FREQUENCY METER SET SCR-211-(*) - DESCRIPTION AND MODEL COMPARISON January 12, 1997 The Frequency Meter Set SCR-211-(*) is a precision instrument designed to measure or radiate radio-frequency impulses between 125 and 20,000 kilocycles (kc). It is a portable, completely self-contained instrument used mainly to calibrate field radio receivers and transmitters by direct comparison with the calibrated variable frequency oscillator of the frequency meter. Each meter contains a 1,000-kc crystal-oscillator circuit which is used both as a source of accurate radio-frequency signals at multiples of 1,000-kc, and for calibrating the variable frequency oscillator of the instrument at a number of points... The principal component of the set is Frequency Meter BC-221-(*), a heterodyne-type frequency meter, which is supplied in either of two types of cabinet: a black wrinkle-finished aluminum-alloy cabinet, or an olive-drab finished wooden cabinet. The upper and largest compartment of the cabinet contains the frequency meter chassis and sometimes some of the spare parts. The next smaller compartment, at the bottom rear, contains the batteries. The smallest compastment, at the bottom front, contains either spare parts or the headset... Frequency Meter BC-221-(*) is calibrated in two ranges: 125 to 250 kc and 2,000 to 4,000 kc. By the use of the 2nd, 4th, and 8th harmonics of the low-frequency range, any frequency between 250 and 2,000 kc can be obtained; by the use of the 2nd, 4th, and 5th harmonics of the high-frequency range, any frequency between 4,000 and 20,000 kc can be obtained... Radio-frequency output, modulated at approximately 400 cps, is available for the alignment of radio receivers from Frequency Meters BC-221-AJ, BC-221-AK, and BC-221-AL. Each Frequency Meter Set SCR-211-(*) must be equipped with the following component parts before it is ready for use: Quantity Component 1 Frequency Meter BC-221-(*), including: 1 Calibration Book MC-177-(*) 1 Crystal Unit DC-9-(*), installed 1 Set of appplicable vacuum tubes, installed 1 Set of batteries, installed, including: 6 BA-2 batteries, 22.5-volt, NEDA 710 4 BA-23 batteries, 1-1/2 volt, NEDA 911 1 Applicable type Headset and Cord The following table identifies the many differences between models of the SCR-211-(*) Frequency Meter Set (the model letters for the Set are the same as those shown for the BC-221-(*) Frequency Meter): CRYSTAL CASE WT AUDIO FREQ MTR MFR* TUBES USED DC-9-** MAT'L LBS OUTPUT Z*** --------- --- ---------------- ------- ------ ---- ----------- BC-221-A CRR 6A7, 76, 77 A ALUM 38.5 High or Low BC-221-B CBK 6K8, 6SJ7(2) B ALUM 38.0 High or Low BC-221-C CRR 6A7, 76, 77 C ALUM 38.5 High or Low BC-221-D CRR 6A7, 76, 77 D ALUM 38.5 High or Low BC-221-E CPR 7A4, 7B8LM, 7G7 E ALUM 38.0 High or Low BC-221-F CZR 6A7, 6SJ7Y, 76 F ALUM 38.0 High or Low BC-221-J CZR 6A7, 6SJ7Y, 76 J ALUM 38.0 High or Low BC-221-K CZR 6A7, 6SJ7Y, 76 K ALUM 38.0 High or Low BC-221-L CZR 6A7, 6SJ7Y, 76 L ALUM 38.0 High or Low BC-221-M CRR 6K8, 6SJ7, 6SJ7Y M ALUM 38.0 High or Low BC-221-N CPR 6K8, 6SJ7(2) P OR AD ALUM 36.0 High or Low BC-221-O CIY 6K8, 6SJ7, 6SJ7Y P OR AD ALUM 39.0 High or Low BC-221-P CZR 6K8, 6SJ7, 6SJ7Y P ALUM 38.8 High or Low BC-221-Q CBK 6K8, 6SJ7(2) Q EITHER 38.0 High or Low BC-221-R CIY 6K8, 6SJ7, 6SJ7Y P or AD ALUM 38.0 High or Low BC-221-T CZR 6K8, 6SJ7, 6SJ7Y T ALUM 42.3 High or Low BC-221-AA CPR 6K8, 6SJ7(2) P or AD EITHER 35.5 High or Low BC-221-AC CIY 6K8, 6SJ7, 6SJ7Y P or AD WOOD 43.0 High or Low BC-221-AE CPR 6K8, 6SJ7(2) P or AD WOOD 36.2 Low BC-221-AF CZR 6K8, 6SJ7, 6SJ7Y T WOOD 39.5 Low BC-221-AG CPR 6K8, 6SJ7(2) P or AD WOOD 36.2 Low BC-221-AH CZR 6K8, 6SJ7, 6SJ7Y T WOOD 39.5 Low BC-221-AJ CIY 6K8, 6SJ7, 6SJ7Y P or AD WOOD 40.0 Low BC-221-AK CPR 6K8, 6SJ7(2) P or AD WOOD 36.0 Low BC-221-AL CZR 6K8, 6SJ7, 6SJ7Y P or AD WOOD 40.0 Low * CBK=Allen D. Cardwell Mfg. Corp.; CIY=Rauland Corp.; CPR=Philco Corp.; CRR=Bendix Radio Corp.; CZR = Zenith Radio Corp. ** Any crystal unit with nomenclature N or higher can be used interchangeably with any frequency meter set with nombmclature N or higher. *** High output impedance means 15,000 ohms; Low means 2,500 ohms. Dual impedance units units specified P-18 or P-20 high impedance headphones or HS-30 (256 ohm Z) headphones with Cord CD-605 (with impedance transformer). Low impedance units specified HS-30 headphones with Cord CD-874 (no transformer). BC-221-AK specified HS-33 (600 ohm Z) as alternate. ---------------------------------------------------------------------- Source: TM 11-300, "Frequency Meter Sets SCR-211-A, B, C, D, E, F, J, K, L, M, N, O, P, Q, R, T, AA, AC, AE, AF, AG, AH, AJ, AK, AL," 20 July 1944. Ken Corwin (kenc@smartdocs.com) Santa Clarita, CA -- EOF --