  Astrophysical sources such as radio halos and relics in galaxy clusters,
supernova remnants and radio galaxies have angular sizes from a few to several
$10$s of arcminutes. In radio interferometric imaging of such sources, the
largest angular size of the source that can be imaged is limited by the
shortest projected baseline towards the source. It is essential to determine
the limitations of the recovery of the extended features on various angular
scales in order to interpret the radio image. We simulated observations of a
model extended source of Gaussian shape with the Giant Metrewave Radio
Telescope (GMRT) using Common Astronomy Software Applications (CASA). The
recovery in flux density and in morphology of the model source was quantified
in a variety of observing cases with changing source properties and the
uv-coverage. If $\theta_{lar}$ is the largest angular scale sampled in an
observation with the GMRT, then $>80\%$ recovery of a source of size
$0.3\times\theta_{lar}$ is possible. The upgraded GMRT (U-GMRT) providing 200
MHz instantaneous bandwidth between 300 - 500 MHz will allow a factor of two
better recovery of a source of size $\theta_{lar}$ as compared to the GMRT at
300 MHz with 33 MHz bandwidth. We provide quantitative estimates for the
improvement in extended source recovery in observations at low elevations and
long durations. The presented simulations can be carried out for future radio
telescopes such as the Square Kilometre Array (SKA) for optimisation of
observing strategies to image extended radio sources.
