Hi Lodger,
Sorry to hear about your reception issues. WPVI is the only station in Philly broadcasting on a low VHF channel (RF channel 6, presenting problems for many an OTA viewer).
Also, a quick read of the customer reviews of your current antenna on Radio Shack's own web site doesn't look good:
http://www.radioshack.com/pwr/produc...r-Antenna.html
You may want to look at purchasing a better antenna to pick up the VHF RF. Outdoor antennae are always best, but if you must stay indoors, there's some good advice above, and I see that the amplified Terk HDTVA antenna is getting good consumer reviews. Do some research, and ask questions when purchasing.
Most stores will accept a return if their antenna doesn't work out for your situation.
I hope this helps...
Bob
http://RobertMillerConsulting.com