The 500 foot tower you see is the old Hennepin County PSAP in Golden Valley (which has now moved right next to the "Workhouse" in Plymouth). Your almost right on top of it so I am thinking that your yagi is too far out of frequency range or you are overloading your scanner with it. Your location is less than 3 miles away and I can't see any simulcast issues in your location. What is your signal quality with a normal telescoping or rubber duck antenna?. Please let us know what model of scanner you have?.
Guys, let me clear up one point here, the difference in the RX using the Yagi is not that much to be a concern. If you were trying to transmit on it, that is a whole different issue.
The big thing here with a yagi, is to make sure your RF connections are good and the coax your using doesn't add too much loos between the antenna and your receiver. Some antennas provide what looks like a short to an ohm meter, so you cant' just put the meter on the receiver end of it and check it out.
I would start with the basics and see if you can hear the tower your looking for with an omni antenna like a whip at the back of the receiver. If so, you can only get a better signal with the yagi once it's pointed in the right direction. With a 10 element yagi, you will have some gain to the front and limited side lobes. So it may take some effort to get it pointed in the right direction. But I will say that it will not be like a flashlight beam where If it isn't pointed perfectly, you won't hear the signal. You will have maybe 10 or 20 degree of pointing slop. Yes the better you get the antenna pointed, but it isn't that critical.
Let me also add another comment. You didn't say if this was a simulcast system your trying to listen to. If it is and your in the no capture zone between multiple towers, you may have to move the antenna round to find a good sweet spot. I don't mean swinging it east or west, I am talking physically moving it a couple of feet in the physical position.
Let the group know how you make out.
Jim
