When you use two antennas to receive signals from two different directions more than 90 degrees apart there are a few things you must do to make this work:

1 Use 2 Channel Master 4221 Antennas. Anything else is taking your chances.

2 Use two 5' mast poles so the two antennas are at least 3 feet apart

3 Use exactly the same amount of cable between each antenna and the combiner

4 Use a Winegard CC-7870 Combiner to combine the two signals into one downlead.

5 Fine-tune the directionality of each antenna using a compass and the chart generated by www.TVFool.com

This is how we do two-antenna installations from Western Mississauga to Oakville and Burlington, and from Eastern Scarborough and points east.
Someone had mentioned the high VHF situation from Rochester - I wouldn't worry about it - the stations are all repeats of Buffalo stations.

Geoff
The Antenna Guy
www.TheAntennaGuys.com
www.HDAntennaStore.com
416-654-HDTV