Hi,
I will build a S1 server with a rpi 4, and need a hat with PPS, no soldering.
Antenna on roof, clear sky. Located south in Norway.
Important is also accuracy (and price).
Anyone have experience on certain hats?
Thanks a lot 
So you need a GPS HAT with soldered 2x20 pins capable of attaching external antenna. Maybe you can check this:
I have 4 PI’s using this module, have been solid, two of them are here in my home lab and have been running continuously for over 2 years.
Thanks alica and ronv42,
I also looked into Waveshare L76K (AT6558R).
It seems like Uputronics is the more accurate(?) with a ublox m8 chip. Also it has aditional software.
This one. see video. GPS/RTC Expansion Board for Raspberry Pi - The Pi Hut
Anyone tried this?
Also i need a 10m active antenna… 
Hi,
ublox m8 chip is a good choice. For good precision with this, you can use PPS signal delivered by this chip. (GPIO18 <== Time Pulse)
For others informations :
I use the Uputronics board on my setup also, and I’m pretty happy with it. It’s easy to get running and performs well. You can also change all the GNSS chip settings via the RPi, which makes it easy to experiment with.
Regarding the antenna, if you have a good sky view you might be surprised at how little antenna complexity you need there. I’ve been doing a bunch of research with my own system, and antenna choice is one of the factors I’ve experimented with: Raspberry Pi NTP Server - Part 6
Thanks, great page, I’ll look into it
Allright, Ive received the hw, trying to understand, working on it.
Take a look !
Your link doesn’t work, gives error 404
my bad, @Bas 
, try now.
Now it works.
Active clients per minute: 12617
That is not a lot, it’s 210/sec.
Meaning you probably set it to 3mbit speed.
Beware, if this server is behind NAT, the modem will probably start acting weird or even reboot.
It may become unstable because of your router.
In ntppool.org, ive set it to 1.5 Gbit. Router is using about 55k conntracks.What do you mean by “weird” or “reboot”? Do you know anything about my router?
No I don’t, but NTP should not be tracked.
I do not even know how it’s connected. 55K conntracks and no problems?
Amazing.
NTP should not be tracked at all.
Not ALL NATed traffic has to be tracked. Google search/AI says (use at your own peril)
Using
nftables(Firewall4 / Modern OpenWrt)For newer OpenWrt versions using
nftables, add the rule inside therawtable via/etc/nftables.d/or custom include files:nft
add rule inet fw4 raw_prerouting udp dport 123 notrack add rule inet fw4 raw_output udp sport 123 notrackUse code with caution.
After adding the rules, restart your firewall: [1]
sh
fw4 restart
I’ve been testing a number of GNSS/GPS HATs on the Pi, one that caught my eye lately was a set of three options from Jimmy Paputto, which are (unlike many of the other newer-u-blox-module HATs) actually available for shipping.
I’ve been using the L1 GNSS HAT (which includes a NEO-M9N) for the past few weeks in a new stratum 1 clock build (I’m resto-modding an old TrueTime XL-AK server), and it’s been stable sub-200ns (a little better with more Pi tuning for thermals), and gets 25+ GNSS servers locked (multi-constellation), with a stable sky view.
There’s also the L1/L5 GNSS RTK HAT which is quite a bit more expensive but has the NEO-F9P. It’s probably best suited for positional accuracy (I haven’t done much with RTK before, so I’m not an authority there), but according to their gnsshat repo on GitHub, there’s also a ‘TIME HAT’ version (maybe still in the works) with the NEO-F10T.
That particular chip isn’t available anymore new (at least as far as I can tell), so they must’ve found some stock of it… though maybe not enough to offer direct sales on their store page.
The current Pi pricing puts a little damper on some of my Pi-based timing enthusiasm, but at least with most timing projects, the base 1GB Pi 5 will do — or even a Pi 4 in many cases.
Thanks @Bas and @MagicNTP for showing me stateless NAT, I did not know. I used step 1-5 from Using an NTP-server behind NAT, it works! After testing a lot. No not many routers/OS can handle it. Really not many
My router did not struggle without stateless NAT, but now it struggle even less
Well hello @geerlingguy - how nice to see you here!
Welcome! 