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I didn’t plan to produce a schematic of the Nano-40, the tiny 40m CW transceiver I built based on Roger G3XBM’s 80m XBM80-2 design as modified by Alan VK2ZAY as I don’t claim any originality for the circuit. I provided the original sources and discussed the changes I made to the circuit and thought that other builders would follow the same path.

However I have been asked by a couple of people already if I could provide a schematic so I have patched a copy of the circuit diagram produced by Alan to show what I ended up with. I hope that will keep everyone happy, but please remember that without Roger G3XBM’s genius and Alan VK2ZAY’s improvements the Nano-40 would never have happened.

A few weeks ago fellow blogger Dominic M1KTA wrote that he was selling off some unwanted projects from his shack, including some unbuilt or part-completed kits. A little while ago he wrote: “I have decided to stop selling off project builds now and I am keeping hold of everything until a rally when I can sell them in person as I have had a complete nightmare after selling one of the projects over the internet to someone I believed was capable of finishing it and has demanded I rebuild and re-align it after they hacked about with it themselves to the point where it no longer functions, they melted the pcb connectors and filed away part of the pcb and at least one track in the process to attempt to squeeze it into a box that was too small and demanded a paypal refund. I am never again selling a ‘built’ project over the internet it is too risky for me.”

I have bought things before, either at rallies (hamfests) or from ads in RadCom, that were found not to work and sometimes revealed some astonishingly ham-fisted handiwork inside. The purpose of some modifications defied understanding. I either fixed them myself or wrote it off to experience.

The idea that someone could buy an unfinished kit and then try to make the seller liable for their inability to complete it just beggars belief. It seems some members of this hobby have no shame and no pride.

I told Dom he should publish the callsign of this so-called amateur as a warning to other sellers to steer clear. I know I would.

Today I finally completed the little 40m CW transceiver based on Roger G3XBM’s 80m XBM80-2 design as modified by Alan VK2ZAY and further modified by me to work on 40m. I tried to think of a name for it that would acknowledge both these sources of inspiration, but I couldn’t come up with anything snappy, so in the end I named it the Nano-40 because it is very small and works on 40 metres.

The circuit is essentially the same as the one given by Alan VK2ZAY with a few component changes determined empirically while the rig was on the breadboard to allow for the fact that it is working on 40m instead of 80m. There is only one stage of low pass filtering instead of two, as I described in an earlier post. This seems to be quite adequate. I checked the output waveform using my new oscilloscope and it looks nicely sinusoidal. I also used an MPSA13 Darlington transistor instead of a 2N3904 in the audio stage for a bit more sensitivity and gain.

With the component values I chose the little rig gives 150mW output on a 12V supply or about 75mW using a 9V PP3-style rechargeable battery. There is no sidetone, but it has full QSK. Using my Elecraft XG1 test oscillator I found that a 1uV signal is just about audible. However, bearing in mind that you can receive all activity around 7.030MHz plus and minus the limits of your hearing, a workable signal would need to be a bit stronger to stand out from the crowd!

The circuit was built on to a small piece of Veroboard and the result is shown above. In case anyone wants to try to replicate it, the reverse side of the Veroboard showing the breaks in the copper is shown below.

The rig was built into a small translucent blue project box. The box I ordered for the project turned out to be just a bit too small for comfort. It was not quite high enough for the crystal, so I had to cut away part of the circuit board so the crystal could be mounted with its base below the board itself. The space was also a bit too tight for the connectors. Consequently final assembly took much longer than it would have done using a larger enclosure.

A fair bit of “fine tuning” with a file was needed to adjust clearances which were down to the last millimetre. With the lid on there is not enough room for the spring loaded contacts of the two 3.5mm jack sockets to fully open so the key and earpiece plugs are a tight fit. There was not enough space for a power socket to be fitted internally so after a lot of thought that was eventually resolved by super-glueing a PCB-mounted power socket to the side of the case.

Although I had tested the circuit prior to assembling it into the case there was a heart sinking moment when I applied power and heard no signals at all. Close inspection showed that I had a solder bridge across the antenna socket. This was quickly removed and then the transceiver was found to perform as well as it always did.

I have put out a number of CQs with the little rig but have yet to make a contact with it. Because I don’t live in a densely populated area I don’t have any nearby hams to make a sked with to prove that it really works. You don’t build a rig like this to make a lot of contacts, of course, you do it to prove that it is possible to make a fully functional transceiver this simple and this small. Nevertheless I do hope to make a QSO with my little Nano-40 one day.

There was a knock on the door this morning and the postman asked me to sign for a parcel from overseas. The customs declaration amusingly – if appropriately – described the item as “Toy”. It was the UNI-T UT-81B Oscilloscope Digital Multimeter that I ordered last weekend from eBay seller hk360radio in Hong Kong.

My first thought on opening the box was: “Wow! All this for a hundred quid? Amazing!” Inside the zip-up fabric carry case was the scope/multimeter, test probes, a BNC oscilloscope probe adapter, an opto-isolated USB cable for connecting the instrument to a PC, a two-pin wall-wart power supply and a two-pin to UK three-pin mains adapter, manual and CD containing the PC software.

The instrument is both a multimeter and a storage oscilloscope. The multimeter is auto-ranging, so the control switch simply selects the function: voltage, current, resistance etc. It measures DC voltages to 1000V, AC to 750V, current to 10A, resistance to 10M, capacitance to 100u and frequency to 10MHz. There is also a continuity tester. It can read volts down to 100uV and current down to 0.1uA. The frequency counter accuracy isn’t good enough to calibrate your radio, but it’s still quite handy.

Many years ago, back before I had a ham radio license, I had an oscilloscope that I built from a design in Radio Constructor magazine. It only covered up to about 200kHz and wasn’t calibrated. I had to sell it when I left my parents home and had nowhere to keep so much electronic stuff, and I haven’t had one since. But there have often been occasions when I wished I had one, so that was one of the main reasons for buying the UT-81B.

The oscilloscope bandwidth of the UT-81B model is quoted as 8MHz, so I can’t use it as a monitor scope for the whole of HF, but it covers up to 40m at least. I was very keen to try this. I connected my FT-817 up to my QRP power meter via a T-piece and connected a cable between that and the oscilloscope. When I spoke into the microphone I could see the modulation envelope on the display.

I was interested to see whether the horizontal scan rate was fast enough that I could see the actual RF waveform. I increased the timebase speed until I was able to see the display above of the carrier wave from the FT-817 in CW mode. The sample rate is given as 40MHz and you can just see that the waveform is a little jagged. You can see that the scope has also displayed the frequency to within 1kHz. There is a full range of trigger functions and also a manual hold you can press to capture the display, which I used to take the photo above.

There is a Windows software application that connects to the instrument via a USB port. It can log measurements over time and also capture scope displays and save them to a bitmap (BMP) file. I was able to capture the waveform shown in the photo. However it was not able to capture an RF modulation envelope when sampling the RF at a much slower time base setting. I just got a thin wiggly line that seemed to bear no relation to the envelope displayed on the scope itself. Not a major issue, though.

I am really delighted with my new “toy”, which cost me £95.50 plus £13 for the shipping (and no tax.)

Suppose you were a member of a village football team that had practised and played on the village green for years. And suppose that one day you turned up for a game and found a new rugby team using your pitch. You’d be pretty annoyed, wouldn’t you? Even though the village green is common land and so legally there for all to use, the football team would not expect its use of the football pitch established over many years to be usurped in this way. So it isn’t all that surprising that when it is, there’s a punch-up.

Turn now to the amateur bands and this is precisely what has happened to users of the Olivia data mode. Someone has turned up with a new game called ROS that requires a much larger pitch and it is interfering with the Olivia users’ ability to play Olivia.

OK, you say, but surely no-one could object to the rugby team using the football pitch when the football team isn’t using it? It’s a fair point, although as the football team uses the pitch off and on throughout the day they wouldn’t be happy about it. But here the analogy starts to fall down, because not only do the football team (Olivia) and the rugby team (ROS) not speak the same language, but they are also blind so they can’t see each other to ask even if they were able to.

The only way for the two teams to both play on the village green without falling over each other or resorting to fisticuffs is for each of them to have their own, separate pitches. Now could someone please translate this into Spanish and show it to the coach of the rugby team?

A few weeks ago I made a rubber duck helical antenna for my TH-F7E. I didn’t get around to writing about it at the time, plus it took a while to get some reports of its performance.

Well, it works extremely well, and I have just added a description of how to make it to the main G4ILO’s Shack website. See A DIY Ducky for 2m.

I’d sworn I wasn’t going to post any more about the ROS digital mode, or even mention it by name again, but the latest bizarre twist in the tale is too much to resist. Here’s the story.

On March 3, Dave AA6YQ called the FCC to confirm whether the statement that ROS was now legal for use in the US which had been posted on the ROS website and which I wrote about on Tuesday was true. The FCC advised that the information (which has since been removed) was not true, and that the matter was still under review. Dave was told that the ARRL was involved and would publicize the outcome. This they have now done, and the outcome is that ROS remains illegal for use in the USA on frequencies below 222MHz.

ROS may still be legal in the rest of the world but I have to ask whether amateurs in Europe and elsewhere really want to be using a mode developed by someone who posts false information and rude remarks on his website and issues threats to any amateurs (including myself) who dare to make any statement against his mode. This is not mature, responsible conduct nor is it in the spirit of amateur radio. We don’t need this sort of behaviour which has come close to bringing the hobby into disrepute. It might be for the best if everyone stopped using ROS altogether. It isn’t as if there aren’t already plenty of other digital modes. And be honest, a mode that offers no chance of working any North American DX is not as interesting as one that can, is it?