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TRF RADIOS
Part 7
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Part of the Ladybird radio
                  circuit


AMATEUR RADIO                                BRMB Radio Birmingham

LINKS to Other Great Websites


The Ladybird Transistor Radio by Dave Bullimore

Ladybird
                      Transistor Radio by Dave Bullimore
The Ladybird Transistor Radio using Germanium Transistors by Dave Bullimore


Hi Mike,

I discovered your excellent site a little while ago, and I was very interested to see the Ladybird radio mentioned. I built one of these as a teenager back in the early ‘80s, and loved it. Sadly, it didn’t survive very long as I needed the parts for other projects, and ever since I have wanted to build another. Finding the original parts are very difficult to obtain, I decided to challenge myself to see if it were possible to make a version of the Ladybird radio using modern silicon transistors.

For the project to remain valid, I decided that the original Ladybird circuit should remain unchanged, and only the bare minimum of component value changes allowed. In the end, I found it only necessary to alter the values of five resistors, and change the semiconductors. I also used a modern tuning cap.

The radio works well, but as I didn’t have a germanium version to compare it too, I decided to build one of those as well!! I have noticed some interesting comparisons between the silicon and germanium versions:

The germanium radio needs a decent length aerial to produce any amount of volume, whilst the silicon one works much better with just an earth connected.

The silicon audio amplifier is rather unstable, and tends to break into oscillation at higher volume settings, especially without the earth connected. I found a 0.01uF capacitor connected directly across the primary of the LT700 makes the amplifier much more stable. On the germanium version this made very little difference.

The silicon radio seems to prefer a slightly lower battery voltage, say about 8V. I used an 8.4V NiMH PP3 battery rather than an alkaline one.

The silicon radio takes about 20 seconds to ‘warm-up’, presumably due to the 680K resistor taking time to charge the 100uF cap.

Finally, the output OC71 on the germanium set does get rather warm, especially when there is little or no signal.

I have attached some photos, and a schematic for the ‘Silicon Ladybird’. You are more than welcome to use any of them on your site.

Keep up the good work!!

Kind regards,

Dave Bullimore.
Derby, UK.

September 2013

Ladybird Transistor Radio by Dave
                          Bullimore
The Ladybird Transistor Radio using Silicon Transistors by Dave Bullimore

Ladybird Transistor Radio by Dave Bullimore
The Ladybird Transistor Radio using Silicon Transistors by Dave Bullimore


Ladybird Transistor Radio by Dave Bullimore
Close up of the Tuning Capacitor arrangement by Dave Bullimore


Ladybird Transistor Radio by Dave Bullimore
Schematic Circuit Diagram of the Silicon version of the Transistor Radio by Dave Bullimore



Ladybird Transistor Radio by Dave Bullimore
Prototype of the Transistor Radio by Dave Bullimore


Ladybird Transistor Radio by Dave Bullimore
Both versions of the Ladybird Transistor Radio
Germanium version is shown at the top, the Silicon version at the bottom. By Dave Bullimore



Hi Mike,

I stumbled across your site and was really impressed by what you and your contributors have created. I was particularly delighted to see the Ladybird Book radio, which, like many other of your contributors, I had attempted to make as a child, but didn't have the parts, or, to be honest, the know-how or help available. Wouldn't it have been great if we'd had the internet in the early 80s! Anyway, it motivated me to pick up a hobby I've done very little with for over 20 years and, with the advice from your website, having recreated some ZN414 circuits, I then decided to attempt the Ladybird.

So I was particularly pleased to see Dave Bullimore's version using silicon transistors, something I had previously wanted to try doing, but wasn't sure where to start. I used the screws and caps method used in the book, as Dave did, which I found very satisfying (have never really liked soldering), but, because of the shorter leads of modern components, had to use a different layout, corresponding more closely to the schematic. The circuit worked, but was, as Dave describes, quite sensitive and prone to oscillation. So I've made some further changes to the circuit, which departs more fundamentally, but is now very stable, but still sensitive.

I used it as an exercise to try to apply what I could remember about transistor biasing from a course at university, but there was an element of trial and error, not least because I wasn't really sure how to deal with the two forward biased diodes in series with each other, in parallel with the base-emitter junction of the first transistor. I have increased the bias current through it, but moved the base resistor to the collector to give it more stability and beta-independence. I also added an emitter resistor and bypass capacitor to the second transistor, and changed the resistor values to put the collector at about half the supply voltage, with a quiescent current of around 1mA. I also added a low value emitter resistor to the third transistor, but reduced the bias transistor to give a quiescent current of around 10mA. I didn't bypass this one, as it seemed loud enough, and I felt a bit of negative feedback wouldn't hurt. I'm sure someone more expert in biasing could optimise it further.

Dave fitted a low value capacitor across the output transformer primary to avoid high frequency oscillation in the audio stages. I was suspicious that RF was getting in from the first stage, so placed a 10n capacitor across the base-emitter of the second transistor, which seemed to fix that.

However, the circuit still seemed very prone to oscillation, even with the 10pf trimmer down to minimum. Given what others have said about the difficulties replacing the OC45 in the original circuit this isn't surprising, especially considering the higher gain of silicon transistors. So rather than have a direct feedback connection I added a loosely coupled reaction coil of 5 turns at the end of the ferrite rod, and connected the trimmer to that. This was just the trick, I can now control reaction easily, but it is much more stable, and doesn't have the sensitivity to hand capacity that it had before, nor does adjusting the trimmer affect the tuning.

Anyway, this has been a very satisfying project! So thank you, and thanks to Dave Bullimore as well. I'd recommend this for others to try, with the much easier to obtain components it should be a good project for interested school children to try, as was the intention of the original circuit.

I've attached the modified schematic, editing Dave's, in case you are interested. A photograph is at the link below. I borrowed some of Dave's construction methods, although it isn't anything like as tidy as his... Note that I used a second small tuning capacitor instead of the trimmer, with a 10pf in series. The reaction coil that I added is clearly visible at the top left hand corner of the photograph. It didn't seem to be particularly critical in its position or number of windings.

Regards,

Marcus
(March 2016)

The circuit diagram of the silcon TRF Ladybird radio built by Marcus



The silicon TRF Ladybird radio built by Marcus






Rosha and Daniel's 'Ladybird' Radio - continued - more photographs:

Hi, I finally managed to make my own Ladybird Radio in Iran. I bought that book [Making A Transistor Radio] in winter 1987. My last attempt was not successful because of mistakes in the third transistor connecting and some other faults. Since I didn’t find any “OC” transistors, I used a Japanese IF Amp transistor (2SA49) instead of OC45. It was acceptable. Other transistors such ac AF117 (General Tr.)  and AF126 (FM  IF  Tr.) didn’t  work.

All of Japanese 2SB series could be used. I  had some 2SB56, 2SB175 and 2SB376.  .

Because I  couldn’t find a radio frequency choke (r.f.c.) I used a Long Wave Coil [This would be of similar inductance]. Unfortunately my 9 volt battery was dead, so I connected a 9 volt DC power supply. My the only problem is noise.

I made some radios but I feel real satisfaction this time! Last night when I was ready to switch it on, my four year old son, Daniel, said to me: “Will you give it to me if it works this time?” ...and he owned it!

Update April 2011:
I have taken some photographs, as you see the radio works with germainium diodes OA79 and IN60 - obviously silicon diodes such as 1N4148 cannot be used.

I bought a tatty PHILIPS radio for just  $2.00 with the intention of breaking it for spares, but I repaired it and replaced my 2SA49 in the Ladybird radio with a Mullard OC45 (hilips I.F. stage). But I still use Japanese one and no re-alignment was necessary.

My radio (It is better to say Daniel’s one!) has 2 trimmers and a power indicator LED. When I connect a 9 volt adapter, the third transistor (2SB376 or 2SB75) warms up - so it is better to use lower ranges such as 7.5V .Connecting a 9V battery, noise will be reduced. I admit that I didn’t spend much time making it’s box.

Thank you very much for your help and advice.

Best regards,

Rosha
Rosha and Daniel's
                      'Ladybird' TRF Radio

Rosha
                      and Daniel's 'Ladybird' TRF Radio

Rosha
                      and Daniel's 'Ladybird' TRF Radio

A
                      Selection Of Germanium Transistors and Diodes
A Selection Of Germanium Transistors and Diodes

A
                      Selection Of Germanium Transistors and Diodes
A Selection Of Germanium Transistors and Diodes

Rosha
                      and Daniel's 'Ladybird' TRF Radio

Rosha
                      and Daniel's 'Ladybird' TRF Radio

Rosha
                      and Daniel's 'Ladybird' TRF Radio

Rosha
                      and Daniel's 'Ladybird' TRF Radio

Long
                      Wave Coil Winding Used As A 4.7 mH Radio Frequency
                      Choke
Long Wave Coil Winding Used As A 4.7 mH Radio Frequency Choke

Rosha
                      and Daniel's 'Ladybird' TRF Radio

Rosha's 'Ladybird' TRF Radio

Rosha's 'Ladybird' TRF Radio
Rosha and Daniel's 'Ladybird' TRF Radio

Persian Translation of the Making A
                      Transistor Radio Book
Persian Translation of the Making A Transistor Radio Book

Back to TRF Radios Part 2  >



See the complete plans here >

Other 'Ladybird Radio' Resources:


A kit based on George Dobb's three transistor radio design, featured above, is available on ebay (as of December 2010 anyway).
As Dominic Tasker suggests, "...he's got lots of kits ready to go for those that done have time to bumble around for parts." See this link:
http://cgi.ebay.co.uk/Ladybird-Transistor-Radio-Kit-Electronic-Parts-/160474963750?pt=UK_Consumer_VintageAudio_RL&hash=item255d0d9f26

Henry's very useful related web page highlights some technical pitfalls and solutions to problems that may be encountered along the way. It also explains why substituting alternative "equivalent" transistors may not work. For example there seems to be no suitable alternative to the OC45 in the RF section in this particular circuit configuration. While the OC71 could be subsituted for an OC81, for example, but still needs a small modification to the emitter circuit. For example if substituting the first OC71 with an OC81 then it will be necessary to connect a 1k Ohm emitter resistor in parallel with a 22uF bypass capacitor to ground, rather than a direct connection to ground. This will stabilise the d.c. operating point while maintaining the audio gain.

http://homepage.ntlworld.com/henry01/ladybird_radio/ladybird_radio.htm




No AM radio stations or transmitters in your locality or country?

http://www.vcomp.co.uk AM Medium Wave
                        Transmitter from Vintage Components

Has your local medium wave broadcast station closed or been moved to VHF/FM or Digital? Don't worry. You can still build and experiment with crystal sets and TRF radios by also buying or even building a simple low power AM transmitter. So, not only can you use your crystal sets but you can also run your own radio station that can be heard in and around your home - playing the music or programmes that you want to hear!


SSTRAN AMT3000 Superb high fidelity medium wave AM transmitter kits from SSTRAN. Versions available for 10kHz spacing in the Americas (AMT3000 or AMT3000-SM) and 9kHz spacing in Europe and other areas (AMT3000-9 and AMT3000-9SM). Superb audio quality and a great and well designed little kit to build: http://www.sstran.com/pages/products.html

SSTRAN AMT3000 low power
                          AM medium wave transmitter
http://www.sstran.com/

Other AM transmitters available:

Spitfire & Metzo Complete, high quality ready built medium wave AM Transmitters from Vintage Components:
http://www.vcomp.co.uk/index.htm  Vintage Components offer a choice of the high quality Spitfire and Metzo transmitters:

SPITFIRE AM Medium Wave Transmitter with 100 milliwatt RF output power:
Spitfire AM transmitter from Vintage
                              Components

METZO AM Medium Wave Transmitter with built in compressor:
Metzo AM Transmitter fromVintage
                            Components




AM88 LP  A basic AM transmitter kit from North County Radio.
http://www.northcountryradio.com/Kitpages/am88.htm



Worried About Soldering?  Don't Be:

For some simple ideas on solderless construction techniques have a look at the Crystal Sets 2 page.  When constructing these small electronic projects it will be necessary to determine the exact value of resistors, which are colour coded, and capacitors, which sometimes have confusing numbers on them.  I have included a table for both Resistor Colour Codes and a Capacitor Conversion Table HERE.


< BACK TO T.R.F. RADIOS PART 1

MORE T.R.F. RADIOS - PART 3 >
Readers Radios >

T.R.F. RADIOS - PART 4 >
Including The Medium Wave Mini  >

T.R.F. RADIOS - PART 5 >

TRF RADIOS - PART 6 >

LINKS to Other Great Websites >


RESISTOR COLOUR CODES
AND CAPACITOR CONVERSION TABLE



Visit my
                  Amateur Radio pages . . . .
Visit my Amateur Radio Pages >


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