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Reviews For: Mercury IIIS HF/6m amplifier

Category: Amplifiers: RF Power - HF & HF+6M

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Review Summary For : Mercury IIIS HF/6m amplifier
Reviews: 71MSRP: $2500/kit $2800/assembled
This solid state HF amplifier uses a single LDMOS for
fully automatic operation from 160m to 6M making 1200W with
input power between 50 and 90W depending on your ALC
setting. Protected against antenna SWR over 2 to 1 and
also against excessive input power. Builtin power supply
for 120 or 240 VAC without changing taps in the
transformer, just changing the power cable plug.
Fans work silent and color front panel display. Output to
three antennas selectable in the display with operator
Available as either a kit or starting in early 2022 factory assembled.
Product is in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
KA9EES Rating: 2021-10-07
Fantastic Customer Support! Time Owned: 3 to 6 months.
I want to echo all those that have bragged about this amp kit. It is so easy to put together. Operation is smooth as silk. I have it paired with my Palstar HF-AUTO, and Flex 6400M. I've even figured out how to monitor it with W1TR's HF-AUTO program and control it with some relays using NODE-Red.

Now the really good part. Mine developed a problem. I turned it on one morning. It was fine for about a half hour. Then it shut itself down. Then It restarted. It did that a couple times. After which I killed the AC to it.

As soon as I explained the situation. They sent me a label to ship it back to them! What company does that? Turn around was about two weeks door to door. It would have been far less if FedEx hadn't given it a week long tour of the southeast US.

Problem turned out to be a bad capacitor on the 53v input of the power amplifier board.

Again. Great amp! Even better customer support.

Fithian IL
KF4ZCL Rating: 2021-09-30
Great, Mercury IIIS HF amplifier kit Time Owned: 6 to 12 months.
After using this amp for 6 months and making contact nationally and internationally I am extremely satisfied with the amplifier kit.
It is very simple to assemble, even someone with little to no experience in electronics can build it in up to 5 hours using the info on Kenny's website. The automatic band selector is also a great feature. The IMD3 is also better than the ARRL suggested of -30db.
Furthermore, the design is very sleek and modern, very fitting for an amplifier of its quality. In my opinion, it outperforms all other amplifiers in its price range in terms of value, reliability, and ease of use.
I highly recommend this amplifier kit to anyone in the market for an amplifier that will give you more than your money's worth.

Jesus Toledo
K0UA Rating: 2021-09-28
Excellent and beautiful Time Owned: 6 to 12 months.
What can I say that others haven't already said? The amp goes together quickly, and the assembly is mostly nuts, bolts and screws. Sure soldering in the power supply leads to the AC receptacle was a little tight, but it sounds like they have made some modifications since I got mine to make it a bit easier. Take your time when centering the beautiful 7 inch touch screen to get it just right in the cabinet opening. I got if first time and it looks great. If you can follow instructions and can solder at the most basic level for the few coax ends you solder down to the boards and the SO239's and RCA jacks on the back panel you will have no trouble. Worked first time and has been working hard every day since mid December 2020, so coming up on 10 months now. If you run SSB or CW, you will likely never hear the 2nd stage fan which is still pretty quiet. If you run full bore digital like FT8 at 700 watts (maximum for 8 seconds) you will see it kick on at 51 degrees C. It is best to "get ahead" of the automatic high speed fan by going in to high speed if you intend to run digital so that the amp stays cooler longer. Have I tested the safety aspects of the controller algorithm yet? Yep, several times. Wrong antenna, too much drive etc etc. They have worked every time to protect the amp from myself. It is a nice simple beautiful and so far tough amp. It does not have some of the "bells and whistles" of some other amps (band tracking, or remote software operation) Etc, but is does not cost nearly as much either. Mine was $2499 shipped to the door back in December of 2020, but I understand you have to pay for shipping now. Still way cheaper than an Acom 1200, which would be its nearest competitor. I use the thing every day (retired) and it was invaluable for 6 meters this summer. Good amp good price. 73 James K0UA
AA9YE Rating: 2021-09-26
100% happy Time Owned: 6 to 12 months.

I have had my new Mercury 3 in use now for a bit over six months. The exciter is a Kenwood 590, my simple main antenna is an OCF 80 thru 10 using a Balun Designs 4116 4 to 1 balun. The coupler is a Swan ST-1A. With my cheat sheet for the tuner I can change bands and be ready to transmit in just a few seconds, usually about 5 seconds. All I have to do is if in SSB is click the mic on my Kenwood and the amp instantly follows band changes (when the amp is set to auto). On 40 meters I drive it with ten watts and easily get around 750 to 850 hundred watts out with normal voice into the hand mic. Takes a bit more drive on twenty meters and up. The amp will easily put out 1200 watts. It runs very cool and quiet. Under normal voice operation I have NEVER had the fans go to high speed no matter how long I talked. The temperature has never gone anywhere close to where it would kick the fans on high.
I only faulted the amp one time (so far) when I forgot to flip my antenna switch from ground position to the OCF and it instantly protected itself and let me know I had blundered. I put the antenna switch to where it needed to be, hit the reset and no problems, no disaster, back in business.
When I first got the amp I had a few questions and Kenny and Angel answered with an email literally within 15 minutes. I e mailed them a few more times in the next few days and every time I had my questions answered in less than 30 minutes. That kind of service is remarkable today.
I am 100 percent satisfied with this amplifier and during the just over six months I have had it, ZERO problems.
I also own the Elecraft KPA-500. It has been sitting under its dust cover since I got my Mercury. It is also a good amp and I like it, but I love my Mercury 3.

NJ8M Rating: 2021-09-20
Excellent Simple Amplifier Time Owned: 0 to 3 months.
First off, I have owned many tube amplifiers and a few transistor amps. This is not my first rodeo. Having had the lid off of every amp that I have ever owned and also no longer wanting to mess with high voltage dangers I have gone the transistor route.

My primary mode of operating is CW at 35 WPM during contests. I hate QSK because during a contest you are always listening to noise. Noise fatigue is lessened with semi-breakin. The amps that I use have to be capable of a high duty cycle on CW. I don't give a tinkers damned for FT8 because there is little if any interaction by the operator and it is not a demonstration of skill.

One of the best amps ever made was by Tokyo Hy-power (SK). I could not kill their amp but the company is now out of business. I tried the KPA1500 but it is way too noisy and at best it is a 1KW amp due to its heat problems. So I sold the Elecraft and bought 2 Mercury III amps from KM3KM.

The Mercury III amp is a kit that takes 13 solder connections to complete and a small nut driver set or pliers, a phillips screwdriver, and 3 different sized allen wrenches to assemble. I have made 2 of these amps and they are extremely easy to assemble. All of the boards are first rate commercial production with no shortcuts what so ever. The most critical part of a transistor amp is the heat handling dissipation system. The entire PA board is mounted on a 1/2 inch thick copper slab. The slab is then mounted to a huge thick aluminum heatsink and 2 fans are mounted to the fins of the heatsink. These run quiet. They have 2 speeds. High and low. They run all the time. The auto setting is great. Because they are so quiet, I just leave them on high. This keeps the amp between 29 and 32 degrees C. Cool even when running 1kw with 35wpm CW. Goal met. The first amp took me 3 hours and 15 minutes to build. The second one took 2 hours and 17 minutes. On the second amp, I did not need to read the instruction check list. This time includes unboxing and cutting up the box to make a mat to protect the kitchen table. A small 40 watt Weller iron was used with the kit provided solder. Soldering pads were first blob tinned and then reheated when the pre-tinned coax is applied to the molten pad. There are 13 solder joints to be made. The rest of the assembly is just plugging in cables and nuts and bolts work. The black power coated case, lighted on/off and operate switches coupled with the high resolution touch screen gives all the data that one needs to monitor the amp at a glance. The amps match my FTDX101 radios. A keying line/PTT and ALC cable is provided with RCA connectors on each end. I connected this line to my WinKeyer USB from K1EL. It works like a charm.

This amp provides a COOL SOLID 1 KW output on CW. It is the best bang for the buck on the market. This amp is high tech simplicity. Everything is modular and easily replaced if repair is needed which is not likely. Running 1 KW all the time leaves 200 watts of head room and because you are running near max the amp is more efficient and produces less heat than other amps designed to run at 1500 watts when you run them at 1 KW. 1500 watt transistor amps are noisy. The fan noise on a PGXL flex is like sitting on the tarmac waiting for the jet to take off. Level 5 fans on the KPA1500 not quite as bad, but the Mercury III is extremely quiet. It puts out less fan noise on high fan setting than the KPA 1500 put out on level 1 of 5. It runs cool. Now I am rambling. It is a great amp.

Kenny, KM3KM, has thought of everything. His service is first rate. He answers email promptly and his customer support is first rate. Would I buy this amp again, I already did. I have 2 of them.

73, Morgan NJ8M
KO4USA Rating: 2021-09-19
Very Nice Kit - High Quality Time Owned: 0 to 3 months.
While I am relatively new Ham, I have been in the Electronics industry as an engineer for over 35 years in the radar and high power microwave device sector - I have seen my share great technology as well as crap. While I am not benefited by a wealth of experience with HAM Radio products, I do believe I can fairly assess this device.

I ordered my Mercury IIIS months ago...Even as someone with an over anxious personality, THE WAIT WAS WORTH IT.

Assembly of the amp took me about 3.5 hours. (this was at a medium pace) - Note that I did read all the documents and watch the provided videos the day before)

The Assembly manual has sections that could be written better ( they do suggest providing feedback..I will be doing so). Other than the few areas that need "rewording", it was very straight forward and easy to follow.

The components and circuit cards are well built and easily identified. All the all the assembly hardware is provided (I wasn't shorted anything). They were well packaged for shipment and the whole kit arrived in perfect shape. (not something you see a lot of these days!)

The actual assembly of the kit was smooth. I suggest becoming very familiar with the documents, pictures and watching the suggested videos (provided on a memory stick with the kit). Pay attention to the screen positioning steps and the routing of cables and harnesses.

To put the whole build in in perspective, as the final step of the build, installing the case cover and aligning all the screws was one of the more challenging steps! ;)

(This assessment comes with a caveat - you need to have some experience building kits as well as basic soldering skills)

Boot up and testing was without any complications.

I setup the amplifier with my ICOM 7300 and MFJ 998 auto tuner - the two work really well together. The tuner's AMPLIFIER BYPASS CONTROL works flawlessly during tuning and operations. (Yes, I do recommend the MFJ Device). The only oddity I noted is the the PEP reading on the amp seems to disagree with the power readings on the MFJ 998 and my inline power meter. (NOTE: there is a comment in the amplifier manual that states that power meters in line after the amp may affect the display's readings). Numerous radio checks, spectrum analysis and various power measurements were accomplished - All tests show a clean output at the expected levels. Low level exciter input (1 watt) on 40 Meters yielded 45 watts out -
I only tested outputs up to 1000 watts - these looked great and received great on the air reports.

This very long-winded assessment is saying, "I like this amp a lot. In my opinion, as for solid state amplifiers, at this price point, you will not be able to find anything that is comparable in both quality or features. Competitors Beware! This device does it better and less expensive than yours!"

I highly recommend this device!!!

N4DEK Rating: 2021-09-16
ROCK SOLID Time Owned: 0 to 3 months.
Received my kit yesterday morning and it took me about 4.5 hours to complete the kit. Assembly was very easy and went very smoothly by the excellent instructions included. First power up went perfect and the amp came to life. Operated it all night lastnight and received nothing but stellar signal and audio reports. 30 watts in equeals about 1200 watts out. I can't amagine a better value in a near legal limit amplifier than this one. For $2558 shipped to your door it's a steal. To say I am pleased would be a large under statement. Thanks to KM3KM for such a fine piece of ham gear at a very resonable price!
N9PL Rating: 2021-09-05
Great Amp! Time Owned: 0 to 3 months.
I built my first amp, a Heathkit SB-200, in the 60s. An HL-2200 (last of the SB-220 line) followed in the 80s. Added EBS and 10M to it. Had an AL-80A and also added EBS to it. Bought a used Alpha 76A in the mid 90s. Again, couldn't leave well enough alone and converted it to 3CX800A7s, along with adding EBS and grid current protection circuitry. So, I have worked on a few tube amps.

A couple years ago I decided I wanted a lighter solid state final so I got a KPA500/KAT500 combo. Worked fine, but wanted something with a bit more reserve. Don't remember how I got pointed to the M IIIs, but after following reviews for a couple months, decided to order one. By this time, KM3KM was being flooded with orders and lead time was out to 4 to 5 months. The amp shipped in a bit under 3 months.

Assembly went without incident. if you can read and follow directions and solder a few connections, you can build this amp.

I have had the M IIIs in operation for about 10 days. I am using it with the KAT500, which is rated at 1 KW as long as the SWR is under 3:1. I have been running it between 500 and 800 watts out, on both CW and SSB. Output waveforms look fine, and I am getting very good audio reports on SSB.

Made some measurements on 20M (into a good 50 ohm dummy load). 10 watts in gives 525 watts out at 52% efficiency. 25 watts in gives just over a KW out, at 69% efficiency. From 1 to 1.2 KW out, gain probably continues to drop and efficiency rise into the low 70s. Based on the specs for the LDMOS device used, this is about what I expected.

During casual CW and SSB contacts on 40 and 20, I Still have not had the fans switch to high speed. On low speed, I can't hear the fans over band noise. Much quieter than the KPA500. Also quieter when operating at power. I could hear the KPA500 when operating CW. I suspect it was transformer magnetic fields working the steel case. The Mercury uses a SMPS, so its case is not making noise when keyed.

The Mercury costs a bit more than the KPA500. For that you get double the PO, a color touch screen, and cooler, quieter operation, in a package slightly larger and about the same weight (the SMPS really saves size and weight). And I can pick it up and move it by myself.

K7SFN Rating: 2021-09-03
Outstanding! Time Owned: 0 to 3 months.
Received my Mercury IIIS Kit a little over a week ago, along with two other local friends. Took my time assembling the amplifier, but finished it in about half of a day. Plugged the amp into power, pushed the power button and it came to life after a few seconds. Testing took literally less than 10 Minutes and it was up & running. My two firends experienced the same excellent experience as I did. Their MIIIs came up and working without any issues. We are all extremely pleased.

I am driving my M3S with an IC-7610, and measured Output power on a LP-500 Station Monttor is around 1250 Watts with slightly over 30w of drive from the 7610. The M3 sits on the operating desk and purrs like a kitten, Fan noise is not noticeable, but I am hard of hearing anyway. On the air reports have been outstanding. I doubt there is a better value on the Market these days. Buy one, you won't be disappointed.
Frank, K7SFN
N2ZDB Rating: 2021-08-08
Wow....this Mercury IIIS Amplifier is Excellent! Time Owned: 0 to 3 months.
My Mercury IIIS came at least a month earlier then I expected (quote was 4 to 5 months max).

Packaging was excellent and I was able to build it within a day taking my time and not rushing things.
I was surprised to see how well the coaxial cables braid was tinned - these guys know what they are doing!
The quality of the completed printed circuit boards assembly was excellent!

Amplifier works excellent and I love the informative LCD display which shows everything you need to know.

Thanks for a great kit Kenny and Angel and please get the MercuryAT autotuner out as soon as possible!

Michael, N2ZDB