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Old 24th Aug 2022, 4:12 pm   #21
Neil Purling
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Default Re: Ladybird Book Making a Transistor radio

I met someone who had built one of these radios, properly on a piece of wood with the screw-cups etc.
The postage stamp trimmer had a length of plastic knitting needle glued to the screw head.

I think that the audio stage was rather weak. As you say poor biasing. This person had used OC81's and selected those with the best gain.
The radio was in a case that had two transparent sides. The tuning capacitor had a reduction by means of a cord drive which went around the case and included a needle and scale!

I wonder if the radio could be made with Russian transistors?
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Old 25th Aug 2022, 9:21 am   #22
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Default Re: Ladybird Book Making a Transistor radio

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Originally Posted by Sideband View Post
One thing I did notice in the book when showing how to mount the ferrite rod. Wrap sturdy wire around the rod and fix the board. Surely that would result in shorted turns each end of the rod? He doesn't specify Insulated wire.....
I made exactly that mistake when 'tidying up' my latest three transistor receiver. This was when I was about 12 years old, mid 60's. In prototype form (ie flopping all over the kitchen table) it worked a treat and with the reaction advanced to the critical point I could even hear Caroline on it here in east Manchester.
So I decided to build a nice veroboard version, fixing the ferrite rod onto the edge of the board with wire loops. Oh dear. The time wasted in trying to find out why it was not working was monumental, and of course the board became more and more scruffy as I removed parts for testing time and time again.
Inspiration came at school in the middle of a biology class, and I couldn't wait to get home to snip the loops. It worked!
I never forgot THAT lesson....
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Old 25th Aug 2022, 6:36 pm   #23
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Default Re: Ladybird Book Making a Transistor radio

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Inspiration came at school in the middle of a biology class, and I couldn't wait to get home to snip the loops. It worked!
I never forgot THAT lesson....
Hmmm....trying to work out what in a biology lesson would have provided inspiration for cutting a couple of wire loops......or was your mind thinking of things other than biology??

I fairly recently had to sort out why a battery valve set was very deaf. It had (so I was told) recently been serviced by a radio engineer. Peering inside, it took me a couple of moments to notice that the ferrite rod had been repaired.....with a metal collar around the middle that had been Araldited in place....! Fortunately I had a suitable rod in my box of bits and the radio was soon back to normal after a quick realignment.
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Old 25th Aug 2022, 6:52 pm   #24
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Default Re: Ladybird Book Making a Transistor radio

There's currently a display of Ladybird books at the old Music Hall Museum in Shrewsbury.
In a special display there is a copy of the Transistor Radio book, complete with a built breadboard radio.

David.
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Old 26th Aug 2022, 2:04 am   #25
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Default Re: Ladybird Book Making a Transistor radio

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Hmmm....trying to work out what in a biology lesson would have provided inspiration for cutting a couple of wire loops......or was your mind thinking of things other than biology??
I think I have worked it out
The biology lessen must have been about how muscles work and the light bulb moment happened when he realized that muscles needed to be used to squeeze the handles of the cutters to snip the wire loops
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Old 26th Aug 2022, 2:15 am   #26
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Default Re: Ladybird Book Making a Transistor radio

heh hehe it was the muscles in his head

Joe
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Old 26th Aug 2022, 5:45 am   #27
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Default Re: Ladybird Book Making a Transistor radio

The most powerful muscle of all.

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Old 26th Aug 2022, 11:35 am   #28
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Default Re: Ladybird Book Making a Transistor radio

A purely random thought, the kind that happens when you're not paying attention to anything much!
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Old 26th Aug 2022, 12:26 pm   #29
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Default Re: Ladybird Book Making a Transistor radio

Erm... isnt the detector diode on page 31 the wrong way around for the PNP ?
[ducks below parapet...]
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Old 26th Aug 2022, 7:31 pm   #30
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Default Re: Ladybird Book Making a Transistor radio

I thought that too!

There's quite a few things that leave something to be desired... the potential divider biasing WITHOUT emitter resistors... the bare-wire mounted ferrite aerials... Phil G's backward-connected diode...

I seem to remember seeing an edition which used a 'gimmick' capacitor for regeneration, two short lengths of insulated wire twisted together. The picture showed... stripped wires twisted together!

It's not up to the standard that one would expect of a 'teaching' book, which is a shame because the artistic standard of the illustrations is high. But if the technical standard isn't, it's a let-down!
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Old 26th Aug 2022, 10:59 pm   #31
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I think I remember the "Tinytone" (or was it the Terrytone?) Radio Control receiver used twisted wires for a tunable few pF to set the superregeneration
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Old 26th Aug 2022, 11:56 pm   #32
Phil__G
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Default Re: Ladybird Book Making a Transistor radio

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Erm... isnt the detector diode on page 31 the wrong way around for the PNP ?
[ducks below parapet...]
Quote:
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I thought that too!
Thats such a relief, I was expecting a thorough slating for suggesting that...
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Old 28th Aug 2022, 3:06 pm   #33
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Default Re: Ladybird Book Making a Transistor radio

Thinking further, in 1972 when the book was published, a ZN414 radio would have been easier to build, easier to document, and would have had a far superior performance...
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Old 29th Aug 2022, 2:05 am   #34
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Default Re: Ladybird Book Making a Transistor radio

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Thinking further, in 1972 when the book was published, a ZN414 radio would have been easier to build, easier to document, and would have had a far superior performance...
Yes, but building one would have taught you absolutely nothing!

Easier, easier, superior... That's not how it works, at least not for me

Steve.
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Old 29th Aug 2022, 3:25 am   #35
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Default Re: Ladybird Book Making a Transistor radio

You are absolutely right Steve. Painting by numbers does not a Michelangelo make.

Like using a calculator for your shopping, If you can't add up simple math, don't try electronics.

Joe
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Old 29th Aug 2022, 10:40 am   #36
Phil__G
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Yes, but building one would have taught you absolutely nothing! Steve.
You could say it would teach more than a project that didn't work at all because the detector was shown the wrong way around in the book...
Sorry, only joshing, I was a huge Rev Dobbs fan
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Old 29th Aug 2022, 12:14 pm   #37
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Default Re: Ladybird Book Making a Transistor radio

Over on Abebooks website, they have available another copy of the book. https://www.abebooks.co.uk/servlet/S...=9780721403243
Only this time it's a Learnabout title again by Rev. Dobbs. You can see the Ladybird in the bottom right corner of the book so it's probably exactly the same. The publication date is also 1972 like the Ladybird version. I don't suppose the Learnabout version addressed the errors.

Also by Rev. Dobbs, there's another Learnabout title, Simple Electronics. https://www.abebooks.co.uk/products/...=pd_detail-1-v Not sure if there was one with the Ladybird title.

Regards,
Symon.
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Old 29th Aug 2022, 12:26 pm   #38
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Default Re: Ladybird Book Making a Transistor radio

I don't think any of the projects I built from books, magazines or kits worked first time. In fact some of them never worked at all. I did learn a lot getting them to work though.
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Old 30th Aug 2022, 5:55 pm   #39
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Default Re: Ladybird Book Making a Transistor radio

I never did the Ladybird book radios but there was a better book which I kept taking out of the local library, I forget the author but it had a green cover and led you through a succession of radios from a simple crystal set, a reflexed MW transistor set, and different audio stages [headphones or a Class A transistor amp using an OC72 through to a push pull Class B version ].

The end version from what I recall was a SW regen design covering the 41 and 49 Metre bands.

Was it maybe authored by R.A. Penfold??
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Old 30th Aug 2022, 6:35 pm   #40
Philips210
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I never did the Ladybird book radios but there was a better book which I kept taking out of the local library, I forget the author but it had a green cover and led you through a succession of radios from a simple crystal set, a reflexed MW transistor set, and different audio stages [headphones or a Class A transistor amp using an OC72 through to a push pull Class B version ].

The end version from what I recall was a SW regen design covering the 41 and 49 Metre bands.

Was it maybe authored by R.A. Penfold??
Could it have been Modern Transistor Radios by RH Warring? I seem to recall this title was in our local library. https://worldradiohistory.com/BOOKSH...os-Warring.pdf

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