Monday, March 14, 2011

The case of the Unforeseen radiator

It was not until we studied the technical paper released by PRATHAM team on
ground station set up that we realized something very obvious.

“The antenna should be as far away from any radiating systems as possible
(at least 20 meters away)”

‘Radiating sources’ reminded us of the walkie-talkies used by the security
guards. And a minisecond later it reminded us of the transmission line tower
that stands just across the road…

We rushed out of the control room into the adjoining terrace to check out
the giant metal structure… it was there always…so inconspicuous….it was only
now that we were looking at it with a sense of awe.

“But the lines have a frequency of 50Hz whereas our reception signals are in
the UHF VHF range, so how does it interfere with our project?“ enquired Anuj

Saurabh had the answer ready “Although the frequency is 50 Hz, the voltage
is of a gigantic value-around 33kv…KILOVOLTS…. So the transmission tower acts
as a giant radiating source emitting spurious signals much like how the sun,
a hot body, emits a range of value of radiations…”

The new discovery consolidated the need of accurate satellite tracking (read
antenna rotor)

Quote of day “Radio reception can be impaired under a power line, due both
to shielding of a receiver antenna by the overhead conductors, and by
partial discharge at insulators and sharp points of the conductors which
creates radio noise.”


  1. So what can be done to avoid this problem??
    Can we use a grounded metal sheet covering around the antenna suitably high to avoid the radiation and designed to matched the impedance as it will act as a waveguide with low impedance??
    Or why cant we use a horn antenna setup for the ground station...

  2. grounded metal sheet will hinder the useful radiations too right? And horn antenna not suitable due to the payload specifications. We need the vertical and horizontal components of the incident wave... can that be obtained by horn antenna?