[R-390] BFO multi-turn knob+ Bourns near equivalent

[Tim Shoppa]

John Lawson <jpl15 at panix.com> wrote:
>    Although the previous suggestion of an all-vacuum tube BFO pitch display 
> might be alluring...   and I think it could be done nearer the 30-tube 
> figure, counting the Nixies for display.

The HP counter modules used 4 tubes (twin triodes) per decade.

They also had a bunch of neon bulbs and (if a nixie display) used
CdS photocells for reading the neon bulbs and turning them into
a nixie readout! Really massively clever!

I'm guessing a BFO readout would usefully display to the nearest
10Hz and max out at a few kHz, so you'd want two or three
decades of counting. That's only 8 or 12 tubes for the counter
and maybe a couple more for the gating etc.

Of course the reference for the 10Hz count window would be
done with a tuning-fork reference and a electromechanical divider
(think of the old humming Bulova Acutrons). In fact lots of
60's-milspec-space-age instruments used these sorts of references.

I suspect that even harder to find than 4kc mechanical filters would
be the Bulova Acutron modules!

Tim.

P.S. My WJ-8716 has a two-digit thumbwheel (100Hz resolution) and
in this case DIGITAL SUCKS. Continuous knobs are way better!