[time-nuts] PCB layout question for GPSDO

[tom burkart]

Hi Tobias,
additional answers below:

Quoting Tobias Pluess <tobias.pluess at xwmail.ch>:

> a) is it acceptable to route some signals under the GPS module? As  
> one can see, the signals I have routed under the GPS module go to  
> the front panel interface, i.e. they are not highspeed signals or  
> so, but I still wonder whether you experts would worry about it  
> (like "oh no, routing anything near the GPS module will disturb it  
> and decreases its sensitivity" or something).
This violates constraints as set out in the Ublox hardware integration manual.

> b) would you worry about the switching regulators? I know linear  
> would be better, but the professional GPSDOs also have switchers,  
> and besides that a linear regulator would not be so nice because my  
> power supply will be at least 15 volts.
I would, but it can be dealt with.

> c) is the usage of a RS232 chip a good idea or would you kick that  
> out because they produce such massive amounts of EMI that it will  
> disturb my GPS module or OCXO?
Keeping it away from sensitive circuits will probably suffice.

> d) is it a wise idea to use an LC filter for the OCXO power supply,  
> or does this lead to another rabbit hole because the inductors will  
> pick up magnetic fields (50 Hz...) and modulate the OCXO?
All depends whether you will bath the whole thing in 50Hz stray  
magnetic fields. ;-)

> e) anything else important I forgot?
- Please double check your wiring of the GPS module it looks back to front.
- In some places your ground layer is severely broken up to reduce its  
effectiveness.
- Your antenna seems very close to the 1pps output and has traces  
underneath it
- I quite like resettable PTC fuses (no need to replace)

Tom