Antenna and the bandwidth

We put up our first dipole antenna element on Friday (?) afternoon. Here is Roopa trying to keep the antenna wire taut, and Onkar's pic does not need a caption ;-)

The picture on the right shows the band. Even though Onkar tried to measure the length of the dipole as LAMBDA/4 on each side, the band is centered on 71.5 MHz. What gives? The bandwidth is barely 1 MHz, kind of a let down. At the same time, there is a lot of interference from the surroundings. Perhaps our antenna wire (not a co-axial yet) is too prone to pickup from around.