Schomandl  ND1000D     (Jan2009)

F-Nr 10139,  lended by  the company.





DC-coupled phase drift performance :

Locked on the 10 MHz house BVA, level is +5.8 dBm.
Carrier freq  is 820 MHz , RF level is -4dBm



This instrument exhibits a strange  residual phase oscillation that reaches 30degrees pk-pk at a frequency of approximately 0.3 Hz.
On the picture below, the frequency has been set to 820.000001 Mhz for 3 seconds, clearly showing 3 full turns, then switched to 820.000000.
The phase should keep steady. On this instrument it starts oscillating back and forth, by quite a large amount.

This happens for all dialed frequencies. However, the peak deviation is almost proportional to the frequency . This would indicate that the PLL that locks the internal OCXO to the EXTREF has a tendency to oscillate @0.3Hz.  It can be noted that this oscillation is much faster during the warm-up period.

It would be interesting to view the sidebands caused by this modulation but they are too close to be separated by the SA.

However the SA reveals  important lines @100 Hz :

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