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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | Elecraft KPA1500 HF+6M Amplifier Help

Reviews Summary for Elecraft KPA1500 HF+6M Amplifier
Elecraft KPA1500 HF+6M Amplifier Reviews: 4 Average rating: 5.0/5 MSRP: $5,995
Description: 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.
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You can write your own review of the Elecraft KPA1500 HF+6M Amplifier.

W9KNI Rating: 5/5 Jan 25, 2018 20:38 Send this review to a friend
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: 5/5 Jan 18, 2018 08:44 Send this review to a friend
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: 5/5 Jan 15, 2018 11:21 Send this review to a friend
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: 5/5 Jan 12, 2018 17:11 Send this review to a friend
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.

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