To figure out if we can use and Indoor Antenna, we will first figure out the available Noise Margin after estimating the dB loss using the information above. To do this, locate the NM field and find the lowest number for all the stations you require.
Locate the bull’s-eye chart to the left of the table pictured below. Figure out where your antenna will be mounted in relation to that tower.
- Optimally it will be near the exterior wall closest to the tower. If this is the case, only subtract 14 dB for home penetration; otherwise subtract around 34 dBs to account for your house shadowing the signal. Read more here: TV Aerial Installation Wigan.
- If there is heavy foliage that could cast a shadow on your antenna from the direction of the tower, subtract 10 dBs
- If the adjacent house is in the direction of the tower and casts a shadow on the antenna subtract another 20.
If you are left with about 12 dB or more after subtracting loss estimates, you should have enough of a signal to watch OTA TV. If you are below 12db try and find a higher area to mount the antenna. This may be an upper floor, or even the attic. You may want to consider the roof if possible. You can rerun the TV Fool report from a new height to test if it improves the signal.
If there is enough noise margin on the weakest signal, the next consideration is the distance of the antenna from the tower. An important variable when considering the distance is whether the signal frequency is VHF vs UHF. Commercial antennas typically indicate the range at which they can capture a signal. It is a bit misleading as they usually specify the distance for Ultra High Frequency (UHF).
UHF frequency runs at a higher frequency than VHF or “Very High Frequency”. Truth be told, there is little an indoor commercial antenna will do to pick up VHF that can’t be done with just a pair of rabbit ears.
Typically your VHF channels should be within 15 miles, and your UHF should be within 30 miles for an indoor solution to work. This is extremely dependent on how much loss the signal takes before reaching your antenna. I have seen indoor antennas work over 50 miles from the broadcast tower.
The last concept we need to consider is direction. We may or may not need this information depending on the antenna type, but it’s important to know in the event we need to troubleshoot the signal.
To figure this out refer to the channel table report once more. Now we are looking under the “Azimuth” header. Find the number under magnetic (Magn). Note the number next to each.
It’s also handy to circle the channels appearing on the bull’s-eye for ease of reference. Now we have everything we need to know about the signal. We can now cover the types of antennas available and their strengths and weaknesses.