Audio selector (4 amplifiers – 2 speakers) review, teardown and analysis

I bought from Aliexpress this audio switch. It’s a device where you connect several audio amplifiers and several speakers, and

Antenna construction cross Yagi, VHF band, 6 elements, 2 meters long, circular polarization, 9dB gain

Useful links: Notes on 6-Element Wide-Band 2-Meter Yagis http://on5au.be/content/a10/vhf/32m.html Antenna Circular Polarization https://www.qsl.net/sv1bsx/antenna-pol/polarization.html Yagi Uda Antenna Calculator https://www.changpuak.ch/electronics/yagi_uda_antenna_DL6WU.php Coaxial Power