Blog

Musings, small projects, curios & what's new.

JUNE 25

Ladybird Radio

I decided to temporarily replace the ferrite-cored coil with an air-cored one from a very basic crystal radio. that has no variable capacitor and is tuned instead by changing the length of the coil, and hence its inductance, by means of a nail attached to a wire. This in effect provides a tapping point that I was able to use for the Ladybird radio, so after connecting the coil to it, I just held the nail firmly for a good contact near the output end of the coil and tuned the radio the normal way. It  worked just fine, unsurprisingly, both with and without regeneration.

I did try to use this coil without a tuning capacitor and tune the Ladybird radio by moving the tapping point, but was not successful, presumably because I was changing the inductance of both sections of the coil between the tapping point and coil ends.  What is needed is a second, stationary, tapping point to fix the length of the output part of the coil. Will add to my to-do list...

MAY 25

Ladybird Radio: new picture showing the changed transistor biasing to the first audio stage transistor and a resistor to eliminate the potentiometer that isn't being used.

Disappointing outcomes with some other old devices

Buoyed by the successful rescue of an old Android phone (see below), I've just tried some other old devices that have been lying forgotten in the e-graveyard storage box. Unfortunately, for different reasons, I have been disappointed so far in my attempts:

•  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! Now the only hope I have of being able to use this device is if said family member recalls the password after all this time! Thwarted by an over-zealous approach to security - contrast that with the ease with which I was able to take over an old laptop recently from another family member! 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

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. 

Years' ago, when I had an Android phone with external storage, I'd do this by connecting 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 CD-ripping and -playback 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 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. 

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 wifi 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 (see below) 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.

So far, so good, then and it's an obvious solution really. And it hasn't cost a penny! Why didn't I do this before? Well, my last Android phone - a Samsung Galaxy - was stolen while I was going through security in Faro airport before flying back to the UK. Perhaps I would have used that when I first moved to iPhones, but the Moto G had already been unused and languishing for some time in a box in the garage and it hasn't occurred to me to use it until now. Instead, 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!

So, the Moto it is for the time being. My ideal solution would also have a digital output so I could use the Onkyo's internal DAC. Perhaps I could build my own using a Raspberry Pi? That said, I'm no audio buff and the sound quality for now is actually pretty good to my ears, plus I now also have an old-school mp3-type player which has proved useful.

One other thing: the CD player in the Onkyo receiver was playing up recently: the tray was closing almost as soon as it had opened. I took the cover off the machine, but was unwilling to attempt to dismantle the player further to find the cause of the problem, presumably a dusty sensor hidden away somewhere. I vacuumed inside the player carefully and luckily for me, that cleaning and repeated opening and closing of the tray have fixed the issue for now. At some point, however, it will either need to be replaced, or I'll have to go fully digital as far as playback is concerned, although I've no plans yet to stop buying CDs, as I prefer to own physical media.

OCT 24

Updates to A Simple Model of Relativity . 

JUL 24

Some thoughts on a basic radio telescope project for the amateur inspired by memories of one in the 1970s.

JUN 24

Various recent updates to Ladybird Radio, including a possible explanation for its quirky design and a recent mod which means R5L can be easily received without using regeneration. Smooth Radio now also gone from AM in the UK. Also on the reception of SW on the Transistorized Crystal Radio. 

MAR 2024

Ladybird Radio - update to stations received; also to comments on the explanation of regeneration in the book. Highlighted in bold.

FEB 2024

New page -  A Simple Model of Relativity .

Ladybird Radio - update/correction to stations received - including Radio Caroline :-) - and some comments on the explanation of regeneration in the book. Highlighted in bold.

JAN 2024

Now getting the laser communicator to work with a higher gain amp.

NOV 2023

(Originally under What's New. Moved here May '25).

A massive new Pumped Storage scheme is under construction at Coire Glas in Scotland. It has 3 times the capacity of the one at Dinorwig in Wales, but even so, we'd still need around 10 of these to store just one day's worth of the domestic electrical energy requirement in the UK (and that's excluding losses due to conversion, transmission and plant outage).

OCT 2022 

(Originally under its own section in the menu at the left. Moved here May '25).

Pumped Storage

Some thoughts prompted by the move to renewable energy...

An often-heard criticism of reliance upon sources of renewable energy - specifically solar and wind power - is that they're no use when the sun isn't shining or the wind isn't blowing. This is not a trivial point - here in the UK, we do get such days nationwide, particularly in the winter.

Pumped storage schemes, whereby water is pumped from a lower reservoir to a higher one during periods of low demand and then released to flow back down and generate energy during periods of high demand, may look like a possible, if partial, solution. One such scheme is the Dinorwig power station in North Wales. The classic scenario for which it was intended is at the end of or during the commercial breaks of popular TV programmes when there is a rush to put electric kettles on to make cups of tea or coffee, i.e. to meet short bursts of high demand. However, it  can hold around 9 GWh of energy, enough for the daily requirements of about 1 million households, so can also be used for short-term storage. 

(Update: Nov '23: The Times reports that construction of a new pumped storage facility at Coire Glas in Scotland is underway and due for completion in 2030/31. The capacity is 30 GWh, roughly 3 times that of Dinorwig, enough for for about 3 million homes for 24 hours.)

I read a while ago about a proposal to install such a system on a small scale in a high rise tower and this led me to wonder - briefly -  if it might be a practical solution for use in (2-storey) homes here in the UK, where traditionally we have had cold water storage tanks in the loft. There's been a move away from these in recent years with tanks being removed when combi boilers are installed. What if these were left in place and adapted for pumped storage instead? Could they be of use, even if drawn on for brief periods only?

Let's assume such a tank can hold 200 litres of water and is 5 metres above ground level. The potential energy stored in the tank is the weight of the water (200 kg)  times the acceleration due to gravity (~ 10 metres/second/second) times the height of the water (5 m), i.e. 10k Joules. That's 1 kW for 10 seconds, so 1/360 kWh, barely enough to power a low energy bedside light for 40 minutes! By contrast, batteries provided with domestic solar power systems typically store several kWhs. 

Not surprisingly, it's a fraction of the energy needed to boil water for a cup or two of tea, say a half litre of water. To boil this amount from room temperature (perhaps 20 degrees C ) requires the mass of the water, 0.5 kg, times the Specific Heat Capacity of water, 4200 J/kg/degree C, times 80 degrees, i.e. 168k Joules. That's only around one 1/20 kWh, but is still about 17 times the potential energy stored in the cold water tank!

So,  it's a non-starter for our 2-storey home.  What about high-rise accommodation? Let's consider that water tank 100 metres up. In this case, it would store 20 times the potential energy, 200k Joules, enough to power that light for a little over half a day, and also now to boil that kettle! To provide that energy for all the households in the building, there would need to be a lot of water stored at the top, however.  Just think of the extra weight and the need to support it. Even if feasible,  managing peak demand through pricing would surely be a more effective solution. 

And anyone thinking that the problem of balancing supply and demand could be solved by simply building more pumped storage schemes should consider this:  in the UK we would need the equivalent of around 30 Dinorwig  power stations to store just 1 day's worth of electrical energy for domestic consumption alone and that's before considering any losses due to conversion, transmission and plant outages.

Back to those batteries used with domestic solar power:  those could keep an average home going for just a few hours - very useful in times of occasional power cuts of short duration, but much less so during a prolonged shortage of energy-generating capacity. EV batteries on the other hand can store 10s of kWhs of energy, enough for a household for several days of outages. It's an interesting idea to use these to back up domestic supply, even if it does mean people not being able to use their cars as a result. 

However, EVs are still very expensive to buy (even if much less so to run than petrol or diesel ones) and if we want to keep the lights on for everyone, then for the foreseeable future we'll continue to need to have substantial backup generating capacity in the form of gas turbines which can be switched on and off readily (unlike nuclear power stations).