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MFJ
Intellituner
Automatic Antenna Tuner
Model MFJ991
INSTRUCTION MANUAL

scanned by Gale, w7vpk@oasisol.com
Edited by Gary Lee, kb9zuv@arrl.net

CAUTION: Read All Instructions Before Operating Equipment MFJ ENTERPRISES, INC.
300 Industrial Park Road
Starkville, MS 3 9 7 5 9 USA
Tel: 662-323-5869 Fax: 662-323-6551
VERSION 18 COPYRIGHT C 2004 MFJ ENTERPRISES, INC. MFJ-991 Intellituner Automatic Antenna tuner Instruction Manual

Contents
BASICS
Introduction
Features 2
Specifications 2
Front Panel Layout 2
Rear Panel Layout 2
Fast Start
Front Panel 4
SWR/wattmeter 4
C-UP and C-DN Buttons 4
L-UP and L-DN Buttons 4
AUTO Button 4
TUNE Button 5
POWER Button 5
BackPanel 6
Power 6
Remote Port 6
Radio Interface 6
Transmitter 7
Ground 7
Wire 7
Antenna 7
Installation 8
SWR/wattmeter 8
SETUP
Target SWR 9
Auto Tune SWR 9
Meter Range 9
OPERATION 10
Manual Tuning 10
Component Limit 11
Antenna Memory 11
Tuner Status Indicators 12
Grounding Hints 13
Antenna System Hints 13
Location 13
Matching Problems 13
APPENDICES
Firmware Version Number 15
Resetting Tuner 15
Factory Defaults 15
Delete Antenna Memory 16
Total Reset 16
Self Test 16
Power Down Circuit Test 17
RelayTest 18
wattmeter Calibration 18
SWR Bridge Calibration 19
Frequency Counter Calibration 20
In Case of Difficulty 20
Technical Assistance 21
List of Accessories 21
Circuit Block Diagram 22

FIGURES
Figure 1. Installation Block Diagram
Figure 2. MFJ-991 Front Panel 4
Figure 3. ButtonAction 5
Figure 4. MFJ-991 Back Panel 6
Figure 5. Alinco Interface Cable 7
Figure 6. Icom Interface Cable 7
Figure 7. SWR/Wattmeter 8
Figure 8. Power-On Operations 15
Figure 9. MFJ-991 Circuit Block Diagrain 22 TABLES Table I. Antenna Memory Resolution IT
Table 2. Meter Needle Codes 12
Table 3. Failure Messages 17

Basics

Introduction
The MFJ-991 Intellituner let you rapidly tune antennas automatically: unbalanced or single-wire (or balanced, with external balun) MFJ's exclusive Instant Recall, IntelliTune and Adaptive Search algorithms give you fast automatic tuning with more than 1000 non-volatile memories. The tuner includes highly efficient switching L-network with wide matching capability, 1.8 to 30 MHz coverage, cross-needle power meters, port for all accessory remote control, radio interface port, and heavy-duty 16 amp/1000 volt relays. It rated at 300 watts PEP SSB and 150 watts CW. 256 values of capacitance and 256 values of inductance available. With inductance switched between input and output side, this provides total of 131,072 L/C tuning combinations. nominal tuning ranges 0 to 3900 pF and 0 to 24 H.
All MFJ IntelliTuners learn and remember. When you transmit, they automatically adjust for minimum SWR and remember frequency and tuner settings, safely stored in non-volatile memory. next time you operate on that frequency (or close to it) these tuner settings instantly restored and you're ready to operate in milliseconds. tuner can learn and remember more than thousand frequencies and tuner settings.
When you key your transmitter, MFJ's Instant Recall checks its memory to see if you have operated that fiequency before. If so, tuning instantaneous and you're ready to operate. If not, MFJ's IntelliTune algorithin (based on MFJ's famous SWR Analyzer technology) kicks in. It measures complex impedance of your antenna. Next, it calculates components it needs and instantly snaps them in. Finally, it fine-tunes to minimize SWR, and you're ready to operate -all in fraction of second. If antenna impedance not within tuner's measurement range, MFJ's Adaptive Search algorithin goes into action. Frequency measured and relevant component values determined. Only those values searched for fast tuning. If it still cannot find match, search performed again using different search pattern.
The target SWR can be set at 1.5 or 2.0. minimum power to tune approximately five watts. You can manually tune where you can't transmit (for listening out of ham bands)
The optional MFJ-993RC Remote Control provides most tuner controls, allowing convenient remote locating of tuner itself. All MFJ's IntelliTuners support radio ttiner interfaces that compatible with Icom AH-3 and AH-4 tuners and Alinco EDX-2 tuner. Optional interface cables MFJ-5124A (for Alinco) and MFJ-5124T (for Icom) available from MFJ Enterprises, Inc. Interface cables for compatible Kenwood and Yaesu radios will be available in future.
The tuners enter 'sleep" mode when idle and when no transmit signal present, turning off microprocessor clock to avoid generation of spurious signals. Automatically matches antennas from 6 to 3200 ohins impedance Handles 150 watts PEP SSB/100 watts CW
Tune in less than 15 seconds, usually less than 5 seconds Over 1000 non-volatile memories for tuner settings Highly efficient switching L-network matching circuit 1.8 to 30 MHz continuous frequency coverage Selectable target SWR 1.5 or 2.0
Selectable SWR threshold 0.5, 1.0 or :5 Lighted cross-needle SWR/wattmeter with high, low and auto range options Built-in frequency counter
SO-239 coax fed antenna connector
Connector for random wire or single wire antennas Optional remote control
Optional radio interface for compatible radios

Specifications
Impedance matching range: 6 to 3200 ohms Minimum power for tuning: 5 watts
Maximum power while tuning: 100 watts with foldback, 20 watts without foldback RF power limit: 150 watts PEP SSB/100 watts CW Frequency range: 1.8 to 30 MHz continuous coverage Frequency counter accuracy: +1 kHz across HF bands Frequency counter range: up to 50 MHz
Capacitance range: 0 to 3900 pF (256 values) Inductance range: 0 to 24 H (256 values) Relay rating: 6 amp 1000 volts
Relay electrical life: 100,000 operations Relay mechanical life: 10 million operations Memory endurance: 1 million write cycles Memory data retention: 100 years
Power requirements: 12 -15 volts DC, 2.1 x 55 mm coaxial plug, center pin positive
Current consumption: 1 amp or less

Dimensions (approx. 10.1 X 2.8 x 9.2 in. (257 x 71 x 234mm) (width/height/depth) not including connectors

Weight (approx. 3.7 lb (1.68 kg)
Specifications and design subject to change without notice.

Front Panel Layout

Left side, slightly above center: SWR/wattmeter

Right side about center: two rows of buttons

Top row from left to right:
{C-UP]
[L-UP]
[AUTO]
[POWER]

Bottom row from left to right:
[C-DN]
[L-DN]
[TUNE]
(See text for functions of buttons.)

Rear Panel Layout
Facing away so you must reach behind:

Left side, toward top: Binding post for single wire antenna. Immediately right of that: SO-239 connector for coax fed antenna. In center toward bottom: bolt with wing nut for connecting ground. About 2.5 inches right and near top: SO-239 for connecting coax from radio. Below that and slightly farther right: 3.5 MM phone jack for radio interface. Immediately right of that and also near bottom: multipin female connector for remote control.
In bottom righthand corner: 12/15 volt power input jack.

2

1. Connect tuner to 12-15 VDC voltage source capable of supplying at least 1 amp.
2. Connect your transmitter to TRANSMITTER connector using 50-ohm coaxial cable.
3. Connect your coax-fed antenna to ANTENNA connector using 50-ohm coaxial cable, or connect your random wire to WIRE binding post.
4. Connect your ground connection to GROUND post.
5. Press POWER button to turn on tuner. Lock {AUTO] button in to select semi-automatic mode.
6. Key your transmitter to output carrier of 10 watts CW, FM or AM.
7. Press and hold {TUNE] button for one second to start automatic tuning process. When completed, check to ensure SWR of 2.0 or less before increasing RF power.
8. You ready to transmit.

Note: During auto matic tuning process, tuner will make some nOiSe. These relays switching at very fast pace and it normal operation. Do not be alarmed.

Note: When tuner power OFF, tuner in bypass mode and RF from transmitter goes directly to antenna with no matching. When tuner power ON pressing {C-DN] and {L-DN] simultaneously or pressing {TUNE] quickly places tuner in bypass mode (zero inductance and zero capacitance) and indicates hi' reflected needle bouncing to 20-watt mark.

Antenna
RF Ground 12 VDC
Figure 1. installation Block Diagram.

3

C-DN
L-DN
TUNE

MODEL 150 Watts PEP SSB/100 Watts CW
L BYPASS WATTS
MFJ-991 AUTO RANGE Figure 2. MFJ-991 Front Panel. SWR/Wattmeter: cross-needle meter measures forward power, reflected power, and SWR. It operates whenever tuner power on. Full-scale readings 300 watts forward and 60 watts reflected. meter can be set to low power range of 30 watts forward and 6 watts reflected. SWR measured at point where two needles cross. See SWR/wattmeter" on page 8 for more detailed information.

C-UP and C-DN Buttons: Used to manually increase or decrease capacitance of L-network matching circuit. capacitance range 0 to 3900 pF. upper limit of capacitance, dependent on frequency, restricted to limit maximum voltage and current across tuner's components.

Note: Pressing {C-UP] and {C-DN] simultaneously toggles capacitor hetween input and output sides of L-network Forward needle boumces to 30-watt mark when capacitor on transmitter side. Reflected needle bounces to 5-watt mark when capacitor on antenna side.

L-UP and L-DN Buttons: Used to manually increase or decrease inductance of L-network matching circuit. inductance range 0 to 24 H. upper limit of inductance, dependent on frequency, restricted to limit maximum voltage and current across tuner's components.

AUTO Button: Used to select automatic or semi-automatic tuning mode. Button out selects automatic mode -tuning routine automatically started when at least five watts of power applied and SWR preset amount above preset target SWR. Button in selects semi-automatic mode -tuning routine starts only when {TUNE] button pressed.

Note: During tuNing process, tuner will make some noise. These relays switching at very fast pace and it normal operation. Do not be alarmed.

TUNE Button: has three different functions based on length of time you press and hold it before releasing.

Press {TUNE] quickly (less than 0.5 second) to bypass tuner. RF from transmitter goes directly to antenna with no matching.

4

"StickyTune" allows for one-handed tuning operation. Normal tuning requires keying transmitter with one hand and using other hand to push {TUNE] button to start tuning process.
To toggle StickyTune mode on and oft, press and hold {TUNE] button for two seconds.
Reflected Power needle goes to 60-watt mark when on and to 5-watt mark when off.
When StickyTune enabled, tuning process starts automatically when transmitter keyed with at least five watts of power regardless of SWR. This works in both automatic and semi-automatic modes.

POWER Button: Used to turn power on and off.

Note that during power-on analog meter bounces once to indicate model 991. When power off, tuner placed in bypass mode (straight through from TRANSMiTTER to ANTENNA and WiRE).
When power turned on, tuner automatically restores all previous settings.

WARNING: Do not turn power on and off rapidly, otherwise tuning setting memory can be corrupted and unit will have to be reset to factory defaults.

BUTTON ACTION
Press POWER In to turn power on, out to turn power off. Press C-Up to increase Capacitance.
Press C-DN to decrease CapaCitanCe.
Press L-UP to increase inductance.
Press L-DN to decrease inductance.
Press AUTO in to select semi-automatic mode, out to select automatic mode.

Press TUNE less than 0.5 second to bypass tuner press and hold for 0.5 to 2 seconds to start tuning process; press and hold for more than two seconds to toggle StickyTune on and off. Press C-UP + C-DN to switch capacitor between input and output side. Press C-UP + L-UP to increase both capacitance and inductance. Press C-DN + L-DN to bypass antenna tuner. Press TUNE + C-Up to toggle Target SWR between 1.5 and 2.0. Press TUNE + L-UP to cycle Auto Tune SWR among 0.5,1.0 and 1.5 above target SWR.
Press TUNE + C-DN to toggle Auto Range on and off. Press TUNE + L-DN to toggle Meter Range between 300 and 30 watts (disable Auto Range)

Figure 3.

Button Action.

5

Do not connect WIRE and ANTENNA at same time!

Figure 4 MFJ-991 Back Panel

Power

This jack accepts standard 2.1 x 55 mm coaxial plug with positive center and negative sleeve. tuner requires 12 volts DC at up to 1 amp. Use of regulated supply not mandatory but recommended for best performance. optional 12 volt DC .5 amp power supply, MFJ-136, available from MFJ Enterprises, Inc.

WARNING: Do not apply voltages greater than 18 volts to this unit, or permanent damage to unit may result.

Remote Port: female DB-9 connector for connecting to MFJ-993 RC Remote Control, allowing remote operation of tuner. MFJ-993RC duplicates all front panel buttons except {POWER}. In addition, there two LEDs on remote control. red Tuning LED lights to indicate tuning in progress and green SWR LED lights when SWR below target SWR.

Note: To use remote control, {AUTO] button on automatic tuner must be locked in, otherwise, Automatic mode selected.

Radio Interface: 3.5 mm stereo phone jack for connecting to tuner interface connector of compatible radios. tuner should be powered on first (both needles will bounce) and then radio, so radio knows remote tuner present. The Radio Interface works with radios that compatible with Icom AH-3, Icom AH-4 and Alinco EDX-2 tuners.
When connected to compatible radio, it enables Tune button on radio. Pressing Tune button on radio causes radio to temporarily switch to CW mode, transmit 10 watts and stait tuning process. Once tuning process completed, tuner signals radio and radio returns to previous mode and power setting.

WARNING: Make sure +13.8 volts connection on radio's tuner port capable of supplying at least 1 amp of current, since MFJ-991 use up to 1 amp. Interface cables for Alinco and Icom radios available from MFJ Enterprises, Inc. Interface cables for compatible Kenwood and Yaesu radios will be available in future.
MFJ-5124A interface

6

Pin 1 (Ground) connects to Sleeves of both 3.5 mm Stereo Phone Plug and Power Plug.
Pin 2 (+13.8V) connects to Center Pin of Power Plug. Pin 3 (Key) connects to Tip of 3.5 mm Stereo Phone Plug. Pin 4 not connected.
Pin 5 (Start) connects to Ring of 3.5 mm Stereo Phone Plug.

Figure 5. Alinco Interface Cable.

The MFJ 5241 interface cable provides power and control between Icom radio and MFJ automatic tuner. Supported Icom radios IC-706, IC-707, IC-708, IC-725, IC-728, IC-736, IC-738, IC-746, IC-756, IC-765, IC-775, and any Icom radio that supports Icom AH-3 and AH-4 tuners.

Push and hold radio's {TUNER] button for two seconds to start tuning process.
Push {TuNER] quickly to bypass tuner.
Pin 1 (Key) connects to Tip of 3.5 mm Stereo Phone Plug. Pin 2 (Start) connects to Ring of 3.5 mm Stereo Phone Plug. Pin 3 (+13.8V) connects to Center Pin of Power Plug. Pin 4 (Ground) connects to Sleeves of both 3.5 mm Stereo Phone Plug d Power Plug.

Figure 6. Icom Interface Cable.

Transmitter: SO-239 connector for coax cable from transmitter or transceiver. Ground: Wing-nut terminal for RE ground wire connection. wire: Binding post for connecting single wire antenna. Notice WIRE binding post internally connected to ANTENNA connector.

Antenna: SO-239 connector for coax cable from antenna. Notice ANTENNA connector internally connected to WIRE binding post.

Note: To use ANTENNA connector, make sure to remove wire antenna, if any, from WiRE binding post.

7

WARNING
Never operate tuner with its cover removed. Contact with components inside tuner while transmitting will result in painful RF burns. Locate tuner so that rear terminals not accessible during operation. single wire connection may have high voltage while transmitting. Disconnect all antennas from tuner during lightning storms. Always tune with low power (about 10 watts) Apply maximum power only after tuning up.
Never exceed tuner specifications.
Do not transmit with high SWR for extended periods of time.

1. Place tuner in convenient location at operating position. With random wire antenna feed through insulator can have high RF voltage. This voltage can cause serious RF burns if terminal touched when transmitting. Be sure to locate tuner so this terminal cannot accidentally be contacted during operation.
2. Connect tuner to transmitter with 50-ohm coaxial cable (such as RG-8/U) See Figure 1 on page 3.
3. Connect antenna to tuner as follows: Coaxial feedline to SO-239 connector labeled ANTENNA or RandoM wire or single wire line antennas should be connected to WIRE binding post on back of tuner.

Note back panel warning: Do not connect WIRE and ANTENNA at same time! Note: Route all single and random wIRe antennas safely to prevent RF burn hazard.

4. GROUND post provided for RF ground connection. See Grounding Hints" on page 13.

5. Connect 12 to 15 VDC power source to inputjack labeled POWER.

SWR/wattmeter
The backlit cross-needle meter measures forward power, reflected power, and SWR, and operates whenever tuner powered on. Forward power up to 300 watts displayed on left-hand FORWARD meter scale. Reflected power up to 60 watts read on right-hand REFLECTED meter scale. low-power tuning, meter ranges of 30 watts forward and 6 watts reflected available. Divide readings on these scales by ten when in low power meter range.
To toggle between high and low meter ranges, press {TUNE] and {L-DN] buttons simultaneously. (Figure 7. SWR/wattmeter) forward needle will read "300" for high range and "30" for low range until buttons released, to indicate range selected.

8

SWR read from eight red SWR curves that range from 1.0 to infinity. SWR measured by observing point where forward and reflected power needles cross on red SWR Vforward power curved scales across center of meter. No cumbersome or time-consuming SWR sensitivity adjustments required with this meter.
Figure 7 shows SWR of approximately 2.0.

forward power meter also indicates various operational states of tuner. Refer to "Tuner Status Indicators" on page 12 for more details.

Setup
You can set up how MFJ-991 tuner works and behaves. In addition to displaying power and SWR, meter also indicates tuner status when you make setting changes. meter needles bounce, or rise to one point and stay, to provide information. In this mode meters do not indicate power levels. For example, when you press {C-DN] and {L-DN] simultaneously to place tuner in bypass mode, reflected needle bounces to 20-watt mark until you release buttons.

Table 2 summarizes meter needle stationary and bounce codes.

Target SWR
You can set target SWR to 1.5 or 2.0. tuning process will stop when match with SWR less than or equal to target SWR found. default 1.5. Setting target SWR to 2.0 may require shorter tuning times.

You can toggle target SWR between 1.5 and 2.0 by pressing {TUNE] and {C-UP] simultaneously; meter needles intersect at SWR of 1.5 or 2.0 to indicate change.

Auto Tune SWR
You can set SWR threshold to 0.5, 1.0 or 1.5. In automatic mode, tuning process will automatically start when SWR above target SWR by this amount of SWR threshold.
For example, for target SWR of 1.5 and auto tune SWR of 1.0, tuning process will start whenever SWR above 2.5 (5 + 1.0) and there at least five watts of RF power. Default 1.0.
Press {TUNE] and {L-UP] simultaneously to cycle auto tune SWR among 0.5, 1.0 and 1.5 (Reflected Power meter needle reads 5 20 and 60 watts, respectively).

9

Press {TUNE] and {C-DN] simultaneously to toggle Auto Range on and off. Press {TUNE] and {L-DN] simultaneously to toggle between 300 and 30 watts meter range and disable Auto Range.

Operation
Manual Tuning
In certain cases operator may wish to touch up tuner settings For example, if target SWR set at default of 1.5, tuner will stop when match of 1.5 found. In all cases, manual tuning gives user control of tuner if desired.
Manual tuning accomplished by using {C-UP] {CDN] {L-UP] and {L-DN] buttons. Since it not known if more or less capacitance (or inductance) needed, manual tuning must be by trial-and-error. Press {C-UP] one time, and reflected power will indicate if {C-UP] right direction. If it was, press {C-UP] again and observe reflected power. If not, press {C-DN] twice (once to return to original setting of C, and once for one click past it)
Manual tuning of inductance similarly accomplished, using {L-UP] and {L-DN] Since capacitance and inductance interdependent, some back-and-forth between two may be needed, just as in conventional tuner with knobs. Once you familiar with this process, you will learn how to match certain antennas and frequencies.
Pressing {C-UP] and {C-DN] buttons simultaneously moves capacitance back and forth from one side of inductance to other. Factory default with capacitance on transmitter side. To move capacitance to opposite (antenna) side, press {C-UP] and {C-DN] simultaneously. reflected needle will bounce to 5-watt mark. Press {C-UP] and {C-DN] simultaneously again to return capacitance to transmitter side (and forward needle will bounce to 30-watt mark to indicate change).
General rule of thumb that loads with impedance higher than 50 ohms call for capacitance on antenna side; loads lower than 50 ohms call for capacitance on transmitter side.
Pressing {C-DN] and {L-DN] simultaneously or pressing {TUNE] quickly places tuner in bypass mode; i.e. zero inductance and zero capacitance. RF from transmitter goes directly to antenna with no matching. reflected needle bouncing to 20-watt mark indicates changing to bypass mode.

10

Antenna Memory
The memory resolution width of frequency spectrum that tuner recognizes as being same as tuned frequency already in memory. memory resolution approximately 0.1 percent of lower frequency of each amateur band. For example, memory resolution on 40-meter band (7000 to 7300 kHz) 7 kHz; if tuner has memorized setting for 7050 kHz, it will automatically call up this setting for any frequency from 7047 to 7053 kHz. memory resolutions for HF amateur bands 160 through 10 meters

Meter: Frequency Range: Memory Resolution

160: 1800-2000: 2
75/80: 3500-4000: 4
60: 5330.5, 5346.5, 5366.5; 5371.5 and 5403.5: two memory locations 40: 7000-7300: 7
30: 10100-10150: 10
20: 14000-14350: 14
17: 18068-18168: 18
15: 21000-21450: 21
12: 24890-24990: 25
10: 28000-29700: 28

Table 1. Antenna Memory Resolution.

memory resolution for non-amateur frequency bands between 1 60 and 1 0 meters approximately one percent of lower frequency of that band. There more than one thousand antenna memory locations.

To clear antenna memory, turn off power to tuner, then press and hold both {TUNE] and {CDN] buttons while turning on power. Both meter needles will read half scale, forming triangle, asking you to confirm deletion.
Press {C-UP] to confirm delete (both meter needles will read full scale) or press {L-UP] to cancel antenna memory delete (both meter needles will read zero).

Total Reset
erases antenna memory and returns all tuner settings to their factory default states.
To achieve this, ttirn power off, press and hold {TUNE}, {L-DN] AND [C-DN] buttons while turning on power.
meter needle readings will be same as for antenna memory delete: half scale. Press {C-UP] to confirm total reset (needles go to full scale) or press {L-UP] to cancel total reset (needles go to zero).

11

If too much power applied when tuning in progress, tuner will cease tuning routine and Forward Power meter needle will bounce to full scale. This occurs when forward power exceeds 75 watts and SWR greater than 3.0, or when forward power exceeds 125 watts regardless of SWR. If more than 150 watts applied to tuner, tuner will go into bypass mode; both Forward and Reflected meter needles will bounce to full scale.

Default Tuner Status Button Action Meter Needles

Stationary Needle Reads
Meter Range 30 watts {TUNE] + {L-DN] 30-watt Forward Meter Range 300 watts {TUNE] + {L-DN] 300-watt Forward Auto Range OFF {TUNE] + {C-DN]
Sticky Tune OFF {TUNE] 2 seconds 5-watt Reflected Auto Tune SWR +0.5 {TUNE] + {L-UP]
Auto Tune SWR +1 .0 {TUNE] + {L-UP] 20-watt Reflected Auto Range ON {TUNE] + {C-DN]
Sticky Tune ON {TUNE] 2 seconds 60-watt Reflected Auto Tune SWR +1.5 {TUNE] + {L-UP]
Both Needles -Stationary
NO, do not delete {L-UP] 0 scale
Confirm Delete N/Mid-scale
YES, delete {C-UP] Full scale
Target SWR 1.5 {TUNE] + {C-UP] Needles intersect at SWR 1.5 Target SWR 2.0 {TUNE] {C-UP] Needles intersect at SWR 2.0

Bouncing Needle Reads

Capacitor on Transmitter side {C-UP] + {C-DN] 30-watt Forward Insufficient power to tune (Forward 5 watts) {TUNE] 100-watt Forward
Too much power to tune (Forward 75 watts and SWR 3) N/300-watt Forward or (Forward , 125 watts)
Capacitor on Antenna side {C-UP] + {C-DN] 5-watt Reflected Bypass Mode {C-DN] + {L-DN] or (L = 0 and C = 0) {TUNE] 0.5 second 20-watt Reflected
L or C at its limit {C-UP] {C-DN] 60-watt Reflected during manual adjustment
{L-UP] or {L-DN] Both Needles -Bouncing Input Power Overload
(Forward , 150 watts) N/Full scale

Table 2. Meter Needle Codes.

12

CAUtiON
For operator safety, good outside earth ground or water pipe ground should always be installed and connected to case of antenna tuner. Make certain safety ground also connects to transmitter and other station accessories. wing-nut post marked GROUND provided for ground connections. For safety, please use good DC and RF grounds. It particularly important to have good RF ground when using single wire feeder. When using single wire feeder, tuner needs something to "push" against in order to force current into single wire feedline. if good RF ground not available, RF will usually find its way back into power line (RFI) transmitter audio circuits (RF feedback) or operator (RF burns). Metal water pipes and ground rods provide good DC and AC safety grounds, but they often inadequate for RF grounding because they single conductors. Ground rods by themselves almost useless for dependable RF grounding. RF grounds work much better when "spread out" over large area, especially when they employ multiple connections directly to equipment ground point. Metal water pipes, heating ducts, and fences may work (especially if they connected together with multiple wires) but best RF grounds radial systems or multi-wire counterpoises. Radials and counterpoises provide large, low resistance surfaces for RE energy.
RF and lightning travel on surface of conductors. Braided or woven conductors have high surface resistance to lightning and RF. Ground leads for RF and lightning should have wide smooth surfaces. Avoid use of woven or braided conductors in RF and lightning grounds unless lead needs to be flexible.

Antenna System Hints
Location
For best performance, end-fed longwire wire antenna should be at least one quarter-wavelengtb long at operating frequency. Horizontal dipole antennas should be at least half-wavelength long and located as high and clear as possible.
While good RF grounds help signal in almost any transmitting installation, it extremely important to have good RF grounds with long wire or other Marconi-style antennas.

Matching Problems
Most matching problems occur when antenna system presents extremely high impedance to tuner.
When antenna impedance much lower than feedline impedance, odd quarterwavelength

13

One example where this problem occurs on 80 meters when odd quarter-wave (60 to 70 feet) open wire line used to feed half-wave (100 to 140 feet) dipole. odd quarter-wave line transforms dipole's low impedance to over three thousand ohms at tuner. This because mismatched feedline odd multiple of 1/4 wavelength long. line inverts (or teeter-totters) antenna impedance. A problem also occurs on 40 meters with this same antenna example. feedline now multiple of half-wave (60 to 70 feet) and connects to ful 1-wave high impedance antenna (100 to 1 40 feet) half-wave line repeats high antenna impedance at tuner. antenna system looks like several thousand ohms at tuner on 40 meters.
This places enormous strain on balun and insulation in tuner, since voltages can reach several thousand volts. This can cause component arcing and heating. The following suggestions will reduce difficulty in matching antenna with tuner:
Never center feed half-wave multi-band antenna with high impedance feedline that close to odd multiple of quarter-wave long. Never center feed full-wave antenna with feedline close to multiple of half-wave long.
If this tuner will not tune multi-band antenna, add or subtract 1/8 wave of feedline (for band that won't tune) and try again. Never try to load G5RV or center fed dipole on band below half-wave design frequency. If you want to operate 80-meter antenna on 160 meters, feed either or both conductors as longwire against station ground.

To avoid problems matching or feeding any dipole antenna with high impedance open wire lines, keep lines around these lengths. worst possible line lengths shown in brackets]

160 meters dipole: 35-60, 170-195 or 210-235 feet {avoid 130, 260 ft] 80 meters dipole: 34-40,90-102 or 160-172 feet {Avoid 66, 135, 190 ft] 40 meters dipole: 42-52, 73-83, 112-123 or 145-155 feet {Avoid 32, 64, 96, 128 ft}
Some slight trimming or adding of feedline may be necessary to accommodate higher bands.

WARNING
To avoid problems, dipole antenna should be full half-wave on lowest band. On 160 meters, 80 or 40 meter antenna fed normal way will be extremely reactive, with only few ohms of feedpoint resistance. Trying to load 80 meter half-wave dipole (or shorter) antenna on 160 meters can be disaster for both your signal and tuner. best way to operate 160 meters with 80 or 40 meters antenna to load either or both feedline wires (in parallel) as longwire. antenna will act like "T" antenna worked against station ground.

14

POWER-ON OPERATIONS
(Press and hold buttons While turning on poWer.

Press and hold C-Up + POWER to get firmWare version number. Press and hold L-UP + POWER to start self test. Press and hold C-DN + POWER to test relays. Press and hold L-DN + POWER to test poWer-doWn circuitry. Press and hold TUNE + C-UP + POWER to calibrate Wattmeter. Press and hold TUNE + L-UP + POWER to calibrate SWR bridge. Press and hold TUNE + c-DN + POWER to delete antenna memory. Press and hold {TUNE} + {l-DN} + POWER to reset factory defaults. Press and hold {TUNE] + [L-DN] + [C-DN] + POWER to perform total reset. Press and hold C-UP + L-UP + POWER to calibrate frequency counter.

Figure 8. Power-On Operations.

INTERFACE CABLE MUST BE DISCONNECTED FROM TUNER IF RADIO POWER ON.

Firmware Version Number
Make sure meter calibrated. To obtain firmware version number press and hold {C-UP} button while turning power on. version number X.XY represented by meter forward needle for XX and reflected needle for Y. For example, forward needle on 10-watt mark and reflected needle on 2-watt mark represent firmware version number 1.02. Release button to resume normal operation.

Resetting Tuner
Each time tuner powered off, microprocessor saves all memories and configurations to non-volatile memory ready to be used next time unit turned on again. If tuner not working properly, even on initial power on, try resetting to factory defaults.

Factory Defaults
The unit shipped with following default settings:

Inductance 0 H
Capacitance 0 pF on transmitter side
Target SWR 1.5

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Note: Resetting to factory defaults does not erase antenna memory. To reset tuner to these defaults:

1. Turn off power to tuner.
2. Press and hold both {TUNE] and {L-DN] buttons while turning power on.
3. Release buttons when both meter needles read full scale.
4. Resume with normal operation.

WARNING: If tuner behaving weirdly or acting erratic, try resetting tuner to factory defaults.

Delete Antenna Memory
To delete antenna memory, turn off power to tuner, and then press and hold both {TUNE] and {C-DN] buttons while turning power back on. Both meter needles will read half scale.
Press {C-UP] button to delete antenna memory (both meter needles go to full scale)
or press {L-UP] button to cancel (both meter needles go to zero scale) Release button to resume normal operation. Remember that antenna memory will be lost!

Total Reset
To erase antenna memory and reset to factory defaults, press and hold down {TUNE] {C-DN] and {L-DN} buttons while turning power on. Follow confirmation procedures for Delete Antenna Memory" above. Remember that all antenna memories will be lost and tuner setting will return to default!

Self Test
A self-test routine checks functions of tuner. This routine checks meter, front-panel buttons, and internal memory. During self-test, you may stop test by turning off unit however, this should NOT be done during memory test or memory could be corupted. self-test can be completed in approximately 30 seconds. This test also can be used to test MFJ-993RC Remote Control. Make sure to lock in {AUTO] button on tuner before starting self-test, and press buttons on MFJ-993RC instead of front-panel buttons when prompted.

Note: Performing selftest will reset it to its factory default settings.

Here self-test procedure:

1. Turn off power to tuner, and press all buttons to out position.
2. Unplug radio interface cable, if one connected, from tuner.
3. If testing MFJ-993RC Remote Control, connect it to Remote plug and make sure {AUTO] button on tuner locked in; otherwise, go to next step.
4. Press and hold only {L-UP] button while turning power on.

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6. reflected needle goes to 3-watt mark. Now, press each of front panel buttons in this sequence: {C-UP]
{C-DN]
{L-UP]
{L-DN]
{AUTO] and then {TUNE]
forward needle should bounce once for each press, and reflected needle should move up division for each press.

7. unit then tests its non-volatile memory. This will reset unit to its factory default settings.

8. If unit okay, both meter needles will go to full scale. If there problem, forward needle will bounce and reflected needle mark will indicate failure.

9. Turn tuner power off.

Failure
Reflected
Message Needle (watts) Indicates
C-UP FAIL 3 {C-UP] button shorted or improperly connected. {C-DN} FAIL 4 {C-DN] button shorted or improperly connected. {L-UP} FAIL 5 {L-UP] button shorted or improperly connected. {L-DN} FAIL 7.5 {L-DN] button shorted or improperly connected. {AUTO} FAIL 10 {AUTO] button shorted or improperly connected. {TUNE} FAIL 15 {TUNE] button shorted or improperly connected. Radio interface cable connected but radio power off. MEMORY FAIL 20 Non-volatile memory circuitry improperly connected. WAKEUP FAIL 30 Microprocessor wakeup circuitry problem. PD FAIL 40 Power down circuitry problem.

Table 3. Failure Messages.

Power-Down Circuit Test

When 12 VDC power to tuner turned off, tuner saves all settings to non-volatile memory.

Power-Down Circuit Test checks power down detection circuitry. It recommended that this test be done immediately after regular selftest described above.

Note: tuner must be reset to factory defaults before performing this test

Here test procedure:

1. Make sure power to tuner off.
2. If tuner has been reset to factory defaults, skip to step 6; otherwise continue with step 3.
3. Press and hold both {TUNE] and {L-DN] buttons while turning power on.
4. Release both buttons when both meter needles read full scale.
5. Turn power off.
6. Press and hold only {L-DN] button while turning power on.
7. If power down detection circuitry okay, both meter needles will go to full scale. If there problem, forward needle will bounce and reflected needle will read 40, per Table 3 above.
8. Turn power off.

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WARNING: Turn off transmitter power or disconnect transmitter before performing this test; otherwise, damage to tuner can result.

1 To test relays and their control circuitry, press and hold {C-DN] button while turning power on. Both meter needles will bounce.

2. Release button.

relays tested in groups of four as shown in table below.

{C-UP] {L-UP] {C-DN] and {L-DN] buttons used to toggle each relay in each group of four.
Press button to engage relay and release it to disengage relay. Listen for relay clicks.
Press {TUNE] button to proceed to next group of four relays. There 18 relays in tuner.
Repeat above procedure to test all relays. Normal operation resumed after this test.

reflected power needle indicates which group of relays being checked as follows:
Reflected Needle {c-UP} {L-UP} {c-DN} {L-DN} 1-watt mark
Not used 3 4
2-watt mark 5 6 7 8
3-watt mark 9 10 11 12
4-watt mark 13 14 15 16
5-watt mark 17 18 19
Not used Since there no relays number 2 and number 20, pressing {L-UP] button in first group and last button {LDN] in last group will not produce click.

Wattmeter Calibration
To calibrate wattmeter, you will need Phillips screwdriver and tuning tool or small flat blade screwdriver.

WARNING: Never operate MFJ-991 with its cover removed; dangerous voltages and currents can be present during operation. Never exceed tuner specifications.

Note: trimmers involved in this calibration located on circuit board behind front panel; do not confuse these with SWR bridge trimmers.

1. Turn off power to tuner and transmitter.
2. Remove cover from tuner (12 screws) with Phillips screwdriver.
3. Press and hold both {TUNE] and {C-UP] buttons while turning power on. Both meter needles will bounce. Release buttons.
4. forward needle will go up. Use small flat blade screwdriver and adjust FWD trimpot R75, located behind display, to set forward power needle to 100-watt mark.
5. Press {TUNE] to calibrate reflected power needle. forward needle will drop to zero and reflected needle will go up.
6. Adjust REF trimpot R76, located behind display, to set reflected power needle to 20-watt mark.
7. Press {TUNE] to resume normal operation.
8. Turn off tuner power and secure cover back onto tuner.

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WARNING: Do not touch anything inside tuner during operation! Serious, painful RF bburns can occur.

WARNING: Never operate MFJ-991 with its cover removed; dangerous voltages and currents can be present during operation. Never exceed tuner specifications.

Note: trimmers involved in this calibration located on main circuit board in front of TRANSMITTER connector; do not confuse these with SWR/wattmeter trimmers.

1. Turn off power to tuner and transmitter.
2. Remove cover from tuner (12 screws) with Phillips screwdriver.
3. Connect 50-ohm dummy load to ANTENNA connector; connect wattineter between transmitter and TRANSMITTER connector on tuner.
4. Turn on power to transmitter. Select frequency in middle of HF band, such as 7.253 MHz, for calibration.
5. Press and hold both {TUNE] and {L-UP] buttons while turning tuner power on. Both meter needles will bounce. Release buttons.
6. Key transmitter to output 100 watts and adjust trimmer capacitor C9 for minimum reflected power. Notice reflected meter movement exaggerated for easier calibration.
7. Key transmitter to 100 watts output and adjust FWD trimpot R72 until forward power needle indicates 100-watt mark.
8. Press {TUNE] button and observe that reflected power needle goes to full scale.
9. Turn off transmitter and reverse ANTENNA and TRANSMITTER connections; that is, connect 50-ohm dummy load to TRANSMITTER connector and connect transmitter/wattmeter to ANTENNA connector.
10. Turn on transmitter's power.
11. Key transmitter to 100 watts output and adjust REF trimpot R7 until forward power needle (yes, forward needle) indicates 100-watt mark; reflected meter should be at full scale.
12. Press {TUNE] button to end calibration.
13. Turn off power to tuner and transmitter.
14. Remove transmitter/wattmeter and 50-ohm dummy load from tuner.
15. Secure cover back onto tuner.
16. Connect your transmitter to TRANSMITTER connector and connect your antenna to appropriate antenna connector on tuner.

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WARNING: Do not touch anything inside tuner during operation! Serious, painful RF currents can be present during operation. Never exceed tuner specifications.

1. Turn off power to tuner and transmitter.
2. Remove cover from tuner (12 screws) with Phillips screwdriver.
3. Connect 50-ohm dummy load to ANTENNA connector; connect transmitter to TRANSMITTER connector on tuner.
4. Turn on power to transmitter. Set and lock transmitter frequency to exactly 29.000 MHz.
5. Press and hold both {C-UP] and {L-UP] buttons while turning tuner power on. Both meter needles will go to full scale.
6. Key transmitter to output about 10 watts. Adjust trimmer capacitor C118 (located between two big integrated circuits) until tuner's meter needles settle at 0-watt marks. Notice meter movement exaggerated for easier calibration. Nominal tolerance of frequency counter +1 kHz.
7. Turn offthe power to tuner and transmitter.
8. Secure cover back onto tuner.

In Case of Difficulty
If tuner acts erratic, reset tuner to factory defaults by pressing both {TUNE] and {L-DN] buttons while turning power on. If tuner fails to tune, please double check all connections and follow tuning procedures again. Be sure you using enough inductance (through manual adjustment) and minimum capacitance.
If tuner arcs at rated power levels, please double check all connections and follow tuning procedures again. Ensure you not exceeding tuner's rated power handling capability. If you have adjusted tuner manually, be sure you using least amount of inductance and greatest capacitance possible that still allows matching load on operating frequency.

Note: if tuner arcs when operating on 60-meter band, it may be necessary to reduce transmitter output power.
If you still unsuccessful, but tuner does adjust and operate when used with dummy load or another antenna, please read "Grounding Hints" and "Antenna System Hints" on page 13.

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If you have any problem with this unit first check appropriate section of this manual. If manual does not reference your problem or your problem not solved by reading manual, you may call
MFJ Technical Service at 662-323-0549 or MFJ Factory at 662-323-5869.

You will be best helped if you have your unit, manual and all information on your station handy so you can answer any questions technicians may ask.

You can also send questions by mail to
MFJ Enterprises, Inc. 300 Industrial Park Road, Starkville, MS 39759; by facsimile (FAX) to 662-323-655 or
by email to techinfo at sign mfjenterprises.com. Send complete description of your problem, explanation of exactly how you using your unit, and complete description of your station.

List of Accessories
MFJ-993RC: Remote control
MFJ-1316: 12 VDC 1.5 amp power supply
MFJ-5124A: Interface cable for compatible Alinco radios MFJ-5 1 2 4 1: Interface cable for compatible Icom radios MFJ-5409: 6 feet long RS-232 cable, female DB-9 to male DB9 connectors.

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Disclaimer: The information on this site is provided as a public service to the blind and visually handicapped community. While we have done our best to ensure the information provided is accurate, please realize the use of any information on this site is solely at your discretion and we take no responsibility for use or attempted use of this information.