New confused member!

Hello everyone, I'm a high schooler who wants to build a simple, cheap theremin just for fun/to see what happens (no serious purpose, I just want to goof around). Anyway, I found the schematic for the theremin from "103 simple transistor projects" and got really excited that it was so simple and small. Then, while searching radioshack's website, I realized that all of the transistors and inductors are from the 60s and hard to obtain. I also came to the conclusion that there is nothing "simple" at all about it. So, I have a few questions:
1) Will homemade inductors work/how big should they be? Should they be made with "naked" or insulated wire?
2) Must the transistors be exact models, or will a generic radioshack PNP transistor work just fine?
3) Will 100pf variable capacitors wired in parallel with 100 pf fixed capacitors be equivalent to a 200pf variable capacitor?
4) how does one hook up an antenna? will stiff brass wire work?
Thanks for any advice, it is greatly appreciated.

Hi and welcome!

You should post a link to the schematic/circuit description in order to make sure that we speak about the same device.

Generally, I can already tell you:

1) you may wind your own coils but it risks to be frustrating. The wire has naturally to be insulated. But a quick look on ebay (search option: worldwide) will show you that you may buy almost every inductor between 10nH and 1mH for a few cents in Hongkong, often with free shipping.

2) depends on the circuit. Just take a pocket calculator (if you are much younger than me) or your slide rule and determine the DC operating point and the needed AC characteristics of the transistors from the schematic. Than you may study data sheets online in order to find current replacement types. I can help you with that if you provide a link towards the schematic.

3) No. A variable 200pF capacitor will allow you to tune between 20 and 200pF. A fixed 100pF in parallel with a variable 100pF gives only a tuning range from 110 to 200pF.

4) Since it's important to have a non negligible capacitance between your hand and the antenna, you should use a 10mm or 3/8" aluminum or copper (eventually nickel plated for beauty) tube with a length of ca. 40cm or 16".

Thanks for the info! I tried cross-indexing transistors using a very helpful website, but so far no luck. I'll continue the hunt for trimmer capacitors. I'm using the plans from =http://www.ee.qub.ac.uk/dsp/research/vlsi/lpid/home/jon/ThereminNI.html[/url]
Toward the bottom it offers a download of the plans from 103 simple transistor projects. Again, thank you for the hel

Oh-oh, forget it. This is not a real theremin schematic but an theoretical/experimental design which tries to overdrive the mixer of a nearby AM-Radio in order to get perhaps some noisy and distorted squeeeky tones...

If you want to acquire real theremin experience, you should rather start with a cheap kit like this one which can be built and working fine within an hour or two and which helps you understand the different circuit parts and lets enough room for further experiments:
(you'll have to switch between the US, British, Australian, Canadian etc. version depending on where you live)
click here (http://www.jaycar.co.uk/productView.asp?ID=KC5475)
It comes with a printed circuit board, all needed components, antennae and a plastic housing.

oops! good thing I asked here before I got started. Thanks for the warning, and I'll take a look at that kit.