On Fri, Feb 5, 2021 at 08:24 AM, hwalker wrote:
On Fri, Feb 5, 2021 at 01:18 AM, Stephen Laurence wrote:
There have been a lot of postings on the various nanovna groups, saa2 in particular, about static discharge damage, and adding an esd diode diodes across each input. The?ESD101B102ELE6327XTMA1, seems popular, (and cheap) with a bilateral breakdown voltage of 5.5v.
Would this give any protection from input overload to the Tinysa? It is a tiny device and cannot dissipate much power but the very low capacitance is not so important for a spectrum analyser and maybe a physically bigger one, but with a 5v (or lower) breakdown voltage would be better.
Steve,? ??
........
? ? The thing we learned about limiters is that since a diode is a non-linear device it is subject to acting as a mixer when subjected to pulse signals and creating signals that really aren't there.? Its very embarrassing failing a device because of signals created by your test set-up.? We eventually just annually ordered new 2W 6/10/20dB attenuators that were sacrificial elements against accidental frontend overload.? Much cheaper than replacing the front end attenuator inside the spectrum analyzer.
Back to back limiting diodes a the front-end of a receiver or spectrum analyzer can generate mixing products but their level depends on the voltage where the diodes begin to have any significant conduction.? Historically they have been avoided at the front end of a high-performance communication receiver with a low noise floor because they affect the spurious free dynamic range(SFDR) and lower the OIP3.? And the high capacitance of these diodes limited their application to HF/VHF applications.
Today there are many vendors manufacturing ESD protection devices with much higher conduction and clamping voltages and shunt capacitance? that is a? fraction of a pF. They solve the problems described above in many applications.? The one that Steve posted, that is made by Infineon, is one example and they are only a few cents in volume.? I suspect that if these were installed on the TinySa input mixing products would not be seen and therefore? no effect on performance when operating in Spectrum Analyzer and Signal Generator output mode.
There needs to be some sort of ESD protection on the connectors of the TinySA.? Walking around with the supplied antenna attached is just looking for ESD failure.? Years ago I owned a MFJ-259B antenna analyzer and attached a small whip for some measurements.? It was a dry winter day and ESD destroyed the front end.
Roger
Roger Need