TimeServer

Install Raspberry Pi OS on SD-Card

sudo apt update && sudo apt upgrade

Turn off W-LAN

sudo vi /boot/config.txt

add section that says:

[pi5]
# Disable Wifi
dtoverlay=disable-wifi
# Disable Bluetooth
dtoverlay=disable-bt

Bring operating system up to date

sudo apt update && sudo apt upgrade

Configure fan in Raspberry Pi 5 housing

set up fan via raspi-config

Activate UARTs and ops

In [pi5] section:

# Activate UART5 (GPIO #12 and #13)
dtoverlay=uart5

[all]
enable_uart=1
dtoverlay=pps-gpio,gpiopin=4
init_uart_baud=9600

install and configure ntp server

sudo apt install ntp pps-tools

# GPS PPS reference
server 127.127.28.2 prefer
fudge  127.127.28.2 refid PPS
# get time from SHM from gpsd; this seems working
server 127.127.28.0
fudge  127.127.28.0 time1 0.18 refid GPS
#DCF77 Conrad module
server 127.127.8.1 mode 5
fudge 127.127.8.1 time1 0.876

install and configure PTP server

sudo apt install ethtool linuxptp