Thanks to everyone who replied to my query about Crystal Sets. I have firm
plans to purchase a rocket radio for my son. I have built my own crystal
sets in the past but I think for a present the rocket radio is hard to beat.

That aside I have another query for which I would be grateful if people
could provide a response.

When I used to build crystal radios I found that my voltmeter would show a
small voltage when measuring the output of the circuit. For some time I have
toyed with the idea of building a crystal set transmitter which seems to me
to be a logical extension of the idea of a crystal set reciever.

First one would tap a large coil in parrallel with a variable capacitor and
attached to a long wire. Several taps would extract the strongest stations
in the vicinity. Each signal extracted would then be rectified by the use of
4 diodes so that a pulsating DC current is generated. Finally the various DC
currents would be combined and smoothed out to provide a power souce for
the transmitter stage.

Next, a simple single transistor crystal locked transmitter would be built
which would be powered by the dc current mentioned earlier. This could be
keyed on and off to give a morse signal.

Finally, and separately, a short wave crystal radio could be built for
reception on the frequency of the transmitter stage

Is such a project doable or is the power that you would extract out of the
air too low to drive transistors etc?

cheers peter





"peter berrett" wrote in message
u...

Hi all

Cam someone please help me with a query I have about an old crystal set I
used to own.

When I first came to live in Melbourne (1970s) my parents purchased for me
a
small crystal set.at a local, now long gone, toy store. As I recall the
set
was manufactured in England although I may be wrong on this point.

It was housed in a small plastic box (red?) and from memory was about 2
inches long and maybe an inch wide and high.

Inside the box was a small wound coil (about 1/4" diameter) around a thin
cardboard tube. There was a ferrite rod inside this which could be slid
back
and forth within the tube by means of a small rod that stuck out of the
end
of the ferte rod and protruded from the end of the box. This was used for
tuning stations. There was also a piece of wire coming from the box with
an
alligator clip on the end. This was the antenna and by attaching it to a
long piece of wire one could receive stations. There was also another
piece
of twin wire protruduing from the box which went to a crystal earpiece so
that you could listen to stations.

Aside from this I think there were only two other components - a diode and
a
capacitor as I recall which formed the crystal set circuit. Unfortunately
the set is now lost after so many years.

This was my first introduction to radio and despite moving on to bigger
radios and getting my ham license, this example of a crystal set has
always
stuck in my mind as being a particularly simple but efficient example of
electrical engineering. I now have a young son of my own and would like
very
much to buy one of these sets.

Does anyone know who manufactured these sets and whether they are still
available to be purchased?

cheers Peter VK3PB

The old Raytheon ``What to do with your CK722'' project book has
a crystal-set-powered transistor radio, taking the DC from a crystal
set output and using it to power a CK722 amplifier.

They used the same station for both, however, which was a major
conceptual error. You want to use a local for the power, to
amplify a more distant station.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

Thanks Ron

cheers Peter

"Ron Hardin" wrote in message
...
The old Raytheon ``What to do with your CK722'' project book has
a crystal-set-powered transistor radio, taking the DC from a crystal
set output and using it to power a CK722 amplifier.

They used the same station for both, however, which was a major
conceptual error. You want to use a local for the power, to
amplify a more distant station.
--
Ron Hardin


On the internet, nobody knows you're a jerk.