Despite what I wrote earlier, I just purchased a used KX3. The price was right, and you gotta admit, it does seem like a cool, little rig. Not being a hardcore QRP guy, the next step of course is to buy or build a small amplifier. I’ve been Googling and came across the following options:
KXPA100. This is a 100W amp, specifically designed for the KX3. By all accounts, this is a great amp, and obviously, works well with the KX3. the downside is that it costs $700.
HardRock-50 Power Amp Kit. This amp kit costs only $300, but the maximum output is only 50W. One interesting feature of this amp is that the software is all open-source and hackable. I’m not sure what kind of hacks I could make to the software, but I like the fact that I could do so.
WiMO HLA-150. I know very little about this amp, except what I see on the website. One plus, obviously, is that it’s 150W output. Another is the price. With the euro at a very favorable exchange rate against the dollar, it only costs $350. A negative is that there’s no automatic bandswitching. When you change bands, you have to manually switch the amp to the correct band.
Ebay. There are a number of HF amps for sale on EBay, like this 45 W amp for $190. I guess there from China. They are cheaper, but I’m not sure that I want to take a chance buying one of these things. With the three listed above, I’m fairly sure that I could get some support if I ran into problems.
I’m leaning towards purchasing the HardRock-50. I like building kits, and the price is right. The WiMo 150W amp seems like a bargain, though, too. What do you think?
Luke Williams - AE5AU says
I built a HardRock-50 and have been happy with it. Sadly, I haven’t put a lot of time on it, though that’s all my fault.
The build was enjoyable and took a couple of evenings. I need to check for updates and add the ATU to mine as it wasn’t an options when I built.
Dan KB6NU says
Thanks for the info, Luke! I think I’m going to go with the HardRock.
Walter Underwood K6WRU says
I’ve been doing the same evaluation. The Elecraft amp is by far the class of the field.
The HARDROCK is half the price and half the power, a fair tradeoff. They just added an ATU option. You would probably want the QSK option. Note that it has lower power on 6m, 30-35W. The QSK option drops the 6m power another 5-7W.
The HLA amps are all over the place. Some seem OK, some are terrible and don’t come close to meeting FCC requirements.
If you can find an old Yaesu FL-110, that is probably your cheapest high-quality amp. Manual bandswitching.
Or you can find a National NCL-2000 and modify it for low power drive. That will give you a kilowatt and it is the best-looking amp in the batch!
Dan KB6NU says
Thanks for the info, Walt. I’m probably going to go with the HardRock amp, just on price, and like I mentioned in another reply here, give the HLA amp a try. I can always sell one or the other after playing with it.
Walter Underwood K6WRU says
Just be sure that the HLA amp is actually FCC certified. The output filters add a lot of cost. The really cheap ones don’t have them.
Here is a 2013 FCC enforcement action against a place selling RM Italy amps.
ftp://ftp.fcc.gov/pub/Daily_Releases/Daily_Business/2013/db0815/DA-13-1755A1.txt
RickB says
Welcome to the world of SDR.
Have friends with K3s & KX3s. They love em.
The KPA100 and ATU is over $900.
Is this your nnext Field Day rig?
George Mitchell says
Have a KX3 and was set to plunge for the KPA100 at Hamvention. But was expecting a discount on site. No such luck. No deals unless you bought the KX3-KPA100 together. My comment that I bought it 6 months ago earned a response. Thats too bad!
Dan KB6NU says
Yeah. Elecraft is not known for offering deals.
K9SGS says
Same exact response to me at Hamvention.
Bought the KX3 a short time ago, asked if a discount on the KXA100.
A rude no was the answer.
Went back later and asked if maybe they could at least throw in the cable to connect the two.
Nope.
Think I’ll buy the Hardrock-50.
Dan KB6NU says
The guys at HobbyPCB are really great. At Dayton this year, I purchased their RS-HFIQ. When they found out that I already owned a HardRock amp, they gave me the interface board to connect the two.
Barry says
I’d be tempted to get one of the HLA amps to try them out, especially for the money.
Dan KB6NU says
I’m tempted, too. I can always sell it if I don’t like it.
Walter Underwood K6WRU says
Here are some measurements of an HLA150. When run at 150W, the IMD is unacceptable. It is really a 90W amp.
http://www.w8ji.com/rm_hla-150_test.htm
Dan KB6NU says
Hmmmmm. Maybe I won’t waste my time on the HLA amp. Thanks, Walt.
natevw says
The HF-Packer amp (kit, but looks like a variety of partial/complete assembly options are available) also looks like a reasonable contender: http://www.hfprojects.com/
Can be built for 1, 2.5 or 5W input, and approximately 30–35W output, starting at $200 including (manually selected) low pass filters for all the HF bands.
Jerry Nevins says
I would like to put in a plug for the very small MX-P50M amp on eBay from China… There is a lot of negative sentiment on much of the Chinese gear that may be unfounded. I just plugged the MX-P50M in and running my FT-817 on an internal battery with 2.5 watts into the amp, I made my very first contact in central Italy from CT with a good signal report. Sunspots are near 0 these days.
I had two criteria in order to buy…
1) must have low pass filters for each band, check…
2) must be keyed by the rig, check…
3) output power around 35-50 watts…check.
This review is a good user review… https://vk2qr.wordpress.com/2014/11/25/mx-p50m-hf-amplifier-review/
This review has extensive testing for spurious emissions and harmonics.. his conclusion is that the output is as clean as any mainstream commercial rig from one of the big three… http://gm4slv-geek.blogspot.co.uk/2015/03/mx-p50m-amplifier-for-ft817.html
So far, I am a happy camper and at under $180 shipped, may represent the most affordable and good option for a tiny amp to match the FT-817.
Michael J.D. Durkin says
Send me the HLA amp and I’ll see if I can interface it to the ft-818..
https://youtu.be/cOQ1_3HzQfA
Paul says
Hi Dan ,
I recently purchased a Flex 1500 and Tentec 418 amp combination and I couldn’t be happier . I’ve coupled it with an LDG PRO100 tuner.
The Flex at 5 watts is more than enough to drive the amp to 100 watts of nice clean power. The protection and display features on the amp are excellent .
Only drawback is having to take a laptop or tablet to run the Flex , but the filtering and features of the Flex , I feel are worth it.
Paul
Shirley Dulcey KE1L says
The KXPA100 is now over $1000, while the HARDROCK-50 is still $300 ($350 with QSK). That changes the equation and makes the HARDROCK even more appealing.
The miniHFPA is not currently available; Virgil Stamps K5OOR is doing a redesign. It’s a solid choice if you find a used one, and I expect the redesigned amp will also be good.
Terry says
I have a KX3, X5105 and MTR3B QRP radios. I have a KXPA100 in the shack which is always paired with the KX3. For portable operations, I built one of the Hardrock50 kits with the QSK option but no tuner. (I usually use tuned or tunable antennas in the field.) With the “COR” option on the HR50, it can be used with all three radios as a PTT line is NOT needed for transmit. It is a fun kit to build and very dependable. HobbyPCB is just the absolute best regarding customer and technical support. Extremely happy with the amps and the radios. Have done a lot of research and haven’t found any better or more practical. There is a new amp for QRP radios by DIY599 that has been introduced in Europe but not distributed in the USA AFAIK. It does contain a tuner, has a peak 60W output with very low current draw in idle. Current product model name is PA500.
John ve3ips says
At 100w out driven by my Icom 705 with 5 w input the 40m Ham audio boys helped me set my compression and a bit of EQ
Sounds fantastic
A great amplifier that I use a lot for POTA and out in the field if 10w isnt enough
A 30ah Bioenno powers it all nicely
Great feature set as well
John ve3ips