Frequency trim - crystal stability?

[GM3ZZA]

When I connected the RSP to a real antenna rather than the wet string I had been using...

I tuned to RWM at 9.996 MHz frequency reference. I recorded it was 51 Hz out. So I set the trim to +5.04 ppm.

Used the frequency trim facility to change. Listened to RWM at 14.996 MHz. Slightly out again.

Then after leaving the RSP on for about an hour I noticed that a 15.000 MHz signal I was listening to, but not identified, had drifted slightly. then went back to RWM at 9.996 MHz.

I found that I now had to set the trim to +4.41 to match the 9.996 MHz RWM signal.

So I presume that the crystal drifts a bit with temperature, and therefore this is OK.

73 Phil GM3ZZA