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I've heard that it is bad practice to mount a 2.4 GHz RC receiver antenna next to a 5.8 GHz FPV VTX antenna because the transmitting antenna will negatively impact the receiving antenna's reception. For example, this is said to be true in this Rotor Riot video at 1:40.

Is this true? If so, how close is too close and how can I mount the two antennae to minimize the interference between the antennae?

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The distance is dependent on the wavelength of the lowest frequency. You can calculate the wavelength (m) from λ = c / f, where c is the speed of light in a vacuum (ms-1) and f is the frequency (Hz.) Taking the centre frequencies of the ISM bands we get:

2.4 GHz: 299 792 458 / 2 450 000 000 ≈ 0.12 = 12 cm
5.8 GHz: 299 792 458 / 5 800 000 000 ≈ 0.05 = 5 cm
(Quick 'sanity check' tip: 5.8 GHz is about twice 2.4 GHz, so we expect the wavelength to be about half; looks good.)

The smallest separation is usually recommended as a quarter of the longest wavelength, which for 2.4 GHz is only 3cm - quite manageable. That said, greater separation helps so put them as far apart as your frame practically allows.

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  • Perfect! Do you have any resources to cite for your 1/4 λ figure? – ifconfig Jun 7 at 16:35

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