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.