MFJ-989D VersaTuner V Instruction Manual
3
Introduction
Thank you for selecting the MFJ-989D. Over the years, the MFJ-989 has earned an impressive
reputation as the world's most popular legal-limit tuner. Now, the "D" model features a number of
important upgrades that make it even better. Because of these improvements, you'll enjoy higher
efficiency, greater operating convenience, true peak-reading power measurements, extended frequency
coverage, plus many more refinements in both design and appearance. Even the cabinet is new, with a
nearly indestructible multi-color Lexan front panel and an interior layout that improves component Q
and reduces losses. Top to bottom, the Versa Tuner-V has evolved into a truly superior piece of
equipment built to deliver years of faithful service.
Circuit Overview
The MFJ-989D Versa-Tuner V incorporates five highly useful stand-alone station accessories into a
single package. The block diagram below shows how these five building blocks are organized:
1. SWR/
Wattmeter
4.
T-Network
3. Load
Wire
Coax-1
Coax-2
Balun
Bal.
Line
2. Antenna
Selector
Transmitter
Jumper
5.
1.) SWR / Wattmeter: Dual-range (300W/3kW) power meter features precision cross-needle
movements with LED illumination, a compensated directional coupler, and dual detectors for measuring
average and instantaneous-peak power. Circuit is identical to our MFJ-815C TrueActive (TM) stand-
alone meter.
2.) Antenna Selector Switch: Heavy-duty ceramic switch with silver-plated contacts and six positions
for routing a variety of loads to your transmitter or amplifier.
3.) Dummy Load: Precision non-inductive 50-Ohm load resistor, convection cooled and rated for 300
Watts dissipation (same as the MFJ-260C Dummy Load).
4.) Legal-Limit Tuner: MFJ's proven T-network features 500-pF wide-spaced air-variable capacitors
plus our unique 24-uH AirCore (TM) rotary inductor for continuous coverage of the HF spectrum.
These rugged components allow you to match virtually any antenna load you're likely to encounter.
5.) 1:1 Balun: Features two massive 2.4-inch ferrite cores wound with high-voltage polyethylene wire
and terminated to rugged ceramic feed-through posts on the back panel. MFJ's top-of-the-line high-
power Guanella current-style balun.
Before attempting to use your MFJ-989D for the first time, we urge you to read through the entire
manual. Doing so will help you gain familiarity with all of the MFJ-989D's many functions and features.
You'll also find useful technical information applying to all tuners and solutions for difficult-to-match
antennas.
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