Practical Wireless mini-two radio

This radio project appears in a nicely-presented article starting on page 332 of the September 1969 edition of Practical Wireless Magazine. I first came across it, perhaps during a wet break, in the school library during my first term at secondary school in that month and year. I recall reading and re-reading the article with fascination - a real working miniature radio that I could build all by myself!

No doubt the inspiration came from commercially-available micro radios of the time, such as this one, claiming to be the world's smallest radio, from Sinclair Radionics. I suspect the makers of these radios wanted to give the impression that they were miniaturized fully-functional radios rather than the minimalist ones in very small packages that they actually were.

To make the most of the two transistors in the mini-two, the designer eschewed reflexing in favour of (a limited amount of) regeneration, using a gimmick capacitor consisting of a pair of insulated wires twisted together. Since this was inside the case, it would have meant taking the cover off in order to optimize reception for each newly-tuned station!

A complete lack of technical know-how on my part didn't stop me from buying the components, including the hairgrips box (the contents of which may be of use to our longer haired friends, as the author put it) for the container, and obtaining a soldering iron from a friend who was also intrigued by the radio. However, the project had a long gestation and I didn't get around to building it until the mid-1970s.

After all those years of anticipation, I was disappointed to discover that I could only pick up one station with it and only that after wandering around the house trying to get a signal, fiddling with the controls as I went. Sadly it was put to one side before being discarded some time later during a clear-out. Perhaps if I'd persevered, I'd have got more out of it. On reflection, it seems pretty impressive that it could receive any station without an external aerial. 

Fast-forward to a few years ago and I was curious to compare its performance with some other minimalist radios I've been playing with, notably this one that uses a Darlington Pair transistor so I attempted to re-create it. Getting hold of the specified transistors was no problem. To save time, I opted to use the the coil and tuning capacitor in a Maxitronix crystal radio and connected that to a breadboard containing the required components. (IIRC, I used the small winding of the coil to take the signal to the circuit). I used two slightly depleted 9 volt batteries for power, giving around the required 15 volts. I dispensed with the gimmick capacitor and instead used a 25 pF trimmer, no longer being interested in the miniature aspect of this radio.

It did pick up BBC Radio 5 Live, possibly Talk Sport, and others at night, but in order to do so, it had to have an aerial connected to the larger coil, no doubt because there are far fewer MW stations around these days, so we can no longer rely upon the presence of powerful nearby transmitters. Some regeneration was always needed. It was somewhat fiddly to tune. There was some background whistling, not surprisingly, and reception was dependent on the position of the aerial. Volume was acceptable.

Overall, I'd say that while the radio has an interesting design, it's really  a curio of limited usability. As for being an ideal project for the beginner, regrettably, I have to disagree with the author - as a newbie, after all that hard work, the last thing you want is disappointment! Perhaps the series of articles in PW entitled Simple Receivers for Beginners beginning in June 1968 would have been a better starting point?

Old devices refusing to be repurposed

(Originally posted on the RetroMat site in May 25, but sits better here). 

Buoyed by the successful rescue of an old Android phone (see below), I've just tried some other old devices that were lying in my electronic junk box, but unfortunately, for different reasons, I was unsuccessful:

•  Another Moto smart phone, different model, that simply fails to power on when connected to a power supply. Plug and phone get vaguely warm and when disconnected, there's a brief flash from the light at the front. Cause: battery failure.
•  An HTC Desire phone from around 2010. It starts promisingly: the battery gets charged, the phone powers up and displays a logo and vibrates and buzzes loudly, but the screen goes blank after a while. Sometimes it comes back on and the buzzing is repeated insistently, but it won't  go beyond that initial screen. Suspecting the removable battery could be at fault, I've checked it with a multimeter, but the voltage was pretty close to the specified value. I've been able to get to the Android menu by pressing and holding volume down and then the power button. I've then tried a few of the options there, such as erasing data, selecting the 'rescue' (reset?) option and even 'fastboot', whatever that is, but all to no avail. Back it goes into that box! Cause: hardware failure of some type.
• A Hipstreet W7 tablet. IIRC, this came free with a phone contract many years ago. No-one found it remotely useful at the time, so it was consigned to the box of unwanted devices soon after. Perhaps it could find some use at last as a media player? When plugged in, after some time, it starts up and displays a family member's name and a password prompt. There's a reset button, but all that does is restart the tablet, not reset it to factory settings. It seems, in order to rescue the device, it needs to be booted up with a previously-created rescue 'disc' in the usb port. Needless to say, there isn't one. Unfortunately, but not unsurprisingly, said family member doesn't recall the password after all this time. Cause: security policy.
• A 4 GB Sony Walkman (NWZ-A816) from around 2008. It was used often until I had my first smart phone a few years later. The battery had started to expand a while ago, so it was removed and disposed of at the recycling centre. It still powers up, though, if plugged into a power supply by USB cable. It can even be made to continue to function as a media player (music, photos, videos).  What it steadfastly refuses to do, however, is to reliably accept files that I try to transfer to it from my laptop - I keep getting message libmtp error: could not send object. IIRC, I had a similar message when trying to send files directly to the Moto G rather than to a MicroSD card mounted locally on my laptop. It's quite possible that the problem arises from the file transfer protocol as implemented in my laptop's OS (Linux Mint). However, given the limited usefulness of the device (small capacity, no battery, no support for flac files!), it's probably not worth pursuing further. Cause: incompatible standards?

Repurposing an old Android phone

(Originally posted on the RetroMat site in May 25, but sits better here).

For some time, I've been looking for a way to play my digital media through my Onkyo 'hifi' receiver from 2006 which has no USB port or SD card slot. I like the machine - it sounds great, is solidly-built and as well as a  CD player, has a radio, including MW, which I use for receiving distant stations. We have a Chromecast Audio that can be connected to it for on-line audio streaming. In all other respects, it meets requirements and I'm in no rush to replace it.

(I tried using an old QNAP NAS system, but it was a faff. IIRC, I was able to use it from our TV, using twonky, a now defunct standard, but would have had to move the receiver to the TV in order to connect the two and that wasn't convenient. Plus the TV won't play flac files. I think I tried using the NAS from my phone and casting from there, but couldn't find a way to stream from the NAS and instead had to download files. After that, I just gave up).

Years ago, when I had an Android phone with external storage, I'd connect the phone directly to one of the inputs. Since then, I've had hand-me-down iPhones and can't do that and my digital media has been restricted to my laptop.

There are impressive looking machines from Brennan. In time, I'd like to rip (losslessly) my entire CD collection, so one of these could make sense. However, they are bulky and somewhat over-specced for my needs: first I already have a CD player in the Onkyo, second I can rip CDs on a PC, and third, I don't really require all the high-tech connectivity they provide.

I could use a modern mp3-type player, but don't want or need a high-end device from the likes of Astell & Kern, or FiiO. Sony Walkman's are within my budget, but you have to pay up considerably if you want a decent amount of (non-expandable) internal storage. Plus, as with smart phones, such devices seem to be intended to be disposable, having batteries that may not be easy to replace.

For now, I've decided to re-use an old Android Moto smart phone with a MicroSD slot, with support for up to 512 GB of storage. I wasn't overly-optimistic at first that this would work after so many years. In fact, two other candidate phones couldn't be started. However, as I began to charge this one, it started OK and the battery seems OK. I've removed or disabled as many apps as I can, disabled wi-fi and bluetooth and as there's no  sensitive information any more, I've removed the screen lock, leaving what is in effect just an mp3 player. The google search prompt won't budge, but it's not a big deal. For now, it has just a 4 GB card in it and it's being used to play a mix of mp3, wav and flac format files. I'm planning to replace the card with a much larger one - how well it scales up in practice, we shall see.

Two-colour movies using a single filter?

A short movie from 1930, The Devil's Cabaret, popped up in my YT feed recently. It's an early-ish MGM talkie filmed in early-ish two-colour Technicolor. It's pre-code, well worth watching in its own right. Colour and sound are actually quite good. Anyway, it's prompted me to take another look at my old item on the Friese-Greene process, also in two colours.

Two things stand out:

First, each film frame in the former process is in 'full' colour, whereas each frame in the latter process is in a single colour, complementary to that of its neighbours and relies upon persistence of vision to achieve an impression only of colour, making it more of a curiosity, as it can't have been easy to watch at the time. (Luckily for us, the modern F-G digital print doesn't do this).

Second, was I really correct in saying that the camera used in the latter process had a red filter alternating with no filter at all? I made that statement having recently seen the TV programme, but now all I can see online is that Claude F-G used the same process (Biocolour) that his father had invented, with a camera using red and green filters alternately. I would have thought that two filters would have made it easier to provide good colour reproduction in the final print, as well as better mechanical balance for the camera. I'll just have to see if I can find The Lost World of Friese-Greene documentary...

Core memory plane - please help identify!

Following on from the project mentioned below, which uses two transistors and four resistors to store one bit of data, I remembered I have a core memory module where just one ferrite ring does the same job. (Clearly, transistors had to shrink in size a fair bit before core memory like this could be replaced). And data is retained if power is lost! I bought it some years ago on eBay and was told at the time that it came from a computer at a ground station that was part of the network used to track Apollo missions. Unfortunately, I have no more details and have been unable so far to identify it, so please let me know in the comments section below if you recognize it!

It contains 48x64, i.e. 3072, ferrite rings for storing 3k bits of data. On one face, the sides are numbered 1 to 4 in ink and there is some text, also in ink: 363-105, an identifier perhaps. One of the corner holes is highlighted in yellow (paper triangle on one face, paint on the other), presumably to indicate the correct orientation for mounting it in a stack of identical modules. It looks like it was made in a workshop rather than a factory, suggesting it could have been a prototype or from a small production run.

Vintage binary electronic adder & counter project

Spurred on by memories of a large electronics project from my school days, there are two new pages on my RetroMat site: one about the project and background and one about the NOR circuits behind it.

Start and end of the seasons

Some musings originally posted on the RetroMat site in October last year

As we approach Halloween, I am reminded again of the wisdom of the ancients here-abouts who deemed this time of year as being (approximately) when Autumn ends and Winter starts.

Considering the hours of daylight, it makes so much more sense to have Winter starting at this mid-point (more accurately in early November, closer to Bonfire Night* here in the UK) between the Autumn equinox and Winter solstice, rather than as we do now, at the Winter solstice itself, especially as the latter is also known as Midwinter's Day.

(*Celebrating the foiling of the Gunpowder Plot of 1605, but no doubt replacing an earlier seasonal festival).

Similarly, for Summer, which should begin in early May, rather than at the Summer solstice, also known as Midsummer's Day. By the same logic Spring should start in early February, at the mid-point between the Winter solstice and Spring equinox and Autumn should begin in early August, at the mid-point between the Summer solstice and Autumn equinox. This would still mean four seasons of around 13 weeks' duration each, but they would now be centred on the solstices and the equinoxes.

Not surprisingly, these dates were regarded as being important enough to be given names. Also, not surprisingly, the Christian Church would have attempted to assert itself by replacing these pagan (for want of a better word) festivals with Christian ones, so we have:

• end of Winter/start of Spring: Gaelic: Imbolc, Welsh: Gŵyl Fair y Canhwyllau (Mary's Festival of the Candles), equivalent to the English Candlemas, a Christian feast day, presumably replacing an earlier one
• end of Spring/start of Summer: Gaelic: Beltane, Welsh: Calan Mai (first day of May),  English May Day, German: Walpurgisnacht
• end of Summer/start of Autumn: Gaelic: Lughnasadh, Welsh: Calan Awst (first day of August), English: Lammas or Loaf Mass Day, again a Christian feast day, presumably replacing an earlier one
• end of Autumn/start of Winter: Gaelic: Samhain, Welsh: Calan Gaeaf (first day of Winter), English: Halloween for All Hallows Eve in the Christian calendar.

Interestingly, in Welsh, the month of June is Mehefin, mid Summer, and July is Gorffennaf, end of Summer. October is Hydref, the same as the Welsh word for Autumn, although for consistency we might have expected it to be the equivalent of end of Autumn instead.

Here are all the months of the year in Welsh, their equivalents in English and meanings where applicable (sources: here and here):

        Welsh         English Meaning

1. Ionawr                 January -
2. Chwefror                 February -
3. Mawrth                 March -
4. Ebrill         April                -
5. Mai                 May -
6. Mehefin                 June                Mid Summer
7. Gorffennaf                 July End of Summer
8. Awst         August -
9. Medi         September Harvest
10. Hydref                 October Autumn
11. Tachwedd         November Slaughter (of animals for Winter)
12. Rhagfyr                 December Fore-shortening (of days)

I think it's interesting to note that the names of months 1 to 5 and 8 are the equivalents of the names in the usual/standard Western calendar, while the others are either descriptive of the time of year or describe an activity associated with that month. I wonder whether an old name for May could have been the equivalent of Start  of Summer?

Manned mission around the moon - 1955 style

This popped into my YT feed a little while ago. It's from 1955 and in part describes a very futuristic manned mission around the moon, a mere 13 years before Apollo 8 did just that, yet the two missions couldn't be more different in concept.

The following day, I learned that Artemis II could repeat that mission as early as February next year (2026), although unlike Apollo 8 and like the fictional mission, it will go around the moon rather than orbit it.

Telstar in 1915?

Wow - first, a depiction of a spaceship of the future on a cover of The Electrical Experimenter magazine from 1915 and second, communications satellite Telstar 1 from nearly fifty years later!

After a hiatus...

Now picking up this blog again after nearly 20 years!

I created this blog in 2007, posted a couple of items and promptly forgot all about it!

Now, I see a use for it, as a way to complement my RetroMat website with smaller posts, to promote that website and to get feedback.

Constructive comments welcome - either against a relevant post, or below, as appropriate.