The Si4732-based MiniRadios produce an annoying audible Theremin-like effect in SSB mode when the antenna base is touched. An external or internal modification can help.
All versions of the SI4732-based MiniRadios particularly the current Version 4 produce a distinctive sound when receiving a signal in SSB mode.
This “Theremin” effect occurs when the base of the telescopic whip antenna or the pin of the SMA socket is touched. The frequency of any received signal gets detuned creating a very disturbing audible effect In SSB mode .
This originates from an internal 3.4 GHz PLL-controlled VCO leaking to the SI4732’s pins. This effect can be removed with either an internal modification or an external adapter. Both introduce inductance into the antenna path to dampen the 3.4GHz signal.
The external adapter also includes two diodes to protect the receiver’s input from static electricity (ESD), a feature necessary in early MiniRadio versions V1 to V3S.
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