Si473X Radios

The Si47xx-based receivers can cover 0.1 to 30 MHz with both AM and SSB/CW modes, and the commercial FM bands.    

There are many manufacturers and many variants of the Si4732-based ATS-25 and ATS mini (v1 - v4), and the Si4734-based ATS-20.  Some variants also cover the VHF AM air band and the 2 meter amateur radio band.  Some even provide decoding of morse code and FT8 signals.  Others provide decoding of CW or FT8 signals.  Most of these radios include rechargeable batteries that use USB chargers.

The ATS-25 series radios use a touch screen button and menu system to select radio parameters, and the encoder knob to change parameter values.

The ATS-Mini series radios use a single combination press-switch and digital encoder to select and adjust various radio parameters (volume, frequency, mode, etc.).  While ingenious, it is a somewhat non-user friendly user interface.  Luckily, at least for the ATS-mini, KB8QED has come up with new firmware that provides a scalable web  interface to easily change receiver settings.

Many of the small portable radios with video displays based on the Si47xx and ESP-32 microprocessors suffer from internally generated noise when they are used with directly attached whip and loop antennas.  The use of external antennas can reduce this noise.    In addition, the radios have limited dynamic range, which can lead to overload on strong signals.  The use of an external RF preselector and/or step-attenuator can alleviate this problem.   

The County Comm GP-5/SSB and GP-7 series of handheld radios use the Si4735 and Si4734 chipsets, respectively.