It takes 4 to...

Simulations to obtain best u-v coverage possible with 4 antennae

Onkar has some preliminary results from his u-v plane coverage simulations. Here are mouth-watering diagrams first.

Onkar generates the positions of antennas using some logic. This is independent of other details. His top image (u-v coverage of 6 antennas) was made using a logarithmic spiral distribution of 4 antennae. The second image was created when 4 antennae were used in a Y-shaped array, like the VLA.

His (possibly) best result is kept for the last, when is that, Onkar?

Bandwidth and antenna windings

Our dipole antenna element was fixed on wooden frame using nails. The dipole wire was wound around a nail to make it taut. When we introduced a wound around the nail, they acted as an inductors on ends of the wire (Rad's comment with a chuckle).

We need to put plastic caps on each end, and then use some material to fix the dipole wire, possibly some rope or hard plastic cover on usual copper wire. see this link.




As for the interference outside the "allowed band" of the dipole, let us wait for Onkar to fetch the co-axial cable from NCRA/TIFR, Pune.

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.