  The full ATLAS Run 2 data set with time-integrated luminosity of 139
fb$^{-1}$ in the diboson channels in hadronic final states is used to probe a
simple model with an extended gauge sector (EGM), proposed by Altarelli et al.,
and often taken as a convenient benchmark by experimentalists. This model
accommodates new charged $W'$ and neutral $Z'$ vector bosons with modified
trilinear Standard Model gauge couplings, decaying into electroweak gauge boson
pairs $WZ$ or $WW$, where $W$/$Z$ decay hadronically. Exclusion limits at the
95% C.L. on the $Z'$ and $W'$ resonance production cross section times
branching ratio to electroweak gauge boson pairs in the mass range of $\sim$ 1
- 5 TeV are here converted to constraints on $W$-$W'$ and $Z$-$Z'$ mixing
parameters and masses for the EGM. We present exclusion regions on the
parameter space of the $W'$ and $Z'$ by using the full Run 2 data set comprised
of $pp$ collisions at $\sqrt{s}=13$ TeV and recorded by the ATLAS detector at
the CERN LHC. The obtained exclusion regions are significantly extended
compared to those obtained from the previous analysis performed with Tevatron
data as well as with LHC data collected at 7 and 8 TeV in Run 1 and are the
most stringent bounds to date.
