On Fri, 13 May 2022 03:30:35 -0400, [email protected] wrote: time-nuts Digest, Vol 217, Issue 25
> > Message: 2 > Date: Thu, 12 May 2022 07:01:11 -0600 > From: Bob kb8tq <[email protected]> > Subject: [time-nuts] Re: Effect of temperature on cheap puck style > GNSS antennas? > To: Discussion of precise time and frequency measurement > <[email protected]> > Message-ID: <[email protected]> > Content-Type: text/plain; charset=utf-8 > > Hi > > >> On May 12, 2022, at 3:21 AM, Lux, Jim <[email protected]> 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. Before doing anything fancy, I'd be tempted to enclose the GPS puck in a cheap small polystyrene foam beer cooler, to reduce and slow down temperature changes at the puck due to sun and wind, and see how much effect this has. Joe Gwinn _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe send an email to [email protected]
