In her own words:
As a project to use for assessment for entrance to a day release college
course from school I was asked to design a kit radio, the kit is to be
used to introduce electronic construction to pupils in an
extracurricular course.
The design was based on a reflex transistor detector circuit that has
its origins in the late nineteen fifties, and was made popular in the
Sinclair Micromatic miniature personal transistor radios during the
following decade. In my set the detector is feeding its AF output to a
jellybean design three transistor PP amplifier.
My brief was to design a loudspeaker radio with all components mounted
on a PCB. It was done in a bit of a rush but it did work, the hand drawn
artwork for the PCB, (the first I'd ever done!), was converted to
Gerber files by my physics teacher. PCB's were made and the kits were
collated, alpha testing was done and the project pronounced successful.
That left me with the prototype board, (that was made to just mount the
small components on), no provision was made to house the volume control
or the tuning components.
I was given the idea to build a radio using the prototype PCB, but as
far as possible using reclaimed, scrap, and scrounged junk.
A lot of the electronic components were stripped out of a pair of old
broken TV's and an induction hob found dumped in a farm gateway, the
paxolin used for the chassis was some offcuts skip dived for by my late
dad, the battery holder was cut out of the case of an old office
telephone. The back lighting for the tuning scale were some LEDs from a
broken par 38 style lamp. And so on....
Even the cellulose paint was scrounged, and was left over from a spray
job at the local garage, the tin having been on a shelf for over 25
years according to the owner. It was still good!
Any credit for the finish is due to my Great grandmother, who painted
the cabinet for me by brush, and did an excellent job considering the
wood for it was from a broken crate lid.
One big difference from the school project was that the set has a fixed
frequency longwave band, tuned to 198KHz, BBC R4, that addition caused a
problem with the detector because it meant that the collector load
choke inductance had to be made 10 times larger than that would Normally
be used for the MW band to raise the gain to a useful level, and that
had to be balanced with capacitive reaction to help keep the gain level
across the Medium Wave. Otherwise some inelegant switching would have
been needed to change the inductive loading.
Your dad once awarded me the Nobel prize in recycling. I must give it to you. Very well done.
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