Re: Yo! RF dudes!

Jorgen Lund-Nielsen wrote:

John Larkin wrote:

On Sat, 07 Apr 2007 20:55:39 GMT, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:


RST Engineering (jw) wrote:


Dunno, but the sleaziest trick I've ever seen was from a VCO that we bought back in the late '60s from a reputable "name" manufacturer. Opened it up to find that the "trimmer" capacitors were actually NPO disk ceramics that they took a dremel rotary file to, peaked up the circuit, then put coil dope over the exposed capacitor top.


I used nail polish for that when I was young. Until one day my mom got upset because I took the expensive stuff.



Wouldn't you have to squirt epoxy into the hole in the can to really reduce the Q?


No, I believe the air that rusheth in does the trick.



Most xtals, at least cheap ones, are filled with air or nitrogen. Some
of the high-end ones are in vacuum, which does increase Q. We buy some
beautiful vacuum-sealed glass-case oven crystals from Lap-Tech in
Canada. They look like jewelry. I'll post some snaps to abse one of
these days.


I have an old xtal in glass housing which is filled with neon
ant it lits when its been driven with the resonance frequency and
enough amplitude.
Pictures (not mine) from a "Leuchtquarz" could be found here:

http://www.xs4all.nl/~aobauer/leuchtquartz.htm

http://www.xs4all.nl/~aobauer/luminous_quartz_2.htm

http://www.xs4all.nl/~aobauer/leuchtquarze.htm

all is written in dutch, but Joerg can translate it, i think.


Cool! Yes, I can read that but what was not explained in the text is what motivated them to build crystals with optical feedback. What I can imagine is they could have been used as narrowband signal status receivers. But probably these had cost an arm and a leg.

--
Regards, Joerg

http://www.analogconsultants.com
.

Relevant Pages

  • Re: Yo! RF dudes!
    ... Opened it up to find that the "trimmer" capacitors were actually NPO disk ceramics that they took a dremel rotary file to, peaked up the circuit, then put coil dope over the exposed capacitor top. ...
    (sci.electronics.design)
  • Re: Yo! RF dudes!
    ... Opened it up to find that the "trimmer" capacitors were actually NPO disk ceramics that they took a dremel rotary file to, peaked up the circuit, then put coil dope over the exposed capacitor top. ... Absolutely high-end. ...
    (sci.electronics.design)
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