Multi LO

The Multi LO program can be used to generate five different frequencies, e.g. for different transverters. The program can take subsequent multiplication factors into account.

The configuration is done through the USB port.

The different frequencies are activated by pulling-down either A0 for frequency 1, A1 for frequency 2, A2 for frequency 3 or A3 for frequency 4 to ground. If neither are pulled-down then the default frequency 0 is generated.

When GPS signals are received the PPS LED flashes ones per second and when the status of the GPS signal is valid the Valid LED is lit.


To setup the type of display used please use the “wr display” command. If you want to change what is shown on the display please edit the display.cpp file.

Please see the display page for more information.

LCD 16×2

The display shows the UTC, the GPS status, the number of satellites and the HDOP.

Example of an LCD 16×2.

LCD 20×4

The display is a LCD (4×20) that shows the UTC, the frequency number 0-4, GPS status, the number of satellites, the HDOP, call sign and locator.

Example of an LCD 20×4.


The configuration of the program is done via the USB port, 9600 Baud, 8 bits, no parity and one stop bit, using a terminal program (e.g. Arduino IDE Serial Monitor, Termite Terminal (Windows), CuteCom (Linux) or Terminal (Mac OS) or the RFzero Manager (Windows)). Please connect the RFzero via a USB data cable to your computer and connect the terminal program to the right COM port in the terminal program. The RFzero identifies itself as an Arduino Zero (Windows Device Manager).

If you don’t see the RFzero> or RFzero config> prompts please press the enter key. When you want to execute a command you don’t have to enter the prompt but only the command and parameters after the >.

Changes to the configuration does not take effect before leaving the configuration mode.

All input to the RFzero must be in lowercase.

To enter the configuration mode please enter   config   at the RFzero> prompt, i.e.

RFzero> config

To see the available commands please enter   ?   at the RFzero config> prompt, i.e.

RFzero config> ?

To leave the configuration mode please enter   exit   at the RFzero config> prompt, i.e.

RFzero config> exit

When in configuration mode, i.e. when you see the RFzero config> prompt, the most frequent commands are

rd cfg

to see the configuration that will be used after exiting the configuration mode.

wr call CALL

where CALL is your call sign shown on the display if any. Max length is ten characters.


where NUMBER is from 0 to 4, FREQ is the fixed frequency in Hz and MULTI is the multiplication factor used. Set the multiplication to one (1) if no multiplier is used.

Where frequency number 0 is the default frequency when neither A0 to A3 have been pulled down. Frequency number 1 is activate by pulling pin A0 to ground … and frequency 4 is activate by pulling pin A3 to ground.

wr level LEVEL

where LEVEL is the drive strength current in the output stages. This effectively changes the output power by up to 10 dB, but varies somewhat with frequency. Valid LEVEL values are

  • 0: 2 mA
  • 1: 4 mA
  • 2: 6 mA
  • 3: 8 mA, default level

To read more about the drive strength current please consult the Si5351A datasheet.

wr gps MODE

  • 0: hide all NMEA strings
  • 1: show the $GPGGA and $GPZDA NMEA strings
  • 2: show the $GPGGA, $GPGLL, $GPGRS, $GPGSA, $GPGST, $GPGSV, $GPRMC, $GPVTG and $GPZDA NMEA strings

More commands are available so please enter a question mark (?) at the RFzero config> prompt to see them.