Some small electronic devices react to PMR446 adversely temporarily, when exposed to a PMR446 transmitter, during the transmission.

  • Portable DVD player: Green horizontal stripes on screen. Increasing if I hold the PMR446 transmitter near.
  • Portable CD player (discman): Laser lens loses track, CD spins up very fast; also indicating low battery.
  • Boombox CD player: Skips and noise hearable if too near to laser lens + fart sound at speakers.
  • Standalone DVD recorder: Nothing, surprisingly.
  • DECT unit: Display brightness decreases temporarily.
  • USB Multimeter: Display lower current than actually flowing (e.g. 1.2A instead of 1.6a). Sometimes, voltage jumps up to 9.99V (highest displayable amount).
  • CD boombox: Fart sound from speaker.
  • Toy robot: Do random moves.
  • Toy phone benign girl: Decreased speaker volume; ability to be enabled by the PMR446 signal.
  • Portable standalone LED torch gets dimmed.

How can these interferences be explained technically?

  • 1
    \$\begingroup\$ Is this a proper PMR radio or a generic UHF handheld radio tuned to the PMR channels? \$\endgroup\$ – MrGerber Mar 31 '18 at 21:01
  • \$\begingroup\$ @MrGerber It is a Stabo portable PMR transmitter, Freecomm 650. Does that matter? \$\endgroup\$ – neverMind9 Mar 31 '18 at 21:05
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    \$\begingroup\$ Yes, because proper approved PMR446 radios has maximum power output of 500mW, but your run of the mill Chinese UHF radio is typically 5W transmit power \$\endgroup\$ – MrGerber Mar 31 '18 at 21:08

This is electromagnetic interference.

Effectively every wire in every piece of electronics is a radio reciever to some extent. When placed next to a strong transmitter they will recieve a signal, which may be interpreted as a control signal.

Systems are supposed to be designed to minimise the effect of this, but that costs money and is often skimped on.


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