Hello i was wondering If this is possible or not but i have a few Nrf24l01+ modules sending wireless Signal sending to another arduino in the same room that works with no problem. But if one arduino on the first floor and another arduino on the third floor No Signal at all is it Possible use to the ground wire of the house hold power as a antenna to give signal strength to reach from the first floor to third floor sense all ground wires are tired together through out the house? The reason why I'm asking is because this is a old brick home it blocks a lot of things even cellphone Signals we had to put a micro cell tower from AT&T in here for cellphone use.
I would not like to use any mains wiring connection purely for safety reasons.
The earth can still develop dangerous voltages in certain fault circumstances.
Have you tried a stronger wireless system? I am just starting to play with APC220. They have a stated range of 800m plus at full power. The power is adjustable so you could set a level suitable for your situation.
Weedpharma
The [u]X-10[/u] system works that way.
But, I don't know the details or how the RF signal is coupled (safely) to the AC wiring. (I'm sure it doesn't send the signal over the ground wire.)
There is also [u]Ethernet over powerline[/u], but as I recall it was slow and unreliable and Wi-Fi pretty-much killed that technology off.
Well this is a nrf24l01+ module its a 2.4ghz rf going from one arduino to another that's all.
What happens if can use some kind of isolation on it to the ground would it be possible to make that?
DVDdoug:
The [u]X-10[/u] system works that way.But, I don't know the details or how the RF signal is coupled (safely) to the AC wiring. (I'm sure it doesn't send the signal over the ground wire.)
There is also [u]Ethernet over powerline[/u], but as I recall it was slow and unreliable and Wi-Fi pretty-much killed that technology off.
I am aware of this but they have been designed with safety in mind by highly paid engineers.
This is a do it yourself install.
Weedpharma
I'm trying to Send this using my arduino project.
It's doesn't have to be wireless can Easy use the TX or RX of the ardunio.
Please give more information on what you want to do.
What type of information are wanting to send, at what speed?
Can you run extra wires between the Arduinos or are you only able to use the mains Gnd?
Weedpharma
Well here is my dilemma. i have 2 arduino Using the Nrf24l01+ wireless module one Transmitting and one Receiving. The transmitting arduino has a LM35 temperature sensor and a DHT11 temperature/Humidity sensor But I'm not using the DHT11 temperature sensor because it's way off that is why i put in a LM35 Temperature sensor and on the Receiving side the other arduino has a 2.4 Inch lcd screen. If on the same floor it works great but If i put the Transmitting arduino with the sensors on the first floor and I'm on the Third floor with the Receiving arduino/lcd No Signal at all. This is a Old brick house where wireless Signals cut out the cellphone signal even don't work great do had to put in a micro tower so cellphone can work in side. But my problem is i need to find a way to boost the Signal of the nrf24l01+ wireless module on the arduino and one thing i thought of was using the Ground wire of the house power to send the Signal though out the house at least it was a great thought in theory. To make some kind of Isolator and some kind of signal but not sure.
Anyhow thought it was be a good idea. good dreams 
thank you for all the information everyone.
http://arduino-info.wikispaces.com/Nrf24L01-2.4GHz-HowTo
May help, has a reference to possible power increase.
Weedpharma
I have just started playing with a APC220 TxRx and found it easy to use and on its lowest setting I am getting over 30 metres indoors. It is rated at up to 1000m. Might be able to do what you want with a little bit more grunt.
Weedpharma
My experience with NRF24's was miserable. I was never able to get acceptable range with them. I was always suspicious that the problem was interference from other 2.4ghz devices - it's such a crowded band in the city, since that's what everyone's wifi is running on, but I never pursued it. Though, if that's the cause of the issue, you may have better luck if you change up the channel you're using.
I bought some RFM69's to try and see if they're better than the NRF, but I never got around to it; I'm working on my 433/315mhz OOK RF project.
An important thing to know about powerline interfacing - if anything goes wrong, like your house burns down, the moment your insurance company finds out that you did anything other than plug in a commercial device, they'll deny your claim.
Which 2.4GHz modules? Link?
What kind of antenna is on them now?
The website that Weedpharma gave looks like it offers some good tips. As the website suggests, powering the RF module from 3.3V from the Arduino will likely result in low power output due to only 50mA available. Bypassing the power supply is important, too.