Friday, May 19, 2023

Using an SDRPlay RSP1 Clone with CubicSDR on Linux Mint

Here I describe how I've been able to use a SDRPlay RSP1 clone with CubicSDR via SoapySDR on Linux Mint (a Debian/Ubuntu derivative) without using any proprietary software from SDRPlay. This is the device I'm using in this post:

I fully realise that these clone devices are controversial but they are now widely available at low cost and are a copy of an old device, soon to be no longer supported by SDRPlay. 

I respect the folks at SDRPlay and have bought from them in the past. There is some criticism of their closed source driver which runs as root and I think it's great that there is an open source alternative. 

Clicking on the Mirics device will hang CubicSDR.

Unfortunately, the software that ships currently on Linux Mint doesn't work out of the box but some good work by third parties have made it possible with a bit of messing about as I document below.

On a fresh install of Linux Mint 21.1 Cinnamon 64bit on an x86 laptop.

If you plug in the device and look at loaded kernel modules you’ll see two msi… modules like this:

lsmod |head

Module                  Size  Used by

msi001                 20480  1

msi2500                36864  0

To stop these loading, and capturing the device, we need to blacklist them.

  • sudo nano /etc/modprobe.d/blacklist.conf
    • blacklist msi001
    • blacklist msi2500
  • sudo reboot
  • sudo apt install cubicsdr
    • Note that this installs a bunch of soapysdr packages: 

soapyosmo-common0.8 soapysdr-module-all soapysdr0.8-module-airspy soapysdr0.8-module-all

  soapysdr0.8-module-audio soapysdr0.8-module-bladerf soapysdr0.8-module-hackrf

  soapysdr0.8-module-lms7 soapysdr0.8-module-mirisdr soapysdr0.8-module-osmosdr

  soapysdr0.8-module-redpitaya soapysdr0.8-module-remote soapysdr0.8-module-rfspace

  soapysdr0.8-module-rtlsdr soapysdr0.8-module-uhd

That soapysdr0.8-module-mirisdr module has issues and needs to be replaced. While it’s tempting to `sudo apt remove libmirisdr0` this will remove all the other soapy stuff which we need.

We need to build a new version of libmiri and the SoapyMiri driver:

  • sudo apt install libsoapysdr-dev soapysdr-tools
  • sudo apt install git cmake libusb-1.0-0-dev gcc g++
  • git clone
  • cd libmirisdr-5
  • mkdir build
  • cd build
  • cmake ..
  • make
  • sudo make install # puts the library in /usr/local/lib/
  • sudo rm /usr/lib/x86_64-linux-gnu/
  • sudo rm /usr/lib/x86_64-linux-gnu/
  • sudo rm /usr/lib/x86_64-linux-gnu/
  • sudo ln -s /usr/local/lib/ /usr/lib/x86_64-linux-gnu/
  • cd
  • git clone
  • cd SoapyMiri
  • mkdir build
  • cd build
  • cmake ..
  • make
  • sudo cp /usr/lib/x86_64-linux-gnu/SoapySDR/modules0.8/.
  • sudo rm /usr/lib/x86_64-linux-gnu/SoapySDR/modules0.8/

SoapySDRUtil --info will now show:

Available factories... airspy, audio, bladerf, hackrf, lime, osmosdr, redpitaya, remote, rfspace, rtlsdr, soapyMiri, uhd

CubicSDR will now run and show soapyMiri

Now you can configure the mirics device and there's even a "flavour" for SDRPlay that is said to make it work better.

I was also able to get the soapyMiri driver working with SDR++ remote.

I hope this helps someone. At least it will be a note for future me.

Monday, May 15, 2023

MFT-40 a double sideband TX, direct conversion RX kit from Spain

I build lots of little electronic projects, some work well, some work poorly, some just don't come to life. After a few failures I lose confidence and a good way to get my home made mojo back is to build a kit. A kit for a "My first transceiver" MFT-40 (20m also available) from Spain's QRPHamradiokits caught my eye recently.

The designer references Peter, VK3YE's "Beach-40" which I've also built but has improved on the design. Peter's simple circuit suffers from feedback during switching from transmit to receive and uses a diode ring mixer rather than an NE602.

"The MFT-40 incorporates a DC (direct conversion) receiver with a 3-stage front-end passband filter, followed by a balanced mixer, an audio preamplifier and filter using an operational amplifier, and an output amplifier for driving a loudspeaker. The local oscillator is based on a 7.2 MHz ceramic resonator element that allows coverage of a part of the 40m band.

The DSB (double sideband) transmitter uses a DSB generator with input from an economical electret condenser microphone and three stages of amplification which produce 3-4W to the antenna."

The kit is well presented with a top quality board that cleverly can be cut in half to make separate receiver and transmitter sub-boards if you wish.

The instructions are good (and you can see the schematic there) but the designer can't quite make up his mind about the best order to add components. Parts lists are presented both sorted by value and again but sorted by number (R1, R2, etc) which doesn't always group by where they are located in the circuit. Also there's the suggestion that new constructors might just build the receiver first - probably a good idea but maybe there could be a separate kit for a receiver only.

There's some minor errors with carrier suppression pot P4 in the text actually being P3 on the schematic and mic gain P3 actually being P2 on the schematic but it wasn't hard to figure this out. My kit had an incorrect component that was easily found in my junk box.

In use, the receiver works very well although, not-unexpectedly, tuning is very sensitive. The transmitter perhaps suffers from not enough mic gain - the supplied electret mic directly drives the input to the NE602 mixer. (I don't know where QRP Ham Radio Kits managed to source through hole NE602s - they are very hard to find these days).

Here it is in use:

I spotted the biscuit tin while shopping in Kyneton. The size is perfect for this project and others for sure. Drilling was easy. The biscuits are also very nice, if a bit sweet for my taste.

An enjoyable kit.

Sunday, April 30, 2023

SDR++ server mode for easy listening

SDR++ continues to impress as an excellent SDR client. One terrific feature is that it has a server mode built in. You run the server side on the command line with --server after it and then run SDR++ from another machine to connect to it. 

I'm running the server in my low noise shack and using the client in the house. They are connected via wifi at both ends but operation and reception is smooth.

To record this and capture the audio on macOS I use the free VB-Cable to connect the output of the receiver to the built in screen recorder. The problem with this is I can't hear the audio while I'm recording so it's hard to tune around. The solution was to run an audio recorder/editor (in my case Sound Studio) which has a feature to pass through input audio so I can monitor.

Monday, April 03, 2023

New digital mode: FreeData

A Reddit post drew my attention to a new digital mode that uses the OFDM modem code from FreeDV for having keyboard to keyboard chats. It's called FreeData, which I have to say isn't a great name for searching.

As you can see it has some advanced features such as a notification that the other party is typing. Messages are confirmed and the software will re-try until it gets through.

There is a wiki with documentation and an active Discord space to discuss the software. There is also a map which shows Barry, VK3BRT and me looking rather lonely here in Victoria, Australia at the moment.

The software is available for macOS, Linux and Windows. You can download the software, currently in alpha, from the Github project.

Friday, March 31, 2023

Free windows software - read the fine print!

A ham radio friend who runs windows and is using various digital chat modes recommended some software that takes dictation and enters it in to a text field. He said "it's free".

I took a quick look at LilySpeech and noticed the little asterisk next to FREE*. When I drilled in to see what that was about I was amazed.

"The free version of LilySpeech is made possible by doing market research in the background. While there are many examples of what this might entail, the most common example would be a business looking to measure their visibility in search engines such as Google, Bing or Yahoo.

As a practical example, a national insurance company may wish to know where they come up in Google when you search for ‘auto insurance’ within the city of Seattle, or Chicago, or Dallas, etc.

As a LilySpeech user with a unique location and profile, you can provide insight to these companies that nobody else can.

These activities use a dedicated browser meaning no history from these activities will appear in your history or browsing activity. These activities are completely invisible meaning you will never be interrupted or inconvenienced.

Examples of the types of marketing activity that may occur include but are not limited to:

Checking and verifying websites positions in search engines for different search terms

  • Ad placement verification
  • Competition price checking
  • Website uptime monitoring

At no point will any market research be performed in the background that relates to the following industries:

  • Adult entertainment
  • Gambling
  • Pharmaceutical products
  • Any other gray/illegal market

At no point will any of these activities be malicious in intent or violate local, state, or federal law."

Wow. I've got to credit their honesty but they are basically turning your Windows computer into a bot to be used by third parties. This is new to me but perhaps it is done by other "free" software as well?

Wednesday, March 29, 2023

Minimal transceiver with Hellschreiber interface

Some years ago Stephen, VK2BLQ, and I experimented with using low cost CW transceivers and the Hellschreiber mode. This mode works with simple transceivers as it is simply keyed on and off.

Having moved house several times since then I had to re-build the interface. I think this version is neater. FlDigi keys a hellschreiber transmitter by keying a tone on and off and to key the transmitter an interface needs to rectify this audio and activate a transistor. 

I've just had a contact with Richard, VK3LRJ:

He's using an IC-7300 at his end but my side is simpler:

The transceiver, lower left, is a micro mountaineer kit, from an original design by W7ZOI. It's a step up from the Pixie kits and the receiver works much better than on them. There's no keyer to get around so it's well suited to use with Hellschreiber. Here's the interface board:

At first I used silicon diodes but found the audio level was too low. Substituting germanium diodes works better but is even a bit too sensitive so I have to reduce the audio level a bit. Here is the circuit I ended up with:

The 8R:1K audio transformer was purchased at Jaycar.

Thursday, March 16, 2023

Bush 40 transceiver

Inspired by the VK3YE Beach 40, I have constructed the "Bush 40" which is a version tailored to The Australian outback. (Just kidding).

It is a direct conversion receiver and double sideband transmitter. I've replaced the VXO with a very simple, three component, VFO.

I'm joking a bit here too, it has an Arduino Nano, an Si5351 board, and a rotary encoder. On boot up it starts at 7.1MHz and you can tune up and down from there.

The mic amp, mixer, rf power stages and low pass filter are as per the Beach 40.

The receive audio stages are from the Soldersmoke High School DC receiver

Overall, this is a minimal design and the door is open to many improvements.

As you can see, it's a gadget of great beauty. At this stage the receiver is working but is quite deaf - I'll keep working on this.

Notes for future builds:

  • Use a larger baseboard so there's plenty of space for access to the boards
  • Always put a reverse diode on the relay coil - I killed an Arduino Nano presumably from inductive spikes on the power line.
  • Don't try to drive a mixer directly from an Si5351. (I was puzzled about why the balanced mixer was so far off balance when I switched from the VXO to Si5351, the reason is that the output RF is 0-3.3V not AC) A 0.1uF capacitor fixed this.
  • Building modules on their own boards for easy debugging is the way to go. Also, this means the successful stages can be re-used easily.
My thanks to many people including Bill, Paul, & Stephen for suggestions.

Friday, March 10, 2023

Minimal Si5351 VFO for Bush 40 DSB Transceiver

Recently I've been going a bit "old school" and built the Soldersmoke Direct Conversion receiver with its PTO VFO and another VK3YE Beach 40 DSB transceiver with a ceramic resonator based VFO (it can be slightly pulled).

I was thinking about a minimum VFO configuration using just an Arduino Nano, a rotary encoder and an Si5351. If you count a Nano as a single component you could argue that this is a three component VFO.

My implementation boots up on 7.1Mhz and can be tuned up and down with the rotary encoder. There's no display (although that can be easily added) but a frequency counter could be added. 

The wiring is like this circuit on the Arduino project hub but I haven't added the display.

Power enters through the VIN pin on the Nano which can take voltages up to 16V (I'm running 12V) and regulates down to 5V and 3.3V which I feed to the Si5351.

I prototyped this on a breadboard first:

Next I built the same circuit on matrix board with simple point to point wiring. Here it is driving the mixer on the Beach 40.

It's a very compact and usable VFO. I have a few ideas about some extra features such as stopping at band edges and maybe lighting an LED when you hit the band edge.

Observant readers will spot my LEDs on the boards and power wiring - I've been bitten by being buzzed about why things weren't working when the fault of in the power line. Adding a few LED power indicators makes it clear.

Here's my simple source code for this VFO (blogger messes code up so use the link to the Gist):

Simple VFO for a direct conversion receiver.

Si5351 controlled by a rotary encoder.
Based on code from Paul, VK3HN

const unsigned long int FREQ_DEFAULT = 7100000ULL;

#define ENCODER_A 3 // DT
#define ENCODER_B 2 // CLK

#include <RotaryEncoder.h> // by Maattias Hertel
#include <si5351.h> // Etherkit Si3531 library Jason Mildrum, V2.1.4
#include <Wire.h> // built in
Si5351 si5351; // I2C address defaults to x60 in the NT7S lib
RotaryEncoder gEncoder = RotaryEncoder(ENCODER_A, ENCODER_B, RotaryEncoder::LatchMode::FOUR3);
long gEncoderPosition = 0;

unsigned long int gFrequency = FREQ_DEFAULT;
unsigned long int gStep = 100;

void setup() {
gFrequency = FREQ_DEFAULT;
si5351.set_freq(FREQ_DEFAULT * SI5351_FREQ_MULT, SI5351_CLK0);
si5351.output_enable(SI5351_CLK0, 1);

void loop() {
// check for change in the rotary encoder
long newEncoderPosition = gEncoder.getPosition();
if(newEncoderPosition != gEncoderPosition) {
long encoderDifference = newEncoderPosition - gEncoderPosition;
gEncoderPosition = newEncoderPosition;

void setupRotaryEncoder() {
attachInterrupt(digitalPinToInterrupt(ENCODER_A), checkPosition, CHANGE);
attachInterrupt(digitalPinToInterrupt(ENCODER_B), checkPosition, CHANGE);

// This interrupt routine will be called on any change of one of the input signals
void checkPosition() {
gEncoder.tick(); // just call tick() to check the state.

void frequencyAdjust(int delta) {
Serial.print("Adjust: ");
gFrequency += (delta * gStep);

void setVfoFrequency(unsigned long int frequency) {
si5351.set_freq(frequency * SI5351_FREQ_MULT, SI5351_CLK0); //
Serial.print("set frequency: ");

void setupOscillator() {
bool i2c_found = si5351.init(SI5351_CRYSTAL_LOAD_8PF, 0, 0);
Serial.print("si5351: ");
Serial.println(i2c_found ? "Found" : "Missing");
si5351.set_correction(135000, SI5351_PLL_INPUT_XO); // Library update 26/4/2020: requires destination register address ... si5351.set_correction(19100, SI5351_PLL_INPUT_XO);
si5351.set_pll(SI5351_PLL_FIXED, SI5351_PLLA);
si5351.set_freq(500000000ULL, SI5351_CLK0);
si5351.drive_strength(SI5351_CLK0, SI5351_DRIVE_4MA);
si5351.output_enable(SI5351_CLK0, 1); // turn VFO on

Sunday, March 05, 2023

Soldersmoke Direct Conversion Receiver working

I didn't have a smooth run with this project, despite the best of help. Here's how it sounds now:

My tuning is very sensitive but at least it doesn't drift like it was with the original (not NP0) capacitors.

I ran into a few issues along the way that took me way too long to debug:

  • The audio chain was taking off at about 2MHz and upsetting the VFO via the power line.
  • I didn't use NP0 caps in the VFO and it was incredibly unstable at first.
  • The variable linear power supply I was using caused great audio hum - no idea why - another supply and the hum is gone.
My build is not very sensitive. I suspect I have the wrong diodes in the ring mixer.

My thanks to Stephen, VK2BLQ, for suggesting the addition of a 1k resistor to isolate the early stages of the audio chain from the output stage to stop the instability. And, of course, thanks to Bill for the design of this project!


Saturday, February 25, 2023

80m dipole stretched significantly

Very lucky here to have the space, and appropriately placed trees, to allow me to put up a full size dipole for 80m. By all reports it works very well. This week, prompted by VK3LRJ, I tested the antenna and found that resonance had moved down quite significantly.

The band edges (black bars) are 3.5Mhz and 3.8Mhz.

The weekly club net is on 3685 so that's quite a bit away from where the antenna is now. I pulled it down, cut off a bit and folded back the ends. I think I shortened it by about 500m.

Much better! The 7300's built-in tuner has no trouble but it's good to not suffer the losses in the tuner if possible. 

The wire I'm using is figure-8 speaker wire split so I guess it stretches quite a bit. So far it looks to be in good shape but I don't expect it to last forever.