VSG60A With External Reference

Hi,

I’m trying to use the VSG60A with an external 10 MHz reference. Looking at the Signal Hound linux software package I can’t find a way to confirm that the VSG60A is locked to the external reference.

When I check the “Ext Ref” box on the software the VSG60A generates a signal whether I supply the reference or not. I do notice the spectrum of the signal I generate is a few Hz closer to my intended signal when I supply the reference. When I test without the reference signal I unplug the connector.

Thanks for your help!
Devin

Hi Devin,

The VSG60 does not provide indication or feedback that an ext reference is present, other than simply exhibiting a large frequency error (in my bench VSG60, the freq error is 38ppm without an ext ref to lock to). Maybe this freq error is enough to detect?

I apologize for the inconvenience.

Hi Andrew. I was going to open a topic to ask the same question, and found this existing one.
Could you please add this as a customer feature request for the future updates? Spike already provides similar indication for external reference. Would be nice if we can have a similar feature for VSG60A too.

Thanks

To provide additional details: I connected my VS60A to my SA124B option 1 (OCXO) and generated a 1GHZ -20dBm CW. Initial offset was -293 Hz. I let them run for 1 hour. And then the offset was -223 HZ (so around 70Hz drift over 1 hour)

But then provided a reference input to VSG60A. Initial offset: -284Hz. Already after 10 minutes, the offset is -224Hz (so, 60Hz drift in 10 minutes)

So, there’s no way for me to tell if the external clock is correctly detected and in-use by VSG60A based on these 2 scenarios

[Justin Crooks]

I believe the SA124B uses a digital correction for its OCXO frequency (it is not a voltage-controlled OCXO like the SM200). For zero frequency error, put both the SA124B and the VSG on a common external 10 MHz reference.
If you selected an external reference on the VSG, and generated a 1 GHz signal, I would expect the signal to be off by more than 10 kHz if the external reference was not found.

• This reply was modified 3 months, 4 weeks ago by Justin Crooks.

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