Why not start with a fixed aim solution. An Antennas Direct DB4e will outperform the UHF functionality of all the HBU series antennas. Facing about 150° compass you'll do very well receiving the available UHF signals. An Antennacraft Y5713 pointed toward 167° would receive the two High-VHF signals on real channels 9 & 13... you might get lucky and see the signal from real channel 7 from the west. Combine the two antennas with a UVSJ followed by an Antennas Direct CPA-19 preamp.
If you want to pursue the Portland signals, I'd suggest a Winegard HD7698P. You could add a rotator to provide full use of that antenna. Regardless, I'd equip it with a CPA-19 as well. This antenna would need to be cables separately from the first array.
There are several ways to connect a multi-antenna system:
http://forum.tvfool.com/showthread.php?t=2882
http://forum.tvfool.com/showthread.php?t=820
Satellite system splitters which pass 5 to 2000 MHz on all ports are useable in OTA installs. Diplexers look quite similar but will block OTA frequencies on one or more ports. Matrix switches need to be removed.