Contestia - faster, not better

Looking at digital modes for talking with people with high local receive noise I noticed Contestia in Fldigi. It's derived from Olivia but has a smaller character set. It only sends upper case letters. 

Stephen, VK2BLQ, has fairly high local noise. He's about 700km from me. To check if we have a suitable path for a QSO we both ran WSPR on 40m. He received my 2W at +3dB SNR so we switched to Contestia.

I received him perfectly but he wasn't copying me. It turned out Fldigi defaults to having the squelch turned on. Turning that off and he was able to copy me running down to 5W and probably lower.

My, incorrect, assumption was that Contestia used the extra bits compared to Olivia for better error correction. 

Reading from the Fldigi documentation page on Contestia.

"Contestia is a digital mode directly derived from Olivia that is not quite as robust - but more of a compromise between speed and performance. It was developed by Nick Fedoseev, UT2UZ, in 2005. It sounds almost identical to Olivia, can be configured in as many ways, but has essentially twice the speed.

… 

Contestia performs very well under weak signal conditions. It handles QRM, QRN, and QSB very well also. It decodes below the noise level but Olivia still outperforms it in this area by about 1.5 - 3db depending on configuration.”

It seems the objective was faster typing speed which I don’t really think is important.

So… thanks for the experiment but I think we should use Olivia in future.

Now, looking at the Olivia page in Fldigi.

The first tip they give is to turn off (or down as much as possible) the squelch.

There’s a bit of talk about different sub-modes but it seems to be about getting faster speed. They say if you’re on 250/8 and want faster (in good signal conditions) go to 500/8. 

My question is "what is the best keyboard to keyboard chat mode for low signal to noise radio channels?".

Gear for a remote radio guest - Mix minus

Regular readers will know that I'm one of those commentators you hear on the radio. I've always been keen to have my audio sound as close to the studio as possible and I think I'm getting close.

Without a noise dampened studio I need to get close to the microphone to avoid reverberation but I have a tendency to "pop" the mic so I need to monitor my local audio as well as hearing the host. We used to call this "mix minus" where the guest hears a mix of the other speakers and themselves but just the guest's mic would be sent back to the main studio. I've been hunting for how to do this on a computer.

Richard, VK3LRJ, had just the device I needed. It's a Behringer Xenyx 302USB. These aren't new but have the ability to let me hear the mix while sending just the mic up the line. It's also a USB sound card so plugs in to the computer and is powered from that USB port.

One interesting note is that it says the XLR mic socket has phantom power but my Rode mic didn't work. Turns out the phantom power is about 14V rather than the 48V norm so some microphones work but others don't. I'm using a Sure dynamic mic, similar to the studio. These mics have quite low output but this mixer has enough gain.

Anyhow, here's the latest appearance:

Telegram is just one of many messaging apps, being targeted in France over secure messaging, but just how secure is it? AI is the biggest development in technology, and it seems it's also the job that pays the best. Plus, growth in the PC and Phone markets has been slowing, and the next big thing that may stimulate people to upgrade their PC and phone is new AI features that the old models don't offer. Tech Guru Peter Marks, software developer and technology commentator from Access Informatics, with Philip Clark on Nightlife and the latest news and issues in technology. 

You can listen here.

Tech news spot on ABC Radio

A new ID system for Australians. At a speech at the National Press Club today, Government Services Minister Bill Shorten announced the trial of a new way for us to identify ourselves that is more secure than things like our driver's license but will require a phone. Also, have you ever got to the checkout to find that the price is different to what it was on the shelf? Have you ever looked at a price online again and found it has changed? These are examples of "dynamic pricing". Plus, in recent years, particularly in rural Australia, a new internet provider has quietly been gaining market share and now they've grown significant enough to attract the attention of the ACCC. How big of a provider is Starlink today? Nightlife Tech Guru Peter Marks, a software developer and technology commentator from Access Informatics, joined Philip Clark on Nightlife to discuss the latest news in technology.   Listen here.

As an aside, I'm pretty happy now that my audio quality matches the studio quite well despite me joining the program from my home office.

ePaper solar power monitor with Lilygo T5

The house here has 6KW of solar power, when the sun is shining and hitting the panels. I like to watch what's being generated so I can use power from the sun if available so some time ago I reverse engineered the Envoy inverter's web display and made some M5 Stack devices that display the info. They have an ESP-32 for Wifi built in. 

Sometimes the sun also shines on the LCD making it hard to see so I've just ported my code to a Lilygo T5-2.13 E-Paper board also with an ESP32.

E-paper is highly visible although refreshing is a bit slow and ugly. The Arduino compatible libraries are available here. Things didn't quite compile as given but I was able to work through it.

The E-Paper board uses negligible power when sleeping, and the display remains visible, so these could be run from a small battery if desired.

Building a quadcopter drone from parts

It's been many years since I've built a quadcopter from parts. What triggered this project was stumbling across the SpeedyBee flight controllers which have a powerful STM32 F405 and bluetooth so they can be configured wirelessly from a smartphone app. The controller has the motor controller (ESC) board mounted under it which makes for a much neater arrangement than the last time I did this which involved have ESCs on each arm of the drone.

Here's a closeup of the flight controller with ESC board under it.

The SpeedyBee uses a version of Betaflight. It arrived with the latest version. I've added a GPS module and was hoping to get a GPS Hold mode but that doesn't seem to be available in Betaflight. There are comments that even if it were available it doesn't work very well due to the poor accuracy of GPS position.

Here's my list of parts:

Frame

FPVDrone 5 inch frame Mark4 225mm FPV Racing Drone Frame Carbon Fiber 5inch Quadcopter Freestyle Frame Kit with Lipo Battery Strap $79.67 Amazon

https://www.amazon.com.au/dp/B082SPT5D9

Receiver

FLYSKY FS-A8S V2 2.4G 8CH Mini Receiver PPM I-BUS SBUS Output for Flysky FS-i6 FS-i6S Airplane FPV Racing Drone Transmitter

https://www.aliexpress.com/item/1005005699957173.html $12.87

Transmitter

Flysky FS-i6X 10CH 2.4GHz AFHDS 2A $$57.01

Buzzer

5V buzzer $2

https://www.aliexpress.com/item/32996116481.html

Motors 2300KV

RS2205 2205 2300KV CW CCW Brushless Motor for FPV RC QAV250 X210 Racing Drone Multicopter $24.78

GPS

GPS BN220 $12.26

https://www.aliexpress.com/item/1005006319024804.html

Flight controller and ESC

SpeedyBee F405 V3 30x30 Flight controller + 50A BLS 4 in 1 ESC

$109.88

https://www.aliexpress.com/item/1005005486457877.html

Flight controller:

https://www.speedybee.com/speedybee-f405-v3-bls-50a-30x30-fc-esc-stack/

5-inch propellers

5x4x3 5040 three blade ebay.

I already had a transmitter but it's rather bashed up and getting unreliable. I also have batteries in stock.

All up about AU$250.

Once I got the propellors turning the right way and enabled Horizon mode it flys quite well. Next step is to add a camera and transmitter. This will be a good "knockabout" drone for hoisting antennas and other such activities.

Betaflight?

I was surprised to see that the SpeedyBee flight controller runs Betaflight as when I last played with this stuff the Cleanflight fork was the leading software. It turns out the modern Betaflight is now a fork of Cleanflight and is the most popular and up to date. This is explained on the excellent documentation wiki.

QRP operation from a motel room

This year I fulfilled a long term ambition of visiting Uluru in the centre of Australia and I couldn’t help thinking how spots from there might look on a WSPR map. Here's a spoiler (plotted in WSPR Watch):

Operating QRP from a motel room is a challenge in several respects. From past experience I knew that receive noise would be high and while it’s possible to hang an antenna up inside the room, getting it out on a balcony would work much better. The motel at Yalara (where the accomodation is near Uluru) had a decent but all metal balcony.

The first attempt had the wire antenna on the outside face of the balcony. Reception and transmission was not good. Our room was on the second floor and there was a small tree just across a path so a sugar packet was tied to the end of the wire for a bit of weight and I threw it out to the tree. This worked much better.

The end fed wire was cut randomly and is about 4m in length (very short for the 20m band). A small counter-poise of about 1.5m was just laid out on the floor. A QRP Z-match antenna tuner was used and a NanoVNA was used for initial tuning. The Z-match was able to provide a very good match, no external Unun was needed. No doubt there are losses but my signal was received around the world so they can't be too bad.

The Z-match has an SWR indicating LED (you tune for minimum brightness) but I also experimented with a simple RF current detector and found that brightness is maximum close to when the SWR is at a minimum.

There’s promise in this simple RF current detector and in an absolute miniature equipment setup I might opt for one of these combined with receive noise peaking to indicate antenna resonance.

Having said that, the NanoVNA is a remarkable piece of pocket sized test equipment, smaller than any antenna analyser and very capable.

Weak signal operation in a poor location begs for WSPR operation and the rig of choice for me is the QRP-Labs QDX which has many advantages including being pocket sized. I powered it from a block of 8 AA NiMH batteries which were able to run it from about 6pm until 3am local time with 10% transmission. 

WSJT-X was run on an M2 MacBook Air prevented from sleeping with the Caffeinated app. One of the benefits of using the QDX is that rather than mixing WSPR audio tones up to SSB audio, Hans cleverly measures the period of the audio cycle and directly sets the RF oscillator to the right frequency. This makes for a very pure transmitted signal and I’m convinced that WSPR transmitted by one of Hans’ recent transceivers is more easily decoded than the same power from a sideband transmitter.

One 2 minute transmission was reported by 41 stations which is pretty good going given my remote location and compromise antenna.

In this case my end fed wire antenna was black insulated hookup wire. It was not easy to spot from outside and I know that some stations use wire-wrap wire which is virtually invisible even close by.

If you ever get the chance to visit Uluru, go for it. It’s a remarkable feature of the landscape.

If you will be in a motel anywhere in the world consider digital QRP operation.

Tech news spot on ABC Nightlife

Billboards are said to be one kind of advertising that can't be blocked or skipped. That's all about to change with a revolution in outdoor advertising in Switzerland. 

Also, the devastating Windows CrowdStrike raised many questions, but it looks like Microsoft is working to make Windows more robust in the face of software bugs that could bring it down. 

Plus, flying cars were one of the features of the Jetsons cartoon vision of the future, and now it seems like regulators are preparing for this new world happening soon. Nightlife Tech Guru Peter Marks joined Philip Clark to discuss the latest news in technology. Listen here. 

Eyeglasses in Australia are hugely over priced

A recent podcast from Freakonomics titled Why do your Eyeglasses cost $1,000? explains the EssilorLuxottica monopoly we face here in Australia as well as the US.  Their markups are described by one analyst as "obscene". They mention Warby Parker as a possible monopoly breaker but sadly they don't seem to have come to Australia.

My prescription is relatively complex with astigmatism and I've paid $800 for progressive lenses and $300 for computer distance reading glasses.

Despite efforts by eye testers I've been able to get a copy of my prescription and recently ordered some new reading glasses from Zenottic in China for $55 (plus $10 shipping). They are perfect and the frames seem as good as any in the local shops.

I think it's a scandal that we pay 5 times the price, or more, to buy locally. It does take some care to get the prescription down correctly as well as inter-ocular distance but once I got it right I'm able to cheaply get additional pairs.

Note that EssilorLuxottica owns Sunglass Hut, OPSM, Oakley, Ray-Ban, LensCrafters and many more.

Tech news spot on ABC Radio Nightlife

This week on ABC Radio Nightlife, we talked about Samsung's product updates and how much they look like Apple products, a new way to migrate your photos from Google to Apple's cloud, future cars that won't let you speed, Android's coming desktop mode, some old technology (8 inch floppy disks) that are finally being retired and the US ban on Kaspersky Anti-Virus. Listen here. 

Alternative fan control for a Saxon wood heater

Our home came with a Saxon wood heater but the advertised automatic fan control circuit has never worked and I must get down on the floor to turn the fan on or off manually.

The heater works by heating a cement plate at the top of the firebox and a fan runs air over the top of it which warms the room. If the fan isn't on the heat goes up the flu. If the fan is on when the fire isn't going well it cools the firebox and may extinguish the fire. 

I enquired at the company about getting this fixed or getting a replacement board and they referred me to our local agent who basically said they knew nothing.

The circuit certainly looks quite simple although the markings on the IC have been cleaned off.

My solution was to purchase a temperature controller XH-W3001 that can be used either in heating mode or cooling mode. I've set it to come on when the sensor is over 30C indicating that the fire is hot inside.

The sensor range is only up to 120C so I've put the sensor at the back above the heater. The XH-W3001 was AU$5.98 which seems very reasonable. The mains wires are rather flimsy but should be OK for switching a fan.

The way it works is a little counter-intuitive. It has a "heating mode" and a "cooling mode". I'm using it in cooling mode where the output comes on when the temperature exceeds the left hand value and goes off when the temperature drops below the right hand value.

I've set left to 34C and right to 30C. The sensor is at the back just poked in to the top cavity. It seems to be working well and the cat is very impressed.

Broadband RF generator (AKA eBike charger)

My new eBike came with a charger. Even though it's about 10m away from my ham shack the radiated noise level is impressive. 

Here's the "transmitter":

Here's the inside view:

Even with external clip-on ferrites on the mains and output cable there is little difference. How can it be legal to sell noise makers like this? Are all the certifications fake or just incredibly poor standards?

As Ralph, VK3ZZC, suggested I have added 0.1uF silver mica capacitors across the large electrolytic smoothing capacitors on the output and this has made a noticable improvement on the radio.

Talked tech on ABC Radio Nightlife

I joined Philip Clark on ABC Radio's Nightlife program to talk about technology news including new legislation to combat faked sender IDs on scam text messages, YouTube live stream hacks to promote crypto scams and a look at the new ARM based Microsoft Surface laptops that are challenging Apple.

Audio here.

In the story I talked about trying out the new Microsoft Surface laptop powered by ARM. It's a nice looking and feeling laptop, quite similar to the M2 MacBook Air which I imagine it is competing with. Fit and finish is excellent. More ports than Apple and slightly better value in terms of price per GB of storage and RAM.

There's a new Microsoft only key on the right hand side for summoning Copilot AI features.

I pushed the key and not a lot seemed to happen but I guess, like Apple these new features are being rolled out over time.

Micropython thermometer using MCP9808 and SSD1306 OLED display

This little post was triggered by reading Owen Duffy's post titled "Arduino thermometer using DS18B20 and OLED display". Even though I'm quite comfortable writing C or C++, I've been enjoying the clean MicroPython environment. These days I've pretty much switched from classic Atmel Arduinos to RP2040 based boards.

I implemented this little thermometer in just a few minutes with two easy to find and install libraries. Here's how it looks:

And here is the code:

import time

from machine import Pin, SoftI2C

import ssd1306

from micropython_mcp9808 import mcp9808

i2c = SoftI2C(sda=Pin(6), scl=Pin(7), freq=100_000)

display = ssd1306.SSD1306_I2C(128, 32, i2c)

mcp = mcp9808.MCP9808(i2c) # , address=0x18)

time.sleep(0.5)

while True:

    temp = mcp.temperature

    #print(temp)

    time.sleep(5.0)

    display.fill(0)

    display.text(f"{mcp.temperature:.2f}C", 30, 15, 1) # x,y,colour

    display.show()

The imported modules are mcp9808 for the i2c temperature board and ssd1306 for the OLED display.

I use Thonny for editing, uploading and debugging.

One mystery is that the hardware I2C isn't working for me on the RP2040 board but SoftI2C works fine.

When getting started I scan for I2C devices like this:

i2c = SoftI2C(sda=Pin(6), scl=Pin(7), freq=100_000)

devices = i2c.scan()

print("devices: ")

for device in devices:

    print("0x{0:02x}".format(device))

Obviously adjust for the pins you've used. The RP2040 is a wonderfully powerful chip. The board I used here is from Seeed studio.

Cheers to Owen for all his great insights and sharing.

ChatGPT is very good at Micropython

While I'm here, an observation about the utility of the Large Language Models. I have been asking ChatGPT to write code to demonstrate how to do things and it's really good!

Around the house I have little devices that use Wifi to poll my solar inverter and show power use and generation. I've been using a third party JSON parser but I asked ChatGPT how to do it and it mentioned a built-in JSON parser that I wasn't aware of!

Built the Sputnik regenerative receiver

When I was a teenager and just starting to tinker with electronics I built a regenerative receiver kit from the local Tandy (RadioShack) store. It was a great success and I was able to listen to the big shortwave broadcasters on it.

I know that Bill often mentions that regenerative receivers may be haunted on his Soldersmoke blog. The DX Explorer site describes a rather neat regenerative receiver named Sputnik. The author also links to a way to order a very nice board from PCBWay. I ordered and quickly received five copies of a very nicely done board.

Most of the components I had but the ten turn pot had to be ordered in. I used a T50-2 toroid core rather than the air-core inductors. At first it didn't oscillate. My initial thought was that the tickler coil was not the right polarity but it turned out that my 2N2222s have collector and emitter reversed. Ralph, VK3ZZC, suggested that they might be fakes but the gain seemed fine.

The coil has a single turn that can be connected to a frequency counter. I have it going to my CRO and it's helpful for reading frequency and seeing when regeneration is starting. While you can, kind of, listen to single sideband, AM is best. Here's a bit from 7125 this morning.

I didn't have any 1N4001s in stock and tried another power rectifier that didn't seem to work as a varicap diode. I did have a genuine varicap in the junk box but it was too sensitive. Richard, VK3LRJ, gave me some 1N4004s and they work fine although tuning is very sensitive.

The radio is pretty hard to operate and one must juggle, RF gain, tuning and regeneration.

My memory might be rosy but the Tandy pegboard kit was easier to use than this design. It might be this one. There's a lot more electrical noise around these days and many of the big shortwave broadcasters have gone so perhaps the golden age of listening to BBC on a three transistor radio are over.

Flying like a bird, the joy of FPV drone operation

Some years ago I used to accompany Terry to a field in Sydney where he would fly amazingly fast while using a video headset. He would run through an obstacle course with hoops standing on the oval. I tried a few times but crashed immediately - I could never put myself in the drone and was always thinking of the sound.

My current drone is home built and rather bashed about but does the job.

One problem I've had is that I need my glasses to see the screen clearly and the solution was to sacrifice an old pair of reading glasses and apply some hot glue.

There is a bit of open space and a tree in the middle so I started slowly and have had a bit of a breakthrough. I was able to take off, fly around the tree, and return and land without breaking anything.

A few days on and I've probably had about ten successful flights and it is a real joy to experience.

Last night, after a hard landing, the drone was not flying well and I lost control. I couldn't see when it was but could see the video from its point of view. It was stuck in a tree. A squid pole was very handy in dislodging it. Next step is to add a buzzer so I can locate it after an uncontrolled landing.

Listening to the BBC Antarctic Midwinter Broadcast

Tuned to 9585KHz and the BBC's Antarctic Midwinter Broadcast is on. A charming shortwave program with information and messages from family at home. Good signal here in Victoria.

I'm using an Airspy HF+ via SDR++ in server mode. Thanks to Stephen, VK2BLQ for the tip.

ABC Radio spot about technology

Talked technology on ABC Nightlife with Dom Knight: AI seems to be taking jobs already, AI being used to protect call centre workers, NotebookLM a great new research tool and Adobe being sued for misleading customers.

https://www.abc.net.au/listen/programs/nightlife/peter-marks/104000522

USB-C cables have vastly different capabilities

USB-C is a wonderful standard. Apart from the ability to plug it in either way up, it supports Power Delivery and much higher speeds.  I've run in to some mystifying scenarios where a cable would charge but not carry data, would carry data but not charge, and lower than expected data throughput.

I'm a registered Apple developer and was keen to try out the macOS 15 Sequoia beta but I'm not an idiot so decided to install it on an external disk on my Mac mini.

The steps were:

• Used Disk Utility to format a Samsung T5 drive as APFS
• Downloaded the Sonoma macOS installer via the App Store
• Installed Sonoma macOS 14 on the external drive
• Booted from the external drive and enabled Beta Updates in the Software Update settings and chose macOS 14
• When all that was done I booted from the external drive.

Sequoia seems quite stable and I've been able to build my applications with the Xcode beta.

But.... it did seem rather slow! I used the Blackmagic disk speed test to measure the drive and got Write: 38.9 MB/s & Read: 39.3 MB/s. 

The USB3.1 port is capable of 10Gb/s or 1,250MB/s so something is up.

Changing USB-C cables to one marked as 10Gbp/s I re-measured and got Write: 263.6MB/s & Read: 344.9MB/s. Almost 10x improvement but well short of what's possible.

Today, I bought a 1TB Western Digital drive. Blackmagic gave me Write: 804.1 MB/s & Read: 906.8 MB/s.

The Mac mini has two Thunderbolt/USB4 ports that are capable of up to 40Gb/s so I have ordered a Thunderbolt enclosure.

Oh, and just a note that the speed of the internal SSD on a mac is pretty amazing. Blackmagic measures the internal SSD as Write: 3049.6 MB/s & Read: 2856.4 MB/s. I guess that's why I noticed the slow speed.

Summary: If things seems slow, try another USB-C cable. (I wish they had a standard for markings on the cables with their capabilities).

Update: faster external disk

Wanting to get closer to the speed my interfaces are capable of I ordered an NVMe SSD stick and case from AliExpress. Plugged in to the USB-C socket on the back of the Mac mini I get the same speed plugged in to the USB-C hub outlets on my monitor so I'm using that. Speed is pretty good. Close to 1GB/s.

The enclosures are pretty nice. Mine came with a heatsink, sticky pad and even the screwdriver needed to open it. Not as small or neat as the Samsung T5 but five times faster.

Update 2: even faster external disk

On my quest for a faster external drive to boot from I ordered a SanDisk Professional drive and plugged it in to the USB-C socket on the back of the Mac mini. At 2,677 MB/s this is getting pretty close to the internal drive speed.

It came pre-formatted as APFS.

How to spread misinformation

I've been seeing a lot of misinformation lately and noticing the techniques used. While discussing this with friend Tony, I wondered if ChatGPT could list ten effective ways to do this.

"Spreading misinformation effectively, while unethical and harmful, often employs psychological and social manipulation. Here are ten techniques commonly used:

1. Emotional Appeals: Crafting messages that trigger strong emotions, such as fear, anger, or joy, can bypass critical thinking and make the information more memorable and persuasive.

2. Repetition: Repeating a false statement frequently can make it more familiar, leading people to believe it's true (the "illusory truth effect").

3. Selective Presentation: Sharing only specific facts or stories that support the misinformation while omitting contradictory evidence creates a biased view.

4. False Authority: Citing fake experts or misrepresenting the credentials of individuals can give false information an air of credibility.

5. Echo Chambers: Sharing misinformation within closed or like-minded groups reinforces the false beliefs, as members are less likely to encounter opposing views.

6. Manipulated Content: Using doctored images, videos, or audio clips to create convincing but fake evidence supporting the misinformation.

7. Bots and Trolls: Deploying automated accounts and paid individuals to amplify misinformation across social media platforms, making it seem more widely accepted.

8. Headline Manipulation: Crafting sensational, misleading, or clickbait headlines that can spread quickly even if the actual content is less inflammatory.

9. Conspiracy Theories: Developing complex narratives that explain events through secret plots, which can be compelling and difficult to disprove.

10. Astroturfing: Creating the illusion of widespread grassroots support or opposition through fake reviews, comments, or social media activity.

These methods exploit cognitive biases, emotional responses, and the structure of information dissemination in the digital age to spread and entrench misinformation."

I wonder if some sort of score-card could be made that analyses a published story in terms of these factors?

Raspberry PI Pico with USB-C not working? Try a USB-A cable.

It's a pity the Raspberry Pi PICO comes with the horrible micro USB socket. I purchased what, I guess, is a PI Pico clone board with a USB-C socket on it from AliExpress but was disappointed when none of them seemed to appear on the USB bus.

On a whim, I plugged one in to my computer with a USB-A to C cable and up it came! My guess is that somehow the USB-C wiring isn't right and a proper USB-C port doesn't power on. Anyhow, they work fine and I've now flashed MicroPython v1.23 on to them and all works well.