Cable and Frequency Inputs
Cable Loss Results
Cable Comparison at Selected Frequency
Compare all cable types at your selected frequency and length. Lower loss is better.
| Cable Type | Total Loss (dB) | Power Delivered | Loss Rating |
|---|
Cable Specifications Reference
| Cable | Impedance | Velocity Factor | Diameter | Max Freq | Typical Use |
|---|---|---|---|---|---|
| RG-6 | 75 ohm | 0.82 | 0.275 in | 3 GHz | TV, satellite, CATV |
| RG-8 | 50 ohm | 0.66 | 0.405 in | 1 GHz | Ham radio, HF/VHF |
| RG-8X | 50 ohm | 0.82 | 0.242 in | 1 GHz | Portable ham, short runs |
| RG-58 | 50 ohm | 0.66 | 0.195 in | 1 GHz | Mobile, CB, short runs |
| RG-59 | 75 ohm | 0.66 | 0.242 in | 1 GHz | Video, CCTV, analog |
| RG-174 | 50 ohm | 0.66 | 0.100 in | 1 GHz | Jumpers, very short runs |
| RG-213 | 50 ohm | 0.66 | 0.405 in | 1 GHz | Ham radio, marine |
| LMR-240 | 50 ohm | 0.84 | 0.240 in | 6 GHz | WiFi, cellular, VHF/UHF |
| LMR-400 | 50 ohm | 0.85 | 0.405 in | 6 GHz | Low loss, VHF/UHF/microwave |
| LMR-600 | 50 ohm | 0.87 | 0.590 in | 6 GHz | Ultra low loss, long runs |
| Belden 9913 | 50 ohm | 0.84 | 0.405 in | 2.3 GHz | Low loss ham, commercial |
Understanding Coaxial Cable Loss
What Causes Cable Loss?
Coaxial cable loss occurs due to two primary mechanisms:
- Conductor Loss (I²R loss): Resistance in the center conductor and shield causes power to be converted to heat. This loss increases with the square root of frequency.
- Dielectric Loss: The insulating material between the conductors absorbs some RF energy. This loss increases linearly with frequency.
Higher frequencies always result in more loss, which is why VHF and UHF installations require special attention to cable quality and length.
How to Minimize Cable Loss
- Use larger diameter cable: LMR-400 or RG-8 have much lower loss than RG-58 or RG-174
- Keep cable runs short: Loss is proportional to length, so minimize the distance from transmitter to antenna
- Choose low-loss cable for VHF/UHF: At higher frequencies, the difference between cable types becomes dramatic
- Avoid sharp bends: Kinking or bending cable too tightly can increase loss and damage the shield
- Check connectors: Poor quality or corroded connectors can add significant loss
- Match impedance: Use 50-ohm cable for 50-ohm systems and 75-ohm for 75-ohm systems
When to Use Each Cable Type
RG-6, RG-59: 75-ohm cables for TV, satellite, CATV, video distribution. RG-6 is preferred for modern digital systems.
RG-58: Thin 50-ohm cable suitable for short runs, mobile installations, CB radio. High loss at VHF/UHF limits usefulness.
RG-8, RG-213: Standard 50-ohm ham radio cable. Good for HF, acceptable for VHF. Heavy and stiff but durable.
RG-8X: Flexible mini-8 cable, easier to route than RG-8 but with higher loss. Good compromise for portable and short runs.
LMR-240: Low-loss cable similar in size to RG-8X. Excellent for VHF/UHF, WiFi, and cellular applications where space is limited.
LMR-400: Very low loss cable, the gold standard for VHF/UHF and microwave. Same diameter as RG-8 but significantly better performance.
LMR-600: Ultra low loss for long runs or when every dB counts. Large and expensive but unmatched performance.
Belden 9913: Popular low-loss alternative to LMR-400, widely used in ham radio. Slightly more flexible than LMR-400.
Power Loss Impact
Understanding dB loss in terms of power:
- 1 dB: 20% power lost, 80% delivered (excellent)
- 3 dB: 50% power lost, 50% delivered (half your power)
- 6 dB: 75% power lost, 25% delivered (one S-unit lost)
- 10 dB: 90% power lost, 10% delivered (very poor)
For transmitting, aim to keep total feed line loss under 1 dB if possible, and definitely under 3 dB. Remember that losses are the same for receiving, so cable loss reduces your ability to hear weak signals as well.
Frequently Asked Questions
How is coax cable loss calculated?
Coax cable loss follows the formula: Loss(dB) = k1 * sqrt(f) + k2 * f, multiplied by cable length per 100 feet. The k1 term represents conductor loss (increases with square root of frequency) and k2 represents dielectric loss (increases linearly with frequency). Each cable type has different k1 and k2 values.
Which coax cable has the lowest loss?
Among common cables, LMR-400 and Belden 9913 have very low loss. For example, at 146 MHz, LMR-400 loses about 1.5 dB per 100 feet, while RG-58 loses about 4.9 dB per 100 feet. Larger diameter cables generally have lower loss because the center conductor is bigger.
What is an acceptable cable loss?
For amateur radio, total feed line loss under 1 dB is excellent, 1-3 dB is acceptable, and over 3 dB means you are losing more than half your power. At VHF/UHF frequencies, cable loss increases significantly, so shorter runs of low-loss cable are essential.
Does coax cable loss change with frequency?
Yes. Cable loss increases with frequency. The same cable that has 1 dB loss at 10 MHz might have 5 dB loss at 450 MHz. This is why VHF/UHF installations require higher quality, lower loss cable than HF installations.
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Coax Cable Loss Calculator FAQ
How is coax cable loss calculated?
Coax cable loss follows the formula: Loss(dB) = k1 * sqrt(f) + k2 * f, multiplied by cable length per 100 feet. The k1 term represents conductor loss (increases with square root of frequency) and k2 represents dielectric loss (increases linearly with frequency). Each cable type has different k1 and k2 values.
Which coax cable has the lowest loss?
Among common cables, LMR-400 and Belden 9913 have very low loss. For example, at 146 MHz, LMR-400 loses about 1.5 dB per 100 feet, while RG-58 loses about 4.9 dB per 100 feet. Larger diameter cables generally have lower loss because the center conductor is bigger.
What is an acceptable cable loss?
For amateur radio, total feed line loss under 1 dB is excellent, 1-3 dB is acceptable, and over 3 dB means you are losing more than half your power. At VHF/UHF frequencies, cable loss increases significantly, so shorter runs of low-loss cable are essential.
Does coax cable loss change with frequency?
Yes. Cable loss increases with frequency. The same cable that has 1 dB loss at 10 MHz might have 5 dB loss at 450 MHz. This is why VHF/UHF installations require higher quality, lower loss cable than HF installations.