Constructing The 1972 Ladybird Book Transistor Radio

If you're enjoying these pages and you have an interest in hobby type electronics or repair jobs, you might like to visit my other website www.usefulcomponents.com, where there are details of various components for sale and some good radio kits as seen below.

If you want to make a radio kit with modern parts that doesn't require soldering, I heartily recommend the following:

The HJW Electronics Choccy Block Six Transistor Radio Kit

This is a much more stable design than the final radio described in the 1972 book, and it uses no funny electronic tricks.
 
The HJW Electronics Breadboard Six Transistor Radio Kit

This is the same circuit as above, it is somewhat cheaper, and is quicker and easier to build.

The HJW Electronics Crystal Set Radio Kit

This comes with an additional single transistor option. Both the crystal set and the single transistor option are a whole lot better than those options described in the earlier sections of the 1972 book. All the kits are available in the HJW Electronics Amazon Store and on my HJW Electronics Pattern Site

Background From 2008

There's more recent information and pictures lower down the page.

Recently I was bought some Ladybird books for my birthday. I got "How it Works, The Computer," "How It Works, Television," and "The Story Of Nuclear Power," all of which were mid-1960s easily digested thin children's hardbacks. This encouraged me to buy, "Learnabout... Making A Transistor Radio," which I'd had as a kid. It certainly tought me one thing about how to make a transistor radio, that being one specific method which, try as I might, I could not get to work. So, as I happened to have all of the parts available, I thought that I would have a go at it in these enlightened times of the 21st century. Any excuse to blow out the dust from the 1960s germanium transistors drawer, after I'd writen my "Thankyou letters," of course.

Well you can see the pictures of the one I've made and the similarity to the illustrations in the book. There are some places where you could trip up. The OA91 diodes that I had would have been inserted the wrong way around if I'd followed the pictures, which show the 'red' end of the transparent OA91as being the anode. This is probably due to design changes over time, and in my modern diodes the end with the red encapsulated termination was the cathode. You can tell which end is really anode or cathode by looking carefully to see which end the point contact wire is attached to, and which has the germanium crystal on a little mount.

Ladybird Radio Extra Components and Diodes



I also found that the first audio amplifier stage was fully saturated with the OC81 transistors that came out of my drawer. This would probably not have been the case with a scabby old low beta OC71 in that position, but the transistor that I had there was quite good and so would not work correctly. Before you complain that I used the wrong type, the parts list text says that you can use any red spot audio transistor. Sorry Ladybird books, but transistor beta dependent design is bad design. The symptom in my set was very low audio level which could only just be heard when the R.F. stage was in full oscillation. The simple solution is to fit a 1K Ohm emitter resistor in parallel with a 22uF bypass capacitor to ground, instead of a direct connection to ground. That stabilises the D.C. operating point while maintaining the audio gain.

Ladybird Radio Schematic



Interestingly, there is a spare screwcup position just where these parts are required. They fit neatly between position 5 and the previously unused position 6. Perhaps these components were present in an original design and were removed in a misguided attempt to save parts before publication. The final stage does not suffer in the same way, partly due to it operating in a transformer coupled class-C fashion, where the stored energy in the inductance provides half of the output swing. It is rather distorty, but cheap on current.

I'm not sure why my attempt to build this in the 1970s failed so miserably. I suspect the problem with transistor beta mentioned above may have played a part, but I never even got mine to whistle. I do remember that the RF transistor that I had was a metal canned one. These were well known for failing even when "new," with internal tin whiskers growing out from the pure tin plating on the inside of the transistor can, and then shorting out to the internal leads of the transistor. Maybe that was my problem. These trannies were pretty ancient history even in 1977, so that wouldn't be too surprising.

The selectivity is very good indeed, though the whole set is rather 'live' and detunes a little when you move it or the short wire antenna. The setting of the reaction trimmer is, as stated in the book, a little tricky but neither of these phenomena stop the radio being usable, especially if you prefer one station. It's not stunningly loud, but I'm not going to grumble too much from 3 transistors.

Ladybird Radio Rear Components



If you were going to give the kids something to do for their science project at the weekend, then you'd avoid this design due to the ancient transistors and the fairly expensive Jackson capacitor. They are no longer available. There is something to be said about building something up completely from separate parts though, and the brass screwcup on softwood technique is solderless, cheap, and has a bit of olde worlde charm to it. A Radio 4 Longwave version might be interesting and this could dispense with the main tuning capacitor.

If you really want to make one of these in an authentic fashion for nostalgic or artistic reasons, the variable capacitor, transistors, and the big RFC are going to be a problem. (Date: 26-JAN-2026)

While making up this radio I found some other interesting things relating to the substitute parts list which is in the back cover of the book. High leakage low Vbe transistors, which all tend to go together in any given example can cause the output stage to do a miniature version of thermal runaway and cease to give any output at all. The transistor warms up a little then saturates, pulling 100mA or so through the D.C. resistance of the output transformer. The transistor and transformer usually survive, providing you're just using a small PP3 battery. Really, the output stage needs a low value emitter resistor and bypass capacitor like I've suggested for the previous audio stage. Using an OC71 here ensures that this shouldn't happen as there is some inherent emitter resistance and lower gain anyway. Also, I've had great trouble getting anything other than OC45s to work in the RF stage. OC44s and working AF116 or AF117s tend to go into high frequency oscillation rather than operate with usable regeneration. I think that this is due to them having higher Ft, basically more gain at high frequency, and coupling around the loose layout involved with the screwcup design results in unwanted high frequency oscillations.

I think what may have happened is that the Rev. Dobbs designed his circuit and used cheap basic parts with the minimum of extras and simplest layout. Then along came the book, and a need for more general parts, so someone else had a look through the 1971 Mullard data book to look for alternatives, suggesting the newer parts listed by Mullard as replacements for the cheap but obsolete items. Not realising that in this design, the 'improved' transistor parameters could leave the target audience in heaps of trouble.

Don't try to use plywood, MDF, a piece of solid oak from Grandad's wood shed or any other hardwood type substance as the baseboard. You will spend most of the afternoon trying to get the screws to go in, and get very bored when you find that the first hole that you've eventually mangled out with the bradawl is now too big for the screws to get a grip in. Some soft pine is what you want, and offcuts from the local DIY store are about 50pee.

Well, if I get bored again I might decide to try a few variations. Replacing the transistors with something more modern is simple enough, and it would be good to get rid of that Jackson dilecon, perhaps replacing it with a "Mr Slidey," variable inductance ferrite on a stick arrangement. It would need more screwcups and perhaps smaller, no.8 ones, but a second output transistor in a class B stage would get rid of that transformer as well. Beyond that, we're probably talking superheterodyne designs with IFTs wound on biro plastic. But at that point it would probably be getting a bit complex, a dual gang variable capacitor would be back in and the fun element would be rapidly disappearing.

Reflections In 2026

I certainly don't supply a kit for the original Ladybird radio any more, and the Jackson capacitors are definitely not still being made. I think I bought the last of them which were manufactured from the remaining stock of bits. The audio transistor problems are more to do with leakage due to ion diffusion over time than saturation due to high gain. I've tried replacing the diodes with Schottky BAT48s and they are OK. Replacing the big RFC with a 470uH SMCC ferrite cored inductor just about works. I occasionally still use this radio to test germanium audio transistors and OC45s, after they've had a go for D.C. parameters on an Atlas DCA55 tester. Don't rely on a standard multimeter to test germanium transistors. They assume a silicon Vbe of about 0.65V and take no account of leakage. This tends to give you a massively inflated Hfe reading. Pictures of the radio as it currently exists, and a short video follow shortly.

How is transistor leakage Ice0 defined? It is the collector to emitter current with the base open circuit. That's from the 1960s Mullard valve and semiconductor data book, so if it sounds a bit unfair for normal in-circuit use, tough. That's the definition. The 0 in "Ice0" is a zero for zero base current, whether that's going into the base or being pulled out of the base due to the bias resistors.

Did I mention the ferrite rod mounting method? It's so tempting to use two loops of non-insulated wire, twisted around and secured under two screwcups. That would be two shorted turns on your ferrite rod which would eat up a lot of the signal. Gosh. That's exactly what's shown in the book! I just tried it, and you'll see it used above in my 2008 rendition. On this radio it's not so terrible, because the regeneration compensates for the loss. It's also used in the crystal set earlier in the book though. In that situation, or this, no. Use something non-conductive like the PVC sleeving shown below.

The Completed Ladybird Radio Front Angle, Now With New Improved Chicken Head Knobs



The Completed Ladybird Radio Rear Angle Showing the Current Components

The Completed Ladybird Radio Showing OC45 and OC71 Transistors

A leakage measurement of 340uA on an OC71 is not good, but it will still work.



The "Using The Radio," Text From The Ladybird Radio Book Page 48



The Schematic Diagram Of The Final Regenerative Reflex Transistor Radio From The Ladybird Book

Ink, other than bright pink is clearly at a premium in 1972, as printing a zero before .01uF was deemed unnecessary. Worse, the variable capacitor has the correct preceeding zero shown, "0.0005uF." Sometimes, in fact often, you'll see 1960's electronic hobby books where a capacitor might just be labelled "100," and you're supposed to know if that's 100pF rather than 100nF or 100uF. Maybe. Such laziness drives me crazy. How are you supposed to know unless you're an electronics engineer?  Is that too picky? You'd be surprised. Passenger aeroplanes have fallen from the sky due to such omissions, and it confuses everyone else. Reference? Mentour Pilot on YouTube, who know's his stuff and does fab detailed videos including The Varig Flight 254 Crash. Also in that episode, some fascinating insights on longwave radio beacons and night time LF propagation.

Click here for A Short Video Of The Ladybird Radio Working

I'll see if I can dig out a picture that I took down a microscope of the insides of a hairy AF117. Yes, I can:)

A Hairy Tin Whiskered AF117 With Scale

This was taken down a decent stereo microscope by putting a mobile phone camera up to one eyepiece. Not great, but not terrible.



Tin Whiskers Growing On The Insides Of An AF117 Can

You can actually see where some of the whiskers are penetrating the non-conductive gel, so filling the can with delicious jelly didn't work, did it Mullard? I got inside some of these by de-soldering the can. The picture shown is not atypical. Most of them are like this to some extent.



Tin Whiskers On The Outside Of A Hairy AF115

This was in an old Roberts radio. Most of them have probably dropped off, but the whiskers can grow on the outside as well. The last time I did some research, even NASA didn't understand the exact mechanism for this peculiar phenomenon. In the past, it has been known to disable satellites when relay contacts have become shorted across. Using very pure tin plating seems to encourage it. You can see some extraordinary examples elsewhere online.



Henry's email address

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