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

[Bob kb8tq]

Hi


> On May 12, 2022, at 3:21 AM, Lux, Jim <jim at luxfamily.com> wrote:
> 
> 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.

The ceramic typically used for antennas is unlikely to have that much change 
over any reasonable temperature range. The ceramic filters are very different
beasts …. The impact of the antenna should be down in the “couple of ns” range 
at most. 

Since this is a “who knows what” antenna, there is no way to be *sure* of what it’s 
doing. A properly designed small / low cost antenna should do pretty well. 

Bob

> 
> 
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