DX FT8 notes

DISCO Board

The DISCO board is STM32F746G-DISCO from STMicroelectronics. The PC utility "STM32 ST-LINK" is downloaded and installed before firmware is loaded into the DISCO board. This is described in the user guide DX_FT8 FT8 DIGITAL MODES HF GUI TRANSCEIVER Programming And User Guide_REV1.3.pdf.

Below are screen-dumps and pictures I took during installation.

Figure 2. DISCO screen after power up (no firmware loaded).

Figure 3. ST-LINK Utility (not connected).

station data

Figure 4. StationData.txt is created by Notepad
and saved on the flash card.

utility connected

Figure 5. ST-LINK connected to the DISCO board via yellow USB port.

LEDs

Figure 6. DISCO connected to the PC utility via USB.
LD4 is flashing. PWR is constant. Comm. is flashing when there is traffic on the USB interface

download from github

Figure 7. Download the .bin file from Github by pressing the "Download" icon.

Download the .bin file from Github exactly as shown in figure 7 above.
Do not download via your browser's "Save as" function. The saved file won't work. I speak from experience!

load file

Figure 8. Select "File > Open file" to open the desired file.
Please disregard the questionmarks in the ASCII column (they were caused by an error in my PC).

press start

Figure 9. Select "Target > Program"
and press "Start" to download the firmware.

DL finished

Figure 10. Download finished.

DX FT8 runs

Figure 11. DISCO screen after download completed.

RF Board

The RF board was builty from a kit purchased from K5BCQ. The RF board in the kit is populated, except for a few components Follow the "hardware build guide" to fit remaining components.

I cut off 3 legs (plastic) on the battery holder in order to fit the PCB. The two SPDT slide-switches were mounted vertically - they can be operated using a pen.

The measurements below were taken after the RF Board was connected to the DISCO board. Multimeter: Fluke 17B+. Oscilloscope: Owon HDS272S (BW 70 MHz) with 10x probe.

Figure 12. RF Board test points.

Prepare measurements:
Terminate J1 with 50 ohm. PSU 12.0 V DC connected to J3. All measurements refer to Ground (TP4).
SW1 position EXT; SW2 position HIGH

Receive 14.074 MHz		Transmit 14.074 MHz
U12 pin 4	4.97 V DC	4.97 V DC
U5 pin 2	3.30 V DC	3.30 V DC
I from PSU	280 mA	505 mA
TP1 (I)	fig. A	fig. D
TP2 (Q)	fig. B	fig. E
TP3 (CLK0)	no signal	fig. F
TP5 (V_PA)	4.67 V DC	6.58 V DC
TP6 (CLK1)	fig. C	fig. G
TP7 (TR1)	no signal	fig. H
Pout	no signal	812 mW (29.1 dBm)
Output waveform	no signal	fig. I

Figure 13. RF Board measurements.

Click each picture to enlarge

fig. A	fig. B	fig. C

Click each picture to enlarge

fig. D	fig. E	fig. F

Click each picture to enlarge

fig. G	fig. H	fig. I (output waveform)