Coax Cable Loss Calculator
Estimate RF attenuation, splitter loss, connector loss, retained power, delivered signal, and link margin for home lab and antenna coax runs.
| Cable type | 50 MHz | 150 MHz | 450 MHz | 1000 MHz | 2400 MHz |
|---|---|---|---|---|---|
| RG-6/U quad shield | 1.5 dB/100 ft | 2.4 dB/100 ft | 4.3 dB/100 ft | 6.6 dB/100 ft | 10.6 dB/100 ft |
| RG-11/U | 1.0 dB/100 ft | 1.6 dB/100 ft | 2.7 dB/100 ft | 4.2 dB/100 ft | 7.0 dB/100 ft |
| RG-58/U | 2.5 dB/100 ft | 4.5 dB/100 ft | 8.8 dB/100 ft | 14.5 dB/100 ft | 24.0 dB/100 ft |
| RG-8X mini | 1.7 dB/100 ft | 3.0 dB/100 ft | 5.8 dB/100 ft | 9.2 dB/100 ft | 15.0 dB/100 ft |
| LMR-240 | 1.1 dB/100 ft | 1.8 dB/100 ft | 3.6 dB/100 ft | 5.9 dB/100 ft | 9.8 dB/100 ft |
| LMR-400 | 0.6 dB/100 ft | 0.9 dB/100 ft | 1.5 dB/100 ft | 2.2 dB/100 ft | 3.8 dB/100 ft |
| Application | Typical frequency | Preferred impedance | Practical loss target |
|---|---|---|---|
| OTA TV high UHF | 470 to 608 MHz | 75 ohm | Under 6 dB before amplifier |
| DOCSIS downstream | 108 to 1218 MHz | 75 ohm | Keep splitters and barrels minimal |
| Satellite IF | 950 to 2150 MHz | 75 ohm | Use RG-6 or RG-11, avoid RG-59 |
| VHF ham 2 m | 144 to 148 MHz | 50 ohm | Under 3 dB is a strong goal |
| UHF ham 70 cm | 420 to 450 MHz | 50 ohm | Low-loss cable matters quickly |
| ADS-B receive | 1090 MHz | 50 ohm | Place preamp near antenna if needed |
| Passive part | Typical loss | Where it appears | Planning note |
|---|---|---|---|
| F connector pair | 0.1 to 0.3 dB | TV, modem, satellite | Compression fittings are more predictable |
| N or BNC adapter | 0.1 to 0.5 dB | RF lab, ham, SDR | Adapters stack up faster than expected |
| 2-way splitter | 3.5 dB | TV and cable modem | Half power plus internal loss |
| 4-way splitter | 7 dB | Home distribution | Often worse than one long clean run |
| 8-way splitter | 10.5 dB | Headend closet | May need designed amplification |
| Ground block | 0.1 to 0.3 dB | Service entrance | Still count both connector transitions |
| Project size | Example run | Primary risk | Good design move |
|---|---|---|---|
| Small SDR desk | 15 ft RG-58 at 150 MHz | Adapter clutter | Use one correct pigtail |
| Attic TV antenna | 75 ft RG-6 at 600 MHz | UHF attenuation | Avoid splitter before tuner |
| Roof ADS-B antenna | 50 ft LMR-400 at 1090 MHz | Receiver noise floor | Shorten run or add mast preamp |
| Ham base station | 100 ft LMR-400 at 450 MHz | Transmit power loss | Target less than 3 dB cable loss |
| Satellite dish | 125 ft RG-6 at 2150 MHz | High IF loss | Use solid copper RG-6 or RG-11 |
Coaxial cable loss is the name give to the fenomenon wherein the signal strength of a radio frequency signal weaken as it travels along coaxial cable. Coaxial cable loss occurs as a result of the energy of the radio frequency signal being convert to heat within the copper and plastic components of coaxial cable. Because coaxial cable loss diminishes an amount of signal that reaches the equipment that receives that signal, it is essential to understand the concept of coaxial cable loss.
Should the coaxial cable loss be too high for the signal that is traveling along coaxial cable, the tuner or radio receiver may not be able to properly process the signal. One of the main factor that contributes to the amount of loss that occurs along coaxial cables is the frequency of the radio frequency signal that is traveling along those coaxial cables. Coaxial cable loss increase as the frequency of the signal decreases; high frequencies suffer from more greater loss than low frequencies.
Why Coaxial Cables Lose Signal and How to Measure the Loss
This is due to the fact that high frequency radio waves travel along the outer edge of the center conductor of the coaxial cable, causing those high frequencies to interact with dielectric insulation of that coaxial cable. The friction that result from these interactions causes the signal to lose energy. Thus, a coaxial cable may have very low loss at low frequencies, but experience high loss at high frequencies.
It is essential, therefore, to calculate coaxial cable loss at the highest frequency that the system will be use. Connectors along coaxial cable systems can contribute to the total loss of the signal that is traveling along the coaxial cable. Coaxial cables dont comprise of a single section, but instead include many connector and adapter sections.
Each of these connectors (F-connectors, barrel adapters, ground blocks, etc.) will allow for the signal to weaken within the system. The signal loss cause by each individual connector may be small, but signal loss from many connectors can become significant. Thus, in the calculation of the total coaxial cable loss, you should account for the loss caused by each of these connectors.
Splitters along a radio frequency signal system will also cause signal loss. Signal loss at splitters is cause by the fact that the signal is divide, and dividing a signal causes loss of approximately 3 dB of signal strength. This is in addition to the loss of signal strength caused by the internal hardware of the splitter, suggesting that total signal loss at splitters is between 3.5 dB and 4 dB.
If multiple splitters are connect in series (a process known as daisy-chaining), the signal loss continues to increase. Because signal loss at splitters is so high, amplifiers are often necessary to ensure that the signal remains strong along the system if many splitters are use. The length of the coaxial cable that is used in the signal system is another factor that determine the total loss of signal strength along the coaxial cable.
The longer the coaxial cable, the more higher the signal loss along that coaxial cable. The length of the coaxial cable that you should measure is not just the distance between the two location of the radio frequency signal system, but also any additional length that is require for the coaxial cable to go around corners, or go through walls. Additionally, any length of coaxial cable required for a service loop should be accounted for in the length of the coaxial cable calculation.
It is often recommend to add 10 percent to the calculated length of the coaxial cable to allow for any additional length that may be require during installation of the coaxial cable system. The purpose of calculating coaxial cable loss is to ensure that the link margin created by the system is positive. The link margin of the system is the difference between the strength of the signal that is received by the equipment, and the strength of that signal that is require by that equipment to perform its function.
It is important that there is a healthy link margin created by the coaxial cable system, as this ensure that the system will continue to function correctly even if the strength of the signal within the coaxial cable diminishes due to age of the coaxial cable, changes in temperature, or other factor. Should the link margin be zero, the system may fail to perform its functions due to the environmental changes to the signal. Thus, by calculating the coaxial cable loss caused by each of the factors discussed above (frequency, connectors, splitters, length), the coaxial cable system can be ensured to create a link margin high enough to permit the system to function correctly.
