The PI4 + CW + chirp + carrier beacon program makes the RFzero capable of transmitting on any frequency from 100 kHz to 200 MHz and beyond running on the fundamental frequency.
The configuration is done via the USB port. It is possible to wait for the RFzero to warm up for up to 255 s before starting to transmit. It is also possible to wait for the GPS to be valid before starting to transmit.
During the PI4 part of the sequence the TX LED will flash at half the symbol rate, i.e. 3 Hz, during the CW part of the sequence the TX LED will flash with the CW and during the carrier part of the sequence the TX LED will be constantly lit.
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.
The beacon sequence
When the GPS time is valid the beacon transmits PI4 for the first 24 1/3 s, then followed by a short break of 2/3 s, then the call sign and locator is sent, then follows a sequence of five 2 s 1 kHz chirps which is then followed by a carrier until the full minute. Then the sequence repeats again.
If the GPS signal is invalid the beacon suspends the PI4 and just transmits CW and a fixed length 20 s carrier.
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.
The display shows the UTC seconds, the GPS status, the number of satellites and the HDOP.
Example of an LCD 16×2.
The display shows the GPS status, the number of satellites, the HDOP as a bar graph, the UTC, call sign and locator of the beacon and the frequency.
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)). Please connect the RFzero via a USB B 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.
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
to see the configuration that will be used after exiting the configuration mode.
to set most of parameters to their default values. Please see the actual program for the specific default values.
wr t1 MODE
to set the T1 H/W mode where MODE is
- 0: Transformer (default)
- 1: Combiner
- 2: None
wr display MODE
to set the display mode where MODE is
- 0: None
- 1: LCD 16 characters and two lines, HD44780 interface
- 2: LCD 20 characters and four lines, HD44780 interface
- 3: LCD 16 characters and two lines, HD44780 via I2C PCF8574 interface
- 4: LCD 20 characters and four lines, HD44780 via I2C PCF8574 interface
- 5: Graphics display, ILI9341 SPI interface
- 6: Graphics display, ILI9488 SPI interface
wr bcn CALL
where CALL is the beacon call sign, max 15 characters.
wr loc LOCATOR
where LOCATOR is the locator up to eight characters, i.e. AA00AA00.
wr mgm MESSAGE
where MESSAGE is the PI4 message, max eight characters where space, ” “, is replaced with an underscore, “_”.
wr cw DURATION
to set the CW DURATION, i.e. duration in ms, 1 ms to 255 ms. 100 ms = 12 WPM/60 LPM.
wr key STYLE
to set keying STYLE where 0: is on-off keying (OOK), or 1: for frequency shift keying (FSK).
wr freq FREQ
where FREQ is the nominal on-air beacon frequency in Hz from 100 kHz and up.
wr multi MULTIPLIER
(multiplied beacon only)
where MULTIPLIER is the harmonic/multiplication factor. Valid values are from 1 to 255, e.g.if using the fifth harmonic on 902 MHz
wr multi 5
wr warmup SECONDS
where SECONDS is the number of seconds to wait for the RFzero to warm up.
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 wait ONOFF
to turn on or off waiting for the GPS to be valid before transmitting where ONOFF is either 0: for off/don’t wait for the GPS to be valid, or 1: for on/wait for the GPS to be valid.
wr echo 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.