Saturday, June 19, 2021

ATS-20 Si4732 receiver firmware update

I recently purchased a nifty shortwave and FM receiver from AliExpress built around an Arduino Nano and Si4732.

I pulled mine apart to try to see if there was a label that would provide a clue about which version to write it it - there isn't. A tip: you can just undo the top screws front and back to get the lid off. Watch the speaker connected by short wires

On power on, it displayed V1.1.5 of the library by PU2CLR. After upgrade it now shows 3.04.

I followed the instructions on but used Arduino 1.8.13 on macOS just fine.

Basically the steps are:

  • Select Arduino Nano
  • Select ATMega 328P (Old boot loader)
  • Install libraries:
    • SI4735
    • Tiny4kOLED
    • TinyOLED-Fonts (it's a dependent)
As well as plugging in to the Nano I had to power on the radio to program it.

The source code is available here. For my hardware, I found the version titled "SI473X_ALL_IN_ONE_OLED_RDS_CHINESE_V3" was the one that matched the buttons on my front panel.

In the source code of the sketch there are some settings to adjust if you like such as default volume.

Before upgrade here's the splash screen:

After the update it looks like this:

The display in operation is a bit different too.

It's quite a sensitive receiver and sideband works pretty well. Here's an example.

There is no bandpass filtering on the input so it would probably be overloaded if connected to a broadband antenna. It's wonderful to have the source code to play with - all credit to PU2CLR.

Thursday, June 17, 2021

My first SOTA - cold and wet but not disappointing

Paul, VK3HN, kindly invited me along to a Summits On The Air (SOTA) activation today at Mount Disappointment close to Melbourne.  

The weather did not look promising but we decided to risk it and while it was rather damp and cool, it could have been worse. 

David, VK3KR, generously drove and Owen, VK3EAR cleverly opted not to come and stayed at home to monitor.

I took a loop antenna and an IC-705 with external battery. Paul had two home brew rigs and used an end fed antenna. David was on 2m with a home built beam.

Paul has created a video that captures the day very well:

Here is Paul's latest home brew rig. It is a crystal locked CW transceiver. I really admire his construction and recommend his video about how he hand makes printed circuit boards.

The mountain was beautiful but there was intermittent rain and the temperature fell to about 7C. We were all soaked through by the end of the outing.

SOTA is a great idea in that it encourages bush walks to mountain peaks with a bit of ham radio activity. David was the most successful and even had a contact with Peter, VK3YE on 2m.

Things I learned:
  • Use pencil for the log - my ink ran in the rain
  • Less weight is good - even though the loop was pretty light an end fed wire would be better
  • Don't take a chair - I thought I was being clever by bringing a folding chair but it turned out that there was a picnic table there anyway so that was unwanted extra weight to carry.
I'm looking forward to trying this again in better conditions.

Monday, June 14, 2021

Games on Netflix? My comments on ABC Download this show

Topics on ABC Marc Fennell's Download This Show were the Apple Developer Conference announcements, Facebook's ban on Trump, paying for extra Twitter features and the prospect of renting games on Netflix. Here's a video segment:

The full radio version of the show is available here. I enjoyed meeting Dr Emily van der Nagel who has done some very interesting research into social media platforms.

A book I mentioned in the radio show is Influence by Robert Cialdini.

Saturday, May 29, 2021

Wonderful new SDR design described by Ashhar Farhan

A video of a presentation by Ashhar Farhan, VU2ESE, has been posted and I can't recommend it highly enough. He describes a new design for what looks to be an easy to build SDR based around a Raspberry Pi. Along the way, Ashhar also clearly explains many of the key parts of how a Software Defined Radio works.

The paper that goes with it can be viewed here. Thanks to Stephen, VK2BLQ, for drawing my attention to this and for Bill at Soldersmoke for the link.

Today is a bit sad for me as I'd hoped to be going to MayHam at Wyong but due to a pandemic lockdown in Melbourne I'm unable to leave my home.

Thursday, May 20, 2021

A visit to Paul Taylor, VK3HN.

I have been a fan of Melbourne ham radio home brewer Paul, VK3HN's blog and YouTube channel for some time. We met a few years ago at Peter, VK3YE's QRP by the Bay but I discovered that he lives not too far from my new home in Thornbury so I invited myself over for a visit.

Paul's blog is of a very high standard, well written, with extensive technical information about his projects. In recent years, projects have been demonstrated and explained with well made videos as well.

Projects cover the spectrum from small portable CW rigs all the way to a high power AM transmitter using the efficient Class E mode.

There's a few things that stand out to my eye - Paul tackles complex projects with a logical modular approach, often building on tried and tested standard designs but without fear of trying more challenging designs. 

Circuit boards are manually etched using the resist pen method.

Most striking of all are the cases which are custom fabricated from aluminium angle stock and sized to snugly fit the enclosed circuitry.

Thanks Paul for an entertaining and educational evening tour of the shack.

Incidentally, you can hear more from Paul at HRDX via SolderSmoke and a terrific interview on QSO Today episode 298.

Sunday, May 16, 2021

Low cost loop antenna for 40m from VK2BLQ

Stephen, VK2BLQ, and I test the Sydney - Melbourne path using WSPR and we have been comparing our noisy external antennas with loops in various positions. 

Today he sent details of his latest loop made mostly with bits of Bunnings.

He writes: "The loop is approx. 900 mm diameter as it was a 3m coil of copper from Bunnings, when it was cheap.

I let it run on 40 m wspr yesterday and this morning and pretty much was only received along the east coast but not by Peter. Only the wire antenna which is 3 m above the loop reached USA Canada and all over other places.

WSPR is ok but the only real test is for two way communications; I could hear VK3XU at good  level this morning and VK2ARZ a bit later. I need a small changeover switch between keyer and key.

The tuning capacitance is the double sided pcb, the actual value of capacitance depends on the thickness and type of the fibreglass, so it was a case of measuring a piece and cutting off small pieces until I can see the minimum swr on a Nano VNA. The PCB has a coat of lacquer and soldered to the loop, it probably is not too resilient outside.

The Coupling loop is a 1 m length of RG 11 75 ohm TV cable with only the braid and foil shield being used. It is longer than the customary 20 %, and perhaps that is why the Q is low.

Some heat shrink to cover the joints and definitely only temporary.

Next version will be a 6 m perimeter octagon as I have four 1.5 m lengths of copper. I read somewhere that the capacitor should be at the bottom with the feedpoint at the top for a better angle of radiation. This is possible if I re-solder the PCB capacitor".

Stephen is certainly covering Australia on 40m WSPR but oddly missing the bit of Melbourne where I am located.

We are travelling to MayHam at the end of the month and if it fits in the car we'll bring it along for the Home Brew display.

Saturday, May 08, 2021

Attended a rally in support of the ABC

Josh Frydenberg, Federal Treasurer, did not attend the meeting at Hawthorn Town Hall - despite a respectful invitation - but about 450 people did. A letter from Mr Frydenberg was read in full to the assembled audience prompting some laughter and astonishment as he repeated the Coalition’s position that there have been no cuts to the ABC while also arguing that all media hurting and so should the ABC.

Speakers at the evening included ABC Friends’ President Michael Henry; past Chair of the ABC Advisory Council and Director of the Victorian College of the Arts, Professor Andrea Hull; Professor Ed Davis AM; Vice President of the Media Entertainment and Arts Alliance, former ABC journalist, Karen Percy; and Former ABC journalist and ABC Alumni member Jim Middleton.

Tosca Lloyd showed a film produced by GetUp titled “Murdoch and Morrison vs the ABC” which drew together the broad community support for the ABC and illustrated the concerted campaign by Murdoch media and the Institute of Public Affairs (IPA) to weaken or even privatise the ABC.

The panel discussed the impact of cuts to the ABC experienced so far including cuts to key programs and staff levels during the government’s time in office. More subtle attacks on the ABC including efficiency reviews and frequent criticism of program makers in Murdoch media were also discussed.

A video of the event is available.

It was a very professional, focussed and well-run event. It was my pleasure to work in a small way with Michael Henry and in particular key organiser Marcus May in the preparation of the event. My thanks to Jim Middleton for stepping up to speak and be on the panel.