Welcome to the ‘Learn to Radio’ general.

If you have no experience of radio and want to learn welcome to the place. The links below will take you to a webSDR, which is a SDR (Software Defined Radio) you can access on the web. The benefit to this over using your own SDR is they have good antennas and you’re guaranteed to find a signal. Simples.

HF (High Frequency)
>http://hackgreensdr.org:8901/

VHF (Very High Frequency) / UHF (Ultra High Frequency)
>http://hackgreensdr.org:8902/

The HF / VHF / UHF terms make sense in historical context, if they were being named today though it would be different. Ultra High Frequency (UHF) being around 440MHz and your Wi-Fi router being up to 5900MHz. We don’t say your Wi-Fi router runs at Superduper Mega Ultra High Frequency however so whilst the bands may sound like they are ‘high frequency’, compared to modern advancements in radio, they’re not.

Radio waves are usually measured in frequency and in their physical length. When somebody says the 40m band it means each radio wave is 40m in length. The 70cm band, also called UHF, is 70cm in length, and so on. Radio waves travel at the speed of light, so the formula to turn band length into frequency is simple.

λ = v/f

λ = wavelength, v = velocity, f = frequency

For sake of ease, the speed of light can be rounded up to 300,000,000 m/s. This is the velocity. So if we want to find the wavelength of 10MHz, remembering of course that 10Mhz is 10 million hertz, it would be as such.

λ = 300,000,000 / 10,000,000

After crunching the numbers this shows us that the wavelength for 10Mhz is roughly 30 meters. Why not try to do the below

1) Calculate the frequency of a 50 meter wavelength.

2) Calculate the wavelength of a 20MHz frequency.

3) Calculate the wavelength of a 10GHz frequency (10 billion hertz).