RSA ...... Without Buying DataVu-PC

Question

Hi all 
 Tektronix has produced the "DataVu-PC" app that do almost every data analyzing function, but you should buy this software. 
 I'm working on a project to invest the (SCPI, or VISA) to build cheap customized apps that get benefit of the real time spectrum analyzer as a wide band signal acquisition kit. 
 are any body think this is the right way to do that or I should use the SDR option.

Gough Lui · Answer

Alaa0000 said: I'm talking about what I have used in the past, where I used SCPI and VISA to program R@S FSH8 and other instruments 
 Unfortunately, that is not particularly relevant here. The FSH8 and indeed many units out there are swept SAs which is different in principle to a real-time SA of which the RSA series is. If you don't know the difference, I'd encourage you to do some research, but basically a swept SA acts like a narrow receiver that is tuned quickly across a band to produce a power spectrum, while a real-time SA actually behaves like a software defined radio (SDR) and block-downconverts a part of the spectrum (the IF bandwidth) and samples that, allowing for the signal to be reconstructed with (practically) a 100% PoI. 
 This is why your last question regarding SignalVu-PC is so pertinent - the SignalVu-PC software provides an interface which takes this data and analyses this in ways resembling what a swept-SA might present, but also providing other more sophisticated capabilities that swept-SAs can't usually do (things like recording the IF waveform, IQ/FM/AM/PM analysis, protocol decoding analysis for standards such as Wi-Fi/Bluetooth/LTE). 
 Alaa0000 said: cheap customized apps that get benefit of the real time spectrum analyzer as a wide band signal acquisition kit 
 I have no idea why this is relevant to DataVu-PC as this works on recorded files only. As a result, it will be limited to the IF bandwidth of the recorded file, which is typically 40MHz (calibrated range that the SignalVu-PC exposes to us) or about 56MHz (raw from the sampled data, with some non-linearities at the edges for amplitude). This is not "wideband" depending on what you are analysing. 
 Secondly, "customised app" tells us nothing. If your app merely plots spectra over a wider range than 40MHz, guess what? SignalVu-PC does that for free already by operating the RTSA as a quasi-swept SA by moving the centre frequency, plotting a chunk, then moving it again. 
 
 For example, I made this spectrum plot of an 800MHz wide chunk of IF from a satellite LNB ... no cost required, all SignalVu-PC base. I reviewed the RSA306 (before the face-lift to the "B" version) many years back , so that is from my personal RSA306. 
 So what are you "analysing"? No matter what, if you're relying on this hardware to capture the spectrum for you, you're most likely limited to the hardware's ability anyway. 
 The things people pay for are often the things that are complex - i.e. can you implement the full LTE specifications to decode what is being transmitted, to extract parameters like SINR/EVM, BER, etc., analyse the protocol signalling events, tune into a given RU and create constellation plots, etc. Because of the complexity of the specs, designers will often pay for this so they can get the analysis directly without having to do much work of their own (because they can't or they won't). But in return, they'd expect it to be correct and reliable - and a cheap app won't often inspire such confidence. 
 Alaa0000 said: right way to do that or I should use the SDR option 
 You still haven't explained what you mean by analysis, what sort of signals and how you are analysing them, what sort of bandwidth and precision you need, etc. While SDRs are much cheaper, commercial SDRs are not calibrated so the amplitudes across the IF bandwidth are not guaranteed to be linear (although, often they may be quite linear out-of-the-box if well designed). Their IF bandwidths also vary, but typically top out about 64MHz or so. The other issues may include poor dynamic range resolution (e.g. not-enough resolution - some cases just 8-bit or 12-bit ADCs, or impairments due to I/Q mismatch causing "ghost" aliasing of signals across the bandwidth or inter-modulation results to interfere). 
 Using an instrument like the RSA306 offers the assurance of calibration when using SignalVu-PC (or RSA API) to analyse the data as it performs alignment and applies correction to the computed figures, as long as you're not recording the raw data and analysing that (which is uncorrected and thus behaves like an SDR). 
 For those who just want to analyse the recorded files, someone's already written a script to convert the r3a/r3h/r3f type files into decoded numerical data for use with third-party tools (e.g. MATLAB/Octave/Python/etc) - https://forum.tek.com/viewtopic.php?t=138470 and https://github.com/tkzilla/r3f_reader 
 Finally, for those who really want to weaponise the concept of RTSA ... well Aaronia is perhaps somewhat famous for having something with 980MHz real-time IF bandwidth ( https://aaronia.com/en/produkte/spectrum-analyzer/spectran-v6-cc ) at EUR60,000 or 245MHz real-time IF bandwidth ( https://aaronia.com/en/produkte/spectrum-analyzer/spectran-v6-x ) at EUR10,000. Because that's all real-time bandwidth, within that bandwidth, the PoI is practically 100%, but the data storage/transfer requirements are immense (multi-100GbE, hundreds of TB of SSD in the control centre). The other problem? I could never afford one ... but also, if the truly wideband RTSAs. 
 But if the market is willing to spend so much on an RTSA, what's a few thousand dollars for analysis software? Just a drop in the water, as they say. You being able to offer it for less is not likely to mean much when they might need the assurance of a brand when generating reports for customers or to satisfy legal requirements. How many people do you think actually own an RTSA right now, and how many of them know what it means to have an RTSA versus just a conventional swept SA? I hazard to guess it is not so many ... 
 - Gough

Gough Lui · Answer

DataVu-PC is more of a software used for post-recording analysis of r3h/r3a files created through the recording feature of SignalVu-PC. 
 Unfortunately, your question is unclear - DataVu-PC has nothing really to do with SCPI or VISA. It works off recorded files for "offline" analysis of recorded spectra. 
 - Gough

RSA ...... Without Buying DataVu-PC

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