Thursday, February 18, 2021

Dallas, VK3EB, demonstrates a bush antenna for low noise

Now that the brief pandemic lockdown in Melbourne has ended, I've hit the road in the van again and first stop was Shepparton to see Dallas, VK3EB and check out how he puts up antennas in the bush to get wonderful low noise reception.


Great to see you Dallas and thanks also for the tour of your home brew end fed tuner.

Friday, February 12, 2021

Built the QRPKits BLT+ Z-match antenna tuner

Locked down here in Melbourne it seemed like a good time to build a little antenna tuner. This is the Balanced Line Tuner Plus (BLT+) from Pacific Antenna or QRPKits.

As the radios I'll be using this have built-in SWR measurement I chose not to build the LED SWR indicator that's included.

The kit went together easily and the case is really excellent.

The manual, with circuit diagram, is available here

I tested it by throwing some wire out over the clothes line and running a counterpoise on the ground. The two controls interact a lot and you must adjust one and then the other and then the first.... but in the end it gets there and I'm happy with the result.

One minor note is that my kit came with version 2 of the SWR indicator but the link to the construction notes re-directs to version 3 which is a different circuit. This was enough discouragement for me to skip it.

Update

After a gentle prod from veteran home brewer, John, VK2ASU, I went back and completed the built-in SWR indicator.



Tuning for a dimming or extinguishing of the LED does work but the meter on the radio is much easier to work with. The LED SWR indicator is worth having for simple QRP gear so I'm glad I've now put it in. It can be switched out of circuit of course.

China's BBC ban reminds us of the value of shortwave

China's announcement this week that the BBC World News TV channel will be blocked is another reminder that modern content distribution technologies, those that use the internet, have made censorship easier rather than harder.

When I worked in Hong Kong for CNN we knew that the satellite downlink for distribution of the TV signal in China went through a party controlled facility and that if the image of the Tiananmen Square "tank man" was used in any way, the signal would go dead for a time. 

International newspapers would sometimes arrive a little late with stories blacked out.

Shortwave stations with content the party didn't approve of would be masked by high power jamming signals. It was sometimes possible to receive the original signal by moving the antenna or off-tuning to some extent.

In those days readers, listeners and viewers at least knew something was being hidden from them.

As the Internet spread around the world it was thought that it would bring unfettered access to all of the worlds knowledge and opinion. It turns out that rather than decentralising network access, the modern internet has done the reverse and centralised monitoring and controlling of all of our communications.

A software developer who had migrated from China told me of the amazing experience of working for a US company that had the US version of the internet available in the office. This person was astonished to read Wikipedia articles that presented a far different view of modern Chinese history than had been available to them. 

In recent years, many countries, including Australia have shut down shortwave broadcasting as the audience is small and hard to measure. Radio Australia used to have good coverage of our region including China.


I recently visited the decommissioned Radio Australia transmission site in Shepparton. It was an impressive facility.

Low earth orbit (LEO) satellite internet has the potential to provide internet services all over the world but I expect it will be regulated by each country and the penalty for not complying will be that customer billing will be blocked or perhaps the uplink signals will be jammed in some way.

A low cost news distribution proposal

Digital communication over shortwave radio has improved massively in recent years. The combination of a low power shortwave transmitter and a personal computer can be detected around the globe. WSPR is just one example.

I propose a shortwave service that transmits respected world news and information programs using a variety of digital modulation systems. It should have periods of "old school" radio teletype, PSK, and more advanced modes such as MFSK that have been shown to get through despite weak signals and even deliberate jamming.

Software to decode the audio signals, such as fldigi is widely available for personal computers and phones and this would need to be explained and promoted around the world so that the audience could find out about it despite undoubted censorship.

The audience for this stream of uncensored text news would be very small but the content would be highly valued by those who found it. Stories could be shared through secure messaging within the country. Single use domains could be used as a way for readers to acknowledge reception.

Sunday, February 07, 2021

Readly for digital magazines in Australia - a review

Readly in browser
Readly is a subscription service that gives you access to a large collection of magazines and some newspapers from around the world.

It works well in the browser and there are apps for iOS and Android (including Amazon Fire).

Magazine pages scroll sideways. In the browser arrow keys didn’t always work for me although they do work if you zoom to full screen.

Text and image quality is good. I have to say that retina screen iPads make magazines look fantastic. This is what the iPad is surely for.

The first magazine recommended to me, based on no usage, is Maxim which was a bit of an odd choice. You do get to choose a bunch of topics of interest to help the algorithm along.

Navigation in the app is logical and the hierarchy of content makes sense.

Content topics are: Aeroplanes & Transport, Animals & Equestrian, Art & Culture, Boats & Watersports, Business & Finance, Cars & Motoring, Celebrity & Entertainment, Comics, Craft & DIY, Crosswords & Sudoku, Education & Tutorials, Family & Parenting, Fashion & Beauty, Food & Drink, Gaming, Gardening, Health & Wellness, History, Hobbies & Collecting, Home & Renovation, Hunting & Fishing, Interior Design & Architecture, Kids, Lifestyle, Luxury, Music, News & Politics, Photography, Running,  Cycling & Fitness, Science, Sport, Tech, Teen & Young Adult, Travel & Regional, TV,  Film & Cinema, Wedding.

Readly remembers what you’ve read and you can “favourite” publications and bookmark pages.

I was excited to see a large number of Linux magazines but then noticed that many were not in English - I think it might be better to now show magazines in other languages unless the user asks. (There is a language selector that can do this but it defaults to all rather than detecting the browser language). Readly mingles magazines in different languages together which Apple News+ does not.

In Australia, Readly costs AU$10 a month.

Competitors include Apple News+ which is AU$15 a month but includes newspapers including The Australian and the Wall Street Journal. Apple News+ also includes some “higher end” magazines such as National Geographic, Scientific American which are missing from Readly.

Another major competitor, also more expensive, is Kindle Unlimited which is AU$14 a month but seems focussed on print and audio books with some magazines. It seems like the selection of magazines on Kindle Unlimited changes each month.

Readly is a great way to read a selection of popular magazines, it’s slightly cheaper than the competing options and worth a try as a first experience of consuming digital magazines.

My thanks to Readly for giving me a free trial to take a look. 

Friday, February 05, 2021

Appeared on ABC's Download This Show

It's always fun to be invited to be a talking head on a radio or TV show and this week I was again on Download this Show talking about small traders, communicating on Reddit who cost hedge funds a lot of money by buying when they were not expected to.


The full radio show, with more stories is here.


USB Microscope works well with macOS

Magnified headsets, magnifying glasses, a lamp with a big magnifier - I must be getting old, but trying to see surface mount components is getting harder. This week I purchased a USB Microscope via eBay. I didn't get the cheapest model, this one is AU$20.

This one came with a suction cup mount, which isn't great. The zoom feature has a side-effect that at high zooms the lens has to be very close to the subject which probably means it would get solder flux vapour depositing on it if used for soldering.

It came with a mini-CD with drivers but I found that when plugged in to macOS 11.2 it just worked and appears as a camera in apps that let you select cameras. I used the built-in Photo Booth app.

The photos come out at 640x426 for me.

Here's a picture of some tiny LEDs on an Arduino board.

I am impressed with the resolution and colour. Sometimes exposure can blow out highlights and there's no manual override that I can see. 

This will be useful for inspecting small solder joints. Recommended.

Wednesday, February 03, 2021

GP4 HF vertical antenna review

With little space in the back yard here I decided to try a cheap vertical I saw on AliExpress. The name GP4 presumably refers to the claimed four bands as a ground plane.

The claimed bands are 40m, 20m, 15m and 10m.

The antenna cost me AU$120 plus $128 shipping. It arrived in ten days via FedEx but it's sometimes painful to pay more in shipping that the price of the item.

Boxed nicely in cardboard completely covered in tape. The tubes were protected with plastic and foam so it arrived in excellent shape and does look to be pretty good quality.

There are no instructions in the box but on the ad there are pictures and a machine translated note mostly about the counterpoises.

It goes together pretty well and the size of the aluminium tubes forces you to put it together the right way. The matching stubs are clearly labelled so I don't think you can go wrong.


Well packed:


Some of the holes didn't quite match up for me and I had to drill them slightly with a 4mm bit:


The kit comes with one M4 bolt and nut for each join and then pop-rivets for the other holes. I guess the aluminium pop-rivets might be a good idea from the perspective of metal corrosion but I chose to use marine grade nuts and bolts for all joins.

The mount spacing seems rather short for an antenna of this height (5.65m) that does catch the breeze.


The nuts on the back of the U-bolts are hard to tighten as they are close to the U section of the aluminium plate.

I've run out 6 x 2.5m and 2 x 5m counterpoise wires (which is what I think they're asking in the instructions above). They provide a copper lug and you supply the wires. I've covered it in heat shrink tubing (which makes everything look professional). I will cover the PL-259 connection in self-annealing tape soon.

The antenna works well on 40m but 20m is a bit off.


I have slightly shortened the low span which moved the resonance near 20m slightly closer but also moved the nice 40m resonance higher too.

Initial tests using WSPR show that transmissions are getting out very well but my reception seems rather noisy. Noise here varies quite a bit and I'm seeing S7 noise which is better than the end fed which is currently over S9.


I would recommend trying this antenna, it's much cheaper than alternatives promising similar features. My concerns are the torque on the closely spaced U bolt mount in high winds and whether the matching coils will survive in the Australian sun.

Perhaps the higher bands aren't working well because I need to "Change the form and length of the tiled ground network to coordinate the standing waves".

Working well on 40m:



Tuesday, February 02, 2021

WSPR Watch coming in Dutch but German is needed

After my app WSPR Watch was mentioned in QST I've been receiving a lot more email about it and one person kindly offered to help with a Dutch version which is coming soon.

The most common language after English is German and I'm looking for someone who would be prepared to translate the strings for me. Please let me know either in a comment here or via the contact button in the app is you're able to help.

Thursday, January 28, 2021

Raspberry Pi Pico

As soon as I heard about the Pico I placed an order. These boards are more like an Arduino than a (linux capable) Raspberry Pi. Like the blue and black pill, they are much more powerful than most Arduino and have a dual core Arm chip.

Hackaday has done an excellent job of describing the new chip and this board in their writeup.


While you can program in C++, I'm tinkering with the MicroPython environment. To get started, you download Thonny and run it. Hold down the button on the board and plug it in to the computer with USB. Thonny will see it and offer to install MicroPython. Next, the board reboots and when it comes back there's some sort of serial protocol running between Thonny and the board. 

Here is the blink example.

I find that sometimes I get a device busy message and must click the stop button and then the run button again.

Hardware access is via a module called machine. This provides a well organised set of interfaces to things like threads running on the other core, interrupts, low power sleeping, timers and serial interfaces including I2C and SPI.


After playing with the Python environment, I've gone ahead and installed the C++ tools by following the instructions on Ubuntu Linux. All went smoothly for me but I do miss the huge number of libraries that exist in the Arduino world - good news is that a port of the Arduino core is on the way.

It's a bit fiddly having to plug in the USB cable while holding the BOOTSEL button down and so I've ordered a little USB hub with port switches on it.

A couple of improvements for a future version - please use a USB-C connector rather than the flimsy micro USB socket, also it would be handy to have the pin markings on the top of the board rather than the bottom.