Tower Locator Blog

OTA DTv

Getting Free TV


One of the first steps to getting free DTv is to Find Broadcast Towers in your area. Then with a little planning (see below), and understanding Signal Factors, you can get the most stations possible.

Sponsored links

PLANNING STEPS
1.) Find Broadcast Towers.
2.) Calculate Cable Loss.
3a.)
3b.)
Calculate Antenna Gain needed,
or estimate Existing Antenna Gain.
4.) Calculate Signal to TV's.
5.) Install an amplifier if needed.
-- Preamp for weak signals.
-- Booster or Distribution amp for cable loss.
Planning Steps

reception factors 1.) FIND BROADCAST TOWERS
Use the TV Tower Locator to find stations in your area.

Note;

2.) ESTIMATE CABLE LOSS
RG-6 Coax Cable is the industry standard for TV reception, but other cable types / losses can be used (see TV Coax Cables & Signal Loss). Cable loss mainly depends on cable length(s) and the number of signal splitters. Connectors and adapters introduce a small loss.

Cable loss also varies with RF channel, the higher the channel the greater the loss. The loss difference is relatively small, usually 1 dB or less. In most cases using the average of a frequency band is close enough for calculations.

3a.) ESTIMATE ANTENNA GAIN NEEDED - New Installations

Estimate Antenna Gain Needed
Band or Channel:
Receive Signal: dBm

Cable Length(s):
Signal Splitters: 2 Ports , 3 Ports
4 Ports , 8 Ports
Connectors:
Adapters: 300 / 75 ohm

SIGNAL POWER
AVAILABLE TO ANTENNA
Cable Loss
Splitter Loss
Connector loss
Adapter Loss
SIGNAL TO TV
Required: -65 dBm
GAIN
NEEDED

A negative gain indicates any antenna will work.

Gain needed is an estimate and should be padded 3 to 6 dB or more. Also see Signal Factors.

3b.) ESTIMATE ANTENNA GAIN - Existing Installations
Antenna gains average from around 3 dBi for an indoor antennas, to over 15 dBi for a large outdoor antennas.

Antenna Type Gain (dBi)
Indoor Antenna 2 to 4
Attic / Outdoor Antenna 5 to 10
Large Outdoor Antenna 11 to 15+

4.) ESTIMATE SIGNAL TO TELEVISION
Signal power to the television equals broadcast signal at the receive antenna plus antenna gain, minus cabling loss. Signal strength is a function of transmit power and distance from the broadcast tower.

Broadcast Signal (dBm)
+ Antenna Gain (dBi)
- Cable Loss (dB)
= Signal to TV (dBm)

Estimate Signal to Television
Band or Channel:
Receive Signal: dBm

Antenna Gain:
Cable Length(s):
Signal Splitters: 2 Ports , 3 Ports
4 Ports , 8 Ports
Connectors:
Adapter: 300 / 75 ohm

RECEIVE
-SIGNAL
ANTENNA
-GAIN
Cable Loss
Splitters Loss
Connectors loss
Adapters Loss
TV SIGNAL

A good signal is from 8% to 50% (-60 to -35 dBm).
A strong signal is greater than 50% (-35 to -5 dBm).

5.) AMPLIFIERS
A preamplifier can be used to improve weak broadcast signals. A distribution or booster amplifier should be used to overcome cable loss.

Sponsored links

SUMMARY

The above calculations are for an optimum scenario -- antenna 30 feet above the ground, pointed directly at the tower antenna, in tower antenna main beam, and has a clear line-of-sight. See Signal Factors that reduce the signal strength, and adjust calculation results.

ANTENNA
Placement
  • As high as possible.
  • Clear of clutter in tower directions.
  • Pointed in direction of broadcast towers.
Frequency
Bands
  • Most broadcast are in the UHF band.
    In some cases a UHF antenna works for VHF signals.
  • Use a VHF / UHF antenna to get all bands.
Weak
Signals
  • Use a high gain antenna.
  • Install an antenna pre-amp.
Distant and
Spread Out
Headings
  • Use 2 or 3 antennas.
  • Use an Omni antenna (360° coverage).
  • Rotor antenna (high gain and 360°).
CABLING
Coax
  • RG-6 coax cable (F-type connectors).
  • Cable runs as short as possible.
Connectors
  • Make sure all connectors are tight.
  • Check outside connectors for corrosion.
  • Outside connectors covered with a
    rubber weather boot or electrical tape.
  • Unused ports capped with a 75 Ω load.
Long Cable(s),
multiple Splitters
  • Use a distribution / booster amp.

otadtv.com Over-the-Air Digital TV (OTA DTv)
Getting Free TV
otadtv.com/reception/index.html