United States Military
Radiac Set

US Military Issue Radiac Set
Measures 0 - 50,000 Milli-Roentgens Per Hour

The AN/PDR-39A is an ionization chamber instrument used to detect the presence
of gamma-emitting  radioactive materials.
This model had a built-in beta check source,(removed in July 1978) activated by the
 control knob just to the left of the meter face.

Case Dimensions: 6.2" Wide x 10.4" Long x 8" Tall including handle.
Case is all steel. - Accuracy ± 15% - I did not receive the 1½" wide carry strap or manual.
Controls include: Off / Battery / Set (zero) / 50K / 5K / 500 / 50 / 5 Range selector switch.

Manufactured by: Piasecki Aircraft Corporation - Essington, Pennsylvania

Serial Number: 146
This model must have been made in 1955 or later, as that was when
the Piasecki Aircraft Corporation was formed.
The contract number indicates a date of 1959, it was last calibrated in October 1964.

Left & Right Inside Views

Inside View
Battery box is shown upper left, with layout shown in case. Batteries used include:
 Two BA-51, 67½ volt for the ionzation chamber supply. One BA-42 for meter illumination.
 One BA-1278/U Pack which supplies 5.2 volts for calibration, 45 volts for the plate supply and,
22.5 vots for the bias supply. One BA-1277/U supplies 1.3 volts for the filament.

Schematics are glued to the case bottom,  2 wrenches are  included for adjusting the control linkage.

Close Up Views Of Meter & Controls
Meter face is lit by a BA-42, 1½ volt battery placed in the handle post, and activated by
pressing the rubber coated button in the center of the cap.

The switch for changing the scales is connected by cams and linkage to the meter face on which the
different scale ranges are indicated, much like the Victoreen 247-B. Each range is color coded, see below:
0 –5 Green / 0 –50 White / 0 – 500 Yellow / 0 – 5,000 Orange /  0 – 50,000 mR/h Magenta

The AN/PDR-39A is almost identical to the AN/PDR-T1B  Training Unit except for some
internal changes to some resistors and switches.

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