Source of cheap plastic/air variable tuning capacitors? - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

TonyDuell · 14th Sep 2016, 5:13 pm

There are a couple of interesting (to me, anyway) books :
Voice of the Crystal
Instruments of Amplification

The first is how to make the components for a crystal set using no commerical electronic components. So you make the tuning coil, fixed and variable capacitors, the detector (point contact on a crystal of course) and headphones.

The second is similar, but for amplfiying devices -- the earpiece/carbon microphone audio amplifier, simple triodes, (copper oxide) transistors. The devices described are, I will admit, not good performers, but they are intended as a starting point.

Anyway, Voice of the Crystal descibes at least one home-made plastic dielectric tuning capacitor.

MrBungle · 14th Sep 2016, 5:33 pm

Excellent - those look really good! Thanks for posting the titles.

Crystal Sets to Sideband has a section on such things as well: http://www.qrparci.org/wa0itp/chap4.pdf

TonyDuell · 14th Sep 2016, 5:44 pm

Do you need more details on said books? I know where mine are, so I can look up the author, etc.

G4XWDJim · 14th Sep 2016, 5:46 pm

What physical size are you looking for. I have several two and three gangers removed from valve portable radios and bigger. Let me know the size and I'll have a search. Presumably 365 to 500 pf.

Jim

MrBungle · 14th Sep 2016, 6:11 pm

Ideally after a dual gang ~300-400pF unit with end stops to start with. Vernier/reduction drive not important as this is for doing frequency sweeps (which are nigh on impossible on my Marconi 2019A). I've got a dual 200pF one extracted from a military ATU which I'm using both gangs in parallel at the moment with switched inductors to control range but it isn't ideal as it has no end stops and the thing is knackered.

The ones that spectrum communications are nearly spot on to be honest so i will probably go down that route. Thanks for the offer anyway.

Quote:

Originally Posted by TonyDuell

Do you need more details on said books? I know where mine are, so I can look up the author, etc.

Have found details on Amazon fortunately. Will see if I can locate a copy. There are a few at a silly price so far.

greg_simons · 14th Sep 2016, 11:07 pm

Mr bungle,
If you're really stuck I have about a dozen of these all sizes that came in a job lot of junk, they're new unused.
Greg.

14th Sep 2016, 5:13 pm	#21
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Source of cheap plastic/air variable tuning capacitors? There are a couple of interesting (to me, anyway) books : Voice of the Crystal Instruments of Amplification The first is how to make the components for a crystal set using no commerical electronic components. So you make the tuning coil, fixed and variable capacitors, the detector (point contact on a crystal of course) and headphones. The second is similar, but for amplfiying devices -- the earpiece/carbon microphone audio amplifier, simple triodes, (copper oxide) transistors. The devices described are, I will admit, not good performers, but they are intended as a starting point. Anyway, Voice of the Crystal descibes at least one home-made plastic dielectric tuning capacitor.

14th Sep 2016, 5:33 pm	#22
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	Re: Source of cheap plastic/air variable tuning capacitors? Excellent - those look really good! Thanks for posting the titles. Crystal Sets to Sideband has a section on such things as well: http://www.qrparci.org/wa0itp/chap4.pdf

14th Sep 2016, 5:44 pm	#23
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Source of cheap plastic/air variable tuning capacitors? Do you need more details on said books? I know where mine are, so I can look up the author, etc.

14th Sep 2016, 5:46 pm	#24
G4XWDJim Octode Join Date: Oct 2008 Location: Littlehampton, West Sussex, UK. Posts: 1,465	Re: Source of cheap plastic/air variable tuning capacitors? What physical size are you looking for. I have several two and three gangers removed from valve portable radios and bigger. Let me know the size and I'll have a search. Presumably 365 to 500 pf. Jim

14th Sep 2016, 11:07 pm	#26
greg_simons Octode Join Date: Jul 2004 Location: Evesham, Worcestershire, UK. Posts: 1,421	Re: Source of cheap plastic/air variable tuning capacitors? Mr bungle, If you're really stuck I have about a dozen of these all sizes that came in a job lot of junk, they're new unused. Greg.