Signal Attenuation (Insertion Loss)
What is Attenuation (Insertion Loss)?
Attenuation, also known as insertion loss, occurs when a cable's signal strength weakens as it travels to the receiving end of the cable.
Attenuation or insertion loss measures energy lost in decibels.
What Causes Attenuation (Insertion Loss) in a Cable?
- Attenuation can be caused by the effects of the resistance of the cable.
- Other nearby cables can also introduce noise which can cause signal attenuation.
How to Reduce Signal Attenuation (Insertion Loss)
- Using a shorter cable is an effective way to reduce attenuation or insertion loss.
- Using solid wire, instead of stranded wire can also reduce attenuation.
- Use a larger diameter wire to reduce attenuation. For instance, a 12 gauge wire will have less attenuation than a smaller 8 gauge size of the same wire.
- Transmitting data at slower frequencies will also reduce attenuation.
Attenuation vs Frequency
As the frequency of transmission increases, attenuation or insertion loss also increases. The following chart demonstrates how changes in frequency
affect attenuation for the same cable type.
Attenuation (Insertion Loss) by Frequency Chart
(dB/100 meters)
Frequency
(MHz) |
Thick
Coax |
Thin
Coax |
Cat 3
UTP |
Cat 4
UTP |
Cat 5e
UTP |
Cat 6
UTP |
| 1 |
0.62 |
1.41 |
2.60 |
2.20 |
2.00 |
2.00 |
| 10 |
1.70 |
4.26 |
9.70 |
6.90 |
6.50 |
6.00 |
| 20 |
--- |
6.00 |
--- |
10.00 |
9.30 |
8.50 |
| 50 |
3.94 |
9.54 |
--- |
--- |
--- |
--- |
| 100 |
--- |
13.70 |
--- |
--- |
22.00 |
19.80 |
Freq
(MHz) |
1 |
10 |
20 |
50 |
100 |
Thick
Coax |
0.62 |
1.70 |
--- |
3.94 |
--- |
Thin
Coax |
1.41 |
4.26 |
6.00 |
9.54 |
13.70 |
Cat 3
UTP |
2.60 |
9.70 |
--- |
--- |
--- |
Cat 4
UTP |
2.20 |
6.90 |
10.00 |
--- |
--- |
Cat 5e
UTP |
2.00 |
6.50 |
9.30 |
--- |
22.00 |
Cat 6
UTP |
2.00 |
6.00 |
8.50 |
--- |
19.80 |
Note: UTP figures are based on TIA/EIA requirements for horizontal cable.
How to Measure Attenuation (Insertion Loss)
Attenuation or Insertion Loss can be calculated by measuring either the change in Voltage or the change in Power over the length of the cable.
Standards and specification sheets typically report attenuation or insertion loss numbers for a cable of 100m in length.
Power Method for Calculating Attenuation (Insertion Loss)
To calculate attenuation using power, use a meter to measure the signal power at the transmitting end of a 100m cable (PIN) and then measure the
signal power at the receiving end of the cable (POUT).
Use the following Attenuation Formula to calculate power attenuation or insertion loss.
Power Attenuation or Insertion Loss Formula
AP (dB/100m) = 10log10(PIN/POUT)
Voltage Method for Calculating Attenuation (Insertion Loss)
To calculate attenuation using voltage, use a meter to measure the signal voltage at the transmitting end of a 100m cable (VIN) and then measure the
signal voltage at the receiving end of the cable (VOUT).
Use the following Attenuation Formula to calculate voltage attenuation or insertion loss.
Voltage Attenuation or Insertion Loss Formula
AV (dB/100m) = 10log10(VIN/VOUT)
Browse Our Cables, Accessories, and Tools
Other Helpful Cable Reference Guides:
Warning: When using this information to perform electrical work, call a licensed electrician and consult the NEC® for safety.
All licensed electricians have passed examinations covering the National Electric Code®, know state and
local building codes, and may carry insurance to cover damages.