"Matt" ) writes:
What sort of kit can I get for 6th grade kids to interest them in
radio/electronics? And where could I get same inexpensively (so I don't go
broke if I got a bunch for a classful of kids)? Crystal radio? Something
else? Does anyone have experience/stories of doing something like this with
a group of kids?

Thanks for your time.

73,
Matt Thomas
KD7PPK


I would think commercial kits would tend to have a price that when multiplied
by a classroom would be quite costly. An individual paying $20 might
not find that too costly, but what they'd really be paying for is whatever
instructions come with the kit.

If you can scrounge parts, likely the cost will be low or zero, though
there it will require time, to do the scrounging and to test the parts.
Though, that could be part of the assembly process, so instead of
detailing how the kids should assemble the parts, you'd start with
using a DVM to check the diode and/or transistor.

There isn't much in a crystal radio. Some sort of tube, wound with
wire, A variable capacitor would be nice, but that's going to be costly
if buying new. A fixed capacitor would get some results. A germanium
diode would be the best choice for the detector (unless you actually
build cat's whiskers, but that likely would increase cost), and they
won't cost much, but you may have to look to find them. The biggest problem
will be headphones that will have enough impedance to work well with the
detector. Though there have been workarounds suggested in recent years
in the magazines, such as transformers, and even IC amplifiers working
merely for impedance matching rather than outright gain.

Make it a scavenger hunt, and each kid needs to bring in a junk
transistor radio, which will offer up a variable capacitor. Either they'd
have one just sitting around at home, or they could get one for a dollar
or so. The advantage of them scrounging is that you won't have to
buy thirty radios at different garage sales or rummage sales.

Charles Kitchin has written quite a few articles in the past decade
about renerative receivers. Some have been intended for the beginner.
Except for the variable capacitor, they have all been common parts (and
I think he might have used a varicap in one, which likely is cheaper
than buying a new variable capacitor). The local surplus outlet was
selling 99cent boards, some sort of game I think it was originally,
that would have offered up most of the parts for one of his regens.
Common bipolar transistors, some bypass capacitors, an audio amplifier
(though not the one he used), some diodes, and maybe some of the resistors.
But a lot of junked consumer equipment would provide most of the parts.
He even used a 35mm film canister for his coil form, and those can
be had by visiting a friendly photo shop.

A regen requires more parts, and of course requires more assembly work,
but it just might come in cheaper than buying parts for a crystal radio.

Michael VE2BVW