Midian NFBF-10A, NFBF-10C, NFBF-10B User Manual

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)

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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.

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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.

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