MFJ-998 1500 Watt Automatic Tuner Review

[Moleculo]

While working with the Ameritron ALS-1300 1.2 killowatt HF amplifier, I quickly became spoiled with the instant satisfaction of changing bands and not having to deal with retuning a tube amplifier. However, when I operate on bands other than those my wire antennas are cut for or even on their designed band edges, I was still forced to constantly retune using my Ameritron ATR-30 antenna tuner. The instant gratification of switching bands with the amplifier was kept in check by the need to manually adjust the tuner on dramatic frequency changes. When I made this anecdotal observation to Martin Jue, owner of MFJ Enterprises, he suggested that I try his MFJ-998 1500 watt auto tuner which he said would match the Ameritron ALS-1300 amplifier nicely. When he offered to send one to me to review, I obviously couldn't refuse an offer to play with one of the few auto tuners on the market that can handle over a killowatt or RF.

MFJ-998 Basic Features

These are the important operating characteristics of the MFJ-998 legal limit autotuner:

• 1500 watt continuous power handling
• SWR matching range is up to 32:1 for antennas
• Impedance matching range from 12 to 1600 ohms
• Typically takes between 5 and 20 seconds to tune
• 2 coax antenna connectors, one wire connector. You must decide to use either the Antenna 1 coax or the wire connector, not both.
• Over 20,000 memories to remember tuner settings.
• Adjustable target SWR, from 1.0:1 to 2.0:1
• Built in amplifier bypass to protect amplifiers from high SWR while tuning
• Firmware upgradeable
• Radio interfaces available for most transceivers.

As always, the first thing I do when I acquire any new radio equipment is take some pictures of both outside and then open it up to see what is inside. Here are a few pictures of what I found:

Auto tuner face:

In this picture, you can see the typical MFJ/Ameritron cross needle meter, the digital LCD display which shows various settings and antenna adjustments, the buttons that control antenna switching, as well as automatic and manual tuning.

Right back of tuner. Notice that you use either the Antenna 1 connection or the wire connection, but not both:

Left rear of tuner:

The "Amp Enable In" RCA connection is the amp key interface from the transceiver. The "Amp Enable Out" RCA connection goes to the amplifier. These connections are important if you want to enable the tuner's built-in amplifier protection. The "Radio Interface" is used if you purchase an optional interface for your transceiver to trigger tuning. The Serial Port is used for firmware upgrades, and the 12v power adapter requires a 1.5 amp power supply to work the tuner.

Inductor network:

This picture shows the relays and inductors used to handle the potential 1.5 KW of power that the tuner is rated for. As you can see, the size of these inductors is fairly beefy.

Capacitance network:

This picture shows the large number of capacitors and relays needed to work in conjunction with the inductors.


LCD Display Options

The MODE button on the front panel toggles between several LCD display options. As you can see, the LCD display usually shows your operating frequency on the top row along with the current SWR.

The "standard" display shows forward and reflected power:

If you tap the MODE button, the LCD display changes to a graph, showing power output on top and reflected power on the bottom:

This picture demonstrates one oversight on the tuner's front panel; if the power output on the LCD display is on top, the label below representing the scale should also have power on top with SWR on the bottom. As you can see, the label is reversed.

When you hit the MODE button again, the graph displays only the SWR relative to the label below:

Another MODE key press shows the antenna selected, the present inductance and capacitance settings, and the power output:

The capacitance figure is shown toward the right side of the display and indicates that it is being applied to the transmitter side of the tuner. This setting is accompanied by two beeps.

If you hold the C-UP and C-DN buttons, the tuner applies the capacitance to the antenna side of the tuner. As you can see, the SWR has also changed as a result.

The tuner needs about 5 watts of input power to load up the antenna. If it doesn't see that much power, you get this message:

This message will be accompanied by the phrase "QRO" sent as beeps in CW.

If you supply too much power while tuning, the amplifier displays a message to decrease power, while sending "QRP" in CW:

Coming up next, basic setup instructions and my setup...

 

[Justme]

Nice article, thanks.
Using the MFJ 998 at the bottom of the inverted L ( 77 feet high, 77 feet horizontal) to tune it from 160 - 20.
I have several antenna's for each band, and the MFJ 998 regularly gets 1000 watts to tune on 160 - 20, never let me down, except the filament lamp on the analog meter, just replaced it with a warm white led.

I'll be reading the rest of your follow up with interest

Cheers,
Cor

 

[Moleculo]

Nice article, thanks.
Using the MFJ 998 at the bottom of the inverted L ( 77 feet high, 77 feet horizontal) to tune it from 160 - 20.
I have several antenna's for each band, and the MFJ 998 regularly gets 1000 watts to tune on 160 - 20, never let me down, except the filament lamp on the analog meter, just replaced it with a warm white led.

I'll be reading the rest of your follow up with interest

Cheers,
Cor

Cool! As an owner of the MFJ-998, please feel free to contribute to the review!

 

[Justme]

LOL

Limited review then, because it is only used here to feed the inverted L at the bottom directly with anything of 10 to 1000 watts from the FT 2000 D and Heathkit SB-1000.
The inverted L is 77 feet high, and another 77 feet wire sloping down to some trees 35 yards away ending at 11 yards above the ground.
Total length of ground radials ( buried) 2700 feet.

The ground is young sea clay good for H.F.
The tuner is set to tune when the SWR is worse as 1 - 1:5.
The MFJ 998 tunes the inverted L from 160 - 20 meter, and does so for the last 2 years without a hitch, mistake or any fault.
Just a short 20 watt AM carrier on the other band is enough to use one of the 20.000 memories to find the right mix of L and C and where the C needs to be, before or after the L.

On 80 meter the L is almost a 5/8 antenna, still a reasonably high impedance but the 998 never protests even with the 1000 watts put through.
Same for 40 just over a full wave antenna ( 46 meters long) but no problems, no protests.

I'm very active on 160 with a group of guy's here, worked Eurasia ( 6000+ KM) Canada, USA etc in SSB on 1.850 plus minus QRM.

The other tuner, 300 watts is the MFJ 993 B 4 years old, used to tune the OCF and verticals for the higher bands if need be, most are resonant and the SB-1000 will have no problem putting it's power in them directly without tuner.

The 993 B is mostly used on holidays in France to tune some experimental wires or the throw in a tree Holiday OCF ( home brew 160 - 10.)

The only nag i have about both tuners is the light bulb behind the analog meter went kaput after a few weeks, i replaced them by a few warm white LEDs, and had no problem after that.

For the 998 i use an 3 Amp power supply, during long tune sections the tuner does use some power switching the relays.... 1.5 Amps was just borderline there.

I can tune the inverted L from 160 - 10 meters without problems here, the tuner does not mind, but there the other verticals on the roof do a lot better.
But if the need arises, yes, it will tune the L over all frequencies.

So far my experiences, i didn't use the tuner for any other antenna, the 993 B is a different story
That saw some weird antenna experiments here and on our Holiday's.

So far i judge the MFJ 998 as a 5 out of 5.
Same goes for the 993 B that saw some serious abuse.

 

[office888]

Those inductors look woefully small!

 

[Justme]

Depends on your criteria, they do the job well.

Those inductors look woefully small!

 

[RickC.]

Thanks for the review!

I've been eyeing the LDG 600W autotuner for use with my old SB-200. I've found Martin Jue to be a nice man and have always enjoyed talking to his guys at hamfests.

To be honest though, I have had such problems with simple things such as power supplies and antenna switches bought from MFJ and slow-to-nonexistent product support that I'd be reluctant to spend money for an MFJ product that had to "think". I have stuff sitting in the boxes, as new, that never were used and were not worth the shipping again both ways to exchange. I can be in Starkville in 3 1/2 hours.

To be fair, the 941-E tuner I bought new from them has never let me down and has always done what I've asked of it-- and if I can get a deal on a used 986 tuner I'll buy one. The knock on MFJ has always been QC, and I'm afraid that's been my experience also.


Rick

 

[Justme]

Rick,

One of the points i took in consideration was the bad rep MFJ had buying the MFJ 993 B but when it arrived home i opened it up to check it out.

Compared to other products i've seen from the MFJ line i was pleasantly surprised to see the innards of the 993 - B and i just touched up a few points i thought they could be done better.
That tuner is working fine for the last years here, and i abused it quite a lot...

The 998 had the same quality when i got it, all soldering was done well, just from both tuners the incandescent lamps went in a few weeks, replaced them by a few warm white LED's.

I just checked if all screws were tight, checked connections, soldering etc, to see if all was done right.
The price is compared to other tuners quite low, but the tuner does it's work fine here with the inverted L on several bands with a wide range of impedances it gets to work at.

73,
Cor

 

[dxhound]

How is the tuner as far as loss? I currently use a ten tec 238b. Very good tuner that tunes everything and has minimal loss.

 

[RickC.]

Rick,

One of the points i took in consideration was the bad rep MFJ had buying the MFJ 993 B but when it arrived home i opened it up to check it out.

Compared to other products i've seen from the MFJ line i was pleasantly surprised to see the innards of the 993 - B and i just touched up a few points i thought they could be done better.
That tuner is working fine for the last years here, and i abused it quite a lot...

The 998 had the same quality when i got it, all soldering was done well, just from both tuners the incandescent lamps went in a few weeks, replaced them by a few warm white LED's.

I just checked if all screws were tight, checked connections, soldering etc, to see if all was done right.
The price is compared to other tuners quite low, but the tuner does it's work fine here with the inverted L on several bands with a wide range of impedances it gets to work at.

73,
Cor

Thanks Cor,

I just bought a used 962 (with the switched inductor, not the roller), we'll see how it goes.

Rick

 

[Justme]

The MFJ 998 is a L tuner, quite good in efficiency.
Even losing a few % will not be detectable at the other end.
Running the 46 meter long L on 80 meters where the tuner has to work quite hard to tune the L to the SB-1000 amp output, the innards don't get hot, meaning the efficiency is quite good.

( input 1000 watts then)
Looking at my L with the MFJ 269 analyser it really needs to work hard then :tongue:
The MFJ 998 will tune that L from 160 to 10 without missing a hitch, the complex impedances the tuner sees are handled quite well.

As ham i never had a problem with MFJ, cheap as chips, and indeed some designs needed some work when you bought them....
The MFJ 993-B and MFJ 998 were a surprise to see their innards and actually quite good build quality.

Rick, good luck with your tuner, i'm sure it will work quite well.

 

[Moleculo]

Tuner Configuration Screens

The MFJ-998 has quite a few optional settings to allow you to make it behave in the manner you want. In this section, I'll run through most of the options and explain their operation.

If you don't purchase an optional rig interface cable (more on this later), you can put the tuner into Auto mode, Semi-Auto mode, or "StickyTune" mode. Auto mode simply automatically starts the tuning process whenever more than 5 watts is input and the SWR is higher than the preset tuner level. Auto mode is indicated by an "A" to the right of the antenna port indicator, which is also to the right of the frequency. In this picture, the "1A" next to the frequency indicates that antenna 1 is selected and the tuner is in Auto mode:

Semi-Auto mode is another option that allows you to control when the auto-tuning procedure is started. When this setting is activated, the tuner will only start the tuning procedure when there is at least 5 watts input and you press the TUNE button between 0.5 and 2 seconds of duration. It is indicated by an "S" next the the "A" near the antenna port. In this picture, you can see that the "1A.S" indicates that the tuner is in Semi-Auto mode:

"StickyTune" is a mode that causes the tuning process to activate whenever at least 5 watts is input, regardless of the present SWR. It is indicated by a bar over the top of the "S" as seen in this picture:

The "TARGET SWR" setting is one of more important settings to control tuner behavior. This is the SWR that the tuner will attempt to achieve during it's tuning procedure and will continue to search for until it finds something less than or equal to that setting. The default setting for TARGET SWR is 1.5:1. In this picture, you can see that I've changed it to search for SWR less than or equal to 1.2:1.

The "TARGET SWR" is also the baseline used to determine when the tuner should activate the tuning cycle. The setting shown on this screen is the variance in SWR from the baseline at which the tuner will automatically start the tuning process when in Auto mode. As you can see from the previous both the picture and this one, I've set it to start tuning when it sees an SWR of 1.7 or higher:

As I mentioned earlier, the tuner has an amplifier protection feature that will disable the PTT relay on the amplifier when a high SWR is detected. This sets the threshold at which the protection will be engaged. The 2:1 SWR setting shown is the default which means that the amplifier will be disengaged whenever an SWR higher than 2:1 is detected.

This amplifier protection circuit is a neat and important feature, but it has a caveat: If the amplifier also has a fast SWR protection circuit, it is likely that the amplifier's protection will trip before the tuner can engage it. The Ameritron ALS-1300 that I'm testing behaves in this very manner. When the tuner's tuning process is engaged the amp will trip into protection mode if a high SWR is presented at any point during the tuning process. While this behavior isn't a problem when the amp is within reach to toggle the reset, it could be an issue if you have the amplifier mounted remotely and have no way to cycle the amp's protection circuit. Ideally the tuner would bypass the amp more quickly than the amp's protection circuit can engage, but I'm not sure how possible that really is. The bottom line is that this behavior is NOT a design flaw and everything is performing as designed.

In the next segment, I'll finish up the optional settings...

 

[Robb]

Did you ever have a chance to compare the meter readings against analog meters for power and SWR? I'm sure that you - like many other people - aren't geared up like "UL"/Underwriter Laboratories to do exhaustive testing. Just was wondering if the brain inside this tuner is accurate - and possibly even adjustable to become more accurate. Does it correspond to your amp's reading; or maybe a Cantenna and a Bird are enough to sort it out.

I'm guessing that the MFJ-993B that I have is the same processor inside. Sounds like the same features - although yours is built for more power in mind. But I have never tested it for accuracy as yet. But since you are the one writing this review, well.

Waiting for the next part to come . . .

 

[Moleculo]

Robb,

Yes, I have done that and have some interesting observations. I plan on getting to that part soon.

Tuner Options Continued

Meter range: You can set the internal power meter to one of three settings. The Low range setting is used when you want the forward scale read 300 watts or less and the reflected sale to read 60 watts or less. The High Range setting is used when you want the forward scale to read 3000 watts or less and the reflected scale to read 600 watts or less. In this picture, you can see the Auto setting, which automatically changes the scale based on the power detected:

There is a peak hold meter feature which keeps the highest power output reading bar displayed for about one second:

As I referenced earlier, the tuner has four antenna banks for each antenna port. Each antenna bank can store over 2500 memory settings, and you can turn each bank on and off as needed. The setting shown here has the memory bank A for antenna 1 turned on:

The antenna banks are particularly useful if you have more than one antenna hooked up to an external switch on each port. In this use case you would use each memory banks to automatically save the tuner settings for selected antenna. This feature allows for the tuner to be used effectively for up to 8 antennas.

IntelliTune is name that MFJ has given to the tuner's algorithm. If it can't find the appropriate setting in memory, it engages the tuner function to search for it. You can turn off the searching function by changing this setting to "Off":

The SWR beep setting causes the tuner to play a series of audible beeps depending on the SWR condition. If the SWR is too high, it even sends "SWR" in CW:

Another Beep function allows you to make the tuner completely silent, except for the sounds of the relays. This Beep setting turns off all acknowledgments and also disables the sending of CW for QRO, QRP and QRT.

The tuner has the capability of either displaying all of the tuner setting changes as they are happening or delaying the display update until the tuning operation is complete. If you want to see the screen update as it passes through all of the capacitor and inductor changes, you would change the following menu to ON:

The tuner even allows you to change the behavior of the TUNE button. The default setting (shown) is that it will bypass when tuner when pressed for less than 0.5 seconds. The other option is to reverse the behavior and make the tuner tune when it is pressed for less than 0.5 seconds.

This screen allows you to erase the memory for the current frequency/antenna/band combination. You simply key the transceiver so that the tuner can detect the frequency and change to it's stored setting, then go into the MODE setting until you get to this memory item. When displayed, you just hit the L-UP button to clear the memory:

It's also important to understand that the tuner gives the ability to delete entire memory banks for each antenna individually or delete all memory settings completely. There are also procedures to restore all of the factory settings to default.

Next in the review: Transceiver interface options.

 

[Moleculo]

Interfacing to the Transceiver

This is the block diagram from the manual that describes how the MFJ-998 should be installed in your shack:

Notice RCA cable interface between the transceiver amp key and the amplifier key. This is the necessary cabling to implement the amplifier SWR protection circuit described earlier

Other than the typical coax antenna connections, an additional transceiver cable interface is available as an option. MFJ sells optional rig interfaces that work with most Alinco, Icom, Yaesu, and Kenwood transceivers. Of course, you can homebrew your own, and MFJ provides a pin out diagram for the interface if you choose to do so:

If your rig has the necessary circuitry and interface, the optional MFJ cables allow you to simply press the TUNE button on the tuner, which will cause the rig to change to CW mode and emit a low power carrier, after which the tuner will start it's tuning process.

In my case, I'm using the MFJ-998 with an Elecraft K3, which does not implement the compatible tuner interface. In this case, you put the tuner in "AUTO" tuning mode via the setup menu. You can then choose to use the tuner in completely automatic mode, or switch to semi-automatic mode by pressing the TUNE and ANT buttons simultaneously. Full auto mode causes the tuner to start the tuning process whenever it sees approximately 5 watts input, while semi-auto mode requires you to press the tune button when there is enough input power.

In the case of the Elecraft K3, it implements it's own low power tuning control via the TUNE button on the rig, which causes the rig to change to CW and emit a tone at a low power setting of your choice. When used with the MFJ-998, the easiest method is to put the tuner in AUTO mode, then just hit the TUNE button on the K3, causing the tuner to find a suitable match. When it does, just hit the TUNE button on the K3 again to return to normal operating.

Coming next, my personal experience with the tuner, with some (hopefully) interesting insights...