Why does holding the TV aerial improve the picture?

We posed this question to Phil clark from the Particle Physics Laboratory in Edinburgh...

Phil - Essentially, when you grab the aerial, you're effectively increasing the size of the aerial by making use of your body's conducting electrolytes.

A good example of this would be, in a laboratory, if you have an oscilloscope and you look at the pick-up from the [electrical] mains frequency, you can see a 50-Hertz signal, which is the pick-up from the resonance circuits in the room. And if you hold the probe in your hand, the amplitude of the pick-up increases dramatically. [Because your body is also picking up the electrical signals from the mains, producing small currents that the oscilloscope can detect.]

The same thing happens, effectively, when you grab the TV aerial: you're improving the pick-up and it's then using you to resonate within the circuit to produce the signal in the television.

The TV has to be tuned quite closely to the right frequency, but when you touch the aerial you will improve the signal dramatically.

The other thing to bear in mind is, when you grab on to the aerial, the connectivity between your fingers and aerial; the tighter you squeeze on the aerial, or if your fingers are wet, the conductivity between you and the aerial will be improved. So [the picture improving effect] also often depends on how hard you squeeze the aerial.

Diana - And what about the difference between analog TV signals and digital?

Phil - The digital signal is a sequence of 'on' and 'off' bits that come down the aerial and effectively it will either be receiving those or it won't; you may, with the aerial, be able to increase the chances of it picking out 0's and 1's correctly, but you have to get it all right for it to work. This is also why you need quite good signal for digital antennas to work correctly.