Iranian man on the train

Today I caught a train from Southern Cross bound for Bendigo. At Footscray a man got on. He looked confused and clearly had almost no English. He was asking if this train went somewhere but we couldn't work out where he meant.

Several passengers tried to figure out what he wanted and when we finally figured out that he wanted to go to Melbourne it was too late, the doors had locked and we were under way north.

Unfortunately for him, this was an express and the next stop was Sunbury, about 40km away.

He slumped into the seat next to me and I showed him on the map where we were headed. He said he had just arrived from Iran and was going to meet his boss. I said I was sorry to hear what is happening over there. Talking to the boss on speakerphone, he explained he'd caught the wrong train. The guy on the other side offered to pick him up! I explained that that might not be the best approach, better to catch the train back at Sunbury.

He asked if I was a technician? I said yes and he told me he was working for someone who worked for someone who was a technician.

The conductor came through checking MyKi cards and my new friend pulled out an infringement notice he'd been given earlier for not having a ticket. (He seemed to think that was a ticket). I spoke with the conductor on his behalf and explained the situation. He kindly let it pass.

When we got to Sunbury a bunch of fellow passengers got up and pointed to where he should go and explained what colour train he should catch to get back to Southern Cross. It was heartwarming to see.

Our train system is confusing, even for me, I can't imagine how hard it would be for a visitor with little or no English. Signs are poor, trains leave Southern Cross on different platforms and you can't find out from within the ticketed area. 

I was proud of my fellow Australians today and their open and helpful attitude to a new Australian.

Tech Talk on ABC Radio - Israel's use of technology for war

As the world watches tensions and conflicts swell in the Middle East, what stands out is the use of technology in the military.

From hacking, to the iron dome, it is a new era of defence.

To take stock, Peter Marks, software developer and technology commentator from Access Informatics, joins Chris Taylor to discuss Israeli military technology.

https://www.abc.net.au/listen/programs/nightlife/techstuff-peter-marks/105429550

Remembering Bill Atkinson

Very sad to hear this week that Bill Atkinson has died. 

I vividly remember seeing a Macintosh computer for the first time. 

At the time I was heavily into CP/M and WordStar. At work we produced a newsletter by printing text columns on a daisy wheel printer. Headings were made by rubbing letters from Letraset. Photos were turned to dots with a high contrast process camera with a transparent dot screen. The pieces were cut up and pasted together.

When I saw a Macintosh with a graphical screen that showed the fonts and graphics as they would appear I was stunned.

Later I learned that it was a programmer called Bill Atkinson who was one of the very clever people who managed to make all this work in the constrained environment of those early machines. Bill wrote low level graphics code that was incredibly efficient. "QuickDraw" doesn't fully capture the achievement. He wrote MacPaint, with its box of tools including the pencil and "FatBits" which influenced all the bit map editors that followed including Photoshop and friends.

Even later, Bill created HyperCard, a user friendly development environment that could be used by almost any computer user. I loved it.

I went to a MacWorld expo in the early 90s. (This is before Apple withdrew to have their own events). To get a seat in the front row for Bill's talk I attended the session before and claimed my seat. He walked in clutching a bunch of gear strung together with SCSI cables.

He told stories about his work including the ImageWriter printer but also talked about the work he'd done to improve the dot pattern that could turn a greyscale image into a pattern of dots that smoothly simulated it. "Atkinson Dithering" it came to be known. He said that one day, when he was working on it, a colleague came to the door of his office and, seeing a nice greyscale image on his Mac's screen - commented that it was great that Apple was going to release a greyscale screen Mac! (Of course, they weren't but the dithering looked very real from a short distance away).

Bill was a visual person. I have a beautiful book of photographs of textures from nature that he published.

Thank you Bill.

Tech Stuff on ABC Radio

Do you feel that AI is advancing faster than anything else you've seen in history? And the pace at which AI is developing is overwhelming? 

New analysis from Mary Meeker finds that we are in the AI boom. 

Also a look at the merger between OpenAI and ex-Apple head of design Jony Ive's io.

GUEST: Peter Marks, a software developer and technology commentator from Access Informatics.  Listen here.

Built the QMX kit - watch out for enamelled wire joints

Like many people I was very excited by QRP-Labs work to bring sideband to the excellent, compact, high performance, digital rig, the QMX. I ordered a built version and have been using it in the field.

My setup, in a small waterproof box is quite compact but I plan to put together a portable radio with a QMX, rechargeable battery and some sort of antenna tuner. For this project I ordered the kit version and have now completed construction. It's a dense six layer board. The surface mount components are all pre-soldered so most of the work is toroids and connectors.

The QMX has built-in diagnostics, including RF bandpass and low pass filters. After my build I could see some problems all of which were due to me not managing to solder to enamelled wire. At times, inspection under high magnification revealed a solder joint where the solder seems strongly repelled by the wire. After a bit of debugging the radio is working well.

On the bench I run it from 12.0V via a linear regulator (I built the 12 not 9V version). (My bench supply of 13.8V is too high. I get 5W out on 80m and about 4W on 40 and 20m. Performance as a WSPR transceiver is really excellent.

If you run in to trouble there's some great resources including Hans' troubleshooting guide which includes a faultfinding log of fixes he's needed. 

Also there is an active QRPlabs discussion group where people help each other.  I've enjoyed this kit very much and it's a really wonderful radio.

I've been running it receiving and transmitting WSPR almost continuously for about a week. Rock solid. Sometimes reception of my signal is amazing (when there aren't solar flares that kill the bands). Here's a single transmission on 40m reported by 94 stations:

It also receives exceptionally well.

On the media's "The divided dial" series about shortwave

A friend alerted me to an interesting series of programs about shortwave from WNYC Studios.

"Season Two of On the Media’s Peabody-winning series The Divided Dial is the untold story of shortwave radio: the way-less-listened to but way-farther-reaching cousin of AM and FM radio. The medium was once heralded as a utopian, international, and instantaneous mass communication tool — a sort of internet-before-the-internet. But like the internet, it also took a turn for the chaotic. And like AM and FM talk radio, it also went hard to the right, with extremists and cults still finding a home on the shortwaves".

THE DIVIDED DIAL EPISODE 1: Fishing In The Night

THE DIVIDED DIAL EPISODE 2: You Must Form Your Militia Units

THE DIVIDED DIAL EPISODE 3: World's Last Chance Radio

THE DIVIDED DIAL EPISODE 4: Wall St. Wants Your Airwaves

First I've heard of The Shortwave Modernisation Coalition which proposes to use shortwave for high speed trading.

I think there is a role for shortwave broadcasting but today I think it should broadcast a hard to jam, easy to receive digital data format.

The silencing of Voice of America - ABC RN program

Thanks to Thomas at The SWLing Post for drawing this to my attention. ABC Radio National, of which I'm a past contributor, has a documentary program called Rear Vision and this week they have a program about the demise of VOA which most of us will be familiar with from our lifetime of shortwave listening.

It's a really well done program with archival material that triggered great nostalgia as a long term listener.

You can listen here. 

"The US funded international news network Voice of America started broadcasting into Germany in 1942. 

It now broadcasts in nearly 50 languages to  more than 350 million people around the world. 

But in March this year,  US President Donald Trump signed an executive order dismantling the US Agency for Global Media - the independent government body that oversees Voice of America.

Now, Voice of America has been silenced for the first time in 83 years. 

Guests:

Patsy Widakuswara is Voice of America's White House Bureau Chief and lead plaintiff in VOA's legal case against the Trump Administration.

Dr Nick Cull is Professor of Public Diplomacy at the University of Southern California, Annenberg, and he specialises in the historic role of communication in foreign policy. 

Dr Kate Wright is Associate Professor of Media and Communications at the University of Edinburgh and co-author of Capturing News, Capturing Democracy: Trump and the Voice of America by Kate Wright, Martin Scott & Mel Bunce

Produced and presented by Kirsti Melville".

Great work!

Sideband receiver project in Silicon Chip magazine

Fantastic to see a serious ham radio construction project in the June edition of Silicon Chip magazine.  The project by Charles Kosina, VK3BAR, is a general coverage sideband shortwave receiver covering 3-30MHz.

The VFO is an Arduino nano and Si5351. IF is at 9Mhz and uses a crystal filter board sourced from AliExpress. Interestingly there is RF preselection using electronically switched capacitors and a varactor diode.

Audio output is an LM386. There's AGC and the radio even has squelch.

What is, perhaps, missing is AM reception. 

It is wonderful to see such a project in Silicon Chip. 

Tech talk on ABC Radio

The competition for our smartphone dollars is about to enter a new round. Google is previewing Android 16 this week and Apple will preview iOS 19 next month. 

Peter Marks, a software developer and technology commentator from Access Informatics, joined Chris Taylor on Nightlife to discuss the latest news in technology. 

https://www.abc.net.au/listen/programs/nightlife/nightlife-tech-talk-with-peter-marks/105315754 

It was good to meet Chris Taylor who's filling in while Philip Clark is on leave. Chris was one of the Chaser gang and I fondly remember watching VHS cassettes of CNNNN when I worked at CNN 25 years ago.

QRP-Labs QMX excellent for portable operations

I've been staying in Tasmania this week, on the north coast, near Devonport and naturally I wanted to bring some sort of radio gear along. The QRP-Labs QMX recently added the ability to transmit sideband. I've had a few contacts with this and reports are good. The QMX (and QDX) are particularly good at FSK modes like WSPR I think due to the direct synthesis rather than audio mixing.

My travel case is quite small and fits everything I need including a pill bottle microphone.

The station was set up overlooking the ocean with a 29' wire pretty much just resting on some bushes.

Operation was on 40m at first but 20m was the standout. I was heard as far away as Europe in the first transmission.

I'm embaressed to admit that the very compact tuner was purchased from China and is clearly a copy of the QRP Guys' Ununtenna Plus. I have ordered the real thing which they say has much better quality toroids in it. The design is good and it's the most compact antenna tuner I can carry with me.

The QMX has a built in tuning mode with SWR display but I find nulling the LED on the tuner is easier.

At first I tried operating inside the house with the wire running out through a metal sliding glass door but I couldn't get it to tune. I think the close coupling to large metal earth threw things off. Operating outside was pleasant and signals were very good.

Moorabbin Hamfest a blast again this year

The Moorabbin & District Radio Club Hamfest must be one of the biggest in Victoria and it's always a good excuse to pick up some parts and catch up with friends.

My feeling was that it was a bit smaller than last year but still worth a visit. I purchased a Bird power meter with a fault (but it came with the needed part). A few pushbuttons and a vintage morse key being sold from an SK estate by Drew. A few impressions of the show:

The in-line power/SWR meter I bought was said to be faulty due to a burnt out diode. The Seller supplied me with a replacement and said he hadn't got around to fixing it.

When I got it home, I opened it up and tested both diodes and they seem to be OK. Attaching a transmitter and it seems to work. I'm not too concerned about calibration so I'm happy with the purchase. It came with 2x N to BNC adapters which are probably worth what I paid for the whole thing.

I headed off early to visit VK3ZZC who's unwell at the moment. We wish him all the best for a speedy recovery. Great to catch up with Drew VK3XU, Peter VK3YPG, Nigel VK3DZ, Dave VK3ASE, Peter VK3YE, Chris VK3AML, Jim VK3ZKK, and others.

Technology talk on ABC Radio

Artificial Intelligence continues to revolutionise our lives. Predictions from experts state that AI will likely automate or transform 50% to 60% of jobs. 

How long until it takes over our lives or jobs completely? 

Also self-driving trucks on the road and we bid farewell to Skype.

Peter Marks, a software developer and technology commentator from Access Informatics, joined Philip Clark on Nightlife to discuss the latest news in technology. 

https://www.abc.net.au/listen/programs/nightlife/nightlife-tech-talk-with-peter-marks/105261180 

AI in FreeDV presentation at the Bendigo Technology Festival

The Bendigo Amateur Radio and Electronics club today held their first Bendigo Technology Festival. It was an ambitious affair with information and sales tables and a series of technology talks.

The Macedon Ranges Amateur Radio Club had a table with information for potential new members. 

ALARA, WIA and many others had tables and there was quite a bit of gear for sale at excellent prices.

I presented a talk on how AI is being used in the new versions of FreeDV.

Congratulations to the organisers and I hope they do it again.

RF Noise Bridge for antenna tuning?

An early electronics project for me was to construct an RF noise bridge. This remarkably simple device, combined with a receiver, let me measure resistive and reactive impedance by adjusting for a null in the noise on the receiver.

I'm putting together a compact station for portable operation and it occurred to me that a noise bridge might be a good way to adjust an antenna tuner used to match an end fed wire in a tree. Sometimes it's hard to find the resonant point.

I tried this with a random wire, a Z match and a QMX transceiver (with the recent SSB software). It was not a good way to tune up, partly because of the QMX's excellent AGC.

To see what's going on I hooked up an SDR as the receiver, so I can see the noise over a broad bandwidth:

The antenna is an off centre fed dipole and the tuner is a simple L match. The dip can be seen above up the top end of 40m after tuning. A traditional antenna analyser confirms the tuning:

So it does work but is difficult compared to other options such as minimising an LED on the Z-match or using a NanoVNA. 

I wonder if I'm not doing this correctly. I'm not seeing what I would characterise as a "deep null".

The Palomar bridge is a nice bit of gear and I rather like the warning on the back of the manual:

They have an article about using the noise bridge for antenna tuning. Oh, and this story is another example of Betteridge's law of headlines.

Rotary encoder in MicroPython

Sample code for rotary encoder handling that I've found seems to double step with my encoder. I guess there's other that have half steps or something. Anyhow, here's how I've been doing it and it's working just fine.

CLKPin.irq(trigger=Pin.IRQ_FALLING, handler=rotary_callback)

def rotary_callback(pin):

"""Interrupt handler for rotary encoder falling edge"""

global frequency

if DTPin.value() == 1:

frequency += int(math.pow(10, step_power))

else:

frequency -= int(math.pow(10, step_power))

setFrequency(frequency)

So, the interrupt triggers just on the falling edge of the clock pin and then looks to see if the data pin is high (for clockwise) or low (counter-clockwise).

A full project is stored here.

Thonny alternative for MicroPython - MicroPico

Recently, I've been enjoying developing embedded projects on an RP2040 zero board using MicroPython. The RP2040s are fast and cheap and the zero board is much more compact than the Pi Pico but has more than enough I/O for my needs. (Actually, all the I/O is there if you need it).

MicroPython is a wonderful language and I like the fact that the source code is on the device so I can always find it again.

The normal way to develop MicroPython is Thonny. It's fine but the editor is rudimentary compared the modern code editors with completion and AI suggestions.

Recently I've discovered the MicroPico extension for VSCode and it is working pretty well.

The environment does all the things I need including showing the files on the board, letting me run the current file, stop it, and use the REPL console.

Most impressive is the AI code completion which often stuns me with its guesses about what I was about to type. (The suggestion is the italic stuff after time. below).

MicroPico doesn't do the firmware install but that's quite easy on the RP2040 (hold the boot button and plug in). 

The files stored on the device are shown in the "Mpy Remote Workspace" area on the left and a project folder is above. You can drag files up or down between areas but it moves the file. To copy a file on macOS you option-drag as is the normal convention here.

I wish single step debugging was available for MicroPython but if I'm debugging pure python algorithmic code it can be debugged locally if needed.

There are other MicroPython extensions for VSCode but this one seems to work quite well for me.

Low cost display and rotary encoder board for VFO building

As part of my objective to take the SolderSmoke DC receiver forward to be a double sideband transceiver I've been messing about with an Si5351 based VFO. The CPU is an RP2040 Zero board which I program in Micropython. I've just bought a couple of these handy boards that include a 1.3 inch OLED display, a rotary encoder and two extra push buttons.

No documentation comes with it but the edge pins are nicely labeled on the back.

When I hooked it up and tried my existing code, written for an SSD1306 OLED, the display showed mostly noise. It turns out the boards with a larger, 1.3 inch, display require the SH1106 driver which I found here. Both drivers subclass the Micropython Framebuffer class which is a very interesting thing in its own right.

The display / encoder board has nice big mounting holes on the corners as you can see.

I paid AU$6.79 each for the larger display version on AliExpress. For you in America I guess they'll be about $100. ;-) The board seems to be widely available and is called "0.96/1.3-inch OLED Display Module With Button EC11 Rotary Encoder IIC Interface LCD Screen"

MicroPython OSError error numbers on RP-2040

I've seen an OSError stack trace when trying to talk to an I2C device on the wrong address and wondered what EIO means. It would be nice to have a list of all the error codes and what they mean.

From what I've read, error numbers are different for each hardware port of MicroPython. I'm using a Raspberry PI PICO and can get a list like this:

MicroPython v1.24.1 on 2024-11-29; Raspberry Pi Pico with RP2040

Type "help()" for more information.

>>> import errno

>>> print(errno.errorcode)

{1: 'EPERM', 2: 'ENOENT', 5: 'EIO', 9: 'EBADF', 11: 'EAGAIN', 12: 'ENOMEM', 13: 'EACCES', 17: 'EEXIST', 19: 'ENODEV', 21: 'EISDIR', 22: 'EINVAL', 95: 'EOPNOTSUPP', 98: 'EADDRINUSE', 103: 'ECONNABORTED', 104: 'ECONNRESET', 105: 'ENOBUFS', 107: 'ENOTCONN', 110: 'ETIMEDOUT', 111: 'ECONNREFUSED', 113: 'EHOSTUNREACH', 114: 'EALREADY', 115: 'EINPROGRESS’}

But it doesn’t really tell much. They all start with ‘E' and so 'EIO' just means IO error, which makes sense.

In face they're all more readable if you know to drop the E.

{1: 'PERM', 

2: 'NOENT', 

5: 'IO', 

9: 'BADF', 

11: 'AGAIN', 

12: 'NOMEM', 

13: 'ACCES', 

17: 'EXIST', 

19: 'NODEV', 

21: 'ISDIR', 

22: 'INVAL', 

95: 'OPNOTSUPP', 

98: 'ADDRINUSE', 

103: 'CONNABORTED', 

104: 'CONNRESET', 

105: 'NOBUFS', 

107: 'NOTCONN', 

110: 'TIMEDOUT', 

111: 'CONNREFUSED', 

113: 'HOSTUNREACH', 

114: 'ALREADY', 

115: 'INPROGRESS’}

Technology talk on ABC Radio

Cyber criminals were able to breach a number of super funds, stealing hundreds of thousands of dollars from members.

The breach was unsophisticated, and likely came about because some super funds had not implemented basic security protocols on members' accounts

Peter Marks, a software developer and technology commentator from Access Informatics, joined Philip Clark on Nightlife to discuss the latest news in technology. https://www.abc.net.au/listen/programs/nightlife/nightlife-tech-talk-with-peter-marks/105152996

How DRM is shaping the future of digital radio

An interesting discussion of Digital Radio Mondiale. Some comments about how the west has retreated from Shortwave broadcasting are particularly pertinent at the moment.

The good news, to me, is that there are modules coming that will make it easy to make consumer receivers with DRM reception.

Thanks to the good folks at World Radio TV Handbook.

Fascinating talk on the Shepparton International High Frequency Transmitting Station

The Melbourne chapter of the Radio Amateurs Old Timers club had an informative and entertaining presentation by Nigel Holmes, VK3DZ about the role of the Shepparton International High Frequency Transmitting Station in researching the ionosphere and even reflecting HF signals from the Moon’s surface.

It turns out that quite a few of my fellow members of the Macedon Ranges Amateur Radio Club are also members of the Old Timers.

There's a good train service from central Victoria down to Melbourne and then on to the Caulfield RSL where we meet so, naturally, we ended up on the train together. Here is VK3MO, VK3ACR, VK3XW, VK3WQ and VK3RV. Also in attendance was VK3CCR.

The meeting was well attended and the food was very good. 

The Radio Old Timers Club is a national organisation but to my knowledge only Melbourne and Perth have lunch events.

Technology talk on ABC Radio

If you are a 23andMe customer, like me, you should consider deleting your data. Are you a Windows 10 user? Microsoft is suggesting that you trade in your old computer soon to upgrade to 11. Do you read the lengthy terms of use many sites require - there may soon be an alternative that puts the user in the drivers' seat. Apple's Intelligence rollout hasn't gone well and now they're being sued for false advertising. All in Nightlife tech with Peter Marks. https://www.abc.net.au/listen/programs/nightlife/nightlife-tech-talk-with-peter-marks/105095170 

QRP field ops with VK3CDO

Graeme, VK3CDO, came and gave a great presentation about portable operations gear at the Macedon Ranges Amateur Radio Club recently. He brought along a terrific folding chair and table which I immediately ordered. He suggested an outing and I was up for it. We set up on a beautiful day here in Victoria on Mount Macedon.

The weather was perfect. We both brought our chairs and tables. I brought a tent in case the weather turned (not likely). Graeme used a very nice MA-12 vertical antenna which was easy to set up and worked well. I strung up an end fed but had problems tuning it to either 40 or 20m. (I think the Unun I grabbed was not working).

Graeme operated a low cost, uSDX QRP radio with just the internal battery and easily made a contact.

We both brought small metho stoves which worked very well for cups of coffee & tea. Later we each cooked up a lunch. Graeme went for gourmet sausages while I tried a freeze dried meal which was very nice.

Graeme put me on to the chair and table. Both excellent: "Naturehike Camping Chair, Portable Backpacking Breathable Chair with Storage Bag, Compact Collapsible Lightweight Camp Chair (Green-M)" & "Naturehike Camping Detachable Table with Aluminum Alloy Material, Portable, Lightweight, Outdoor Furniture for Camping, Picnic, Hiking, and Other Outdoor Activities".

The tent is a "Night Cat Backpacking Tent fo 1 Person 2 Persons Easy Setup by Clip Waterproof Lightweight protable Camping Hiking Tent for Adults Kids Scouts Tent". I like it because it's under 2kg and has a convenient side entrance.

I kept John “lofty” Wiseman’s excellent SAS survival handbook at hand but luckily there were no emergencies requiring reference to it.

I look forward to even more ambitious outings in the future.

First sideband contact on a QRP-Labs QMX

The much anticipated wait for the amazing software update to the QRP-Labs pocket radio, the QMX, is out in beta. Today I installed the third release and called CQ from my location in central Victoria. Dave, VK7DD in Northern Tasmania responded and gave me up to a 57.

The radio is sure to be popular with portable operators. It must be one of the tiniest SSB transceivers available.

Reports of my transmit audio are good and as you can hear in this clip, reception quality is beautiful.

Hans has a page about the beta software and as you'll see it's been a huge project for him. 

The microphone plugs in to the paddle port and is wired with PTT on the tip and audio on the ring. I had several mics around from Xeigu radios and they have the connections the other way but it wasn't hard to swap one over.

I found that extra audio gain was needed but this is easily adjusted via the serial terminal interface or built-in menu.

Even without SSB capability the QMX is a fantastic transceiver for FSK digital modes (and CW) but now it can do modes that need SSB such as PSK31.

Fantastic work from QRP-Labs!

A simple Si5351 VFO for RP2040 zero in Micropython

Having had a wonderful time with the Soldersmoke direct conversion receiver and after that a very simple double sideband transmitter, I'm now formulating a DC/DSB transceiver. From the experience of those that have tried, it seems that a traditional VFO on the transmit frequency is not a good idea as the transmit signal gets back in to the VFO and causes problems.

My plan is to use an Si5351 clock generator (<$2) based VFO which should not be affected. Recently I've been playing with the tiny RP2040 Zero boards which can be purchased for under $2 and are an impressively powerful computer.

The RP2040 CPU is powerful enough to run MicroPython. While I'm comfortable in C++ I love python's clean syntax and library. The code is quite simple and I've put it up on GitHub here: https://github.com/peterbmarks/micropython_vfo

Pushing the rotary encoder button changes the step size. You can see it in action here:

My display is a tiny 128x32 OLED board with an ssd1306. I imagine many builders will swap this out for something grander.

The hard part is done with libraries created by smart people:

ssd1306.py from https://github.com/kwankiu/ssd1306wrap/

si5351.py from https://github.com/hwstar/Si5351_Micropython

I like the way all the source code is stored on the MicroPython device.

You can see which pins I've wired the i2c and encoder devices to in vfo.py. You may wish to change these.

This is early days and there are sure to be bugs and improvements to be made. Send me a pull request!

Guest spot on ABC RN's Download This Show

I'm on ABC RN Download This Show again this week. Generative AI has officially infiltrated the world of gaming, could games created entirely by AI be the future we've all been dreading?

Also, speaking of, so many games, so little time... could a dating app for choosing games be the answer?

Plus, what are personality rights and could they help us defend against deepfakes. And what ever happened to those astronauts stranded in space?! 

https://www.abc.net.au/listen/programs/downloadthisshow/gaming-app-artificial-intelligence-deepfakes-astronauts/104970260 

Technology talk on ABC Radio

AI is being used to check for errors in research papers, but just how accurate are its results? And is your collection of classic DVDs still playable? You might be surprised. Peter Marks, a software developer and technology commentator from Access Informatics, joined Philip Clark on Nightlife to discuss the latest news in technology.  

https://www.abc.net.au/listen/programs/nightlife/nightlife-tech-talk-with-peter-marks/105039402 

Rebuilt the Soldersmoke DC receiver in compact form

Lots of fun and lots to learn from the Soldersmoke Direct Conversion receiver.  It seems simple but there are some traps for young players like myself. Building with others and being able to compare observations is incredibly helpful.

My approach is Manhattan construction spaced out and arranged to look like the circuit diagram. This makes it easier to spot the inevitable errors but there is a downside that it's more likely to have instability. In the past few days I've re-built each stage in a more compact form and the result works well and has no instability. As an example of before and after here's the diode ring mixer prototype laid out for clarity:

Here's the new compact version of the mixer:

The compact VFO board:

Most challenging and most improved is the audio chain which is now stable even with the gain turned all the way up and the pot off the board connected with platted wires.

I did have a wiring error on the audio board that took me a little time to figure out. Having a working board to compare with really helped of course.

I'm about done with this project but it has been a wonderful learning experience. I would recommend this as a group project for any beginning constructors like me.