Author Topic: Some Si5351 spectrum measurements  (Read 2597 times)

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Offline dcarr

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Some Si5351 spectrum measurements
« on: July 10, 2015, 05:37:48 am »
Hi eevblog,

I recently had a Si5351 hooked up to my spectrum analyzer and took a few measurements.  My particular application needs a VHF LO and I was curious how clean the Si5351 is.

Here's a shot centered at 146.72MHz with 25MHz span:

You can see a fairly large spur (-46dBc) offset 3.26MHz on both sides along with a fair number of other signals.

Here's a shot of the first few harmonics:

The second harmonic is -16.1dBc and the third is -11.7dBc.

Lastly, the harmonics out to 3GHz.  Still a respectable -36dBm signal way out there at 2.7GHz!

I also took some measurements near 12.2MHz and 5.1MHz and found the situation to be much better.  No screenshots unfortunately but there were minimal/no visible spurs at those frequencies.

Hopefully interesting information for some.
« Last Edit: July 10, 2015, 05:39:37 am by dcarr »

Offline mvdswaluw

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Re: Some Si5351 spectrum measurements
« Reply #1 on: July 10, 2015, 08:29:30 am »
Not really surprising as the SI5351 outputs a square wave...

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