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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
WA6QMQ Rating: 2023-05-23
Best Amp ... & Support Time Owned: 0 to 3 months.
Update 5/23/23
This Amp has been flawless, normally drive it with 12>14w and get 600>700 pep on 110 or 220. Easily dose 1kw+ with 25w drive in ssb
CW follows the same curve with less drive.
Got the LUX today will update it in a month or 2
Support is a 5+
Beyond excellent Support. Easy build, minor basic soldering, excellent updated instructions on included usb stick. Had an issue with the power supply, emailed Kenny he responded on a Saturday and sent me info to return the amp to make sure nothing got damaged, shipped on his dime got it back in 10 days, Works flawless, will order another one to replace my Elecraft KPA500
K1AP Rating: 2023-05-21
Excellent Amp Time Owned: 0 to 3 months.
After 44 years using tube amplifiers, I decided it was time to add a solid-state amplifier to my station. Pros (not in any particular order): small size (W 12" D 13.5" H 5.5"), excellent fault detection, low cost (other amplifiers with the same power are 1K or more), no warmup time, attractive (XYL was impressed), quiet fan, auto band switching, simple to operate (KISS), excellent customer service (feedback from other HAMS), and for a nice touch you can type in your call sign to the display. Cons: long wait time (13 months). All I can say, it's an excellent amplifier and worth the wait. If you are looking for more power and remote capability, there is the Mercury LUX amplifier.
WA2ZPX Rating: 2023-03-12
Great Amp Time Owned: 0 to 3 months.
Two month update

The amp was performing flawlessly until I turned the master power switch on one day. There was a bang, with sparks and smoke coming out of the rear. I contacted Angel via email and received a quick response with a return shipping label. They repaired the amp the same day it was received, and it was on its way back the next day. It turned out to be a shorted master power switch. Great Communication, Great Service.

The documentation that comes with the Amplifier does not have any meat to it. It is a basic manual. It does not indicate what the maximum power is that can be run through the amp with it in the off or stby mode. Also missing is a schematic or parts list. It would be nice to at least have a parts list. The company's current repair policy is no labor charge, only parts cost after warranty. From my location, its about a 180 dollar round trip shipping cost.
I finally received my MercuryIIIs after a 10 month wait. I was amazed at its small size, reasonable weight, and sexy display. I decided to to go with the ALC connection, and had it adjusted within a minute. The amp works as advertised. It has consistent output on all the bands. The temperature stays well within limits. I tried running FT8 at 450 watts and put the fans on high speed. Again, the temp stayed within limits. The fans are quiet even at high speed, well withing the acceptable range. I am using it to replace my Alpha 86. Nothing like hearing a DX station and hitting the power button and having instant power.
A couple of things to note. With the amp in the off position, the antenna reverts to the number 1 slot. Also, there are two power switches. One on the rear (master), and one on the front. When you turn the master on, the power supply and the power supply fan are on all the time. The front switch controls the amplifier power.
All in all, beautiful, well put together, great performing amplifier.
N5SKT Rating: 2023-03-04
Amazing kit and amplifier Time Owned: more than 12 months.
Update: The amp continues to perform well. I did have an issue with the Amp that was self inflicted and Kenny took it from me, fixed that problem and more and returned it to me. Angel called me along the way to explain what was needed and when it would be returned. How often does a support team call you? Excellent product. Great customer service. Highly recommended. I know it is a long wait but the wait is well worth it.

I just finished my build. The build was difficult for me but I am not a kit builder. However, even with my poor soldering skills, I was able to complete the build and it powered on and worked beautifully. I have it hooked to a Flexradio 6600 and I can't believe how low I have to turn down the power on the radio to achieve great results. This is a magnificent Amp and I highly recommend it.
W9JLF Rating: 2023-02-25
Best amp on the market Time Owned: 3 to 6 months.
After anxiously waiting 10 months to receive the amp, I had it connected to my FTDX101MP within minutes and has worked flawlessly ever since. It is extremely easy to use, and the built-in protections work perfectly. I regularly use it at about 500 watts for FT8 operation, and have never had a problem.
W0GD Rating: 2023-02-22
Awesome Amp Time Owned: 6 to 12 months.
I rarely do reviews but the Mercury amp with the mercury antenna tuner works flawlessly. Enough said.
AD4C2006 Rating: 2022-11-06
A very good HF amplifier kit Time Owned: more than 12 months.
After two and a half years of daily use, I still feel very pleased with this great amp.
Never has had any issue with it, as many other users I never use it over a KW on SSB and never over 700W on CW, also for FT8 never over 300W.
I have been able to work over 100 countries in different bands using just bazooka dipoles, If I hear a station no matter where is, I call just once and they will pick me up inmediately thanks to the Mercury power.
Kenny KM3KM has gain a very high reputation among hams comunity not only because of the high quality of all his products but also because an outstanding customers service. He will respond very quick to your problem IF you have one and act the best way possible for your satisfaction.
I will recomend this amp to any ham worldwide who wanted to own an excellent reliable HF amp.
Thanks Kenny.

After been using this Mercury amp for almost two years, I can tell its very reliable, never has failed a bit, use it daily for at least two to three hours at full power on SSB, 700W on CW and 300W for FT8-FT4-PSK31, never has broken and all protections work as they do,
I strongly recomend this amp to all hams who can afford its price which by the way is way lower than any other amp of its power in the market.
Thanks again to Kenny Martinez for having designed and built this very excellent amplifier.


Coming from a previous solid state amps owned like the SPE Expert 1.3K and the PalStar 1KA, I can tell the builtin of these amps are more professional.
I actually own the Mercury III that work from 80 to 6M making 1200W easily with just 40W IN. There is no way to destroy these kits because of using a very rugedized single LDMOS and its own protection against antenna high SWR over 2 to 1, and against excessive input power.
I checked personally with a professional spectrum analyzer the IM distortion been as low as any other imported amp or built within the US, my test showed always not less than 35db in most cases 37db and the reports received from other stations using professional panadapters were that my transmissions at full power was very clean and narrow banded.
To put together these kits is very simple just following the manual instructions.
This newer model III has a very well designed RF sensing to save a band switch and fast band switching with just pressing the radio PTT. Power output will be the same as previous models I and II but it will need little bid more power input now.
One very attractive thing this new kit has is its price been very affordable for hams wishing to have a very good HF amp.

After almost one year using this Mercury III amp I am more than happy.Never has had any issue with it except that sometimes I use it in a non resonant antenna in which case it goes in a fraction of a second to standby showing on the display the High SWR alarm.

Its been a concern of some hams about the linearity of this amp kit in terms of IMD3 after we put it together at home and after talking to the designer and builder of these modules we had access to several videos showing the professional tests performed at his shop showing the third order products are always better than the ARRL suggested of -30db.
Always remember if your radio already has bad linearity because its defective or you have not configured it properly the amp will give at its output the same dirty signal at higher level so before using this kit check the purity of your radio used to drive it.

KE8DAX Rating: 2022-11-06
Outstanding Product, Great Customer Support Time Owned: more than 12 months.
12 Month Update - I have had absolutely no issues with this amp and use it on a daily basis. There is nothing about this amp that I don't nits to pick. IMOA it is the best amp value on the market....period.

6 Month Update - I have had absolutely no issues to date. This amp has been a game changer with my station. Great signal reports. I typically run around 1 kw, or a little better, into a six band hex beam with no tuner. I have had the fans go to high speed one time when I was running about 1,100 watts CW for an extended period. I was always told not to take a knife to a gun fight and this amp is a 44 magnum! :-)

Original Post - My entire experience with km3km exceeded all of my expectations. Quoted delivery was 4 to 5 months from time of order. I received the kit in a little less that 3 mo. The packaging was first rate and everything was well organized. The assembly was a blast and not difficult (my first kit in over 60 yrs) using the clearly written assembly manual. You really appreciate the professionalism that was put into the design as you do the assembly. Lastly, this amp just rocks. Great signal reports. i don't know how anybody could be disappointed with a Mercury IIIs. I would do it again in a heartbeat.

N9CHM Rating: 2022-10-03
EXCELLENT Amplifier, well designed Time Owned: more than 12 months.
12 Month UPDATE: This amp is the best amplifier value on the market. I've had several dozen amps over the last 40+ years, both tube and solid state, and this amp beats them all in ease of use, dependability, customer service, and electrical design. I am so impressed that I bought a 2nd MERC IIIS, and 3 of my friends have also purchased a MERC IIIS. I am now waiting on the legal limit version (LUX) to arrive. The waiting line is long, but worth it.

My kit arrived exactly 90 days after I placed the order on June 23 (quote was 4-5 months). I've had many amps, but this is the first kit (of any kind) I've put together in 45yrs as a Ham. As others have said, it's pretty easy, even if you, like me, have minimal soldering skills. The video provided on the USB drive, which had a demo on soldering was good, and should give you the confidence needed to complete the amp. The only difficulty I had was with the RG142 coax used as a loop trap, it's pretty stiff and checking my solder points the shield junction on the PA wiggled a bit. I re-heated the solder on the pad under the shield, pushed it down better into the melted solder and added more solder on the shield, now it's a solid connection. It's nice that the power supply leads now have spade lugs which you just push on to the AC terminals, instead of trying to solder them onto the AC terminals (not much room). Although it would have been nice if the ground wire to the ground terminal would have been just a half inch longer, it was a tight squeeze to get in there to solder the ground post. I bought an 8' AC power cord, NEMA 6-15P C13 off of eBay. It took 5+hrs to assemble, over 2 days when I had some free time. For 1100W out (LDMOS is a BLF189XRUA which is rated at 1700 watts), the input with my FLEX 6300 (or 6500) was 37W-160M, and 23W for 75-40-20. So, pretty much what everyone else is seeing. All my antennas (just wire dipoles) are well under 1.5 to 1, so no tuner needed. The fans are extremely quiet, better than the Palstar LA-1K or the SPE 1.5K amps I've had, both of which were noticeably louder than the MercIII. Rag chewing (1KW) on 160M for several hours, and the amp never got above 39C, so the fan never switched to high (which is at >50C). This is a very well designed amplifier ($2559 shipped), hat tip to Kenny and Angel for providing this to the Amateur market.
EA5J Rating: 2022-09-07
I have had this amp for 7 months and I have to say Wow!! It's fantastic and I'm delighted with it.
I met him through a friend who told me about this amp and I started following his progress by reading all the Eham reviews, watching how many videos were posted and keeping track of him.
I received it already assembled from the factory, with correct packaging and well protected against knocks.
Although I had already seen it at my friend's house, the first impression when taking it out of the box was very good. It has a compact size my FTDX101D and can be placed anywhere on my shak.
When it´s put ON a large and very intuitive touch screen and easy to read all the parameters and to handle.
I have another amp that puts out much more power but I use the MercuryIII on all days on CW and SSB with wattages between 500 and 700 watts. It's very easy to squeeze 1200 watts out of it, when you need it. It delivers that power with an excitation of between 5 and 40 watts depending on the band. It has never given a problem or loss of power with long operating times.
The ventilation is perfect and there are no problems with its cooling. Very quiet fans, nothing to do with my OM2500A.
I have used other solid state amplifiers and they were really a headache, with problems in the relays and loss of power with long operation times and some more problems with their handling.
I have also used other tube auto amps, OM and Acom2000. Currently I have an OM2500A a great amp, a beast of power, but also much louder and when you have been operating with it for a while, the noise makes you faint.
Conclusion: it is a great amplifier, compact, with which you can work from 6 to 160 meters on the amateur radio bands, which delivers up to 1200 watts without problems of heating or loss of power, with a large touch screen, easy to read or handle and countless advantages.
If you read this and are thinking of buying an amplifier, don't hesitate, buy a MercuryIII.

Tengo este amplificador por 7 meses y he de decir que Guau!! es fantástico y estoy encantado con él.
Lo conocí a través de un amigo que me habló de éste amplificador y comencé a seguir su progreso leyendo todas las reviews de Eham, viendo cuantos vídeos se publicaban y haciendo un seguimiento de él.
Lo recibí ya montado de fábrica, con un embalaje correcto y bien protegido contra golpes.
Aunque ya lo había visto en casa de mi amigo, la primera impresión al sacarlo de la caja fue muy buena. Tiene un tamaño compacto, como mi FTDX101D y se puede colocar en cualquier parte de mi shak.
Al ponerlo en operación, se enciende una gran pantalla táctil muy intuitiva, fácil de leer todos los parámetros y de manejar.
Aunque tengo otro amplificador que da mucha más potencia, uso el MercuryIII a diario (CW y SSB) con potencias de entre 500 y 700 vatios. Es muy fácil sacarle 1200 vatios, cuando te hace falta. Entrega esa potencia con una excitación de entre 5 y 40 vatios según banda. Nunca ha dado un problema o perdida de potencia con largos tiempos de operación.
La ventilación es perfecta y no hay problemas con su refrigeración. Unos ventiladores muy silenciosos, nada que ver con mi OM2500A.
He usado otros amplificadores en estado sólido y realmente fueron un quebradero de cabeza, con problemas en los relés y perdida de potencia con largos tiempos de operación y algunos problemas más con su manejo.
También he usado otros amplificadores automáticos de válvulas, OM y Acom2000. En la actualidad tengo un OM2500A un gran amplificador, una bestia dando potencia, pero también mucho más ruidoso y cuando llevas un tiempo operando con él, el ruido te hace desfallecer.
Conclusión: es un gran amplificador, compacto, con el que puedes trabajar de 6 a 160 metros en las bandas de radioaficionado, que entrega hasta 1200 vatios sin problemas de calentamiento o perdida de potencia, con una gran pantalla táctil, fácil de leer o de manejar e infinidad de ventajas.
Si lees esto y estás pensando comprar un amplificador, no dudes, compra un MercuryIII.