The Tv transmissions are VERY STRONG , As In --> VERY STRONG , at your location.
Does the antenna you have now have Any Type or Kind of amplifier , If so remove ALL parts and pieces of the amplifier.
The Tv transmissions are So Strong that a amplifier will be over loaded and Be The Cause bad reception or no reception.
The transmissions are SO Strong that I am recommending a much smaller All band antenna , the HD7000R.
Your location has easy to receive Tv stations channels in All 3 Tv bands.
VHF low band channels 2 thru 6 .
VHF high band channels 7 thru 13.
UHF band channels 14 thru 51.
Hense the All band HD7000R antenna.
And are you saying that WLIW-DT Real channel 21 , Virtual channel (21.1) , PBS Is Not received with the antenna you have now even with the antenna aimed at WLIW at about 89 degree magnetic compass .
The signal strength of WLIW is , 29.6 NM (dB) , and that is not a weak signal.
I am doing my best to have reception with one antenna.
If one were to add a second antenna that the purpose of the antenna is to receive WLIW , then install a Winegard HD9022P UHF antenna.
The second antenna can not be combined with the other antenna no matter if the other antenna is the antenna that is in place now or the HD7000R.
The HD9022P antenna will have a separate coax.
http://www.solidsignal.com ,
http://www.winegarddirect.com ,
http://www.amazon.com.