  The quasar B2005+403 located behind the Cygnus region, is a suitable object
for studying the interplay between propagation effects, which are extrinsic to
the source and source intrinsic variability. On the basis of VLBI experiments
performed at 1.6, 5, 8, 15, 22, and 43GHz between 1992-2003 and parallel
multi-frequency monitoring of the total flux density, we investigated the
variability of total flux density and source structure. Below 8 GHz, the
point-like VLBI source is affected by scatter-broadening of the turbulent
interstellar medium, which is located along the line of sight and likely
associated with the Cygnus region. We present and discuss the measured
frequency dependence of the source size, which shows a power-law with slope of
-1.91+/-0.05. From the measured scattering angle at 1GHz of 77.1+/-4.0mas a
SM=0.43+/-0.04 m^{-20/3} kpc is derived, consistent with the general properties
of the ISM in this direction. The decreasing effect of angular broadening
towards higher frequencies allows to study the internal structure of the
source. Above 8GHz new VLBI observations reveal a one-sided slightly
south-bending core-jet structure, with stationary and apparent superluminally
moving jet components. The jet components move on non-ballistic trajectories.
In AGN, total flux density variations are often related to the emergence of new
VLBI components. However, during almost eleven years no new component was
ejected in B2005+403. In the flux density variability a trough is observed at
5-37 GHz between 1996 and 2001. This can be explained as a blending effect of
jet component fluxes. Dense in time sampled flux density monitoring
observations reveal intra-day variability at 1.6GHz impling a second, less
dense or turbulent scattering screen at few to hundred parsec distance.
