[time-nuts] New Question on HP3048A Phase Noise Test Set
bruce.griffiths at xtra.co.nz
Thu Jan 17 07:22:45 EST 2008
Martyn Smith wrote:
> I need some help on using the HP3048A Phase Noise Test Set (11848A, 3561A,
> 3585A, 3325A).
> My company makes a ultra low noise frequency standard with ten outputs.
> Apart from very low phase noise (-112 dBc/Hz @ 1 Hz with a -170 dBc/Hz noise
> floor) I also claim all spurious to be < -120 dBc. This includes the line
> frequency spurious.
> I'm happy my test set is making accurate phase noise results as I agree with
> other test results on sample oscillators to < 2 dB.
> But I seem to have an error on measuring spurs.
> As you all know, when the 3048A detects a big peak, it marks it in red and
> shows the actual value, rather than normalizing it to a 1 Hz bandwidth.
> To test the 3048A accuracy I inject a spur at a known level using a
> directional coupler (similar to the single-sided spur calibration method).
> I confirm the spur level on the spectrum analyzer. However the 3048A always
> says the spur is 6 dB lower than it actually is (6 dB plus/minus 0.5 dB).
> Can anyone tell me why this is so.
> I wondered if it had something to do with phase noise and amplitude noise
> not being the same thing.
> Any response would be appreciated.
> Best Regards
> This Email is from:
> Martyn Smith
> Precision Test Systems LTD
> Tel: +44 (0) 1245 329608
> Email: martyn at ptsyst.com
> Web: www.ptsyst.com
3dB since AM and PM components are equal plus another 3dB to correct
measurement from actual DSB to SSB??
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