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SPIKE: improved software for the Signal Hound By JIM ROWE When we reviewed the Signal Hound USB-SA44B mini spectrum analyser in the October 2014 issue of SILICON CHIP, we were very impressed with the performance of both the hardware and its accompanying software. Now Signal Hound has come up with a greatly enhanced software pack­ age to go with the USB-SA44B and their other instruments. I N OUR ORIGINAL review of the USB-SA44B spectrum analyser, we were particularly impressed with the analyser hardware itself. Inside its compact 77 x 27 x 167mm aluminium case there is an advanced narrow-band SDR receiving system tuning over the range from 1Hz to 4.4GHz and delivering a level of performance that compares very favourably with high- end self-contained spectrum analysers – but at a fraction of their price. We were also impressed with its software package which controls the USB-SA44B hardware box (and the optional USB-TG44A tracking generator) from your PC as well as accepting, processing and analysing the output data stream from it to produce the analyser’s output display and measurements. Fig.1: a full-screen grab of Spike in “real time” mode scanning at a centre frequency of 1090MHz, showing Persistence on the spectrum plot (lower centre), with a 2D spectrogram above it. 78  Silicon Chip The software did have a few rough edges but we judged them to be fairly minor and not significant, considering the excellent performance of the USBSA44B hardware. But early this year Signal Hound released a greatly enhanced version of their software package, renamed “Spike”. And in the last three months or so they’ve released a number of upgraded versions of Spike. We’re reviewing the latest version at the time of writing: Spike 3.06. This is now being provided on the CD accompanying the USB-SA44B and other analysers purchased new. Existing users can download it at no charge from Signal Hound’s website at www.signalhound.com/spike It comes as a zip file which includes its matching USB drivers. A PDF of the User Manual for the new software can also be downloaded from the same website. Spike 3.06 is compatible not just with the USB-SA44B but also with the rest of the Signal Hound products, including the USB-TG44A tracking generator. There are two versions, compatible with the 32-bit or 64-bit versions of either Windows 7, 8 or 8.1. Note that although the Spike softsiliconchip.com.au Fig.2: a spectrum plot showing the Sydney DRMT DAB+ signal block centred on 204.5MHz in channel 9A, captured using Spike 3.06 and saved as a JPEG file. Fig.3: another plot centred on 92.9MHz, showing the Sydney ABCFM signal spectrum (bottom) with a 2D spectrogram above it. Spike again saved it as a JPEG file. ware can be downloaded and installed at no charge, it will only work with Signal Hound devices like the USBSA44B. When you start up the software it automatically searches the PC’s USB ports to see if one or more of the devices is connected. When it finds one, it displays the device’s serial number and other information (like internal temperature and firmware revision) at bottom right on its main display window; otherwise it refuses to proceed. What’s new? The first thing you notice when you fire up Spike (in my case, with a USBSA44B) is that the user interface window has been completely revamped. The main display graticule is now centred on the screen, with control panel menus running down either side. It’s less crowded than before, having been proportioned to suit the 16x9 wide-screen aspect ratio used on most modern laptops and PC monitors. As before, the main functions, settings and facilities are selected using a menu bar and toolbar running along the top. The control panel menus on the left side then allow you to set the Measurement trace and marker parameters, any offsets that may be required and settings for Channel Power and Occupied Bandwidth measurements. The menus on the right side control panel allow easy setting of all sweep parameters: Frequency (Centre, Span, Start, Stop and Step, plus the ability to set the analyser for either Full Span or Zero Span [more about this later]); siliconchip.com.au Fig.4: this full-screen grab shows Spike 3.06 in real-time scanning mode, centred at 1090MHz (the frequency used by commercial aircraft for ADSB). The 2-D spectrogram is shown above the spectrum plot itself. Amplitude (Reference Level and Graticule Divisions, plus the ability to select either manual or automatic internal gain, attenuation and preamp enabling); Bandwidth (RBW and VBW); and finally Acquisition options such as Video units, Detector mode and Sweep Time. This is not Spike’s only display graticule or control menu panel, as will become clear shortly. So Spike’s initial window is much snazzier than that of the original Signal Hound software. But that’s only the start of its new features and capabilities, because the new software can now take full advantage of the capabilities of Signal Hound’s analyser hardware – including those of the USB-SA44B. For example, you can now select either of two different types of spectrogram to accompany the analyser’s main amplitude vs frequency display: a 2D spectrogram which gives the moving “waterfall” display or a 3D spectrogram which gives a series of sweep displays receding into the distance. These can both be helpful when you’re trying to look for significant events. Another nice new feature applying to the main graticule display is persistence. When you enable this feature, the current signal trace is accompanied by a “community” of earlier traces, in colours representing their time prior to the current trace. It’s a bit like having a fixed spectrogram displayed directly behind the June 2015  79 Fig.5: another screen grab showing Spike in real-time scanning mode, centred at 1090MHz, this time with a 3-D spectrogram shown above the spectrum plot. Fig.6: this screen grab shows Spike 3.06 in “zero span” mode – another of its exciting new features, designed to facilitate modulation analysis. It shows the actual spectrum plot at lower left, with the modulation plotted against time at upper left and the I/Q IF output stream at lower centre. A summary of the signal and modulation data is shown at upper centre. trace itself, in the main graticule. There’s another new feature that’s even more impressive: Spike now provides a real-time spectrum analysis mode, to allow capturing occasional short-term events which can easily be missed in normal sweep analysis if they occur during the “dead time” between sweeps. In real-time analysis mode, Spike takes advantage of the ability of Spectrum Hound’s analyser hardware to stream its full IF bandwidth back to the PC (via the USB cable) continuously, with no time gaps. So by limiting the sweep span to the maximum instantaneous bandwidth, Spike is now able to process and analyse every spectrum sample in real time. Incidentally, the spectrogram and 80  Silicon Chip persistence features can be applied in real-time mode just as easily as in sweep mode. If this isn’t enough, there’s now a zero-span analysis mode too. This might sound a bit strange but it’s really quite easy to understand. In zero span mode, Spike directs the analyser to stay locked to the centre frequency you’ve set, while it again streams the full IF bandwidth back to the PC. This allows Spike to demodulate any AM, FM or PM modulation which may be present on a signal at that centre frequency. As a result, when Spike is in zero-span mode, the screen changes dramatically, with the RF amplitude vs frequency spectrum graticule reduced in size and moved to the lower left, while the modulation is displayed plotted against time in a new graticule across the top. In addition, the I and Q components of the analyser’s IF data stream are displayed in a third graticule at lower right, alongside the amplitude vs frequency plot. Then if you enable Spike’s AM/FM modulation analysis feature, the upper modulation vs time graticule contracts to the left, and quite a bit of modulation analysis data is displayed in the top right quadrant. You’re shown a continuously updated summary of RMS, Peak+ and Peak- modulation percentages, plus the modulation frequency and RF centre frequency, together with the SINAD (dB) and THD (%) figures. Other features There are other noteworthy features as well, including: (1) The ability to call up an Audio Player function, to listen to any AM or FM modulation of the centre frequency signal via the PC’s speakers; (2)  The ability to call up a Measuring Receiver function, to display various key parameters of the centre frequency signal; (3)  The ability to record the data from an analyser session as a file on the PC, and also to replay a recorded file for further analysis; (4) In zero-span mode, there’s also the ability to save a short duration I/Q capture, either as a binary file or in a text-based format such as a CSV (comma separated variable) file; (5)  The ability to plot phase noise and (6)  If you add a USB-TG44A Tracking Generator to your set-up, the software can be easily set up to perform scalar network analysis. In short, Signal Hound’s new Spike 3.06 software really expands the measurement applications of their USB-based spectrum analysers (like the USB-SA44B) dramatically, as well as taking full advantage of the hithertohidden performance features of the analyser hardware. The new User Manual for Spike is also a significant improvement on the original manual, which was already pretty good. In Australia and New Zealand, Signal Hound products like the USB-SA44B and the USB-TG44A are distributed by Silvertone Electronics, now based in Wagga Wagga, NSW. You’ll find their website: www.silverSC tone.com.au siliconchip.com.au