See if you can answer this question.

[Spycam]

Which common component used in electronics is often called the
"electronic lobster pot"?

[noel]

Transistor?

[Spycam]

An interesting answer noel. I was thinking of the diode, transistors are switched diodes so aren't really like a lobster pot. It would have to be a lobster pot with the means to stop and start the lobsters getting in.

A diode lets electricity flow in one direction only, and if it happens to be AC then this will be converted to DC through the diode.

When I was 10 I saved pocket money to buy the parts for a crystal set,
about 12/6d.
A Long Wave coil
An oc71 diode
A condenser
A pair of high impedence head phones


wired it up to a long wire down the garden and a bit of pipe knocked into the ground....Aerial & Earth.

I got loud reception of the Light programme, 1500 m Longwave.
It worked well for months then, for Xmas, I got my first soldering iron and soldered the connections in the crystal set.

I looked nice and tidy.....but never worked again !!

I only found out years later what I had done wrong....
Does anyone know what it was ???

[noel]

I have to admit this is too technical in a field I never studied, however a shot in the dark, is it to do with electrode potentials of differing metals?

[DavidBatty]

It could be a diode, letting current flow but not return, similar to a lobster pot letting a lobster in but not out. It could be a valve because of it's intricate construction which can look similar to some form of lobster pot.

Re. the crystal radio, you probably didn't use a heat sink to dissipate heat?

[MjO]

Hi Roy,

Very interesting regarding the 'Electronic Lobster Pot' I am - or was - for my Sins! an Electrical Engineer specialised in Industrial Electronics and Automation, and have never heard that term before, so you learn something every day! However I think you have got your wires crossed - if you will pardon the pun! - regarding the OC71, which I think you will find I have mentioned previously in one of my forum postings, the OC71 was a Germanium PNP Transistor, originally made by Mullard and cost in the early 60's 21/6d + P.T and was generally known as the 'Red Spot' because of the red spot to denote the positions of the Collector, Base and Emitter, but you could have course used the base-emitter NP junction as a detector diode. The early diodes which were germanium point-contact diodes and used in detector and demodulator applications was the OA90 and OA91. A Crystal Set is, as it suggests, is a combination of a Crystal(usually Gallium) in a brass holder and cats whisker to use as the detector. It seems like only yesterday that my early studies were confined to thermionic valves, and the big 807's and EL34's used in my big power amplifier designs, prior to the IGFETS and power MOSFETS that followed them, a long way from the new LSI technology. Hope you are keeping well ...

MjO ...

PS. I like your Sunset Photo from the above link, any chance of a plain copy to use in my reflection-water ripple applet?

[Spycam]

DB. yes it is the diode and yes also the heat damaged it while soldering.

MjO. I bow to your knowledge & memory. I do now remember the red spot transistor oc71. I also remember that the special headphones cost
around 15 Bob (75p).

Would you like the photo emailing to you?
I want a place for people with PD to email in with their story or
symptoms etc. I can;t compete with all the big websites out there but
maybe look at a different angle on things in a people's site.

[MjO]

Roy,

Thanks for your response, and would indeed be delighted if you could mail the photo over to me, I cannot say that my memory is that sharp, it just so happens that I have 2 x brand new boxed Mullard OC71's showing the price of 21/6d + Purchase Tax. I also have a small tin containing 2 Gallium Crystals and Cat's Whiskers for Crystal sets, the age of these are uncertain, and would think these date back to the 1930-40's the price was 2/6d and look very similar to marcasite as used in the jewellery. You are quite correct about the Headphones, Hi-Z or Crystal headsets were expensive even in those days, but the old Lo-Z war surplus types were no good for crystal sets. I will provide you with a link to the Applet when I marry it up with your Photo, what this does, is take the photo invert it and place it at the bottom of the actual picture and processed to simulate a rippling water reflection.

MjO ...

Addendum: I have e-mailed you my mail address

[Spycam]

MjO. Could you sent your address again please, I lost it in anti-spam software I've been testing, sorry.