MFJ Enterprises MFJ-722B

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Summary

MFJ-722 B Specifications

Notch Filter Specifications

Details frequency range and depth of the notch filter.

High Pass Filter Specifications

Specifies roll-off rate for frequencies below 375 Hz.

SSB and CW Filter Specifications

Defines low pass limits for SSB and bandwidths for CW.

Audio Output and Power Supply Requirements

Outlines audio output power and required DC voltage range.

MFJ-722 B Instruction Manual

Introduction to the MFJ-722 B Optimizer

Overview of the tunable notch and selectable filters.

MFJ-722 B Installation Guide

Steps for connecting power, speakers, and input signal.

MFJ-722 B Controls and Operation

Explanation of front panel controls like ON/OFF/BYPASS, NOTCH FREQ, and WIDTH.

Selectivity Modes and General Operations

SSB Mode Selectivity Options

Describes high-pass and low-pass filter combinations for SSB signals.

CW Mode Selectivity Options

Details the bandpass filter bandwidths for CW signals.

Bypass Mode Functionality

Explains how the signal is passed directly to the output.

General Operations Guidance

Instructions on using the notch and selectivity features for signal optimization.

Full 12-Month Warranty Information

Warranty Coverage and Terms

Details on product warranty, proof of purchase, and service procedures.

Out-of-Warranty Service Policy

Procedures and charges for repairing products outside the warranty period.

The MFJ-722B Optimizer is a versatile audio filter designed to enhance desired signals and reduce interference in SSB (Single Sideband) and CW (Continuous Wave) communications. It combines a tunable notch filter with switch-selectable highpass/lowpass (SSB) and bandpass (CW) filters, allowing for precise signal optimization.

Function Description:

The MFJ-722B Optimizer integrates three primary filtering capabilities:

Tunable Notch Filter: This filter is designed to remove specific interfering signals, such as heterodynes, tuning-up stations, or nearby CW signals, without significantly affecting the desired audio. Its frequency and bandwidth are adjustable.
Highpass/Lowpass Filter (SSB Mode): In SSB mode, the device offers a highpass filter to reduce low-frequency noise and hum (like 60 Hz and 120 Hz) and selectable lowpass filters to narrow the audio bandwidth, improving clarity.
Bandpass Filter (CW Mode): For CW operation, the MFJ-722B provides multiple bandpass filter options with varying bandwidths, centered around 800 Hz, to isolate CW signals and minimize QRM (Quadratic Residue Management) from other signals.

Important Technical Specifications:

Notch Filter:
- Frequency Range: 300-3000 Hz
- Depth: 70 dB
High Pass Filter:
- Roll-off: Below 375 Hz at 12 dB per Octave
SSB Low Pass Filter Options:
- 2.5 KHz
- 2 KHz
- 1.5 KHz
CW Bandpass Filter (Center Frequency approx. 790 Hz):
- 3 dB Width Options: 180 Hz, 150 Hz, 110 Hz, 80 Hz
Audio Output: 2W
Power Supply: 9-18VDC

Usage Features:

Installation:

Power Connection: Connect a 9-18 VDC, 300 mA power supply to the POWER jack on the rear. A 12 VDC, 300 mA supply is recommended for maximum audio output. Use a 2.1 mm coaxial plug with a center-positive pin. An optional AC adapter (MFJ-1312B) is available.
Output Connection: Connect a 4 to 16 ohm speaker to the SPEAKER jack or stereo headphones to the PHONE jack on the rear.
Input Connection: Connect a shielded lead from your receiver's or transceiver's external speaker/headphone jack to the INPUT jack on the rear. The INPUT jack accepts an RCA phono plug.

Controls:

ON-OFF/BYPASS SWITCH:
- Depressed: Power is applied, and the front panel LED illuminates. The filter circuit is active.
- Out: Power is removed, and the input signal is routed directly to the SPEAKER and PHONE jacks, bypassing the filter circuit.
NOTCH FREQ: Varies the frequency of the notch filter section from 300 Hz to 3000 Hz.
NOTCH WIDTH: Adjusts the bandwidth of the notch filter section. A wider bandwidth is easier to tune but removes a larger portion of the signal. A very narrow bandwidth makes tuning critical and the notch frequency hard to locate.
SELECTIVITY Switch: This multi-position switch allows selection of different filtering modes:
- NOTCH: Only the notch filter is active. The notch filter is operable in all other SELECTIVITY switch positions except BYPASS.
- SSB MODE:
  - HP: Highpass filter active, passing frequencies above 375 Hz and rejecting frequencies below 375 Hz at 12 dB/octave. This reduces 60 Hz and 120 Hz hum and low-frequency noise. The notch filter is followed by this highpass filter.
  - 2.5: HP filter followed by a lowpass filter rejecting frequencies above 2.5 KHz.
  - 2.0: HP filter followed by a lowpass filter with a cutoff frequency of 2.0 KHz.
  - 1.5: HP filter followed by a lowpass filter with a cutoff frequency of 1.5 KHz.
  - In SSB modes (2.5, 2.0, 1.5), the range of frequencies passed to the speaker or headphones becomes progressively narrower.
- CW MODE (Center frequency approx. 800 Hz):
  - 180: A single-stage, 2-pole active bandpass filter with a 3 dB bandwidth of approximately 180 Hz, suitable for light QRM.
  - 150: A two-stage active filter, useful for moderate to heavy QRM.
  - 110: Three active bandpass filter stages provide steeper skirts, suitable for moderate to heavy QRM.
  - 80: Four active filter stages provide a very narrow bandwidth and steep skirts. This position requires slow tuning and may exhibit a "talking in a barrel" or slight ringing effect, which is normal. This is useful for heavy QRM.
- BYPASS: All filter sections are bypassed, and the signal is fed directly to the output amplifier, providing an unfiltered output.

General Operations:

To use the notch filter, set the SELECTIVITY switch to NOTCH (or any SSB/CW position), tune in the desired signal, and then adjust NOTCH FREQ to attenuate unwanted signals.
The notch filter is active in all SELECTIVITY switch settings except BYPASS. If the notch function is not desired in SSB or CW modes, rotate the NOTCH FREQ control fully clockwise to minimize its effect.
Care should be taken when adjusting NOTCH WIDTH. If too low, the notch filter may seem inoperable; if too high, tuning becomes very critical.

Maintenance Features:

Full 12-Month Warranty:

Warranty Period: 12 months from the date of purchase, covering defects in material and workmanship.
Proof of Purchase: Retain dated proof of purchase (bill of sale, canceled check, credit card, or money order receipt) to validate warranty claims. MFJ Enterprises, Inc. may deny warranty without dated proof of purchase. Any alteration or forgery voids the warranty.
Repair/Replacement: MFJ Enterprises, Inc. will repair or replace defective products at its option, provided the product is returned postage prepaid with a $12.00 fee for postage and handling.
Replacement Parts: MFJ Enterprises, Inc. will supply replacement parts free of charge upon request, with a dated proof of purchase and an $8.00 fee for postage and handling.
Self-Repair: The warranty is NOT void for owners who attempt to repair units. Technical consultation is available by calling (662) 323-5869.
Exclusions: The warranty does not apply to kits sold or manufactured by MFJ Enterprises, Inc. Wired and tested PC board products are covered only if the PC board itself is returned; boards installed in cabinets or connected to other components will be returned unrepaired at the owner's expense.
Limitation of Liability: MFJ Enterprises, Inc. is not liable for consequential damages to person or property from the use of MFJ products.
Out-of-Warranty Service: MFJ Enterprises, Inc. will repair out-of-warranty products if shipped prepaid. Repaired units will be shipped COD to the owner, with repair charges added to the COD fee unless other arrangements are made.
Warranty Scope: This warranty is given in lieu of any other expressed or implied warranty.
Design Changes: MFJ Enterprises, Inc. reserves the right to make design or manufacturing improvements without obligation to install such changes on previously manufactured products.
Service Address: All products for service (in-warranty or out-of-warranty) should be sent to MFJ Enterprises, Inc., 300 Industrial Park Rd, Starkville, MS 39759, USA. Include a letter describing the problem in detail, a copy of your dated proof-of-purchase, and a telephone number.
Legal Rights: This warranty provides specific rights, and other rights may vary by state.