[sdiy] The Visible VCO

[john mahoney]

> > ... the plastic "Visible Man" models.
>
> Something where I am lost, being on the other side of the pond...
:-P

Right, LOL! These things were advertised like crazy a couple of
decades ago:
    http://www.anatomy-resources.com/human-anatomy/sh740.htm


> > But... but... doesn't that Frequency Vernier adjust the voltage?
It
> > looks to me like a VCO without a CV input.
>
> Its roughly defining the current.

So then it's a current-controlled oscillator (CCO). And all (or most)
of our VCOs have CCOs in them. So, this could become a VCO with the
addition of a voltage-to-current source? (I am not proposing to do so.
Just wondering if this thing is almost a VCO.)


> > What about the Retrace Balancing Signal, maybe that's for high
> > frequency compensation?
>
> Its to blank out a CRT. All in all this is the timebase for a scope
or
> something. Or maybe just the timebase for a "wobbler". In either
case
> the retrace blanking signal would go to the luminance ("Z") input of
the
> scope (-tube).

Oh, it's an *output* not an input. :-/

> I would say this was used in schools for demonstrations.

Yeah, it's surely an educational item. (Like the Visible Man! ;-)


> > So it's a sawtooth with curved slopes? What's the frequency
spectrum
> > of that? (Magnus!!) I wonder, though, because a linear sweep
generator
> > is a lot more useful.
>
> Hmm, if the thresholds are closely together, i.e. the amplitude is
> small, and so the vernier-resistor approximates a current source,
the
> slope could be almost linear.

A TV-related circuit would have to be fairly linear. This is only an
educational model, though, so it may be much simpler than a real,
TV-worthy sweep gen.
--
john