Flameout

I was (and still am) using a mobile Nagoya UT-72g and although it works, it's very touchy as to it's position. I am using it inside my garage, on a vehicle and it needs to be in a very specific spot to hit the one repeater I'm using. If I move it even a foot, I can't hear the repeater, but in that one specific spot, it picks up great I bought a GMRS specific Slim Jim, mounted on my roof, with a clear shot to that repeater, which is about 14 miles away and it will not pick up that same repeater at all. How can that mobile, inside my garage pick it up but the roof mounted one can't? Could it be that cable or maybe the connectors? I made a PVC "C" to hold the Slim Jim (I attached a photo - the other antenna in photo is my 2m/440 Comet GP-6) I think I may eventually just get a Comet CA-712EFC. The other photo is the view from my roof and that repeater is over in that direction

Sorry, Im in Pittsburgh PA at an elevation of about 1250'. One of the highest areas of the city, so that may be an advantage. It looks like I may be about 22-23 miles from nearest repeater. I just ordered the antenna from Buytwowayradios.com and also asked about my 805G. It would normally be here tomorrow, but USPS tracking updated since it shipped.

I just joined this forum today in hopes of finding repeaters near me. I was surprised that there were none. The closest thing to me is a blue spot with the #2 in it, but I have no idea what that means. Clicking on it doesn't do anything. What is that? I do have 3 repeaters within 20-45 miles, but aren't they too far for a handheld? I'm also new to HAM aad GMRS. I have a Wouxun KG-UV9P and waiting on my KG-805G, so as of now, I haven't made any contact with anyone (hoping to take my Tech class test next week)