The tvfool radar plot report shows that the Main groups of Digital Broadcast Tv stations are to the north.
With No Tv stations to the south.
Tv antennas receive better when nothing is in the way of reception.
Is there a window or patio/balcony window to the north??
If so , put a Terk HDTVi (not the HDTVa) at the window or at the patio/balcony window.
And run a Looong coax to the Tv.
Aim the antenna north , here is how to aim indoor and outdoor antennas ,
http://www.kyes.com/antenna/pointing/pointing.html
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What directions do the apartment windows face??
What directions do the patios/balconies face??
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Here are some places to buy antennas and etc. ,
http://www.solidsignal.com ,
http://www.amazon.com.
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The least obstructive building construction for reception of Digital Broadcast Tv is , wood with wood or vinyl siding and composition single roof.
The following is a - non complete - list building constructions that will further reduce or block Digital Broadcast Tv reception.
Concrete , concrete blocks , bricks , big rocks for walls , metal siding , metal roof , solar panels , metal backed insulation , stucko Wire , and etc. .
As always trees and tree leaves do a real fine job of reducing or blocking Digital Broadcast Tv reception and so do buildings and other obstructions including the apartment building.
It is best to install antennas at a location that has the least amount to no amount of obstructions of any type or kind in the directions of reception including the apartment building.
The Tv must Channel Scan for the Digital Broadcast Tv Channels , sometimes named the 'Air Channels' or 'Antenna Channels' in the Tv setup menu because the Digital Tv transmissions travel through the air from the transmitting antenna to the receiving antenna.
Digital Tv tuners can develop - Digital Glitches - that are not cleared out with a simple channel scan.
Do a Double Channel Scan.
http://www.fcc.gov/rescan.html.
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DO NOT channel scan for cable tv channels.