RIGOL DSA815 with external reference issue.

[outremer]

Hi all !

I noticed an issue with my DSA815-TG spectrum analyser when I use an external 10 MHz reference. When looking at a signal with a narrow span of (say 20 kHz) I notice a trash response like "sidebands" about 10 kHz away from the signal. These are about 35 dB down from the signal itself. After 10-15 minutes of warmup the spurs disappear after a brief increase and the signal is then displayed normally.
I thought first that my GPSDO reference was the culprit due to the oven heating in the OCXO... So I tried several other 10 MHz references but the issue was still the same. As soon as the external reference is disconnected the display becomes clean. After the "warmup" connecting or disconnecting the ext reference causes no change...
I also tried several signal sources with no change. The issue is the same from "0" to 1.5 GHz.
So the conclusion is that the DSA815 has a trouble trying to lock on the external reference during warm up.
I noticed that when room temperature is higher (air conditionning off) the issue clears faster.
Has anyone noticed the same issue on his DSA815 ?

See the attached pics (note : just before normal I caught the picture a little too late as the issue cleared just before the peak of the signal was displayed)