When you touch the antenna, or even get really close to it, you literally become part of the antenna through capacitive coupling. If the antenna needs the size boost that your leg gives it, I suspect the NBC affiliate is broadcasting on a VHF channel, which may be different from the channel number it displays on screen. VHF broadcasts = longer wavelengths than UHF signals = a bigger antenna needed to receive the signals properly. Can you give us a station callsign (i.e., WABC or KXYZ), or at least which market we're talking about here? Does the antenna have both "rabbit ears" whips and a loop in the middle?