[time-nuts] Re: Effect of temperature on cheap puck style GNSS antennas?

[Lux, Jim]

On 5/11/22 11:50 PM, Matthias Welwarsky wrote:
> Dear list members,
>
> My DIY GPSDO has a rather well defined dependence to the environmental
> temperature, which correlates almost linearly with a frequency shift of the
> OCXO. However, at times I see the error against the GNSS reference increasing
> with its case temperature not warranting such effect.
>
> My antenna is one of those cheap, magnetic, active antennas you'd put on a car
> roof. It's facing south and has full exposure to the sun, obviously.
>
> During sunrise I see the TIC error increasing 20ns-30ns over lets say 2000
> seconds. The GPSDO case temperature rises, too, during that time as the room
> temperature increases, but it is only by 0.3°C.
>
> I'm wondering if the temperature of the antenna, which of course rises much
> faster than the room temperature, can have an effect of this magnitude?


Very possible. I've seen fairly large changes (nanoseconds over a 0-40C 
temp range) in delay in the LNA and bandpass filter for GNSS receivers 
with temperature. If they're using any sort of ceramic filter or ceramic 
antenna, then that can have a fairly large tempco in the time delay.