On Sun, 17 Jun 2007 17:26:46 -0400, "john"
wrote:

I wanna get some powerful dog alarm that only dogs can hear..this way he'll
think twice about hopping on my yard..something really poweful..anybody know
of any?

I never built one of these (parabolic reflector) :-))

http://www.matthope.org/matt's%20plans/dish/dish.htm

--
Oren

...through the use of electrical or duct tape, achieve the configuration in the photo..