Products > Test Equipment
Advantest R3477 9kHz to 13GHz spectrum analyzer
<< < (5/12) > >>
cncjerry:
Nctnico, no, that's really clean.  If you are in the UK at 50hz, I would think if they were there you would see them at +/- 100 or 150.  So your shielding and supply is pretty clean. 
nctnico:

--- Quote from: rf-loop on August 19, 2016, 06:42:04 am ---
--- Quote from: nctnico on August 18, 2016, 11:47:36 pm ---I tried to find those spikes (I'm in 50Hz country so I guess I would be looking at 100Hz sidebands) but I can't see them. First I tried the calibrator output but that seemed to have a lot of noise. Then I tried a -70dBm 100MHz sine wave (from an HP E4421B) so I only get the noise from the SA itself but still no spikes.

--- End quote ---
Your marker is around -80dBc in first image  and in previous msg cncjerry talk aput -100dBc peaks. Your noise level is 20dB over this level where he look sideband peaks.  Next image your marker is around -60dBc  if 50Hz modulation sidebands are at this level it mean quite high 0.2% (am) modulation.

--- End quote ---
It seems to me the noise is coming from the signal sources I used so if there are 50Hz modulation sidebands they are masked by the noise from the signal sources. I think I need a cleaner signal source for this test to get a better signal to noise ratio.
Wuerstchenhund:

--- Quote from: nctnico on August 19, 2016, 09:18:05 am ---It seems to me the noise is coming from the signal sources I used so if there are 50Hz modulation sidebands they are masked by the noise from the signal sources. I think I need a cleaner signal source for this test to get a better signal to noise ratio.
--- End quote ---

If you have access to a 10Mhz Reference source like a GPSDO or Rb source try this. They usually come with a lot less noise than the old HP ESG Series generators.
nctnico:
I did some further reading into phase noise and I found a document called 'Spectrum analyser basics' from Agilent. I'm by no means an expert when it comes to spectrum analysers but I like to learn more to have confidence in what I see on the screen. However my typical SA use does not involve anything which has to do with radio communication (so far).
Anyway I did some further testing and decided to see if I could make some meaningful measurement for the phase noise 10kHz from the carrier which seems to be the norm. The R3477's manual doesn't specify the phase noise (at least not directly in dBc). I used 50MHz @-10dBm from my E4421B (yellow) with the 10MHz references connected and the  R3477's internal calibrator output (blue):

I think it is needless to say the E4421B's output is noisy indeed but that may be caused by my self made output amplifier.

I did find some peaks in the blue trace and put some markers on them. However they don't quite match the mains frequency although you could argue there are some small peaks which could be mains frequency related:

cncjerry:
So is the blue trace the average?  The 52 offset could be line related.  The 74 could be a slight oscillation in the voltage regulator.  I've had a hell of a time removing those regulator sidebands with decoupling.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod