen Shot 2019 05 08 at 15 18 16