In regard to re-ordering boards, I can't count how many engineers I know, that have been down that road, too many times, so don't feel bad about it.
When you are all done, you need to measure phase noise.
Have fun!
SL
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BinaryRock
- Thread starter brandon7861
- Start date
When you are all done, you need to measure phase noise.
Have fun!
SL
Yep, I fully intend to. My first adventure with the 5351 was an adafruit board. Perhaps the amazon store I bought it from was pretending to be adafruit, but that 5351 was 100% counterfeit. It did output a signal, but the phase noise was TERRIBLE. With the scope triggering on it, it wouldnt sit still. I ordered two 5351's from mouser and swapped it. It was stable after that. Even the markings were obviously lasered off and reprinted.
All mine are direct from mouser so they should be ok but I will check anyhow.
I have a bunch of 5351's, only one is adafruit. I have put my DDS projects on the back burner, probably till winter. I probably have some fakes too. I need to look at them more closely.
Not sure my gear is good enough to get a real measurement. The datasheet on my analyzer says < -98 dBc/Hz @ 1 GHz, 10 kHz offset, but I know it should be better than that at HF. Whether that's good enough or not, I have no clue. I've never done a legit phase noise measurement before and I have no clue what to expect from this 5351. May have to measure the SA's phase noise first, IDK.
@SuperLid
I connected a rubidium standard to the SA reference input and connected the reference output to the front input hoping that the rubidium source had a better phase noise than the SA in hopes to get an idea what the phase noise of the SA is.
I got this, 85.85dB down at +100Hz offset with RBW at 1Hz:
I then programmed the 5351 to output 10MHz and measured that. Since I did not calibrate the frequency yet, I simply offset the second marker by the same 100Hz and ran the averaging again. This time it showed 88.43dB. Somehow it is better than the rubidium source even though the rubidium was still being used as the reference.
Not sure how to interpret that, but if I adjust the voltage on the binaryrock board, the carrier peak and the second marker (and the entire noise floor) move in sync.
I don't know if the phase noise of the SA is limiting the measurement, but I am going to call this good enough. I did notice that the SMA on the rubidium was a tad loose when I took it all apart though, so maybe that should have been tightened better.
I connected a rubidium standard to the SA reference input and connected the reference output to the front input hoping that the rubidium source had a better phase noise than the SA in hopes to get an idea what the phase noise of the SA is.
I got this, 85.85dB down at +100Hz offset with RBW at 1Hz:
I then programmed the 5351 to output 10MHz and measured that. Since I did not calibrate the frequency yet, I simply offset the second marker by the same 100Hz and ran the averaging again. This time it showed 88.43dB. Somehow it is better than the rubidium source even though the rubidium was still being used as the reference.
Not sure how to interpret that, but if I adjust the voltage on the binaryrock board, the carrier peak and the second marker (and the entire noise floor) move in sync.
I don't know if the phase noise of the SA is limiting the measurement, but I am going to call this good enough. I did notice that the SMA on the rubidium was a tad loose when I took it all apart though, so maybe that should have been tightened better.
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