Hi calmat,
For a start you service provider should have some sort of security built in for their customers. Check with them.
It is a little hard to believe, but not impossible I SUPPOSE, that someone switches on at the same times each day.
More on interference later.
Security.
If your wireless network is left open, any passing user with a wifi-enabled device - such as a laptop or even just a smartphone - could simply access your broadband by parking up outside your house.
While this won’t cost you money, it could slow down your connection and, also leaves your connection wide open to hacking, allowing users to access your personal information, bank details and even see what web pages you’ve been visiting.
WPA and WPA2 are the latest methods of wireless broadband encryption and are far harder to crack than the older WEP codes. However, this type of encryption is not backward compatible with all types of hardware so check which type of encryption you should be using before you set up your security.
This is information advised by my own provider.
Do you have on your computer details of your installation by your provider. Connections, broadband help?
Their details should give you an idea of their own security, then if not good enough you will have to boost ,as above.
For now, back to interference:-
Again info provided by my own provider, although on different continents, I should think the same would apply.
Here are many things that can disrupt the DSL signal and cause a dropout, such as the random electrical interference from a nearby item, a fault on the phone line or a problem with the modem or the exchange equipment.
An intermittent broadband connection (possibly accompanied by a flashing light on your modem or router) may be caused by the broadband service automatically adjusting your speed in order to maintain the fastest possible stable connection. This is known as 're-synching' and it's usually triggered by electrical interference affecting your phone line. The re-synch process requires the broadband signal to be dropped for 20-60 seconds while a new stable speed is identified.
If you can, keep electrical devices five feet or more away from the router, especially:
Halogen desk lamps with dimmers
Any electrical dimmer switch
Stereo or PC speakers
Televisions, monitors and microwave ovens.
AC power cords running parallel to the telephone line
Electronic insect electrocution devices (bug zappers)
Low quality 900MHz cordless telephones
Any other emitter of high frequency electromagnetic radiation.
These are examples.
I would look into the security aspect first, to me that's the most important to sort out, then we can look at interference.
Other members, I am sure will assist in sorting out this problem for you.
Get back to me when you can with updates.