FREQUENCY METER SET SCR-211-(*)
DESCRIPTION AND MODEL COMPARISON
January 12, 1997
BY
Ken Corwin, KF6NUR
kenc2@pacbell.netThe 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 compartment, 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 applicable 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):
|
FREQ MTR |
MFR |
TUBES USED |
CRYSTAL DC-9-? |
CASE MAT'L |
WT LBS |
AUDIO OUTPUT IMPEDANCE |
|
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 |
MFR:
CBK=Allen D. Cardwell Mfg. Corp.; CIY=Rauland Corp.; CPR=Philco Corp.; CRR=Bendix Radio Corp.; CZR = Zenith Radio Corp.
CRYSTAL DC-9-?:
Any crystal unit with nomenclature N or higher can be used interchangeably with any frequency meter set with nomenclature N or higher.
AUDIO OUTPUT IMPEDANCE:
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.
References:
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, KF6NUR (kenc2@pacbell.net) Santa Clarita, CA