Re: tinySA Tracking Generator article
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BTW:? Zener diodes make wonderful BB noise generators when biasef just breaking into the Zener knee!? Follow that with a few MMICs to increase amplitude and finally a 6 dB resistive attenuator for impedance stabilization.? You're ready to roll.
Dave - W?LEV
May I suggest yet another cheap solution for a tracking generator for use with the TINYSAs?? This has been used extensively with many SDRs as well.? A good flat output noise generator makes an excellent substitute for a tracking generator.? Build or buy one and use it.? If there is not enough output, use one or several MMICs to increase the amplitude.? You might even want to envoke the MAX HOLD or AVERAGINGoptions for archiving smoother records of the plots.? I've used this technique many times with my SDRs.? Of course, I have a number of SAs, vector network analyzers, and signal generators, but just using the broadband noise source is just "fun" if you didn't have all these instruments.? Personally, I see no need with this option to build a tracking generator for the TINYSAs.
Dave - W?LEV
On Fri, Jan 17, 2025 at 4:28?PM valentino barbi via <barbivalentino= [email protected]> wrote: Il giorno ven 17 gen 2025 alle ore 17:21 Erik Kaashoek via <erik= [email protected]> ha scritto: There are some problems with building a tracking generator for the Ultra
LO output is possible through the CAL port using CONFIG/MORE/LO OUTPUT but the level is somewhat lower then with the tinySA basic. Not a big problem.
Having good isolation between the almost 1 GHz LO in the tracking generator and the IF of the tinySA Ultra will be VERY difficult. At 1 Ghz almost everything becomes transparent which will reduce the dynamic range
But the biggest complicating factor, in my view, is the tuning mechanism used in the Ultra. The frequency steps of the main LO are in the order of kHz which is not good enough when using a 200 Hz RBW. This is solved by tuning both the LO (for the coarse steps) and the IF frequency (for the fine steps). Furthermore the IF filters have some manufacturing tolerance and for optimal performance the IF frequency is at startup time optimized for IF filter. And then there are some situations where the IF is shifted to solve various problems in the architecture.
As there is currently no way to know for sure the frequency of the IF at every point of the sweep you can only use the widest RBW with a tracking generator which also causes a loss of dynamic range.
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