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.
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