This telescope is no more existent. I am using it here as a good example
of a telescope which uses a combination of beam forming and synthesis-imaging
techniques. This was a fully steerable deca-metric array. This was a 
array of
conical spiral antennas, 
km by 
km. It had the best sensitivity
in the 
MHz to 
MHz. Both its operating frequency and beam position were
adjustable in less than 
ms (see Erickson et al. 1982).
The basic element is a long spiral element utilising eight wires wound
around a support system that consists of eight parallel filaments. Each element
is circularly polarised with a diode switch at its apex that rotates its excitation
and thus adjusts its phase. Steering of the array is accomplished by putting a
linear phase gradient across groups of 
elements, called banks. There are
16 banks in the 
m 
arm and 
banks in the
m 
arm.
The output of each bank is brought separately to the central observatory building.
A separate receiver channel is attached to the output of each of the 
banks. Each channel employs a superheterodyne receiver7.4 to down convert the signal to
MHz. The MHz output of
each of the receiver channel is sampled at a frequency of
MHz digitally delayed
and then cross-correlated in a 
channel two-bit three level complex correlator.
An off-line processor removes the fringe rotation7.5 introduced by the earth's rotation
and integrates the data for periods up to 
minutes. A Fourier transform then
produces a map of the area of the sky under observation. These maps may be averaged
to effectively integrate the signal for periods of hours.
It's total collecting area was 
. The synthesised beam
at 
MHz had a width of
at the zenith. The confusion limit
of the telescope was around Jy. It produced 
picture elements in a field
of view roughly
.