
NFBF-10A
Notch Filter & Band-Pa
Manual Revision: 2014-08-20
Covers Hardware Revisions:
NFB
F-10: B & Higher
NFBF-10B
Notch Filter & Band-Pa
NFBF-10C
Notch Filter & Band-Pa
ss Filter (1200-2600 Hz)
ss Filter (700-3000 Hz)
ss Filter (80-200 Hz)
1

SPECIFICATIONS
Operating Voltage 12-18 VDC
Operating Current 3.8 mA
Operating Temperature -30 - +60 C
Input Level 20 mV – 1 V RMS
Input Impedance 600 Ohms
Frequency Range
NFBF-10A 1200-2600 Hz
NFBF-10B 700-3000 Hz
NFBF-10C 80-200 Hz
Band Width 0.5%
Device Gain or Loss Unity
Notch Filter Depth 30 dB
Audio Output Impedance 600 Ohms
Dimensions 3.6” L X 2.25” W X 1.52” H
GENERAL INFORMATION
Notch Filter: As a notch filter, the NFBF-10 will remove the undesirable tone from the incoming audio while
passing the rest of the audio. The NFBF-10A is often used to remove 2175 Hz keying tone from tone remote
systems going into a voice recorder. The NFBF-10C is used to remove CTCSS tones from audio.
Band-Pass Filter: As a band-pass filter, the NFBF-10 will block all audio except for the de sired frequency.
2

HARDWARE INSTALLATION
Be certain to follow standard anti-static procedures when handling any of Midian’s products.
Note: This product should be located at the destination point for the audio and not at the source of the audio on a
dry line.
J1: Input Connector: Connect pins J1:2 (red) and J1:3 (green) to the dedicated line coming from the audio
source.
J2: Output Connector: Connect pins J2:2 (red) and J2:3 (green) to the dedicated line going to the destination.
PL1: Power Input: Plug the supplied wall power adaptor into this connector. The wall power adaptor is 18 VDC
output and 110-220 VAC 50/60 Hz input.
HARDWARE ALIGNMENT
Band-Pass: Send the unit a 700 mV p-p signal on the Input line. Monitor P4 with an Oscilloscope or Sinadder. If
using an Oscilloscope tune R-13 (15 turn potentiometer) for maximum amplitude. If using a Sinadder tune R-13
for -12 to -10 dB of sinad. Use an Oscilloscope or Frequency Counter to read the tone frequency on the output.
Notch Filter: Send the unit a 700 mV p-p signal on the Input line. Monitor P5 with a Sinadder. Tune R-14 for -27
to -42 dB of sinad (-30 dB recommended). It may be necessary to tweak R-13 to get R-14 lower.
THEORY OF OPERATION
The NFBF-10 employs a High Q state variable filter. It also uses a 15 turn potentiometer that adjusts the
frequency based on the version ordered. The notch filter function is accomplished by summing the band-pass
audio with the incoming audio, resulting in phase cancellation at the adjusted frequency.
3

TECHNICAL NOTES
MIDIAN CONTACT INFORMATION
MIDIAN ELECTRONICS,
2302 East 22
nd
Street
INC.
Tucson, Arizona 85713 USA
Toll-Free: 1-800-MIDIANS
Main: 520-884-7981
E-mail: sales@midians.com
Web: www.midians.com
4

1
1
2
2
3
3
4
4
5
5
6
6
D D
C C
B B
A A
15K
R4
750K
R7
820K
R3
5.6K
R9
7.5K
R5
100K1%
R6
.001u 1%NPO
C4
100K1%
R10
.001u 1%NPO
C5
56K
R11
62K
R8
10K
R1
10K
R2
P1
P2
TONE IN
P3
TP5
GND GND GND GND
VA
GND
GND
2
1
3
PL1
.47u
C2
.47u
C3
470R
R15
4.7u
C7
10K
11
33
22
R13
*
F1
*
F2
*
D2
*
D3
*
Z3
*
Z4
*
F3
*
F4
*
D4
*
D5
0R
R17
0R
R21
0R
R25
0R
R26
500K
11
33
22
R27
10K
11
33
22
RP2
10K
11
33
22
RP3
10K
11
33
22
RP4
*
11
33
22
10K
RP1
200K
R34
.47u
C21
3.3K
R41
33K
R39
100K
R40
1K
R35
10K
R43
B25
Q1
200K
R38
4.7u
C27
5460
G
S D
Q2
VA
BALANCED OUT
UNBALANCED OUT
BALANCED IN
UNBALANCED IN
560p
C16
560p
C20
560p
C24
.47u
C15
.47u
C18
.47u
C22
LM660
-
+
2
3
1
411
U1:1
LM660
-
+
6
5
7
U1:2
LM660
-
+
9
10
8
U1:3
LM660
-
+
13
12
14
U1:4
VA
.47u
C9
.47u
C19
4.7u
C26
560p
C25
BLACK
J2:2
GREEN
J2:4
YELLOW
J2:5
BLUE
J2:6
RED
J2:3
WHITE
J2:1
YELLOW
J1:5
GREEN
J1:4
WHITE
J1:1
BLACK
J1:2
RED
J1:3
BLUE
J1:6
.47u
C12
620R
R16
.47u
C14
AGC
BYPASSED DC/RING VOLTAGE
UNBALANCED IN
MIXER1 IN
UNBALANCED IN
MIXER2 IN
560p
C17
33K
R12
*
R30
VA
FOR RF BYPAS
LIGHTNING PROTECTION
10K
R28
MIXER/NOTCH/BP/AGC/ADJUSTABLE GAIN OUT
MIXER/NOTCH/BP
AGC/ADJUSTABLE GAIN OUT
AGC PATH
ADJUSTABLE
GAIN PATH
NOTCH/MIXER
NOTCH/MIXER
WITHOUT AGC
WITH AGC
10K
R33
ADJUST
FREQUENCY
OUTPUT GAIN
NOTCH
0R
R22
10K
R31
DEPTH
*
R24
*
R19
*
R36
*
R42
10K
11
33
22
R14
1
2
3 4
5
6
T1:1
1
2
3 4
5
6
T2:1
LM7815
IN
1
GND
2
OUT
3
VR1
VER
A
B
C
R5 R9 R6 R10 R11
5.6K7.5K
1.8K 2.7K
1.2K 33K
100K1%
100K1%
100K1%
100K1%
475K1% 475K1%
56K
56K
51.1K1%
*
Z1
*
Z2
600 OHM
600 OHM
*
C29
*
C30
2.2u
C1
2.2u
C23
JP1:1
JP1:2
JP1:3
JP2:1
JP2:2
JP2:3
JP3:1
JP3:2JP3:3
JP4:1
JP4:2 JP4:3
BP OUT
JP5:1
JP5:2
HP OUT
JP5:3
LP OUT
JP5:4
HP FILTER
BP FILTER
LP FILTER
JP6:1
JP6:2
JP6:3
1u
C31
VAN VAN
VAN
VAN
VAN
VAN
EARTH GND
TP1
27K
R32
560p
C8
560p
C10
560p
C11
560p
C13
EP
CJS
2012-08-08 AWS
2014-09-15
D-1
1 of 2
7735
MIDIAN ELECTRONICS, INC.
DATE:
DESIGN:
UPD BY:
REV:
APPR
REV
SHEET
PROJECT NUMBER
DOCUMENT NAME
SCHEMATIC
Copyright © 2014
NFBF 10
-
+
3
1
4
52
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