Amplifiers for Low Power Field Communications 

I’m a pretty hardened qrp operator. Very rarely have I seen the need to use more than 5 Watts. If I need more than 5 Watts it’s probably because I’m trying to break through a pile up of phone operators all trying to reach the same operator at some distant location.

There are also those times during poor band conditions when I’ve been known to use 20 30 or 40 Watts. If we’re being honest here, I have also arrived at the conclusion that the right antenna and the right digital mode, will often offset the need for additional output power. Even so there are those times when increased output power is Justified and required. Especially when talking about emergency Communications.

I received this question from Larry.

Larry asked me about the amplifier he saw in my RaDAR challenge video from April 2017. That amplifier is not a commercial product and actually came from a friend.

Lets answer his question
You are too kind Larry.
The amp was Homebrew from a friend of mine, but there are some which I would consider recommending for others. First of all we should consider a few things.

  • Firstly do you want an amp for a qrp radio, or should you invest in a more powerful radio, dialing it down to qrp level!? This could be a more efficient and ergonomic way of achieving increased output power as required.

For example I’m considering the FT-857 for emergency communications. I’ll certainly be limiting the output power to 20 watts wit a btown wire mod. Still, using an 857 means I also have to upgrade my off grid batteries and solar panel, in order to increase the operating time which I currently enjoy with the 817. The reason is radios like the ft-857 and ft-891 have an increased current draw over the 817. Even if you’re just using 5 Watts you’re still drawing more amps on RX, than you would have if you were using the 817 or other QRP rig at 5 Watts or less.

  • Another option is keeping the QRP radio that you might already have, and adding an amp. 

Just like a more powerful radio, an amplifier will also reduce your operating time in the field. So you may have to consider upgrading your batteries, solar panel, charge controller, … to enjoy longer operating duration in the field. The plus side of using a small amplifier is you can always turn it off! It’s not drawing any additional power unless you’re using it. 

  • Next is a point that I touched on at the beginning of this article. Do you already have the best antenna you can have for your operating style? 

This doesn’t necessarily mean the most efficient antenna system. This means the best antenna suited for your operating location, operating style, support structure, … After you’ve investigated these few points and you’ve decided that an amplifier or whatever solution is the right one for you, here are a couple of kits/products to look at. This list is by no means exhaustive and I’ll update this article as we go along. The most important information was above this paragraph So you’re already a lot wiser than you were before you asked your question.

Kits

Hardrock 50 (by Tim Huffaker)
I would rather build the Hardrock 50 amp and add the tuner option. It gives you 50W with a tuner you can use QRP at low power or with the amp running. It has a simple cable that allows an FT-817 to control it to change bands. I built it and it works. 

https://www.hobbypcb.com/products/hf-radio/hardrock-50-hf-power-amp



10 Watt Single Band Amplifier Kit from Pacific Antenna

These are single band 10w amplifiers available for 40m, 30m, & 20m.

Naturally the ideas that you will build these yourself and put them inside an enclosure. The upside to this is you can build it in the form factor that you require for your specific project. The downside for some operators will be the single band. For emergency communications however I see the 40 meter kit as a win-win.

You can find more information on this 10 watt amplifier here

HF Packer Amp from www.hfprojects.com

HF Packer

Unfortunately this kit is out of stock at the moment  but they do have two different kits  on their website that are still available. I listed it here because every other amplifier you consider, should be compared against this one

You can find all the information you need about this amplifier here

Commercial eBay/China
Many of my friends are using these eBay special amplifiers for HF with good results. Honestly speaking I can’t recommend these amplifiers in good conscience, but I also can’t deny operators I know, are having good results with them.

Here is one you commonly found from eBay. Being upfront this link supports the channel and website without costing you a penny extra.

MX-P50M HF Power Amplifier For YAESU FT-817 IC-703 Elecraft KX3 QRP Ham Radio

I’ll spare you all of the Chinglish language marketing information and simply point you in the direction of the amplifier on eBay

You can find all the information you need about the MX-P50M here

I’ll add more to this list as I validate which are the best sellers, add links, information, … as I receive them.

Finally, try to remember an s-unit isn’t really a big deal. You can get an additional s-units out of your current qrp station, by optimizing your mode, antenna & operating location.

I hope this helps you Larry and others who might be reading this.

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