🚀 go-pugleaf

I am building a Theremin (an electronic musical instrument) from a
schematic published in a very old (1967) issue of "Popular Electronics".
The schematic calls for "50-300 uH RF coils".  I am told that this is
a very wide spread for adjustable coils by a mail-order house that carries
a very limited selection of same.  Furthermore, I can't find anyone locally
who stocks ANY coils whatsoever.  Does anyone know of a source,  or know
enough about the topic to suggest a substitution (I have to tune two RF
oscillators so that their difference frequency is audible)?

While I'm at it, the design also used "polystyrene capacitors", rated in
picofarads.  Can I substitute polypropylene, for which I have found a
source?  Any other substitutions?  (My, but there are a lot of capacitor
types out there;  ceramic, electrolytic, tantalum, Mylar... what's the
difference between them besides voltage rating?)

E-mail is appropriate.  Many thanks from an amateur.
Roger Rohrbach                                  sun!wrs!roger    roger@wrs.com
- Eddie sez: ----------------------------------------------- (c) 1986, 1990 -.
|   {o >o                                                                     |
|    \ ^) "I'm afraid of widths."                                             |