From my understanding, the Bluetooth signal is using a 2.4 GHz frequency.

However, when someone is playing with a 40 MHz RC vehicle, the Bluetooth signal keep on getting interrupted or disconnected.

Does the 40 MHz RC vehicle is the root cause that cause the Bluetooth to get interrupt or disconnect?

If it is not the RC vehicle, what might likely cause such interference to the Bluetooth signal?

Thank you.

  • 3
    \$\begingroup\$ I there seems to be a relation between the two, I wouldn't exclude the RF noise produced by the controlled motors. The remote control should be reasonably clean. \$\endgroup\$
    – jippie
    Sep 1, 2014 at 5:16
  • 2
    \$\begingroup\$ It's certainly possible for the 40 MHz to have harmonics that are up in the GHz range. Is it your RC vehicle? You should be able to play around and figure out if that is the problem. (Try turning the receiver off, but leave transmitter on.) \$\endgroup\$ Sep 1, 2014 at 13:08
  • \$\begingroup\$ Are you sure that is actually a 40 MHz RC set? Most of the RC gear sold over the last few years is 2.4 GHz, both hobby grade and for all but the cheapest, simplest toys - it's really only legacy hobby-grade equipment that would be on 40/72/75 MHz with any power. The length of the antenna is often a prime clue. \$\endgroup\$ Jan 4, 2015 at 21:45

3 Answers 3


Just like any radio receiver, the front end/antenna wanted signal is very tiny - maybe about a couple of micro volts. Along comes a big signal from a relatively more powerful 40MHz radio transmitter and the front-end circuit is swamped into overload and this compresses the wanted signal.

It's called compression: -

enter image description here

Here is a site that should explain this

  • 4
    \$\begingroup\$ A 2.4 GHz front end shouldn't look very receptive to 40 MHz energy. \$\endgroup\$ Jan 4, 2015 at 21:44

In theory, harmonics of 40MHz multiplied by 60 is 2.4GHz. Practically, every next harmonic frequency has much less power than previous one. So at 60th harmonics the influence can be considered as 0.

Microwave, some Wi-Fi networks, nRF module, ZigBee, some proprietary devices use 2.4GHz carrier RF.


Motors create broadband (wide spectrum) RF noise. It's possible that it's actually the motors in the vehicle, rather than the intentional RF from the controller, that's causing the interference.


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