Do crystal radios still pick anything up?

[Syd Rumpo]

You may like this...

Cheers

[charles]

we "experimented" with transitors at school in 1957. I still have a copy of the Mullard Book - Transistors for the Experimenter - published in August 1956!

[michael adams]

Clive's 3 pages of adverts start on page 379 including the Sincro Micro 6 the Worlds Smallest Radio for 59/6 on page 380

michael adams

...

[The Natural Philosopher]

You can still buy oc71s all right

But why not use something better?

[Dave Plowman (News)]

I don't think so. The world service being easily available at all times in the UK is relatively recent.

The most likely transmitter to receive (apart from a very local one) would have been Droitwich LW. Which transmitted the Light Programme when I were a lad. Later changed to R4 during the day, WS at night.

[Dave Plowman (News)]

Plenty of equivalents you could use. For rather less than 7/6d each. ;-)

[Dave Plowman (News)]

Ah. I really can't remember the last time I used AM. I do have an AM tuner, but it's switched off until needed, being valve. ;-)

[Johnny B Good]

Low Pass Filter. In this case, the placement of a smoothing capacitor of a few tens of microfarads (as opposed to a few nanoFarads usually used to block only the rf ripple after the detector diode) - (modern stand-in for the original lead galena crystal and cat's whisker used to build the very first crystal sets) so that it smooths not only the rf ripple but the audio frequency modulation as well - you're only interested in harvesting a few milliwatts at best (unless you live right next door to the Tx in question) of DC voltage produced by the detector diode that's rectifying a conveniently strong signal to power a simple transistor amplified radio receiver tuned to a wanted but weaker radio station.

If you're lucky enough to pick up a very strong 198Khz signal to power a MW transistor receiver, it's job done. However, if you're relying on a very strong MW signal to power your MW receiver, you'll have to get a bit more inventive and use a second detector diode wired to give opposite polarity with the usual rf ripple capacitor to allow the modulation to get through, via a HPF, unmolested via a variable attenuator to the detector of the transistor assisted reciever so as to null out the unwanted audio that would otherwise swamp the weaker signals you're trying to listen to. I have to admit though, this isn't something I've ever tried. It's purely theoretical on my part (and it's just possible there might be a flaw in this excellent theory of mine :-).

[tabbypurr]

Unusual method of biasing/driving the OC71. Last time I looked you could still buy germaniums, albeit a very minimal range.

NT

[Bill Wright]

I built one, using the carbon rods out of two U2 batteries to produce an arc. A lovely white light as I remember.

Bill

[Bill Wright]

We're considering leaving the EEC, not Europe.

Bill

[Chris Hogg]

At about that time, I had a Henry's Radio 'Major' two-transistor radio built from a kit, that I had at boarding-school. Red spot and white spot transistors,

. In those days Henry's Radio was a cramped little shop at the top end of Harrow Road, No 5. Stuffed full of ex-WD equipment; you could hardly move in there. Then the whole area was massively redeveloped, and by 1964 they had moved into Edgeware Road, and look at them now! Their ad from 1964 is on the back page of that issue of PW linked to earlier.

[charles]

The item shows refers to shortwave coverage. It used to be reasonably accessible in the UK. When I joined EID, the car radios had a short wave band and I did listen.

Droutwich carrying World Service is relatively new. Until Orfordness was opened (late 70s?) the medium wave came from Crowborough (Aspidistra) which used quite directional aerials, so not much UK coverage)

[charles]

Rubbish! we're going to cut the mooring ropes and row the islands across the Atlantic.

[charles]

The Edgeware Road flyover was the culprit.

They've left the area They're now in Edgeware itself.

[Ian Jackson]

In message , charles writes

IIRC, overnight, Droitwich has been carrying the BBC's Overseas Service / World Service for a long, long time - long before they stopped the MW transmissions.

[Syd Rumpo]

The EEC hasn't existed since 1993.

But I know what you mean, and you knew what I meant.

Cheers

[Dan S. MacAbre]

I have the Ladybird book, too. The illustrations are just beautiful. Without that, I'm not sure that I would even have tried to make one. For years after, everything I made was built on a piece of board with brass screws, just like the Ladybird radio. It added an amusing and personal touch to everything.

[Dan S. MacAbre]

I remember digging some of those out to do chemistry experiments at home. And doing electrolysis with the filament stalks of a broken and smashed light bulb.

[The Natural Philosopher]

Indeed. The first transistor radio I built was a 27Mhz RC radio and it was biased like that. It worked. Until I left in on a window sill in the sun. I then discovered things like 'temperature stability'...

lots of dealers in old new stock as it were. Same as valves.