Network Rail put up the signalling mast overnight.
But residents say they weren't told anything about it and have now started a petition to get it removed.
Pensioner Margaret Kirby, of Nicholas Crescent, Fareham, said: 'I believe this mast will significantly devalue our homes.
'I think it is terrible that it was just put up by Network Rail without them telling us anything about it.
'We just woke on the Sunday morning to find it had been put up.
'I suspect they didn't consult us as they knew we would have objected strongly to it.'
Network Rail did not have to inform Fareham Borough Council about the pylon as it falls within their land and does not require planning permission.
The mast is part of Network Rail's railway communication system (RCS), a new national safety system which will allow train drivers to communicate directly with signallers for the first time.
Network Rail spokesman John Cottrill said an investigation was now under way into why the five homes weren't told about the mast.
He said: 'It is our policy to locate sites at least 100m away from schools, hospitals and residential buildings whenever possible.
'We do try to avoid residential areas if we can, but sometimes this is unavoidable.
'If we have to site a mast within 100m of residential buildings we write to the residents before starting work to inform them.
'In this case we did notify the closest residents and are investigating why other residents in Nicholas Crescent were not contacted.'
The new signalling system is the realisation of a key recommendation from Lord Cullen's report into the Ladbroke Grove rail accident in October 1999, which killed 31 people after two trains collided.