By Dave Jensen, W7DGJ

Trials and Errors Issue 4 - Tuning Up a Kilowatt

I’m part of a trend in the amateur radio community. Licensed more than 50 years ago as a Boy Scout, I came back to the hobby in my 60’s. I don’t know how I lost all those years of enjoyment (as well as my QSL cards, logbooks, and a beautiful station) but I’m happy to have radio back in my life. Over the pandemic years, I spoke with many who have dusted off their gear and gotten back on the air, and I’ve noticed that we share many of the same interests when it comes to improving our stations.

100 watts and a wire worked for a long time. But a few years ago, I tapped into another trend, because 100W often doesn’t cut through the noise on sideband. Despite the improvements from our current solar cycle, an increasing number of operators have acquired linear amplifiers. Many are powering up to an average of 800-1000 watts with their first amp acquisition . . . some with tube amps, some with solid state, but all of them adding a critical piece of improved infrastructure to their stations.

Of course, in that process, all the other elements must line up to achieve the benefits of this increased power. After replacing my 20M and 40M dipoles with a Kilowatt solution that would resonate on several of my favorite bands, I found out that none of them are perfect – the SWR “sweet spot” is just too narrow on some frequencies. So, I set out to find a reasonably priced kilowatt tuner. In my house, good judgement demands that the cost of another piece of ham gear be “under the radar,” which means less than a grand. I also wanted something truly practical.

By practical, I mean that I have no interest in tuning up a coat hanger or trying to send RF into a 10-to-1 mismatch – that seems like insanity to me. My goal was to add a band (15M) and improve the band edges on my “mostly resonant” frequencies. While my internal tuner on the transceiver will catch issues up to 3 to 1, sometimes there are spots on the band that rise to 4 or 5 to 1 – plus, that amp means that the internal tuner is pretty much worthless.

Automatic Antenna Tuner Solutions for the 1KW Operator

I’ve never been a fan of twirling knobs, which is why I went the solid-state route on my amp and opted for an automatic tuner. Feel free to label me a “plug and play operator;” I won’t be offended because I just want to play radio with friends all over the world, and not get knee deep into fine-tuning. Because of this, a tuner needs to follow me around the bands just as my amp does with its auto band switching circuits. I found three choices in my price range. While great companies like ACOM, Palstar, and Flex offer the kind of automatic legal limit antenna tuners that I still gaze at fondly in a Hamfest, spending $2000 on a tuner wasn’t in the cards.

My initial budget was in the $500 range, so I first bought the LDG AT-1000PROII, a popular seller ($549). After just a couple of days, however, I decided that this one didn’t work with my configuration because LDG had recently dropped the fully automatic mode and I wasn’t aware of that at purchase time. As a result, this tuner requires a semi-auto approach where the user bypasses the amp, turns down the transceiver to 10W, sends a carrier after hitting the “tune” button, and then cranks power back up when the process ends.  A bargain at its list price, the LDG has lots of memories and it may work for you if you can get used to the lack of real metering and the noise it generates while tuning. I had to take it back to HRO and got hit with a 15% restocking fee.

There were two other products that I wanted to look at, and I had the opportunity to test them before committing. One of these was the well-known MFJ-998 and the other was the MercuryAT, a newcomer to the market (KM3KM Electronics). The MFJ has a few years history and a lot of favorable reviews, with only a few exceptions. The MercuryAT comes from the same company that makes the popular MercuryIIIS linear amplifier. Both of these tuners need to be on your list for consideration if you – like me – want to optimize your station at a kilowatt.

The MFJ is advertised as a full legal limit desktop tuner, and they also make a weatherized version that sits at the base of your antenna. I found it just as noisy as the LDG, but resigned myself to the fact that this clunkety-clunk noise only happens when a fresh tune needs to be generated (and with all the memories this unit comes with, that wouldn’t be often).  I liked the fully automatic operation from my IC-7300 but disliked the odd mix of an analog meter with an old-school LCD readout. All in all, I had no negative experiences to report with the tuner. There is a YouTube video showing how the MFJ-998 can default if overloaded and send all that reflected power back to your power amp instead of killing push-to-talk. I was impressed that I got a call from their Chief Engineer when I pointed out the video, which he was having trouble duplicating. They are now working with the YouTube video poster, and let’s hope they’ve got a fix in the works if it’s a real issue, as that may not play well with solid-state amps. This tuner sells for about $770 through ham radio dealers. As with others, you’ll need to spend a few dollars on the cable for your radio. (I found out that some transceiver brands do not allow the direct control of an external tuner – so it’s important to know your radio.)

Lastly, I tried the new MercuryAT, which is available through KM3KM Electronics at $795. The first thing that catches your eye is the shape and size of the unit, a bit boxy as it is designed around a large, color touch screen. It is rated at 1200 watts on Sideband and a Kilowatt on CW, and it runs cool due to a built-in (and quiet) fan. I’ve kicked it up a bit higher than that on occasion, and haven’t had any excessive heat generated – the specs seem very conservative. There are no memories on the MercuryAT, so I was initially a bit skeptical.

I think we’re all ingrained by marketing departments to expect “thousands of memories,” so you have to prepare yourself for something a bit different. As I began to use it, however, I appreciated why it was designed this way . . . getting a fresh tune FAST is preferrable to pulling an old tune out of memory, as SWR can apparently change with time or weather. KM3KM spent a couple of years developing a multi-stage algorithm that provides a tune in just a second or two. I tested that in my shack and agree . . . most frequencies tune in 1-2 seconds, but with a 6 or 7-to-1 mismatch like my 15M band, it’s 2-3 seconds.  As with the MFJ, I use a cable to the molex connector on the back of my ICOM and all I do is press the “tune” button on the radio. The touch screen controls contain a colorful graphic metering system clearly showing SWR and Forward/Reflected power, your call sign, and more. The touch screen and ease of operation for this one made it a keeper. I understand that this isn’t the tuner to use for certain high-SWR situations in the 10-to-1 range where the MFJ would out-perform, but as I stated up front, that was not my intent. I will always try to find the best most-resonant antenna I can, and then use a tuner for the finer adjustments.

Now that I’m happily tuned-up and rolling with a kilowatt-plus, I’ll be looking for more ways to improve both my shack and my portable to-go box.

73 for now, 

Dave

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 PS - This article (and others in the series "Trials and Errors - Ham  Life with an Amateur") is written exclusively for QRZ. We believe that there are hams out there who want to read and enjoy articles about the ham life, as opposed to an exclusive diet of YouTube videos. If you are enjoying what you read here, please join us in the forum discussion, and offer ideas for future columns. Thank you for being here!  D. Jensen, W7DGJ