Hi,
We've got a brand new PXA (5 weeks old) reporting error 509 "LO Unlocked". The error only seems to come up (so far) running 89601B/custom OFDM software, it does not seem to persist if I put it at the same center frequency in standard spectrum analyzer mode.
I can't find much help in the documentation, is this a common thing?
I've spoken to another user who said that they had seen this before, returned the instrument and gotten a "no problem found" report.
Lance
We've got a brand new PXA (5 weeks old) reporting error 509 "LO Unlocked". The error only seems to come up (so far) running 89601B/custom OFDM software, it does not seem to persist if I put it at the same center frequency in standard spectrum analyzer mode.
I can't find much help in the documentation, is this a common thing?
I've spoken to another user who said that they had seen this before, returned the instrument and gotten a "no problem found" report.
Lance
The LO Unlock may only be seen at certain center frequency and Span settings, or may be the result of a missing, or intermittent reference signal (either the internal freq reference or an external reference.
Sometimes the LO Unlock will appear when the instrument runs its power on alignment or when you manually run the alignment by pressing System, Alignments, Align All, Now. Try this since if the LO unlock is detected, we have an easy way to recreate.
We need to be able to duplicate the failure in spectrum analyzer mode. So, if you can look at the 89601B screen and determine the Center frequency and Span.
Once you go to SA mode and enter the exact CF that causes the problem, set the span to 10 MHz or less (try 9 MHz span). Unlock? This sets the phase lock lops a certain way.
Set the span to 11 MHz. Unlock? Again this span uses a different phase lock situation.
Step the center frequency a few MHz or tens of MHz and see if the unlock goes away, or appears.
Also, on your test setup, is the PXA using an external reference? If so, is this a stable reliable reference, and have you “told” PXA the external reference frequency (press, Input/Output, More, Frequency Ref In and view the External Ref Frequency key to assure the frequency shown is the frequency of the external reference signal that is being fed to the instrument . The analyzer cannot auto detect the frequency of an external ref input, so you need to type in the correct frequency. Default is 10 MHz, but can be changed.
The Frequency Reference In can be set to Internal, External and Sense. Where “Sense” will detect if “something” is connected to the EXT Ref In port on the rear panel (but possibly not the correct frequency) and automatically chose the external ref, or if the external reference should disappear, the instrument will no longer sense the external ref and switch to the internal ref.
Enough detail now on references, please tell me if the Frequency Reference In is set to Internal, External or Sense.
Regards -