Monday, January 30, 2023

Headless Raspberry Pi to run WSJT-X: easier than ever

Normally I use an old Thinkpad as the shack computer. Works well, low RF noise, but takes up a lot of bench space. I've just done a fresh setup of a Raspberry Pi 4 and getting it to work headless is easier than ever. I installed the latest 64 bit Rasparian with the GUI enabled. To get it going headless is done via the raspberry pi config program.

Enable VNC

Choose a headless resolution.

There was a time when I had to use a little HDMI plug that pretended to be a monitor to get decent resolution. Here's how it looks from a remote machine:

Decoding is pretty slow. It can take more than 30 seconds to decode. This might not be a bad thing as WSPRnet gets very busy with all the uploads just after a 2 minute boundary. I have seen one strange thing, a "subprocess error":

Show details indicated that the decoder couldn't access a WAV file. This might be due to a decode taking so long that the files were being written again. Not sure.

The Pi produces a bit more noise via USB to the 7300 but that's compared to the old ThinkPad which is very good. Transmit works fine with no ill effects from RF. I have several clip-on ferrites on the USB cable.

I had a little trouble with unreliable networking over Wifi. Moving the router a bit (it's in another room and was hiding behind a desk) and also turning off Bluetooth on the Pi seemed to fix this.

Disconnecting from the VNC session does not terminate whatever is running on the Pi by the way.

Compact digital station

A headless Pi connected to a QDX makes the most compact digital station I can think of.

It certainly meets my objective of taking up as little bench space as possible. I'm seeing an excellent signal from VK3YE +13dB SNR from his 0.2W transmitted on 40m 154km away.

T95 Android TV box as a cheap raspberry pi alternative?

This is a story of failure, but I thought it worthwhile to share it. There are reports that some of the cheap (~$40) Android TV boxes advertised on sites like AliExpress, can be encouraged to boot Armbian linux and so can be used as a Linux server for very little money. A common one is called T95 so I ordered a 4GB ram version. Here's the board unboxed:

There is a push button switch cleverly mounted behind the 3.5mm "AV" socket so you can poke a toothpick through it to press it during power on to trigger an attempt to boot from the SD card.

The board I got is labelled: “H616-T95MAX-AXP313A-V3.0”

I have downloaded numerous promising linux images but each time I try it just sits silently during the attempted boot.

There are three pins between the SD card and one of the USB ports that are the serial console port. I soldered a header on to these and found that it sends debug messages during Android boot at 115200 8-N-1. Here's a snippet:

HELLO! SBOOT is starting

U-Boot 2018.05 (Jul 29 2022 - 19:51:27 +0800) Allwinner Technology

[01.301]CPU:   Allwinner Family

[01.304]Model: sun50iw9

I2C:   ready

[01.308]DRAM:  2 GiB

[01.311]Relocation Offset is: 75ec5000

[01.351]secure enable bit: 1

[01.354]pmu_axp152_probe pmic_bus_read fail

[01.358]PMU: AXP1530

[01.364]CPU=1008 MHz,PLL6=600 Mhz,AHB=200 Mhz, APB1=100Mhz  MBus=400Mhz


[01.401]__clk_enable: clk is null.

[01.407]drv_disp_init finish

[01.409]gic: sec monitor mode

[01.437]flash init start

[01.439]workmode = 0,storage type = 2

[01.443]MMC: 2

[01.444]get mem for descripter OK !

[01.453]get sdc2 sdc_boot0_sup_1v8 fail.

[01.457]io is 1.8V

Interesting that although I paid for, and the case is labelled, 4GB, the console says it's 2GB.

The box works quite well running Android. The Google Play store works (although you must log in with a Google Account). Installing UserLAnd gives you a pretty good linux command line running on top of Android. The supplied Android has been modified in various ways including a "root" switch.


There are reports of Android TV boxes coming from China with malware pre-installed. Once I had a command line and had switched the root switch on I was able to see that this box has the telltale files they mention.

"Your T95 is infected with malware pre-installed, ready to do whatever the C2 servers decide. Yes, malware from Amazon straight to your door! If they insist on selling these devices they really should add an "Includes Malware" category in the Android TV section.

A few months ago I purchased a T95 Android TV box; it came with Android 10 (with working Play store) and an Allwinner H616 processor. It's a small-ish black box with a blue swirly graphic on top and a digital clock on the front. There's got to be thousands (or more!) of these boxes already in use globally.

There are tons of them available for purchase on Amazon and AliExpress.

This device's ROM turned out to be very very sketchy -- Android 10 is signed with test keys, and named "Walleye" after the Google Pixel 2. I noticed there was not much crapware to be found, on the surface anyway. If test keys weren't enough of a bad omen, I found ADB wide open over Ethernet and WiFi - right out-of-the-box."

ADB is Android Debug Bridge, a command-line tool developed to facilitate communication between a computer and a connected emulator or Android device.

Scammy Play Store apps

I don't use Android very much but playing with this box led me to search for and install some apps from the Play store for things like BusyBox. My goodness! there are some truely evil apps that Google has let in to the Play store. One popular BusyBox insisted on playing a full screen video of a game at every use, another app demanded accessibility privileges which Android explained would give it full access to all keystrokes typed.


To be fair, the Armbian site makes it clear that boxes like this can't be supported. The H616 chip is pretty new and even if I got it working it's likely that vital things like Wifi might not work. Searching for bootable linux images is a bit of a mine field with several links being blocked by my browser's malware blocker.

Oh, and of course this story is an example of Betteridge's law of headlines.

Thursday, January 26, 2023

WSPR Watch - now with grey line display

An often requested feature in WSPR Watch is to display the grey line which is the transition from sun to night. I've had a few goes at this, first by simply drawing a circle on the map centred on the sun's position but now I've ported some code open sourced by John Boiles to swift and included in the app. (I have credited him in the app).

This feature is off by default so you'll need to go to settings to enable it.

App Store review times are better than ever

It used to take more than a week for the Apple App Store to review an app submission. This morning is the fastest I have experienced I think.

  • 08:34 Submitted app and waiting for review
  • 08:40 In review
  • 09:10 Submission accepted
  • 09:11 Approved for the App Store.
That's pretty good. I wish new version numbers didn't have to be reviewed before releasing to external TestFlight testers. One would think that a developer could be trusted after years of app submissions without incident.

Thanks as always to my testers and users who send suggestions and bug reports.

Wednesday, January 18, 2023

Growing tired of AirBNB

AirBNB was a great idea and for years we enjoyed staying at nice, but sometimes quirky, places around the world.

Our last experience, on a visit to Sydney, was not so great. Here are the house rules:

It was a very clean, modern, standalone unit. Everything about the experience lacked generosity. We were there for 5 nights but as you see from the rules above, virtually nothing was supplied. We had to shop for toilet paper, dish powder, laundry liquid, soap and rubbish bags.

There were just three knives, forks and spoons so we had to wash them regularly.

As there are two of us, we asked for a second key. The owner asked why and said no.

I took some ham radio gear but feared the worst if I was found to have run a wire out the window so didn't attempt that.

At least you know what you get at a hotel, even if the shower supplies are not legible. It seems we are not alone in this view.

Annoying trend: Unreadable shower items

I wear glasses, but take them off when I shower. We've been away for a few nights and stayed in hotels for a few of those nights. When I take off my glasses and try to figure out which of the bottles in the shower are soap, shampoo or conditioner they don't make it easy. This is what I see:

Why do shower product people think that their brand is more important than what the product actually is? Also, the graphics give no clue. Here's how they look with corrected vision:

The logical order for me would be soap, shampoo and then conditioner. Curse you Urban Skincare and all of the others that pull the same trick. 

Tuesday, January 17, 2023

40m antenna down

We've been away for a few days and I left the QDX doing WSPR on 40m. It ran for a few days, then stopped receiving any spots. It was still being heard for a day or so but then even that ceased.

The theory was that the Linux laptop had lost Wifi and when I returned I found that it was asking for Wifi authentication - which is puzzling as this is stored. I got it back on Wifi, and rebooted, but still no reception. I noticed that the pass through SO239 on the wall plate was a bit bent. Outside the carnage was clear.

A branch on the dead tree that holds up my various dipoles had fallen. Coax had somehow been ripped from the shack end. I wonder if perhaps a kangaroo had hopped through it and pulled the branch down in the process. Too hot today to go drone antenna flying but I'll get it back up probably tomorrow.

Hmm, now that I look it's clear that more damage was done than initially noticed. One leg of my magnificent 80m dipole was down. Up again now.

The coax to the 40m balun had been somehow ripped from the plate on the wall of the shack but interestingly the other end, normally high in the air connected to the balun, seems to have been attacked by something nibbling at it.

My guess is that a bird was attracted by the bright red heat shrink but there is also bites in the coax near by.

I'll re-terminate both ends and use black heat shrink this time.

Tuesday, January 10, 2023

Which number is coldest on a bar fridge? Google is less than useless sometimes.

I’m in a motel at Gundagai, there is a bar fridge that doesn’t seem very cold. There’s a control but no idea which number is the coldest so I googled for an answer and the top link in Google is:

Fridge Temperature Setting 1-7 - Which is Cold and Better - Freeze Edge

It is full of useless nonsense. I wonder if this is AI generated or low paid human content farms?

"You can use the fridge temperature setting 1-7 on any type of your commercial fridge. I have also shared the temperature which is cold and better for the fridge.

The best way to keep food cold is to keep it in the refrigerator”

They have clearly targeted my question but fail to answer:

"There are a few basic rules if you’re trying to set the coldest setting on your refrigerator. They are as follows:

  • By looking at its temperature dial, you can tell how much refrigerant power the fridge has.
  • Your fridge temperature setting 1-7 can make your fridge colder, which will make it as cold as possible.”

My complaint isn’t that there are pages full of rubbish like this but that Google is ranking them up the top.

The internet is getting worse and all this AI article writing and content farms aren't helping. Google is losing its usefulness in my mind. I fear that future AI will be trained on this nonsense too.

The answer, for this fridge, is that the highest number makes the fridge coldest.

Sunday, January 08, 2023

Improving antenna height with the drone

The cheap Chinese drone is very sophisticated, with GPS stabilisation etc, but my current favourite is a little one I purchased second hand for $200 including remote. I like it because it's light, uses standard batteries, and I can fix it when I break it.

It came with a 4S battery and I had a bit of trouble when I switched to 3S but after some re-calibration of the CleanFlight software it now flies really well. Today I used it to drag a line right over the top of a small tree to support one end of my 40m dipole which had been in an inverted V configuration.

A bit hard to see but my technique of flying the drone over the tree or branch pulling a line and then killing the motors so that the weight of the drone pulls the line through is working reliably for me. (I do have some spare propellors standing by though).


Tuesday, January 03, 2023

Using a clone SDRPlay RSP1 without SDRPlay's software

I've owned a genuine SDRPlay in the past and liked it but have moved over to the AirSpy HF+ as it seemed superior in A/B tests. The low cost of the clones makes them tempting for little reception tasks and where multiple receivers would be handy.

I am sympathetic to the SDRPlay folks who warn about products claiming to be genuine being sold quite cheaply. They have a page warning about all this. The "cloning" of the hardware is a little controversial there are reports that the hardware design is essentially based on a reference design.

One reason that I moved over to AirSpy is that it's very easy to install the driver software:

apt install airspyhf

does it on a Debian derived system. In contrast to get an SDRPlay going you have to download a closed source blob and they ask you to state that you are using it with a genuine product.

Fair enough. I wouldn't want to break my agreement with them.

How to use a clone without infringing on SDRPlay's software

There is a driver for the Mirics chips. libmiris. We live in a golden age of excellent SDR software.

SDRangel has a plugin based on libmirisdr-4 and does not need any software from SDRPlay.

SDRAngel is a little unwelcoming on first run. The main window comes up blank and you must create a Workspace, add a sampling device, then add a "channel" to get a demodulator such as a sideband demodulator.

Have a look at the Quick Start.

I hope that other SDR software, such as my favourite, SDR++, will add support for these devices without requiring the closed source driver from SDRPlay.

The pattern of a western company creating a new design, selling it for a while, then a much lower cost clone from China appearing is not new. Perhaps the way to survive this competition is to keep pushing for the quality end of the market. People who couldn't justify the price at first may enter a space by buying a clone then move up to buy a quality version with new features.

I totally agree that the clones should not pretend to be real though.