Estimating the walkie talkie frequency

On camp for the D of E Silver, we sat debating the frequency of the walkie-talkies. I estimated the aerial at perhaps 20cm. Aerials like this are half wavelength. To make the mental maths easier, I took the wavelength as 0.50m. Using the wave equation, frequency = speed of electromagnetic waves/wavelength = 300 000 000/0.50 = 600 MHz. Same make walkie-talkies on the Internet are claiming 400 - 480 MHz so that not a bad estimate!