Connecting a Power Ampfier

The information on this page is pertinent to the RS-HFIQ, IQ32, IQ64, the PI SDR IQ+ and any other SDR based on the RS-HFIQ.

When 5 watts of power isn't enough, you can connect the RS-HFIQ to the HobbyPCB Hardrock-50, Hardrock-50+ or Hardrock-500 power amplifier.

The connection is designed for use with HobbyPCB amplifiers it may be possible to connect amplifiers from other manufacturers just note that the signals from the RS-HFIQ are open drain opto-coupled outputs with no current spike protection and are not intended to drive a relay. The maximum open circuit voltage is 70V and the maximum short circuit current is 50 mA. Exceeding either of these may damage the opto-coupler.

The Hardrock amplifiers are 5V open circuit and <1 mA when shorted to ground.

The interface board comes as a kit with the following components:

You will need to solder the components to the PCB. Start with the 3.5mm jack, then add the resistor, finish by soldering the DB9 connector to the PCB. It should look like this when you are done.

Since the output of the RS-HFIQ are ate opto-coupled to prevent ground loops, the data line needs to be pulled high. The 2.2K resistor takes care of this for us but we do need to put +5V on PIN 1 of the Hardrock-50's DB9 ACC jack. For rev G or later boards, SJ305 solder jumper that does just that. Use solder to bridge the contacts here:

On earlier versions you'll need to run a small wire from the +5V test point to pin 1 of the DB9.

When everything is done, plug the interface board into the DB9, ACC jack on the Hardrock-50 and connect the 3.5MM stereo jumper to the 3.5MM jack on the interface board and the other and to the 'AUX' jack on the RS-HFIQ. In the Hardrock-50's menu you'll need to set the ACC Baud Rate to 19200 and the KX3 Serial to 'Yes'.