Elecraft KPA500

The KPA500 is a compact 500W “key down for 10 minutes” solid-state amplifier with a 60V FET PA and built-in mains power supply. It uses fast electronic transmit-receive switching and hence gives totally silent and lightning quick QSK - no relays to click and wear out.

It is a no-tune design with low pass filters selected automatically for each band (160 to 6m) using RF sensing or a band data connection from the transceiver - more on that below.

As with the K3, building the no-solder kit involves assembling a set of panels and strengtheners for the case and a few pre-constructed PCBs, the PA unit being the main one with its large heatsink. The kit instructions didn't tell me which way to mount the fan and it had no markings to show which way it blows. In the end I put it with the label outside: it sucks air in through the top vents and blows it out of the rear of the amp, which is the way I like it, voiding into the space behind the shack desk rather than blowing in my face. It is pretty quiet, much better than the intolerable roar of 4 old muffin fans inside my big old LK550 valve amp and the snail-fan in the Alpha 87A.

Aside from silent QSK, the size and weight of the KPA500 were big attractions for me as I plan to use it for DXpeditioning. It is the same size as the K3 so it will fit into a flight case and can be taken in the cabin of a plane as hand luggage. It weighs 12kg, about half of which is the toroidal transformer. If needs be, the transformer can be removed without too much trouble and carried separately in the hold.

QRQ QSK is a joy to use. Not only can I hear immediately when someone comes back to me, or QRMs me, or comes back to someone else, I can also turn the beam when CQing on CW to find the strong reflections on my own signal that usually mean I’m getting out well in that direction. I can time my transmissions to get around the oh-so-helpful frequency kops and other lids on my frequency, and hear when my signal is bouncing twice around the world!

KPA500 firmware updates

Mostly the KPA just sits there quietly doing its thing, as any well-behaved amp ought to do. It talks to the K3, follows me from band to band like an obedient puppy, ramps up its fan if it gets too warm, backs off the power or alerts me to a fault if I do something silly (such as transmitting on the wrong antenna). It delivers.

Elecraft occasionally updates the KPA’s firmware, far less often than the K3 since it is much less complex. Having not updated my KPA in well over a year, I forgot how to do it, so here are my notes as a reminder for next time:

1. Check Elecraft’s KPA software page for anything new (the KPA firmware and KPA Utility programs were both updated since I last checked).

2. If the Utility was updated, download the new version and install it first. If you aren’t sure, run the KPA utility on your PC and check the version number under Help -> About KPA utility .

3. Hunt for a serial/USB adapter that works. Plug it in to the PC. Check which port it has chosen this time from Windows Device Manager (which is accessible using <Windows+Pause>) by unplugging and re-plugging it to see what changes. [It may pick a different USB port if you plug it in to a different USB port than when you last used it.]

4. Plug the serial/USB thingy into the KPA500’s upper serial connector, and turn the KPA on (if it isn’t already on).

5. Run KPA Utility.

6. If KPA Utility doesn’t immediately give you a pop-up status message such as “KPA version 01 .23 RS-232 speed 38400 bit/s” (which means it is already talking to the KPA), select the appropriate com port to kick it into talking to the KPA. You can also click Test communications . Congratulations, your PC should now be talking to the KPA.

7. Open the Firmware tab. The folder location should still be as you left it, if not find the directory where you store your KPA stuff (in my case, C:\Users\Gary\AppData\Roaming\Elecraft\KPA Firmware).

8. Click Copy firmware files from Elecraft . This tells the utility to go to Elecraft’s FTP server to download the latest KPA firmware to the directory noted in the previous step. Wait for it to do its thing. It may give you a message about having found and downloaded something new.

9. If there was something new, click Send firmware to KPA to update the KPA’s firmware. The KPA will click and put itself into MCUload mode, update its firmware, then click back to normal about a minute later.

10. Play with the settings on the Operate tab if you like. You can remotely-control and monitor the KPA with these if it is just out of reach, or somewhere across the planet.

11. Open the KPA configuration tab. Put something useful in the power-on banner, such as your callsign in case it gets stolen and recovered by the police (in the vain hope that someone will work out how to operate the ON button, realise that your callsign is a unique ID, and turn up at your door with the KPA in hand).

12. Click Save KPA configuration to save its settings, just in case you ever need to re-load it and can’t be bothered to reconfigure it by hand.

13. Close KPA Utility, unplug the USB-serial thingummy and hide it somewhere very secret to give yourself something ‘fun’ to do next time.

14. Make yourself a nice cup of tea to celebrate and GET ON THE AIR.