[Milsurplus] WWII Test Bench Instruments

[Miles B. Anderson, K2CBY]

The equipment on the typical repair bench in the WWII era would have been
pretty primitive by today's standards.

You would have had the basic instruments for measuring voltage and current.
These would have been in the form of a multimeter, but one or more
individual separate milliammeters in sloping panel cases were common as
well. A number of early transmitters had closed circuit phone jacks
connecting the cathode of the PA stage to ground. This allowed you to use an
external milliammeter to measure the cathode current in tuning the PA stage.
Separate, individual thermocouple RF ammeters were widely used as well.

The Navy used very excellent signal generators (I believe nomenclatured
"LP") made by General Radio Corp. These were identical to the Model 605 sold
to the civilian market except that they were housed in a heavy aluminum case
rather than the oak case lined with sheet copper. I had one for years, and
the Navy accession date was 1939. These were very relaible, accurate and you
could get repeatable receiver sensitivity measurements down to a few
microvolts.

The Army signal generators of that era that I am familiar with were
repainted civilian "radio repair shop" types made by Standard or Radio City
that gave a solid output signal somewhere near the frequency indicated by
the dial but were subject to so much signal leakage that meaningful level
measurements were impossible.

With respect to frequency accuracy, both services relied on the very
excellent BC-221 series heterodyne frequency meters that were manufactured
in seemingly limitless quantities.

For frequencies in the 20 to 40 MHz range, the BC-906 series of frequency
meters was used.

Vacuum tube voltmeters existed at that time, and General Radio made these as
well. I don't know of any specific military types. The widely-produced ME-26
was a post-War product based on a Hewlett Packard design.

Tektronix wasn't founded until after the War. Although Hewlett Packard
existed,it was a tiny company during the War years and did not develop its
reputation until the late 1940s.

The only place you would have seen sophisticated equipment was an
installation where radar equipment was serviced. This is where you would
find oscilloscopes -- although many of these were special-purpose types like
the TS-100 that were used for radar range calibration. There were also echo
boxes and wave meters into the 10 cm band. Much of this test equipment had
no commercial counterpart. It was developed at the MIT Radiation
Laboratories along with the radar gear it was designed to service, and
manufacturing was farmed out to outfits like RCA and Bendix.

The air museum at Warner Robbins AFB near Macon, GA has an exhibit showing a
typical WWII era communications equipment service bench.

Miles Anderson, K2CBY
16 Round Pond Ln
Sag Harbor, NY 11963
Tel.: (631) 725-4400
FAX: (631) 725-2223
email: k2cby at optimum.net