Making contact by FM radio

[Skvez]

If the transmitting aerial is horizontal then most of the power goes only at right angles to the line of the aerial and you 'loose' a lot of power transmitting up and down. Also the receiving aerial needs to be in the horizontal plane for good reception efficiency. This is fine perhaps ever preferential if you know where you're transmitting towards (and want to minimise the chance of interception) but for general broadcast you want a vertically aligned aerial.