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Hello,
I connect TG44 10MHz output to BB60c reference input, and I expect to see exactly the same frequency, but it’s not.
For example I set 999MHz output in TG44, and measure this frequency in BB60c (set 2KHz span with 999MHz center). When 10MHz reference is not connected to BB60c, I see some small freq error (-42Hz), I think it’s normal. (first picture)
When I connect 10MHz reference from TG44 and use it in BB60c, the freq error becomes much larger (+340Hz). (2nd picture) Why? I expected to see here zero frequency error.
What’s going on here?
I’ve checked TG44 output against its 10MHz ref ouput on oscilloscope.
When I set tg44 output to 10MHz or 20MHz, it generates sine phase locked with reference (frequencies matches exactly). But 30MHz, 50MHz, 100MHz are not in phase and have some frequency deviation. For example, to generate exact 10x phase locked output I have to set tg44 freq=99.999970MHzAs I understand, instead of tuning internal tg44 reference generator to exact 10MHz, you simply set some freq correction parameter into it. This makes useless it’s 10MHz output.
Hi Ivan,
You are correct, there is a frequency correction offset that is applied to the output of the TG. In the original 2.18 software, the correction value was ignored when the SA is configured to accept an external reference. The Spike software currently does not perform this action. I will look into adding this as a parameter in the software.
Regards,
A.J.Hi Ivan,
After further discussion here, we are going to add the ability to specify whether you are using the TG 10MHz reference output, so it will disable this frequency correction. We think allowing the user to manually specify this is the best way forward. It will likely be a new checkbox in the TG control panel. Look for this in the next release.
Let me know if you have any further feedback or questions on the issue.
Regards,
A.J.
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