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G0TEZ > VALVES 17.12.05 18:56l 36 Lines 1445 Bytes #999 (0) @ WW
BID : 17943-GB7FCR
Read: DL1LCA GUEST OE7FMI
Subj: Re: The wonderful acorn valves!
Path: DB0FHN<DB0THA<DB0ERF<DB0EAM<DB0SMG<DB0RES<ON0AR<GB7FCR
Sent: 051217/1648Z @:GB7FCR.#16.GBR.EU #:17943 [Blackpool] FBB-7.03a $:17943-GB
From: G0TEZ@GB7FCR.#16.GBR.EU
To : VALVES@WW
I would just like to add one comment to the subject of acorn valves. In
the 1950, I helped a school friend build a TX and RX to control his model
Tiger Moth. The frequency was somewhere around 300 Mc/s. UHF was thought
to be useless for most practical purposes so they gave it to the
aeromodellers.
We made lecher lines from polished copper tubing with all the soldered
joints carefully made smooth with no spikes. Tuning the things with little
sliders was done with that good old standby the plastic knitting needle.
If we got too close the 'hand effect' changed the frequency.
The wire coat hanger and the plastic knitting needle were the two most
useful accessories you could get.
For what it's worth. Around that time, there were miniature pentodes and
bigger in use. Physically, they were about the size of a Woodbine
cigarrette end. They still had their uses when transistors like the OC 81
and AF 117 were common. More reliable and could work up to higher
frequencies. They were often wired to other components and veroboard and
sealed into an Araldite block. The first integrated circuits.
I wonder who else remembers them?
As for the 'useless' UHF, not too many years later I was working on the
tuners of TV sets which went up to far higher frequencies.
Not the first mistake the BBC has made:-~)
All the best from - Ian, G0TEZ @ GB7FCR
Message timed: 02:55 GMT on 2005-Dec-17
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