Saturday, May 29, 2021

Mercury III S 1200-watt amp kit on the way, slowly...

 

Since buying the Icom IC-705 a few months ago, I have not powered-up the Flex even once. The '705 has become my do-everything rig.

One of those things is QRO operation, usually on 6 meters but sometimes on other bands as well, dictated by band conditions. I can use the IC-705 barefoot (10 watts), with the Hardrock-50 (50 watts), with the KPA-500 (170 watts) or with both outboard amps for 550 watts.

It's nice to have all those options at the flip of a switch(es) but there is a better, less cluttered way. I'll keep the Hardrock-50 for portable operation but the KPA-500 and the Flex are now packing their bags.

Enter the Mercury III S - a solid state 1200-watt amplifier in kit form.

Ten watts in provides 800 watts out and the kit costs the same as an assembled KPA-500. Reviews for the amp on eHam are absolutely stellar. Imagine an easily portable, POTA-friendly, RV-friendly IC-705 QRP rig that becomes almost a kilowatt at home.

There are at least two other LDMOS amps on the market that will provide near-kilowatt levels with a 10-watt drive. One, from Germany, is problematic (and no longer being sold in the US by DX Engineering); the other is significantly more expensive, especially with shipping from the UK.

Here are a few comparisons that put me in the frame of mind to make the switch.

In addition to the items listed in the comparison the Mercury has a bandscope that shows an oscilloscope-view of the transmitted waveform.

There are other differences between these amps as well, most notably that the Mercury is not capable of QSK CW like the KPA-500. But I don't use my IC-705 in full QSK so it's not a priority.

IMD for each amp? I have no idea. It would be helpful if a Sherwood Labs-like comparison existed for transmitters/amplifiers. Even the ARRL's review of the KPA-500 (QST, Feb 2012) doesn't include this information or any spectral plots.

A recent QSO with Jim KD5JDS in New Mexico reminded me that I'd heard of this amp once upon a time, meaning to re-visit the idea of looking further into it at some point. That point has been the last three days. Jim emailed me spectrum plots and oscope images showing the functionality of various protection features built into the amp and its harmonic suppression on all bands.

An email from KM3KM informs buyers (before the purchase commit) that any kit ordered today has a "shipping lead time of Four to Five Months or sooner".

I'm hoping the or sooner part will apply. Other recent buyers report having to wait only 1/3rd the estimated time for their kit to arrive.

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4 comments:

  1. Have been looking on the website John. Very nice looking amp. 73, Bas

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    1. Hello Bas - I think it will be a good match for the IC-705. Everyone who has one seems to love it. There are also a few YouTube videos that show it in action.

      73,
      John

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  2. I want one but I can't live with just one radio

    Best NO sw patches, updates, bug fixes

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    Replies
    1. I'm sure it will play well with your other rigs, whether they are 10W or 100w radios. That's the only reason I'm selling the KPA-500...it can't be used to its full potential with a 10w rig.

      I have to confess that I've updated my KPA-500's firmware only once, a long time ago. I have no idea how many updates (if any) have been released since then. The amp works like a charm and I've never felt a reason to check for an update since then.

      73,
      John

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