HardRock-50 amplifier interface from HobbyPCB for the Elecraft KX2 and KX3

Hi folks,

My friend Jim WA2EUJ from HobbyPCB just sent me a few days ago, for testing purpose, a brand new HardRock-50 amplifier interface for Elecraft KX2 and KX3. This little interface let you use quickly your Elecraft KX2 or KX3 with your HardRock-50 amplifier with standard cable, without the need to build custom cable, and let you use also at the same time your KXUSB cable to control your transceiver with your PC.


With this addition, all HardRock-50 users will not need to make custom cables to drive their amplifier with their transceiver. A cable kit comes with the interface. This way, I was able to connect easily my Elecraft KX2 with the HR-50 by using the 4 conductors 3.5mm cable provided with the amplifier interface. Once properly configured, the HR-50 will change band automatically and will follow the transceiver band change accordingly. The interface will also key the amplifier from the transceiver when hitting the PTT or the TUNE button.


The setup is some kind easy and straight forward. Here is a example for my Elecraft KX2 :

  1. Connect the 4 conductors 3.5mm cable between the Elecraft KX2 ACC connector and the HR-50 interface KX2 ACC.

  2. Set the baud rate in the HR-50 setup menu. It must match the baud rate already set in the transceiver setup menu. Mine is set on both sides at 38,400 baud.


  3. Set also the option KX3 Serial to ON into the HR-50 menu.


  4. On the KX2, the feature called AUTO INF must be set to ANT CONTRL. The transceiver will then transmit over the serial line a text string information, and let the HR-50 know on which band it needs to change. This option is easily found under the TECH SUPPLEMENTAL MENU. To access it, you must set TECH MD prior to ON to be able to set AUTO INFO value to ANT CONTRL.


  5. Optionally, you can also connect the KXUSB serial cable to your PC and into the KXUSB port on the HR-50 interface.


  6. That’s it, you are all set!

Now, with everything properly set, when the band change on the KX2, the HR-50 change also automatically to the correct band. And when the transceiver transmits, the HR-50 also transmits automatically.

Again, this small interface avoid the need to build custom cables to hook the Elecraft KX2 or KX2 with the HardRock-50. It also gives the user the possibility to still use the KXUSB cable for the Elecraft KX2 or KX3 at the same time with the computer, just exactly as the Elecraft KXPA100!

I’m using it with RUMlogNG on my Macbook Pro, and it is working great!

For more information, you are invited to visit HobbyPCB website at http://www.hobbypcb.com

Meanwhile, do not forget to subscribe to my blog and my YouTube channel as well.

Have a great summer and stay tuned!


Jeff | VA2SS