PDR-27 Radiac Set

This Giger-Muller set started out as the PDR-27A which was a tube type set using three different bateries and progressing to an all solid state unit using common "D" flashlight batteries.

Model	Meter	Battery	Probe	NSN	TM
PDR-27A		BA-416 BA-413 BA-401	DT-53	?	11-5543
PDR-27C	IM-74B	"	DT-106	?	11-5543
PDR-27E	IM-74B	"	DT-106	?	11-5543
PDR-27G	IM-74B	"	DT-106	6665-543-1443	11-6665-228-15, -20P, -40P
PDR-27J	IM-141	BA-30	DT-196	6665-00-543-1435	11-6665-209-10, -20, -40
PDR-27L	IM-173	BA-30	DT-196	6665-00-865-3456	11-6665-209-20, -40
PDR-27Q	IM-195	BA-30	DT-196	6665-00-017-8903	11-6665-209-20, -40
PDR-27P	IM-177	BA-30	DT-196	6665-00-975-7222	11-6665-224-15, 20P, -40P
PDR-27R	IM-203	BA-30	DT-196	6665-00-961-0846	11-6665-230-12, -12HR, -20P, -34, -40P
PDR-27S	?	?	?	6665-01-080-4418	11-6665-249-14, -20P, -34P

The PDR-27 set comes in a metal carry case that's 18 5/8" long x 7" wide x 9" high.  The top can be removed to access the contents and has a compartment inside the lid of which contains a paper titled "Maintenance Procedures".
Inside the box there's the PDR-27, the ST-136/PDR-27 carry strap, H-43B/U headphones with a BNC-m connector on the cord.  There are 4 holes in the foam end part of the box to hold something (test sources and/or spare G-M tubes).

Ranges of 500, 50, 5, 0.5 milli R/hour.  Note a 100R dose will make you sick and 500R is fatal.

The newer PDR-27 units run from six "D" flashlight batteries.  The photo at the top of this page shows the handle-battery cover removed (3 captured screws) and the batteries installed properly.  Note: at the bottom of the battery compartment there each battery position is labeled either "positive" or "negative" (referring to the end of the battery that touches the bottom of the box.

Turing the switch to the first position "BAT COND" causes a meter scale to rotate into veiw with the word "b a t t e r y" and a high and low limit mark to come into view.  In my case the needle goes to about the center of the range.

The probe is made up of two seperate GM tubes. 

V101 is a JAN5980 in the 5/8" dia x 5" housing.  This small tube is used for the 500 and 50 MR/hour ranges.  The dead time for the 5980 tube is 45 micro seconds.  3.5 gamma cps/ mR/hr.

V102 is a JAN5979 in the 1 1/4" dia x 7 1/2" housing with the hinged end cap which when opened allows alpha particles to be counted.   Both tubes are connected in parallel for the 5 and 0.5 MR/hour ranges.  The dead time for the large 5979 tube is 100 micro seconds.  45 gamma cps/ mR/hr.

The probe is permanently attached to the coiled cord and the cord is permanently attached to the housing.

Surplus Stuff - GM tubes & probes
United States Air Force, Radiac Set, AN/PDR-27T -
AN/PDR-27 GM Survey Meter -
Geiger-Mueller detectors (photos of many types) - Model 5979 End Window G-M tube
USGS - Terrestrial Gamma Radioactivity -
LND, Inc. - makes many types of probes and instruments with on line docs. - JAN5979 and JAN5980 GM tubes