Unfortunately Barrie does not have any digital stations broadcasting yet.
The channel 3 station you are detecting is analog (CKVR) the local A-Channel affiliate. Their digital assignment will be channel 10 (VHF band), but as of a few months back they had no plans to look at digital implimentation pending the review (recent) of the television landscape by the CRTC.
The other two digital assignments for Barrie are CBLT-DT (ch. 33, CBC - english) and CBLFT-DT (ch. 42, CBC-french). Both are repeaters of their respective stations in Toronto. Neither are broadcasting at this time, and I don't believe we have heard any indications of when/if they will start.
I doubt you would have a shot at even CBC, which is the highest powered Toronto station (38kW) with that antenna. I would suggest turning the amplification completely off, since it is likely there for marketing purposes and is probably injecting more noise than anything else. Try pointing your antenna towards the CN Tower, but at > 80 Kilometers it would be lucky (and unreliable) at best with that antenna.
Reception of Toronto, and maybe some Buffalo stations, is possible in Barrie. But you would need a high gain outdoor UHF antenna and some elevation. If you could buy a proper outdoor antenna that allows has a good return policy (wink, wink,
), you might be able to test the reception at your house.
You might have to wait until the OTA stations in Barrie start broadcasting digital otherwise.