RS-HFIQ Technical Information Site

Welcome to the home of the HobbyPCB RS-HFIQ 5 watt, HF Transceiver.  


The RS-HFIQ is available now from and can be ordered here.

The RS-HFIQ is an open-source project designed to translate I and Q baseband signals to RF in the 80/60/40/30/20/17/15/12/10M Amateur Radio bands. The I and Q signals must be provided/processed by external signal processing which could be a PC running Software Defined Radio software, a stand-alone digital signal processor and some form of analog processing.

There was tons of interest at the 2017 Hamvention in the RS-HFIQ. If you are one of the many folks who stopped by the booth and are looking for more info on the radio, check out theKickStarter page. Even though the campaign is over there's lots of good info, descriptions and our video.

The receiver in the RS-HFIQ consists of 5 band-pass filters to reject out-of-band signals, a LNA with frequency dependent gain and a conventional quadrature down-converter.

The transmitter in the RS-HFIQ uses a Quatrature up-converter followed by the same band-pass filters used by the receivers, a 5W power chain and a low-pass filter bank.

The Local Oscillator is based on a Silicon Labs SI5351 chip that can produce up to 3 RF outputs, the LO signal for the up/down-converter, a built-in test signal for calibrating I and Q offsets and an external signal.

The control of the SI5351 and all switching functions is provided by an Arduino Nano running open-source software and programmed with the Arduino IDE.

Special care has been taken to insure noise and ground-loop set-up. The RS-HFIQ has three separate DC isolated ground planes; RF/Chassis ground, Baseband/Audio ground and Digital ground. This allows the same PC to be connected to the audio in/out and the USB port on the Arduino Nano without creating noise/grounding issues.

Here is a block diagram of the RS-HFIQ transceiver (click on it to see a larger version):

The transceiver board is 100X160mm and slides into an aluminum extrusion or can be mounted using 4 mounting holes.

This is a photo of the Rev B prototype board: (Click on the image to see a larger version)