U3S + 12V = Fried U3S

Well I have now printed a label for the power connector on the U3S enclosure saying 5V, but it’s a little too late for an assortment of components that inadvertently were subjected to not just 12V but closer to 14V! Yikes.
From consulting the FAQ on the QRP-Labs site at https://www.qrp-labs.com/faq.html I have learnt that I’m am by no means the first to commit this blunder! In fact – as the FAQ on this topic reveals – so many have trod this well-worn path that there’s a pretty good understanding of what needs to be repaired and what probably survived the onslaught of unwanted volts.
Net result as I understand it is:
  • the main processor, a 28 DIP ATmega328 chip is definitely fried! I do have the option to program a blank one or order one already programmed from QRP-Labs.
  • The LCD display has been zapped.
  • The relay on the main Ultimate 3S board has most likely been burnt out as well by the higher voltage.
  • It’s supposed to be unlikely that the Si5351A Synth Module has been damaged.
  • On the QLG1 GPS unit it’s probable that the 74ACT08 level converter chip has been destroyed by the high voltage because of the way the LED indicators are behaving when power is applied. Yellow is not pulsing once a second as it should…

This is such an unrare event that QRP Labs have created a product especially for people like me – the QCU QRP labs control unit which components most likely to need replacement after applying the wrong voltage! It includes the 16 x 2 LCD module, 20MHz crystal, BS170 transistor, buttons, resistors, capacitors, hardware and all connectors (4-way sockets, 10-way sockets, 16-way plug/socket for LCD) that are used in the Ultimate 3S kit.

Grandmaster Flash

Last night I watched two more episodes of The Get Down on Netflix with my daughter. About 6 minutes into episode 3 of the first season where members of I think the Notorious gang visit Grandmaster Flash to show him the bootleg cassette, you see Flash sitting at a desk with a fat old 2 or maybe even 5-watt resistor and a multimeter. I think it’s a 2.7k ohm value(!).
In the background, there are some signal generators and a big Tektronics oscilloscope. If you visit https://auction.screenbid.com/view-auctions/catalog/id/83/lot/56599/ you can see the actual prop currently being auctioned off. It’s a Tektronics 545A which was made between 1959-64.
Grandmaster Flash's Tinkering Machine according to the site auctioning props from 'The Get Down'.
Grandmaster Flash’s Tinkering Machine according to the site auctioning props from ‘The Get Down’.
The Smithsonian Institution has one of his actual turntables – a Technics SL-1200 MK2 model.
The Technics turntable used by Grandmaster Flash aka Joseph Saddler
The Technics turntable used by Grandmaster Flash aka Joseph Saddler
The description mentions
“Grandmaster Flash (Joseph Saddler), was born in Barbados in 1958. Growing up in the Bronx, he was influenced by his father’s massive record collection. As a teenager, Grandmaster Flash first experimented with DJ equipment and became involved in the New York DJ scene while attending daytime technical school courses in electronics. The innovations and techniques developed by Grandmaster Flash established him as one of the pioneers of hip-hop and deejaying.”
An electronics geek with scant funds, Flash constructed a stereo system using parts scavenged from scrapyards and discarded cars and asked the girls he dated if their parents had any records they didn’t want.
This makes my walking a wheelbarrow around my 1960s middle-class neighbourhood as a 13-year-old gathering old discarded radios during council clean-ups quite tame, compared to the virtual war zone of the late 70s South Bronx.

Adapting an HP computer power supply for ham radio use

It’s some time since I purchased an HPS 600PB PSU 12V 47A power supply for about $25 from ARNSW. Seeing one in action at our recent club contest station inspired me to dust it off and put it to work.

The HP server power supply popular with hams and radio control fans

These power supplies were designed to be hot-swappable and installed in pairs in racks of HP ProLiant DL380 G4 Rack Servers.

They enjoy a solid reputation for reliability and while designed to deliver 12 volts can reportedly be tweaked to deliver a higher voltage a little closer to ham radio norms, and still deliver high current. The one I saw in action during the recent CQ WW SSB contest was also RF quiet and was comfortable feeding a 100W transceiver for 48 hours straight.

At one end the power supplies are fitted with a regular IEC power socket. At the other end, there is the hot-swap connector.

The business end of the power supply
a close-up of the hot-swap connector

IMPORTANT NOTICE: This article is not intended as a guide, it is merely a record of what I have done, for me to refer to when I need to. You must take every precaution when working on this device. The voltages are lethal and you need to be confident in your workshop and soldering skills.

The key information is that the left-hand pair of large blade connectors are both connected to each other and negative/ground and the right-hand pair are both connected to each other and 12 volts positive.

Between these two pairs of blade contacts are 12 protruding pins in four rows of three. Counting from the top and left to right, you can see in the photo that pin number 6 is shorter than the others.

If you simply plug in an IEC power cord into the unit nothing will happen. You have to connect some of the pins together to start the power supply.

I figured the safest and most reliable way to do this – to check that the power supply is working okay – would be to use a pair of 3 x 2 Dupont female pin connector blocks.

Again counting from the top left, I mounted female pins in the blocks so that pins 6, 8 and 10 would be connected together. Pin 8 is connected to the ground. And pin 10 is PSON. I’ve read that some people have installed an on-off switch between pin 10 and pin 6.

I had also read about a common modification to control the fan speed. Unmodified – with pins 6 and 10 connected to pin 8 – the fan runs at maximum and so could be considered noisy.  Connecting pin 4 to pin 8 slows the fan down, but it is still able to increase its speed when required.

I tried without this mod – to hear how loud the fan actually was – and with the modification – to see what difference it made. This 5 MB 8-second long mp4 clip shows the clear difference in fan noise, before and after grounding pin 4.

The sound level difference is significant enough to leave pin 4 connected to pin 8 ground.

The next stage of my adaptation was to fit Anderson Power Poles in place of the hot-swap connector. People have soldered large terminals to the blade connectors, but I wanted something safer and easier to connect with the rest of my radio gear.

It’s pretty straightforward dismantling the power supply. Be careful to ensure the supply has been disconnected and powered down.

Basically remove every screw you see, except the four holding the small fan. You’ll see three slots inviting you to slide one of the panels along, but you can’t until you break the bond between the aluminium panel and the black plastic insulation material attached to the panel by double-sided adhesive tape. It will come free – and can be helped along with a knife blade to break the adhesion.

Top centre you can see the connector for the fan. This can be left connected throughout. In the centre, you can see I have already removed the screws on the two metal flanges connecting to the main board, and on the bottom, you can see the hot-swap connector.

Remove the screws holding the two metal flanges mounted on the board to pillars on the main board. These carry the voltage through to the blade connectors.

I released the ribbon cable from its clip.

There are two more screws holding the small printed circuit board with the hot-swap connector to the enclosure. Remove these. Also use a nut driver to remove the nut in the centre of the board attaching it to the enclosure.

I unsoldered the blue and purple wires – after taking a quick photo of how they were wired. (Purple to +5V)

Now I could remove the hot-swap board completely from the power supply.

The next step is to remove the connector without damaging the printed circuit board. The amount of metal in the connectors and on the traces of the printed circuit board means that unsoldering is not practical. I have heard of people using a heat gun to dislodge the connector. But again you need to be careful not to destroy the board.

I opted for a more direct approach – slowly using a precision model hacksaw to remove sections of the connector. It was slow and messy but I was left with a clean and largely undamaged board with ample room to install two pairs of Anderson Power Poles.

I trimmed and tidied up the board where the 12 pins were connected. I unsoldered the holes into which I planned to install jumpers – that is 4, 6, 8 and 10. I also cleaned up holes 3 and 9 with plans to install a resistor to effect a rise in the output voltage.

I actually used the square profile wire used for the pins to make first a small link between pins 4 and 8, and then soldered a longer link above it joining pins 6 and 10 to this lower link. I presume it’s important that each of these holes retain a short conductor to ensure continuity between traces on both sides of the printed circuit board.

The bottom of the printed circuit board where the links joining pins 4 and 8, and then 6 and 10 are visible. Pins 3 and 9 are clean and ready for voltage adjusting resistor.

I’ve been advised that the simplest way to install the APPs is to superglue them to the top of the board. But first I cut and prepared some short lengths of heavy wire to connect the power poles to the metal flanges, making sure that the centre hole where the nut came from is not obstructed.

Anderson Power Poles connected and positioned for wiring to clear the central mounting hole.

And that is as far as I have progressed. I’m unsure what value resistance to connect between pins 3 and 9. While it’s possible to raise the voltage up to 13.8 it’s not practical as the overvoltage protection disables the supply under heavy load. I’m happy to settle for a voltage just over 13 volts. It may involve trial and error to see what the best value is. I plan to start with a 470Ω resistor.

Studying the photo of the bottom of the PCB above has revealed an alternative place to mount the resistor that won’t require soldering access to the top of the board beneath the power poles – which is basically impossible. Instead, I can follow the sizeable PCB traces connected to pins 3 and 9 and scratch convenient points to attach the resistor. I’ll put a wire back into the two holes. Also, the resistor should have heat-shrink insulation to prevent unwanted connections.

My main mistake was not doing this resistor testing when I first set up the supply with the Dupont connectors. It would have been easy then to identify the right resistor value.

UPDATE: I installed a 470Ω resistor, superglued the Power Poles and held them in place with a pair of clamps for a couple of hours while the glue dried. Then I reassembled the power supply – reconnecting the blue and purple wires and the ribbon cable and reattaching the board to the enclosure. I re-used the ends of the original hot-swap socket to be able to use the original screws rather than source shorter ones.

The 470Ω resistor installed to adjust output voltage up from 12.5V
Moment of truth – with my power supply 470Ω across pins 6 & 9 changed output voltage to 13.3V

This was a great result. Right in the range I was aiming at.

Milk crate tower

Wacky idea #257 of the day
Since they were invented – apparently by an Australian engineer (see below) – milk crates have been used in many other ways besides holding milk containers.
A milk crate chair by Matt Sutter
Everything from furniture to milk crate versions of the loch ness monster.
Milk crate Nessie emerges from Australian backyard swimming pool!
Six interlocking milk crates stacked is 186cm high.
They feel stable but they need a flat level base.
They lend themselves to cable ties to tie together and offer numerous points for guying and attaching halyards.
Not sure how strong they would be at a height of 10 or 12 metres and whether they are structurally strong enough to withstand the forces exerted by guy lines etc. Presumably they would have a high degree of wind loading comparable to a steel lattice tower.
Not sure of the actual plastic material they’re made of – PE extrusion? It would be important to find out how strong it is especially where shackles etc might be connected for guying and attaching pulleys for halyards etc.
If six crates are 1.86m high, 18.6m requires about 60 crates (!) so I guess 9m equals 29 crates in a stack! 10m = 32 crates and 12m is about 40 crates.
It would not be practical to assemble a tower crate by crate from the base up as the upper crates would quickly become unwieldy and too heavy to lift. The same problem would arise with sections of a number of crates at a time. So there would be the same problem of the stresses involved in tilting and lifting any horizontal structure into a vertical position especially at the base pivot point. All crates would need to be tied together on all four sides, top and bottom, so requiring (4n + 4) ties where n is number of crates. I assume the interlocking crates would be solid when tied together.
The crates are bulky and may not be so practical for portable deployment. External dimensions are 36cm x 36 cm and 32cm high so 9 would occupy 108 x 108 x 32cm or 0.37 of a cubic metre so 40 crates for a 12m milk crate tower would occupy about 1.66 cubic metres.
One other downside besides wind loading might be the actual weight of the structure should it collapse. Long-term exposure to UV may also be an issue for a more permanent installation.
Below, a table listing various – mostly unrelated – pros and cons – the biggest one, of course, being that using them in this (or any other way besides storing milk containers) amounts to theft in the eyes of the makers and owners of the crates.
long/short term “borrow” required
requires no machining or preparation beyond cable ties
high wind loading
ready-made solid structure
weight if tower falls
UV exposure?
Here’s a Sydney Morning Herald report featuring the Australian engineer, Geoff Milton who designed the milk crate for Dairy Farmers and how they designed it with holes big enough for potatoes to fall through to discourage theft. This doesn’t explain why they made their internal dimensions the perfect size for storing vinyl LPs!
Coincidentally these milk crates were made by Nally, the same name as the manufacturer of Nally Radio Towers that shut down in 2015 when the owner passed away.

QCX – All systems go!

I finally found some quality time to spend on the QCX to work out why I wasn’t getting any RF output. In my efforts, I committed one of those predictable errors and very unscientifically changed one more factor than I should have. This resulted in a detour that made the search longer, but it did reveal something interesting about the radio.

I had decided I needed to thoroughly check out all the connections in the bandpass filter and the RF amplifier section, even though I had been very careful visually checking and testing continuity at each step of the build. But the fact of the matter was there was no power at the output. At key down, I was getting 0.01 volts. I re-flowed a number of joints on the printed circuit board. Under magnification at some angles, even the neatest solder joint can look like a cold joint.

I also suspected that some of my earlier ham-fisted testing of the radio may have created its own casualties. I was so keen to try out the built-in test equipment, I connected up my probe incorrectly. I was probably tired. I was definitely woken up by the little spark, then the fact that the wire I was holding suddenly went limp and then a puff of magic smoke emerged from behind the LCD panel! I had connected the SCK pin on the programming header instead of the RF pin nearby to the RF output!

From all the discussion on the QRPLabs email group, I guessed that Q6, the MPS2307A had probably been the source of the smoke. The consensus seems to be that they may be underrated. Hans is now shipping a more resilient transistor the MPS751 in its place. I couldn’t source any of these quickly and locally so opted to replace the original with another MPS2307A. After I had removed the transistor I tested it on a nifty component tester which concluded that rather it was actually a pair of resistors rather than a transistor. This seemed to confirm I must be on the right track.

My next mistake was to decide to test the radio using a  different voltage to earlier testing. I had read that the recommended range of voltage extends from 7 volts up to 16 (see page 5 of the manual), so I thought I’d use 9 volts. I think, also that the only way to reduce output power is by reducing the voltage. In any case, after I re-connected the radio, I noticed first of all that the sidetone was somehow delayed. If you sent a series of dits at say 15 wpm, you wouldn’t hear anything. And you had to hold the dash to hear it eventually.

I had the dummy load connected to the antenna and tuned a local receiver with no antenna connected to the same frequency and noticed that actual signal was not delayed. That’s interesting! Is there component where the sidetone is generated introducing the delay? I also realised that I was actually getting some RF output which I measured at about 1.3 watts. The voltage was just over 9 volts and the RF voltage across the 50Ω dummy load was about 11 volts. The RF output was good but the delayed sidetone was a bit like talking with a delayed echo in your ears. Between this paragraph and the next, there was a fair amount of head-scratching and further checking.

Then I decided I should see what the RF output is with a more regular voltage like 13.1 volts. I was delighted to see the voltage across the dummy load at 20 volts which neatly converts to 4 watts. And I was even more delighted to hear that the sidetone was back in sync with the key! So the lag appears to have been a result of the lower voltage. I’m not sure what the implications are of this if you want to wind back the wick and transmit at a lower output level. The signal sounded clean – it was just the sidetone that was laggy.

Another thing I learnt during this phase of the troubleshooting was that a good way to remove the remnants of a component like a transistor is to melt some fresh solder on the joint to get the heat to flow more readily to loosen things up. I think I became better at using solder wick as well, with a dab of the flux pen. The printed circuit board stood up to my efforts replacing the transistor and other components like one of the toroid coils when checking the leads. I used a fine pointed iron tip at 370° C.

Everyone says that the overwhelming majority of faults with home constructed electronics kits – at least 90% – are to do with the soldering not being up to scratch. So I figure all the time spent checking solder joints during assembly and afterwards paid off. If you tell yourself how much time you’ll save later, it becomes a more enjoyable part of the whole assembly process.

I also finally managed to upgrade the firmware using the Arduino Uno and Avrdudess application. I had to force it but at long last, the application finally recognised the identity of the microcontroller in the radio. There must be a dodgy connection between the radio and the Arduino.

Now I’m confident it’s working as it should I should make some contacts and then work my way through the manual again to confirm all is as it should be. But I will be much more careful checking any voltages!

And then I might start on my 30m QCX.

QCX video resources

There are a number – probably set to grow – of YouTube videos dedicated to the assembly of the QCX.

The most impressive, not just for its length, is the feature film length video by Roberto IZ7VHF. It’s a beautifully filmed love letter to the radio as well as a video record of Roberto’s build. It was recorded in September.

Hans Summers recorded a 20-minute video introducing the QCX in early October.

Kevin KB9RLW has recorded a 42-minute long video on building the QCX.

QCX CW decoding

One of the aspects I’ve been surprised and impressed with is the quality of the CW decoding while sending. While playing with the onboard microswitch as a morse key I felt I needed to emphasise the length of the dashes for the encoder to resolve my sending. So I was pleasantly surprised at how well the decoding worked with a straight key and a sideswiper. These keys didn’t seem to impose the same timing expectations as the microswitch – which is odd because I believe they are wired across each other.

In any case, the decoder was able to present a pretty reliable rendition of what I had sent with both keys. Other systems I’m familiar with are only successful with keyer generated CW sent on a paddle. I’ve only seen sideswiper CW decoded by the Begali CW Machine which is a bit more expensive than the QCX but essentially built around a tiny AVR Butterfly.

Decoding in receiving on the QCX sometimes seems to be jeopardised by noise and static, although some quite clear and strong signals occasionally would not be decoded. I need to experiment more to do it justice and check what impact the speed adjustment has because ultimately it all must be using the same microcontroller code to decode the morse, sending or receiving.

QCX enclosure

One topic on the QRPLabs discussion group is the ideal enclosure for the little radio. The designer Hans G0UPL planned for all controls to be mounted on the small 10 x 8 cm PCB and provided for those who prefer to mount it in a protective enclosure.

As mounted on the PCB the shafts of the AF gain control and the rotary encoder are slightly different lengths and the tiny momentary switches are a long way from any front panel.

Part of the appeal of such a small radio is being able to show it off to friends so in one sense especially for this prospective audience an enclosure denies this pleasure – unless of course its transparent.

For the moment at least I think I may stumbled on to a neat solution. On the kitchen bench.

A suitably sized plastic container

The price is right and it’s tasty too!

Almost made to measure!

This way I can keep tweaking the radio and store it with a degree of protection. I started out with this 40m version with the pot and encoder connected by headers with a view to finding an enclosure later, but this solution feels a little neater and safer. And there may even be space for a battery.

QCX CW transceiver

I plan to use this category of my blog as a kind of sub-site to track the building of this delightful new transceiver kit from Hans Summers G0UPL and his QRP Labs. Since its launch in late August when all stock sold out in a day, sales of the QCX CW Transceiver continue at a pace that still surprises the developer as he prepares his fourth batch of 500 kits.

This is my QCX in action receiving and decoding signals during the Oceania DX CW contest this past weekend

It is a feature packed design focused on delivering an up to 5-watt single band CW transceiver. It includes built-in test equipment to be used during alignment and the QCX can be used as a WSPR beacon.

It’s such a compact design – the PCB is 102 x 81mm with a hard working blue 16 x 2 backlit LCD display – and with its tiny onboard microswitch that can be used a key, it should probably be renamed the QTX!

It boasts a long list of design features that seem amazing for the modest price of US$49. They include a Class E power amplifier, 7 element Low Pass Filter, CW envelope shaping free of key clicks, at least 50dB of unwanted sideband cancellation, a sharp 200Hz CW filter, Si5351A Synthesized VFO with rotary encoder tuning down to 1Hz, Iambic keyer or straight key option, CW decoder, displayed real-time on-screen, S-meter, Full or semi QSK operation, Frequency presets, VFO A/B Split operation, RIT, configurable CW Offset, Configurable sidetone frequency and volume and can be connected to a GPS interface for reference frequency calibration and time-keeping (for WSPR beacon)!

Also super impressive is the quality of the 138-page long assembly instructions that make Heathkit style instructions seem abrupt! Nothing else comes close to the thoroughness of this document. As well as getting a radio that works, Hans clearly wants builders to understand how it works and why he chose the components he did. Prospective builders can download it freely from his site.

Firmware for the ATmega328P microcontroller is up to version 1.00B and available from the QRP Labs groups.io group. It is not open source.

Sputnik 60 years ago today

One of the clearest memories of my childhood is being taken up our steep driveway to the roadside out the front of our house from where there was a commanding view of the western and the southern sky. Sixty years ago today the Russians launched Sputnik and it would have been a few days after this that my father took me as a seven year old boy to watch as the satellite passed over Sydney. He must have chosen a clear night because I do remember seeing it as a fast moving bright light. What was even more impressive was that then my father took me back inside and turned on our radiogram and switched over to the shortwave bands and seemed to know exactly where to tune the radio to pick up the beeping sound of the satellite’s radio signal. The Sydney Morning Herald has just republished its coverage which captures the local mood at the time.

A Russian 400 kopeks stamp showing the Sputnik’s orbit around the Earth

There are youtube videos online claiming to reproduce the actual sound of the sputnik.
Wikipedia links to this sound, but the authenticity of this too is challenged. From the wikipedia entry on Sputnik 1 I learned that there is a direct link between the satellite and the internet. The launch was brought forward to sync up with and maybe upstage the IGY – International Geophysical Year – which began in July 1957. The Soviet success and the US failure with Vanguard led to a major reassessment of the US approach to science & technology. One of the first responses from the US to this challenge to their technological and scientific prestige was to set up ARPA Advanced Research Projects Agency, later DARPA in February 1958. Australia followed the US lead. My generation saw a boost to science education. One of the scientists quoted in the Sydney Morning Herald report, Harry Messel, went on to edit the amazing ‘Science for High School Students’ textbook for high school which I devoured and almost memorised by heart.

The science textbook Harry Messel convened in the wake of the Sputnik crisis for Australian students.

I stumbled across a 55 minute long documentary on Sputnik ‘The Story of the Sputnik Moment’. It’s full of contemporary footage that really evokes the time from the US perspective. From this doco I learned that ‘Leave It To Beaver’ premiered on the same day! This was a popular program in our home – my parents thought I was a double for Beaver, but so did many others as I do remember there was a Beaver lookalike competition even here in Sydney! Anyway this video includes sound of the sputnik. It also echoes in reverse the current impasse with North Korea. There is almost identical footage of marching Soviet troops, admittedly with slightly less energetic steps. But the threat is the same. And the issues impingeing on the technological struggle such as the US civil rights fight remind us the civil war didn’t ever really end.

This is a flight-ready backup of Sputnik 1, on display at the Kansas Cosmosphere in Hutchinson, Kansas

If anything my father seemed more impressed by the achievement than fearful for what it might mean about global nuclear war, but really what would I have known as a seven year old!?! I do remember he had a friend at his work, Tullochs a railway rolling stock and steel building material manufacturer, who was a radio amateur. It was most likely this ham who gave Dad the info he needed to tune into the signals, although I believe it was probably included in newspaper stories. This was probably the same man he took me along to meet after I had started building radios as a 12 year old. I think his name was Bob and he lived in Ermington or thereabouts. I don’t remember his call but I do remember that he had built all his gear and operated exclusively CW on 20 metres into a dipole in his modest backyard, to keep in touch with friends back in the UK where he’d emigrated from.

What I know now as well is that 1957 coincided with the best radio propagation conditions ever. It was the high point of the best solar cycle, so the few feet of copper wire hanging in the air as an antenna would have had no trouble pulling in the 1 watt signal from Sputnik. And of course background interference would have been minimal compared to today. So maybe I’m mostly nostalgic for the quieter and yet more lively radio conditions of times past.

What’s great about this memory is that it’s clear my father had a strong sense of the significance of the event and my potential interest. Even though he wasn’t a technical person he was quick to sense my interests and encourage them. Maybe it would have been hard to miss noticing the young me in the backyard hammering away at a piece of metal downpipe trying to fashion a rocket nose cone! From this day on I remember being given How and Why Wonder Books about rockets and science, and avidly collecting cards from Nestles chocolates for their ‘Adventure in the Sky’ album.

Cover of ‘Adventure in the Sky album published by Nestle to encourage kids like me to buy more chocolate bars to collect images of planes and rockets!

From reading about the launch it’s apparent that what we probably actually saw was the larger remnant of the R-7 rocket that followed the satellite into orbit. It was first magnitude compared to the Sputnik’s sixth magnitude size and brightness in the night sky. That knowledge however doesn’t dim the excitement I remember.