New HF Packer Amp for 2020: comment phase

It seems as though Virgil K5OOR is interested in designing a new version of the Packer Amp and is asking for comments as he enters the design phase. I would think that the SOTA community would be able to provide a wealth of practical suggestions, and now is your chance to be heard! You can make comments and show your interest on the groups,io thread here: | New and Improved HF PackerAmp V2020

These are some of the goals he’s listed so far:

  • Make design changes to not require the DC/DC Converter but maintain a nominal 35W output.
  • The amp will cover 160-10M with resident filter circuits.
  • Slashing or Reducing cost with design changes and labor saving improvements (to be announced).
  • Adding in some features developed in the miniHFPA design providing improved performance
  • Offer a wide range of sales prices:a “bare bones” option as well as a fully assembled and tested version.


For what it’s worth, my direct experience taking an external amp on an activation is that it’s a hassle. Extra bulk, weight, protection, cables etc.

While no one radio/antenna combo works for every activation, I typically use a 10w rig and if I want more power take a Yeasu 857 and dial it back to 35-45 watts.

Your milage may vary…

That written I hope Virgil much luck in the next iteration!



I suggested to Virgil several years ago that an amplifier that could be run directly off a suitable battery would be a good option. I was thinking of a 6S Lifepo4 battery at the time, perhaps not always available now. And always dangerous to have multiple batteries of different voltages, requiring separate unmixable dc connectors to protect radios from higher voltages than they can accept safely.

I think a separate amplifier is better than a higher powered radio, because that allows you to keep the standing current to the same as your qrp radio, whatever it is, and only incur the additional standing current of the amplifier when it is enabled. But yes, more boxes to manage, cabling, complexity.

At the current pricing of the amplifier it was out of my budget. If the new design addresses that, it will be welcome.

Interesting that 160 is in but 6m is not. I know the frequency range is a big ask for the transformers in a push pull amplifier.

Andrew VK1DA/VK2UH

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Hi Andrew,

Probably not as much of an issue as the input capacitance of the IRF510 switching FETS it uses. But they do have the unassailable benefit of being extremely cheap :slight_smile:

73 Paul G4MD

It has to end up costing less than you can buy a ready built MX-P50 amplifier from eBay etc. or offer something much extra or it’s not worth the bother.

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For the most part I have been using the MX-P50 with my KX2 for over 2 years now. Around here some days 12 watts is not enough for 4 contacts. With the amp life is good.
If there is a built in tuner then I would jump at 1.


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My 2 Cents:

Down to 10,5V supply voltage
Rugged construction
Passive cooling
High SWR protection
ATU on-board
25-30W is a good balance
Power in and power outlet connector to daisy-chain from battery to radio reducing cable chaos

Just because it is fun to build own stuff I would accept also a higher price then the MX-P50 especially if an ATU is in.


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I always have two of everything. Would that be a pack-up back-up?

Elliott, K6EL

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My 2 cents:

  • Is voltage really the problem? A 5S LiPo will run the new 50w QCX amp no problem. If the rig doesn’t run on internal batteries, a 300mAh LiPo weighs next to nothing, so no major weight penalty there.
  • What does the new QCX 50w amp lack?
    i. Multiple lowpass filters.
    ii. Not linear.

So, to my mind, the question is: what are you prepared to add to the QCX amp whilst keeping the price down?

     73 de OE6FEG
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Hi Paul,
well a few years back he was talking about using RD16HHF series fets, which would extend the frequency range, I understand due to the lower input capacitance. But that development ceased and the mini version that followed used the tried and true IRF series again.
Unfortunately the exchange rates make the series completely unrealistic for VK buyers. Starting with the US price near $500, the AU price reaches AUD700, which simply does not compare with about $250 (Or less) for the MXP50 amplifiers.
I agree with the low voltage goal and the inbuilt tuner. Price goes up again, low voltage is fine if it has its own inverter, ATU adds more to price. ATU relies on good software.
73 Andrew VK1DA/VK2UH

It will be hard to be price-competitive selling a kit.

This is an entire 25 W transceiver for under $200 (when it is in stock). It uses a pair of IRF520 devices. Works on 80, 40, 30, and 20 meters.

Also, with so many 10, 15, or 20 W transceivers available, going to 35 W just isn’t enough of a boost to matter.