If aliens are rather remote, they are moving away with large speed because of the universe expansion. Thus any signals they sent will experience Doppler slowdown. Moreover, the time needed to build a beacon will be also (observationally for us) diluted. For example, if they need around 100 mln years to build a quasar (by moving stars as I described in another comment here), it may look like 200 millions years for us.
Such delay may be too long according to their goals and they may try quicker ways to send data. Drawing by the use of Dyson spheres is quicker than building a quasar.
However, if we look at the convertor of redshift z to distances and ages, link, than z=1 (equal to slowdown of two times) is corresponding to the age of the galaxies there of 6-7 billions years, which is probably the youngest generation capable to support civilizations. (In other words, the biggest part of the observable universe on higher z is too young to support civilisations.)
If aliens are rather remote, they are moving away with large speed because of the universe expansion. Thus any signals they sent will experience Doppler slowdown. Moreover, the time needed to build a beacon will be also (observationally for us) diluted. For example, if they need around 100 mln years to build a quasar (by moving stars as I described in another comment here), it may look like 200 millions years for us.
Such delay may be too long according to their goals and they may try quicker ways to send data. Drawing by the use of Dyson spheres is quicker than building a quasar.
However, if we look at the convertor of redshift z to distances and ages, link, than z=1 (equal to slowdown of two times) is corresponding to the age of the galaxies there of 6-7 billions years, which is probably the youngest generation capable to support civilizations. (In other words, the biggest part of the observable universe on higher z is too young to support civilisations.)