[Boatanchors] Cheap & Easy Selectivity

[Alex Whitaker]

Bob,

I just remembered an easily found example of a gimmick.......look at the
Swan 350 manual.....check the place where they show how to wire the 100
KHz calibrator....it is coupled to the receiver with a gimmick.  The
gimmick is only wound a couple of turns in one place on the wire that it
couples to.  I've been fixing antique radios for years, and that's
always the way I've seen them.  

Anyway...an interesting discussion.

My $.02,

73,

Alex
AA9XY


On Sat, 2009-08-22 at 17:44 -0400, rbethman wrote:
> Alex,
> 
> I agree that all are capacitors.
> 
> I was using different things as examples of a way to get around a 
> manufactured one.
> 
> I may have stretched it too far, but was trying to also make the point 
> that the definition of "gimmick" can be found readily, and never bring 
> electronics into it.
> 
> My view of the "gimmick" has usually insulated wire attached at ONE end 
> to two different places in a circuit, twisted or wrapped around each 
> other, with the length trimmed to optimized the desired circuit 
> characteristics.
> 
> I haven't run across zip cord being used.  It would seem to be longer 
> for the same effect, but the difference in the dielectric of the 
> insulators would have to be run through to see what the real difference is.
> 
> Bob - N0DGN
> 
> Alex Whitaker wrote:
> > "...it is possible to capacitively couple the antenna directly to the
> > next RF amplifier grid, or to the mixer input grid, by wrapping an
> > insulated wire around any exposed wiring in the grid circuit.  This
> > forms a gimmick, which has a few picofarads of capacitance to the wire
> > around which it is connected."  Electronic Communication - 3rd Edition -
> > Robert L. Schrader.  
> >
> > I personally have only heard the term gimmick in reference to one wire
> > twisted around another in the manner described above.  I believe Bob
> > Bethman's examples of glass between two copper plates, or a long screw
> > used as he states describe capacitors, but not a gimmick.  
> >
> >
> > 73,
> >
> > Alex 
> > AA9XY
> >   
> <BIG SNIP>
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