So, I just built a lightning detector circuit from Techlib.com, and it detects lightning strikes close, but if I ground the antenna from the power outlet ground, the detector detects farther lightning strikes. Is it safe to ground the antenna?

Here's the circuit on Techlib.com:

http://techlib.com/electronics/lightningnew.htm

Here is my circuit down below, with the antenna:

I don't know if it's safe or not but so far, does this actually work? I'd love to make one of these to detect lightning.

  I have mess with old amplified Cystal radio
  yes longwave and med wave radios in the old
 days you have hook up ground wire if you want
 pull in distant stations.  it best to drive a independant
ground rod for these kind of radio experiments
  what ive done and it best ground is to throw ground wire in the lake.

I don't know if it's safe or not but so far, does this actually work? I'd love to make one of these to detect lightning.

Yeah it actually does work. There was a severe thunderstorm, and a strong thunderstorm on Tuesday, and it catched a few strikes within at least 15 miles or less. It uses a PNP Darlington (MPSA63) transistor and 10mH (mila henries) inductor. The circuit was made by Charles Wenzel on Techlib.com.

If everything is inhouse, gtounding it to the mains PE is safe. But itmay the receiver respond not only to natural discharges, but to the mains dirurbations as well, so give false responses. But if you are able to limit the disturbances (if your home does not share the mains grounding with others and you identify and shut down the equipment causing the disturbances), it may work.

But if you want to mess up with outdoors antennas, make damn sure they are up to the code mainly regarding lightning safety.

You are actually using the electrical system ground as an antenna with the benefit of providing a safety ground to the antenna. In the world of radio you have a DC ground (which is connected to your battery), a safety ground (which is now part of your antenna), and an RF ground (that's a complicated subject for this type of application, but mentioned to be complete).

Normally, the grounds are bonded together electrically which is best practice, however, your alternate practice is just as safe. Assuming you are running on batteries, your DC ground can be left floating and since your safety ground and your antenna are the same thing, you don't need an additional safety ground for your antenna.