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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | Elecraft KXPA100 Amplifier Help

Reviews Summary for Elecraft KXPA100 Amplifier
Elecraft KXPA100 Amplifier Reviews: 12 Average rating: 4.9/5 MSRP: $699 kit, 749 factory assembled
Description: The compact Elecraft KXPA100 amplifier is intended for use
with all QRP transceivers. It's particularly well suited to
the Elecraft KX3 transceiver. The amp covers the 160-6 meter
bands, including the WARC bands, and is rated at 100 W
nominal power output (+/- 1 dB). A companion internal
automatic antenna tuner (ATU), the KXAT100, is also

Features include:

100 W output on 160-6 m with 5 W input (+/- 1 dB typical)
13.8 VDC powered; 15-20 A typical current drain
7 lbs with optional KXAT100 ATU installed.
Compact unit ideal for both desktop and mobile use (10 x
5.125 x 4.25")
Solid-state diode T/R switching fast, silent T/R and QSK
Large convection-cooled heat sink for reliable and quiet
Modern design with rugged MOSFET output stage
Internal wide-range automatic antenna tuner (KXAT100 ATU
option) with dual antennas
KXAT100 matches 10:1 SWR (5:1 typical on 160 m and 6 m);
uses Elecraft's fast matching algorithm
KXAT100 settings saved per band, per band segment, and per
antenna for instant recall
Fast, bright LED bar graphs for power and status; KXAT100
ATU option adds SWR bar graph
Seamless integration with the Elecraft KX3 transceiver
Works well with any low-power transceiver, requiring only
RF and PA KEY inputs
RF-based frequency counter automatically switches bands
with any rig
Optional band-voltage input supports the Yaesu FT-817,
Icom IC-703, and other selected rigs
Dual APP power connectors for additional friction-fit if
needed (mobile)
Optional KXPACBL adapter connects KX3 to the KXPA100 for
keying/band data/control
Product is in production.
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AE5QB Rating: 4/5 Mar 20, 2014 00:27 Send this review to a friend
Works Pretty Well  Time owned: 0 to 3 months
This is a good little amp and it works pretty well. I am happy with it as I can get 110 watts out of it as measured on an external meter but I typically run it at about 80 watts. I rate it a 4 because there a couple of niggles everyone needs to know about. None are showstoppers but hey it is a pretty high priced amp.

The mechanical design is well a brick. It looks like the mirage 2m amps. I think they could have done better.

While the build from kit was easy, it is not easy to get back into the kit if needed. In fact you pretty much have to take out 32 little screws to get it open at all. I worked for a company that designed computers and servers, there could be no externally exposed screws and it had to open with one hidden knob, so it can be done - those guys were mechanical engineering geniuses!

The amp is designed to talk to the KX3 and computer through a serial interface, this means you daisy chain the KX3 to the amp to the computer. I have found this can cause comm problems with rig control and software programs.

The ATU on the amp is not as good as the internal ATU in the KX3. I find that the ATU in the amp stops .1 or .2 SWR units higher than the KX3 ATU. I've also noticed that in some instances the tuned SWR is lower than the operational SWR. I am not sure what is going on with that but I am working with Elecraft on it and am confident we will come up with an answer.

I've also noticed that when I stop transmitting, there is a significant delay in the response of the front panel LEDs. The 25W LED and the SWR LEDs will stay on for 1.5 to 2 seconds after key up.

Finally, when the ATU tunes, the firmware puts the amp in bypass mode so it is just the KX3 working with the ATU to tune. After tuning, there is a about a 1.5 second delay before the amp switches back in. So if you tune up and then try to transmit too quickly, you will be transmitting without the PA and at the lower tuning power.

Maybe I just have a problem with my ATU and I will continue to work with Elecraft to figure it out. I think the AMP is fine and does what it is suppose to do, but I may have an issue with my ATU.
W7LRY Rating: 5/5 Feb 3, 2014 19:12 Send this review to a friend
GREAT  Time owned: 0 to 3 months
Well worth the cost. Easy to build, easy to use, and very portable. It is a great tool for those that want to run a low power, low current draw qrp rig and for poor band conditions or emergencies have the extra 100 watts of power. With the cables it is all automatic with the KX3. Just turn on your little qrp radio and use it like any other 100 watt radio. It's a good feeling to have the extra power if needed. Like the other Elecraft equipment it is better than I expected. I haven't had the amp a long time but I can say it works very well. I look forward to using the KXPA 100 for traveling and camping in the mountains of Colorado.
K4ALE Rating: 5/5 Jan 28, 2014 18:10 Send this review to a friend
Strongly recommend  Time owned: 0 to 3 months
I received my kit version, Ser. No. <300, several weeks ago. I have had a KX3, with most of the fixings, since early July 2012. I think the KX3 is about everything I have ever wanted in a radio. As we know, the receiver is amazing, so the real "problem" has been to transmit with enough power to increase the chance that station you could hear will hear you. If you have only wire antennas, as I do, this power addition is very useful.

Construction: I dragged the construction out to about 2 hours, by photographing every single step, and savored every turn of every screw. This thing is so simple, a lawyer can do it.

Operation: As others have noted, I now get quick replies, even in pile ups. Voice quality reports are positive, which is what I got with the barefoot KX3. It is important to adjust the TX equalizer to make your voice work at distance. I have found that PSK 31 and RTTY signals are easily read by others. As with the barefoot, CW is a dream. I have not put this on a spectrum analyzer ['cause I don't have one], but performance suggests the signal is quite clean.

Operation with the KX3 using the optional connector cable set is seamless, and the rig simply becomes a 100 watt Elecraft transceiver, with all that means.

Setting changes are extremely easy, using the same buttons and knobs used for barefoot KX3 operations.

Follow the relatively simple directions in the manual to avoid problems. I have made a couple of mistakes, but the amp tells the KX3 and it promptly tells me I am an idiot.

Computer interface with both the KXPA100 utility and the regular KX3 utility has been flawless. With the amp, I can now reasonably participate in SSB contests. In CW contests, where N1MM allows me to operate mostly from the keyboard [using a simple homebrew interface], I can now move out of the QRP class and hope to make many more contacts.

My generic switching power supply suggests that I am drawing well below the nominal 20 amps in the specs. I have had no problems in this regard. Because of size and efficiency, this is a rig that I can expect to use during ARRL Field Day from the field with marginal power demands [even batteries.]

ATU: The ATU is quite sensitive to antenna conditions, and is consistent with what my analyzer says those conditions are. It matches everything I have tried quickly. Follow the instructions, especially regarding the "programming" into memory many spots in each band. This makes shifts to the next band as fast as you will see with any other ATU. It surpasses my excellent LDG Z-11Pro on the same antennas. Once tuned, it stays tuned.

Summary: The KX3 is still a wonderful QRP radio, and I continue to enjoy using it at 5 watts. The easy settings, quick and steady ATU, and plentiful power provided seamlessly by this amp enable me to make contact with almost everyone I can hear [within the reasonable limits of my wire antennas.] I STRONGLY recommend this to anyone who has a KX3 and wants to make it reach out to all of those folks [and make life easier for them trying to listen to you....]
K2MVR Rating: 5/5 Jan 14, 2014 19:57 Send this review to a friend
Excellent!  Time owned: 0 to 3 months
I recieved my assembled amp SN 484 on January 8, 2014.
The packaging was superb and the instructions are very easy. In a matter of minutes I had it hooked up to my KX3 and after a few minor menu settings had it on air. I ordered it with the internal ATU and it tuned up my Matchbox Endfed antenna quickly. I was on the air with excellent reports from miles away. Clean!

I absolutly love my KX3 and having the KXPA100 in the shack gives me the best of both worlds - QRP portable and up to 100 watts in the shack!

I absolutly recommend this amp for your KX3 (husband and wife).

Thanks to all at Elecraft.

73 de Joe K2MVR
WA9SDJ Rating: 5/5 Jan 12, 2014 10:55 Send this review to a friend
The Best  Time owned: 0 to 3 months
Ordered as a kit, assembly is very easy, even if only a beginner, no soldering required.


- The KXPA seamlessly integrates with the KX3, even computer control/info is passed through with only one cable necessary.
- Amp has a small footprint with a large heatsink, completely silent and no fan necessary.
- KXPA amp software is available for Linux/Mac/Windoze.
- Excellent printed manual/assembly instructions.
- Easy to adapt to other Rigs
- Price is a value considering the flagship device/options/support/performance/continuous improvement you receive.


- Haven't found any yet.
W5MMT Rating: 5/5 Dec 16, 2013 14:54 Send this review to a friend
Built like a tank, works like a dream  Time owned: 0 to 3 months
I got sn 52 with the ATU built in. I have another one on order. Works seamlessly with the KX3 and it really is built like a tank and works like a dream. Elecraft just makes class stuff. This one is going back with me to Thailand where I'm HS0ZAC.

I'll do more detail after a few months of use.
W6GF Rating: 5/5 Dec 10, 2013 11:46 Send this review to a friend
Oh Elecraft you can do better  Time owned: 0 to 3 months
I love to start reviews this way, because it rings Wayne's bell. This is a great flawless product. I am proud owner of S/N 61 with the ATU. My only nit is that for $12.00 dollars per watt [yes with ATU] the instruction manual deserves a cover and binder not just some pages stapled together [one staple I might add].

It may not be the cheapest QRP amp, but WOW.

George, W6GF
AE7WC Rating: 5/5 Dec 5, 2013 18:20 Send this review to a friend
Works as advertised  Time owned: 0 to 3 months
I've got everything working and if I can hear someone I can work them. The thing is quiet and doesn't require any effort on my part. It is a little bit "spendy" but I wanted something that I could work with using battery power and it will. If I have any issues I will update.
K9YEQ Rating: 5/5 Dec 5, 2013 14:48 Send this review to a friend
Best QRP amp I have owned  Time owned: 0 to 3 months
I have tried lots of small QRP amps. Blown a few finals and have had numerous issues. I have plenty of power in the shack, so when I had the opportunity to be a field tester of this amp., I did have to think hard about spending $'s for something I didn't really need. Based on past experience with Elecraft and testing other radios they have designed, I jumped in. It is not so easy being a tester; it requires timely and somewhat intensive activity. What you experience as a user is a result of this thorough testing before the product release. This is rare in the "new age" of HAM radio and consumer goods. I cannot believe how well this amp works with my KX3. The tuner is on par with all the Elecraft tuners.

I get great reports going from QRP to QRO. My unit has the tuner and cable kit. A smart way to go... if you have the $'s. This amp is a "you get what you pay for" purchase.
AE7WC Rating: 5/5 Nov 30, 2013 18:57 Send this review to a friend
good match for my kx3  Time owned: 0 to 3 months
Just got mine yesterday (11/29) sn 0042. Still ringing it out but it looks like I got what I paid for... Will update in a month or so.
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