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Reviews For: Elecraft KPA1500 HF+6M Amplifier

Category: Amplifiers: RF Power - HF & HF+6M

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Review Summary For : Elecraft KPA1500 HF+6M Amplifier
Reviews: 20MSRP: 5,995
The Elecraft KPA1500 is a compact, full-legal-limit, solid-state amplifier designed
for reliability and operator convenience. It has the following features:
* 1500 watts
* 160-6 meters
* Space-saving RF deck and separate power supply unit
* Fast, silent PIN diode T/R switching
* Comprehensive, easy-to-read LCD status display
* Fast, bright bar graph displays for power and SWR
* Advanced thermal design using two PA devices and very large heat sink
* Unique fan control system to minimize noise
* Built-in, wide-range antenna tuner with VFO tracking and dual antenna jacks
* Extensive remote control capabilities
* Compatible with nearly any transceiver
Product is in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
WC4X Rating: 2018-06-30
Fantasic product Time Owned: 0 to 3 months.
The big brown truck showed up yesterday afternoon with my new KPA 1500 S/N 300. It looks like Elecraft is quickly working thru the backlog.

Took a few hours to unpack and do initial testing into dummy load and all went well. Perfect timing---worked the KH1 dxpedition for my first 3 contacts using this amp. (20, 17, and 160 all CW). This amp is a pleasure to use and achieves full legal limit effortlessly and quietly. What a joy!! Integration with the K3s makes operating a real pleasure. For an ultimate station, I do not see how one could beat the K3s/ KPA1500 combination. The K3s digs them out of the noise and the KPA 1500 reels them in. If I could give this amplifier a rating higher than a “5”, I would do so. Expensive---yes. Well worth it---absolutely!!
K9YEQ Rating: 2018-06-26
WOW! Time Owned: 0 to 3 months.
THis amp is beyond my expectations. Just a few hours of operation... I am a simpleton. I ragchew on 75 and 160. Band condx suck. I have experience with other amps... this one is so far beyond expectations for what I do. I had a THP 2.5 KFX which I sold because it was too heavy for me to move (yes I am getting up their in years and the Co went out of business) so I gave a great deal to a very nice fellow HAM. I then acquired a KPA500, which was very nice. When the KPA1500 came out, I decided to get the extra gain and bought this one. My K3S picks signals out of poor condx, so needed to match my receiver to an amp that would match the situation. Tried it tonight for several hours and whatever I could hear, I could work. On the other end, stations not using K3S's could not hear me on low power, but I could hear them Q5, with the amp we connected. Simple. No issues. No faults. But a very simple setup. Fan noise in my operation... could not hear it. I noted the Power supply was running only by putting my hand above the fan. My shack does have dehumidifier and the receiver has lot of atmospheric noise. This is by far the best in my experience. Hats off to Elecraft for another superb piece of equipment!
K6RIM Rating: 2018-05-16
KPA1500 Hits a Home Run! Time Owned: 0 to 3 months.
The KPA1500, Elecraft’s new solid state legal limit amp, is exactly the amplifier for which I have been waiting a long time.

It is instant-on, plug and play, compact, lightweight, legal-limit, quiet, robust, perfect QSK - and it includes a lightning-fast built-in antenna tuner! The fit and finish of the KPA1500 is second to none.

In my six decades of hamming, I’ve owned and operated many amplifiers, and hands down, the KPA1500 is by far the best.

The KPA1500 is not my first Elecraft amplifier. I’ve owned a KPA500 for around five years. My positive experience with the KPA500 gave me the confidence to order the KPA1500 sight unseen. The KPA500 has been 100% dependable and trouble-free. Originally, it was purchased to serve as backup for my big-boy Alpha 9500, but very quickly the KPA500 was called upon 95% of the time. I won’t part with the KPA500; it’s now in addition to the KPA1500.

In choosing any radio product, it’s important to consider the support of the manufacturer. Elecraft has a well-deserved reputation for being responsive to its customers. To date, I have not required service from Elecraft, but my questions always received prompt and courteous attention. I have complete confidence in the company.

The new Elecraft KPA1500 was worth the wait!
K1GQ Rating: 2018-04-29
More Remarks Time Owned: 0 to 3 months.
Fan noise matters to me. My KAT1500 RF Deck is next to my K3, with the power supply in another room. I cannot hear the power supply fans (always running) at all. The three fans in the RF Deck have several temperature-controlled speeds, including off. The first level up from off is loud enough to annoy me without headphones, but actually not much different from the oversized air handler in our home's forced-hot-air heating/cooling system. SoundMeter+ measured 36 dBA with the fans off and 53 dBA with the fans at level 1, with the phone held in front of me at my operating position.

In a slow hour of running EU on CW, with many more CQs than QSOs, the fans spun up at 60C after about 10 minutes. Then the fans toggled between off and level 1, keeping the temperature between 58C and 62C and never reaching the next level up. The passive noise suppression of my headphones was good enough to prevent the fan noise from affecting my ability to copy weak callers. I also noticed that the forward power indicated by the amplifier and two external power meters was consistent throughout the session. I won't admit to owning a microphone; perhaps someone else will remark how whether or not the fan noise is an issue on SSB.

The fans suck air into the back of the RF Deck and force the air out through the top panel and through slots at the front edge of the bottom panel. With the RF Deck tilted up with the bail, the air from the bottom slots wants to flow straight at me -- and can be toasty.

The integration with K3 via AuxBus works flawlessly. The amplifier knows where the radio is going to transmit (even when split) so it can preselect relays as needed. Tapping ATU TUNE puts the K3 in TUNE mode and turns off TUNE mode when the KPA1500 ATU finishes tuning. The BAND buttons on the amplifier change the K3 band; one button tap to change bands is great, and the buttons are arranged with the bands that matter all on the top row in order of increasing frequency -- somebody was thinking about details. Another subtle detail: the brightness of the POWER LEDs various to provide additional resolution in the readout.

When you turn on TECH mode, the number of status screens increases from 2 to 11. There is a lot of information available, but not yet well-documented in the Owner's Manual. There are also quite a few mistakes the Revision A8 manual, including incorrect menu item names and wrong descriptions of the STATUS and MENU button behaviors.

And, love that instant-on (well, maybe 6 seconds).

-- Bill
K7ERQ Rating: 2018-04-14
Elecraft Thank You! Time Owned: 0 to 3 months.
Elecraft has done it again! Congratulations.
My observations on the KPA1500. Serial #76
Quick and Easy Install. The Perfect Desk Top Amp.
Top Quality External Finish and Perfect Packaging.
Easy to understand operating manual. Complete.
Set Up in 10 Minutes, 10 Minutes to Tune Antennas
Seamless operation with K3S, Anan7000DLE, Flex6600
RF Sensed Band switching quick & ready to operate.
Quiet, when Amplifier fans are on, Acceptable!
Love the separate Amplifier & Power Supply Units.
Legal Limit on ALL BANDS with Low Drive Power.
Antenna Tuner Handles 3.0 SWR at Legal Limits.
NO requirement for an External Antenna Tuner.
For years my amplifiers have been SPE 2K-FAs.
one in the home station and one in my remote station. only 1 thing I like about the SPE's better than the KPA1500, SPE's have 6 Antenna connections. In my remote setup that helps.
Other than this feature the KPA1500 is a HIT, out of the park.
AB4IQ Rating: 2018-02-23
Great Product Time Owned: 0 to 3 months.
I have used the KPA1500 (Serial #29) now for two weeks and am really impressed. It bolts my K3S together like I have legal limit transceiver. I made a couple of hundred RTTY contacts last weekend and the fans never turned on running close to the legal limit. It's kind of scary when you key down and don't hear a thing but the LED's are swinging to the right and putting out power.

The memory functions are excellent and once I trained the tuner on the different antennas the operation is seamless even selecting the proper antenna port for the antenna just by changing the frequency on the rig. All I can really say is that Elecraft did an excellent job of listening to their customers and hope that they sell a ton of them.

The separate Power Supply is nice and identical in size of the RF Deck. The fans on the Power supply run all the time but are not very loud. I place mine away from the operating table so I don't even hear them.

The equipment came in one nicely packed box and each piece had it's own box inside and the whole thing including the shipping containers were only 54 pounds total.
W9KNI Rating: 2018-01-25
Solid State Power Time Owned: 0 to 3 months.
I received my KPA1500 a week ago. As reported by earlier reviews here, it was exceptionally well packed. The amplifier is very simple to set up, especially with the Elecraft K3 and the KPAK3AUX data cable which tightly integrates the K3 and the PA1500. But, most or all front line transceiver from other makers will integrate almost as closely; allowing full automatic band tracking. The amplifier manual includes drawings of cable hook-ups making for easy set-up with any transceiver. Data cables for other rigs should be available shortly.

The QSK is flawless, a delight to use for CW. The antenna tuner is very unobtrusive, and easily and quickly set up. Uploading firmware updates is simple and quick, with the required USB cable included. The amplifier is rather quiet; except in heavy competition the fans hardly run at all. A 12 volt line from a switched transceiver outlet can be connected to the amplifier with the benefit that the amplifier will power up automatically when the transceiver is turned on.

Once the amplifier is installed, getting it “dialed in” is quick and mostly intuitive. The manual offers clear and concise instruction. The main issues are correctly setting the drive level for each band and if needed setting the antenna tuner memories. That’s all there is to it.

Bottom line - this is a solid, well designed piece of equipment that is easy and intuitive to use, and is going to be around for a long time.

N6PSE Rating: 2018-01-18
Spectacular new Amp! Time Owned: 0 to 3 months.
I'm happy to echo what Rick-N6XI and Ed-W0YK have written about the KPA1500.

It is truly "plug and play" even with my Flex-6500 transceiver. This amp puts out 1500 watts
with very low drive power. The tuner is quite robust and easily tunes my 80/160 meter antennas.

The fit and finish on this amp is superb. It is very well constructed and designed.

The amp came very well packaged from the factory and Elecraft has been very quick & responsive to
answer any questions that I had.

I've owned many amplifiers and this one is simply the best. Its a thrill to be running the KPA1500 in the N6PSE shack!

Paul N6PSE
W0YK Rating: 2018-01-15
Full Legal Power Amplifier Breakthrough Time Owned: 0 to 3 months.
Finally, a 1500 watt amplifier that is instant-on, whisper quiet, ample headroom, flawless QSK, RTTY-solid, auto-tune, built-in antenna tuner and extremely robust.

Elecraft continues to optimize the KPA1500 final design as I and a few others field-test the initial production build, but frankly the current units are near perfect in what I think an HF linear amplifier should be today.

The separate power supply box has the benefits of reducing operating table space and enabling the amp and PS to be easily moved by normal-strength people.

Gone are the negative characteristics we've all come to accept in a 1.5 KW HP linear. No straining to barely reach the 1500 watt level. No grinding and moaning to make one feel the amplifier is really doing something serious. I'm reminded of an Elecraft K3 field tester who looked inside and quipped, "Where's the radio?". The KPA1500 simply defies our prior concept of what an amplifier has to be. It's kind of strange, in a way, to pay $6000 for a product whose only indication that it's transmitting at 1800 watts is a wattmeter.

I do a lot of CW and RTTY contesting, so my equipment is subjected to severe duty cycles. Remember the Alpha amplifier ads in the 70s with the brick on the key? The KPA1500 handles high rate RTTY contesting so effortlessly that I'm left to wonder if it is even powered up. My first few operating sessions were spent continually checking the wattmeter to be reassured that full legal power was really happening.

What's more, the CW QSK is perfect. Operationally, it almost feels like QRP so, again, the wattmeter must be consulted to confirm 1.5 KW. Being able to clearly hear between elements at that power is incredible. There are no distracting artifacts as with other amplifiers.

While the KAT500 has been superb, the KPA1500 built-in ATU is even better. My antenna farm is currently in disarry with broken, patched and temporary antennas that all have high SWR. The KPA1500 instantly found matches for all of them throughout each band. When I return to a specific frequency in a band, the amplifier goes to its stored tuning values with no further searching. Literally, in minutes the new KPA1500 fully customized itself to my compromised antenna system.

Obviously, I don't yet have experience with long-term reliability, but with final transistors spec'd to handle 3 KW and loafing along with continuous RTTY, my confidence is high that a new bar has been set for amplifier robustness.

I'm sometimes asked if I think an amplifier should be shareable in a SO2R configuration, in order to reduce cost and only require one amplifier. Personally, if such a feature were available I would still use two amplifiers. I value the redundancy of two fully independent equipments sets for SO2R. And, even though I believe a single KPA1500 could handle high-rate RTTY SO2R contesting, I'd still prefer two amplifiers, each of which could loaf along. No matter how robust the product, less stress increases reliability.

In summary, I had the privilege to be on the early focus group for the KPA1500 so I've been aware of the product objectives for quite a while. Yet, serial number 11 has still exceeded my expectations. I can't imagine choosing any other amplifier available today.
N6XI Rating: 2018-01-12
Outstanding Full Power Solid State HF+6 Amp Time Owned: 0 to 3 months.
Like many others, I had waited a long time for Elecraft to introduce a full power HF+6 amp. I loved the KPA500 as a Rig 2 amp in my SO2R station but occasionally wanted just a little more "oomph." I loved my trusty Alpha 87a but felt that its auto-tune motors moaning and groaning in the background were a bit dated and the 3-minute warmup at turn-on was ... well, a turn-off. Also, the tiny, pixel-based remote control app from Alpha was hard to see on a high-resolution monitor and I was uncomfortable operating that amp remotely. As a result, I did most of my remote operating with the KPA500 and really missed full power in DX pileups. I had just about given up hope - and in fact had a back-order in place for an almost-full power solid state amp from another manufacturer - when I got a call from Elecraft offering me the opportunity to field test their upcoming KPA1500. I was delighted but cautious, understanding from personal experience that the last 20% of an engineering project can take 80% of the schedule time. I gave them an enthusiastic "Yes!" but waited for a few progress reports before canceling my pending order with the other company. I'm glad I did.

The KPA1500 is a reality now and it was well worth the wait. It is exactly what I had hoped for, a full power version of the KPA500, seamlessly integrated with my K3 transceiver which now operates as if it were a 1500W radio. Of course, an amplifier is a pretty easy thing to integrate, and the KPA1500 will work fine with any transceiver - just connect to the near universal SO-239 RF input, RCA phono plug key line, and SO-239 coax antenna and you're good to go. With the K3, there is a special 15-pin cable that connects to its ACC connector to provide not only a key line but also BCD band data, Auxbus frequency data, a power-up signal, a tx-inhibit signal, and ALC. Elecraft even provides integration goodies for some competitive transceivers, a magnanimous touch! With some Icom radios, the same 15-pin connector accepts their unique voltage-level band identification in place of the Elecraft/Kenwood/Yaesu BCD. There are also Ethernet, USB, RS232, and AH4 interfaces for use when needed.

There are some interesting and beneficial differences between KPA1500 and the earlier KPA500 amp. While the KPA500 had an internal, linear power supply and an optional KAT500 external antenna tuner, the KPA1500 has an external, switching power supply and a built-in, internal antenna tuner. I like this for several reasons: The KPA1500 RF deck is nicely compact, only slightly larger than a K3 or KPA500, fitting easily into either of my two stations. It is light weight and much easier to handle than typical tube amplifiers like my Alpha 87a or the ACOM 1000 I use at my valley station. The power supply is the same size as but lighter weight than the RF deck, contains its own cooling fans, and fits unobtrusively behind or under the operating desk. (You could certainly locate it on the desk - see comments below about fans.) You'll love the DC power cable with its 75 amp Anderson Power Poles and #4 conductors! It's quite flexible, considering its size. Unlike the smaller APP connectors, the 75 amp units have a robust, detented locking mechanism that produces a healthy “snap!” when you fully insert the plug. I also like having the ATU built-in and included. Even though most of my antennas are well-behaved, the ATU gives me full-band flexibility and an added measure of confidence that my amp is safe. Like its little bro, the KPA1500 has instant-reading LED bar graphs for RF Out and SWR, but its LCD display is larger and more informative. You can cycle through pages displaying just about any operating parameter you would care to monitor, much like the ACOM 1000 that has been my favorite manually-tuned, tube amp. The power graph has more than 30 LEDs, but the logarithmic scale results in only six of them being active between 1000 and 1500 watts where most users will spend most of their time. The engineer in me understands but my inner pedant wishes the scale were somewhat eclectic, with more precision where it's needed most.

What about phase noise from that switching power supply? I've listened casually but have not heard any. I turned the amp on and off while watching the P3 panadapters in my shack and could not detect any increase in noise floor. In fact, the noise floor dropped on some bands when the amp was inline, surprising me until I realized that the ATU was filtering out-of-band noise. Elecraft says they did much more thorough and scientific searching for such noise and also found none. I think both Elecraft and their OEM PS vendor did a good job of filtering out switching noise. By the way, the PS can be placed horizontally or vertically on the desk or floor. It has three LEDs but you really don't have to look at them unless you're diagnosing a problem.

Operators of other Elecraft rigs have been asking me on the air about the ATU: Is it the same as the other excellent Elecraft auto-tuners? Well, yes and better! Like its predecessors in the K3, KX3, KX2, and KAT500, it uses relay-switched inductors and capacitors in an L-network. The tuner can put the caps on either side of the toroids to increase flexibility in finding tuning solutions. Unlike the earlier tuners, though, this one has gobs of memory for tuning solutions. For every 20- or 50-KHz segment of every band, the tuner can retain up to 16 separate tune settings for each of the two antenna inputs, certainly more than ample! When it finds itself wanting to re-tune, it first checks all known settings for the current segment. In less than a second (mere milliseconds in many cases) it can adapt to a change from one antenna to another that it has seen before. Only for previously untried antenna/frequency combinations does it have to do a full tune. Even that is pretty fast as with prior Elecraft tuners. Of course, the amp puts itself into Standby when the ATU is tuning. You can also leave the tuner inline when the amp is standing by so it serves the barefoot exciter. It also has slightly different operating modes than KAT500. The default mode, which I've used almost exclusively, tunes only when requested by a TUNE button. It follows the band segment in which a K3 says it's operating or its fast RF sensing determines is in use with a non-K3 exciter. Currently, you have to tap TUNE and then manually apply RF. New firmware is coming that will let the amp key a K3 exciter by itself, providing one-touch tuning.

Like the KPA500, this new amp operates full QSK with silent PIN diode switching. It's good, clean QSK, not quite as easily interrupted as a barefoot K3, but everything I could ask for. Compare that to amps like the Alpha 9500 whose loud vacuum relay competes with the transceiver's audio output to drive your ears into distortion! Speaking of noise, the fans in the RF deck are quiet and unobtrusive. So far, I have been using a pre-production power supply with a pretty noisy fan - not as loud as the blower in a 9500, but disturbing nonetheless. It actually masks the sound of the RF deck fans unless I listen closely. Elecraft wisely delayed production shipment of KPA1500 so they could re-package the OEM power supply with much quieter fans. I've heard a prototype of the production supply in an Elecraft lab and it is indeed very quiet. I look forward to replacing my field test PS with one of those sleeping babies. At that point, I expect this amp to come close to the quiet sound of the ACOM 1000, my personally-assigned record-holder for amplifier ambience.

On the air, the amp has generated 100% enthusiastic comments. "Great audio," "perfect keying," and "LOUD!" are the things I hear. I've operated a fair amount of casual CW, a few SSB QSOs, broken a few pileups, and put it through about six hours of mainly CQing RTTY Roundup contesting with nary a hiccup. RTTY can be a real challenge for amplifiers, but KPA1500 handles it well at full power for extended key-down periods. Into a dummy load, I've briefly generated up to 1800W at which point the amp limits itself. But the two solid-state devices could each generate full power themselves, so the pair is loafing along at 1.5 KW. I'm a stickler for avoiding the red LEDs, but I understand that headroom is a good thing. K6NV offered the following unsolicited report after the RTTY Roundup: "Friendly neighbor report - That amp is a 10+. No phase noise, no clicks, no spurs, nothing but a nice sig, did not know you were on except for the vertical spike on the P3 with red around it. Very clean, really nice to listen to from a mile away."

I often operate my mountain station remotely from Silicon Valley. I enjoy using the KPA500 Remote app which has a client/server mode that gives me an attractive, remote control panel running on the control site computer. Although the similar KPA1500 Remote program is not yet available ("coming soon"), I found the amp easy to operate remotely using KPA1500 Utility. That provided app has an Operate page that displays numeric values and control switches for just about all parameters and functions. I run it on a server computer at the remote shack and access it with a remote desktop app - very slick! KPA1500 Utility also provides an interface for firmware updates, configuration parameter settings, and firmware command communication. That RTTY RU contest I mentioned above was done remotely, my first attempt at remote RTTY, and it was almost as good as being there.

The KPA1500 PS comes with a built-in AC power cable with a common US NEMA 235V plug. If your socket is different, you can build an adapter or cut off the factory plug and install your own. The package also includes the 15-pin D-sub control cable that connects the PS and the RF deck, a USB cable to connect the amp to your computer, and a high quality, teeny-weeny, RCA-to-RCA cable in case you choose to use it as a dedicated amplifier keyline connection. It's too short for all but the most compact station layouts and I hope they upgrade to a longer one. But it doesn't really matter for me because I key the amp through an optional KPAK3AUX cable (K3 ACC to KPA1500 AUX) which is long enough for most purposes and provides the additional integration signals mentioned above. And it may not matter for non-K3 operators, either, since most homes are blessed with an ample supply of inexpensive RCA-to-RCA cables left over from the days when those were standard audio interconnects. The manual, which I have reviewed in draft form, is quite good, as we have come to expect from Elecraft.

All in all, KPA1500 exceeded my high expectations. It is a noble addition to the Elecraft line of transceivers, amplifiers, and accessories. I look forward to many years of faithful service.

I was wrong about the ATU memory configuration. There are 31 memories per band slot and each can associate with either antenna port.

I was wrong about vertical mounting of the power supply. The official word from Elecraft is 1" top/bottom/sides clearance, 4" behind rear, so horizontal mounting may be necessary. I'll probably build a vertical mounting scaffold that gives me the requisite clearance. I have an old CPU vertical mounting clamp that might do the job.