Electronics > Projects, Designs, and Technical Stuff
Using a PicoScope 4262 as a low frequency recording spectrum analyzer
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dnessett:
Gerry, the tech specialist I referred to in a previous post, got back to me about the duplicated segments when saving files in csv format. It turns out that this only occurs when the maximum number of bins is chosen (1,048,576). If one of the lesser number of bins is selected, there is only one segment. (I checked this out and it is correct). He has submitted a bug report.
jpb:
Hi dnessett,

How are the phase measurements going?

I'm thinking of getting a PicoScope 4262 to do both ADEV (via the beat method) and phase measurements but it is a lot of money if it is not going to do the job. It is also a pity that it is only 2 channels and is only 50ppm on the time base with no option of external clock. The alternative I've been thinking of is the RME UX audio interface - this will accept an external word clock of up to 200kHz so could cover the frequency range 1Hz to 100kHz in 24 bit and very low noise but it would probably require some sort of low noise pre-amp arrangement and is much less convenient than the PicoScope. On the other hand it is cheaper, has 8 channels and better specs for the frequency range up to around 80kHz.

Are you happy with your PicoScope 4262?
dnessett:
At present I am trying to obtain a low phase noise 10 MHz tunable oscillator in order to characterize the noise floor of the HP11729C in a frequency discriminator configuration. The tunable requirement is necessary to use it in a phase detector configuration.

I have located a device that has the spec's I want, but the company that manufactures it does not deal through distributors. This means I have to deal directly with their sales department, which is not used to selling 1 piece orders nor with dealing with individuals instead of companies. It has been slow going and now that we are in the Christmas/New Years holidays, I don't imagine things will speed up until the first of the year. Even then I may not be able to convince them to sell me what I need. They have two pieces in inventory and if both of those are sold to someone else, there is a 14 week wait time from the factory to get additional devices. We'll see what happens.

I am satisfied with the Picoscope 4262 as it is the only low frequency recording spectrum analyzer that is available at a reasonable price. It should do the job. I don't know anything about the RME UX audio interface, but I would be careful to ensure it will actually record down to 1 Hz without signal loss. Audio hardware generally stops at about 20 Hz and trying to capture signals below this boundary may observe losses that would make it difficult to use.(I experienced this with the Spyconverter upconverter, although in that case the cutoff was about 1 KHz).
jpb:

--- Quote from: dnessett on December 22, 2018, 04:34:23 pm ---I am satisfied with the Picoscope 4262 as it is the only low frequency recording spectrum analyzer that is available at a reasonable price. It should do the job. I don't know anything about the RME UX audio interface, but I would be careful to ensure it will actually record down to 1 Hz without signal loss. Audio hardware generally stops at about 20 Hz and trying to capture signals below this boundary may observe losses that would make it difficult to use.(I experienced this with the Spyconverter upconverter, although in that case the cutoff was about 1 KHz).

--- End quote ---
I'm basing the 1Hz lower end on the RME specs where the gain flatness is quoted down to 1Hz and up to 80kHz (for 192kHz sampling). Also others on this forum have stated that some RME devices go down to dc though I don't know which ones as the ones I've looked at are AC coupled.
Using an audio interface though is a pain, the signal has to be conditioned to be somewhere near line level if most of the channels are to be used (there are 2 mic preamps though) and I think the signals also need to be balanced which is more external circuitry.
It is a pity that they don't do a 4 channel version of the Picoscope 4262 - the specs of the 4 channel versions are rather worse. 4 channels would allow a three cornered hat measurement to be made on 3 devices plus the  reference input.
Good luck with getting your low phase noise device. There are a lot of "low noise" Wenzel OCXOs on ebay but they are all expensive and there is no information as to what their phase noise measurements are.
dnessett:

--- Quote from: jpb on December 22, 2018, 09:18:06 pm ---Good luck with getting your low phase noise device. There are a lot of "low noise" Wenzel OCXOs on ebay but they are all expensive and there is no information as to what their phase noise measurements are.

--- End quote ---

I have finally obtained a low phase noise 10 MHz oscillator (actually 3 of them). Since this is not really germane to the topic of this thread, I give details in a more suitable one - found here
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