There was also one generator which you could tune to beat the frequency
in question the generator was a frequency synthesizer without any
digital part that was the famous Schomandl FD! see here
SCHOMANDL-FD1-FDM1 FREQUENCY METER,
https://elektrotanya.com/schomandl-fd1-fdm1_frequency_meter.pdf/download.html
there they have the circuit diagram and a complete service manual
also, the circuit was not that complicated
a similar Dekadischer Service-Frequenzmesser
FD100http://www.radiomuseum.org/r/schomandl_dekadischer_service_frequenzmesser_fd100.html,
on which I worked to was made with solid-state components
73
KJ6UHN
Alex
[Dr. Alexander Pummer a former design engineer of Schomandl KG in Munich
Bavaria/Germany]
On 2/12/2017 6:07 AM, Bob Camp wrote:
Hi
Counters go back at least into the early 1950’s. I started out with fully vacuum
tube (except for diodes) counters obtained as surplus in the mid 1960’s. They
used some odd gas filled triodes. Everything in them could have been on the
market
in 1947. They were not a common thing until the late 50’s.
Prior to that (WWII era) the standard approach was to use a heterodyne frequency
meter. They could be quite complex. I once passed up a “deal” on one that spread
out over several rack cabinets. The idea was that you produced a beat against
this or that
and then beat it again against something else. Ultimately a meter or scope
showed
you the phase offset.
The heterodyne approach lived on in the era of the counter using a synthesizer
as
the reference. The beat note went into an analog meter based audio frequency
meter.
It allowed you do do cute things like servo to a target when grinding or
plating something
to frequency.
One key thing to keep in mind: in the 1930’s it is rare to find a frequency
spec that is
not stated in percent (with some zeros involved). A tight spec was in the 20
ppm
(or 0.002% ) range. The idea of a heated crystal as a reference was a “national
standards” sort of thing in 1935. The crystal industry as we know it today
really only dates
back to 1939. Before that the number of producers and the volume produced
was *very* small.
Bob
On Feb 12, 2017, at 1:08 AM, Scott Stobbe <[email protected]> wrote:
I was inspired recently coming across a Lampkin 105 frequency meter, as to
how frequency measurement was done before counters.
Certainly zero-beating a dial calibrated oscillator, would be one approach.
Is there a standout methodology or instrument predating counters?
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