Residents as far away as Kiama may have been affected by the temporary loss of ABC and SBS TV channels.
The issue is due to technical problems relating to the retune for those residents whose TV sets get their signal from the Illawarra tower.
The retune is required to free up space on the broadcasting spectrum.
While most of those will be in the northern suburbs, some Kiama homes may also receive their signal from the same transmitter.
A federal Department of Communications spokeswoman said the technical issue saw ABC and SBS either transmitting a weak signal, or none at all.
Engineers have been working on the problem between midnight and 5.30am, during which time the two networks were off-air.
However, for homes at the outer edge of the broadcast area - like those in Kiama - the signal may have been too weak to reach them during the day.
The spokeswoman said that SBS is now broadcasting as normal and the ABC is expected be returned to full signal by 5am Friday.
The spokeswoman said any homes that experienced a loss of the ABC and SBS channels will need to retune their TV sets.