Siglent SSA3021X Plus & 10MHz Reference Sine Signal

[hpw]

I measured lately the 10MHz reference output signal as local loop back.

So would tell the as about coherent, as in ADC & DAC with equal master clock. 

Than I did the 10Mhz center & 500Hz freq. span 

Now, it clearly shows jitter / spurious as measurements goes on. See picture 

In other words, the 10Mhz PN is unknown as the PLL synthesizer contribution.

Did also feed for alternate measurements  the 10Mhz with a DSO AWG sine as the SDS2104X Plus at 10Mhz,  jitter / spurious increased... 

So the questions rises: How the spectrum analyzer would gain with a LOW PN 10MHz reference OXCO (without GPS!!)

Hp

[tv84]

Why did you use such a thread title and why didn't you include your question in the forum's main SSAX+ thread? 

[hpw]

Changed now the tittle ..

[Kibabalu]

don't understand your point!

You are talking about phase noise?

Maybe later this night I will find some time to produce a measurement with a separate BG7TBL OCXO that I usually use to feed all reference inputs of all of my devices.

But it will not be that different to the measurement made by you using the internal reference.

[hpw]

There are 2 parts of a digital based spectrum analyzer:

a) the reference as 10MHz, here the jitter & PN of interests

b) the synthesizer to provide the related freq. sweep (start to stop freq) of the span. Also a culprit of jitter & spurious contributor.

so on the given issue: a) & b) are involved. In addition using the a DSO AWG as 10MHz ref, the result is even worst. IMHO influences the synthesizer in a negative way.

So the question rises, if one have a sine OXCO 10MHz and could feed into the F-Ref Input (not GPS triggered), how the or a result would alter or benefit...



 

[Kibabalu]

the benefit of using ONE OCXO reference for ALL involved devices is, that for all devices the absolute value of the frequencies are the same.

this doesn't affect the measured phase noise at all, except the phase noise of the separate OCXO is much smaller as the phase noise of the internal reference.

Sorry if I don't get you!

[Performa01]

An OCXO does have a much lower phase noise than the standard (TC)XO in a Siglent SSA indeed.

I don't have experience with the Siglent SSA, but from the results with other SA I would expect a noticable improvement for the close-in PN, i.e. for distances to the carrier up to a few hundred Hertz.

[hpw]

An OCXO does have a much lower phase noise than the standard (TC)XO in a Siglent SSA indeed.

I don't have experience with the Siglent SSA, but from the results with other SA I would expect a noticable improvement for the close-in PN, i.e. for distances to the carrier up to a few hundred Hertz.

Yes, lower PN smaller signal bell.

What me puzzles more are the little side peaks as symmetric jitter/spurious around the carrier, who alter mark able over time... see marked at the picture

[hpw]

An OCXO does have a much lower phase noise than the standard (TC)XO in a Siglent SSA indeed.

I don't have experience with the Siglent SSA, but from the results with other SA I would expect a noticable improvement for the close-in PN, i.e. for distances to the carrier up to a few hundred Hertz.

Did some measurements with even a Morion MV89A.... see attached

Some point about the internal crystal oscillator:

- crystals require about up to one hour to stabilize

- The noise fan shakes and will induce vibration to the Siglent Master clock   

Does someone know more about the SSA used FFT & FFT Windows calculations `??