Two Way Radio Antenna Cable
RG (Radio Guide) is a military term. The RG series was originally used to specify the types of coax cables for military use. The presence of the letter U supposedly indicated it was for multiple uses. All current RG specifications are based on this obsolete military designation and the current specifications are very loose. You can just about give a coat hanger stuffed in a hot dog an RG designation today.
- Attenuation of Coaxial Transmission Line
Attenuation is the reduction in the strength of a signal. Attenuation of RF cable refers to signal loss. The coaxial cable is used to transfer power between the radio and antenna, in one direction, at any given time. Due to limitations of the cable, some power is lost along the length of the RF cable, known as attenuation.
Attenuation is defined in terms of decibels per unit length, and at a given frequency and 100 ft length is a common reference for comparison since the longer the cable the more attenuation occurs.
Contents
Attenuation Charts
Common Cable Attenuation Chart
| Table of data for common coax cable types | ||||||
|---|---|---|---|---|---|---|
| Coax Type | Characteristic impedance |
Outside diameter |
Velocity factor |
Atten @ 100 MHz |
Atten @ 1000 MHz |
Comments |
| RG5/U | 52.5 | 8.4 | 0.66 | 1.0 | 3.8 | |
| RG9/U | 51.0 | 10.7 | 0.66 | 0.66 | 2.4 | |
| RG10A/U | 50 | 12.1 | 0.66 | 0.66 | 2.6 | |
| RG20A/U | 50 | 30.4 | 0.66 | 0.22 | 1.2 | |
| RG58C/U | 50 | 5.0 | 0.66 | 1.8 | 7.6 | |
| RG119 | 50 | 11.8 | 0.5 | 1.8 | ||
| RG120 | 50 | 13.3 | 0.5 | 1.8 | ||
| RG122 | 50 | 4.1 | 1.7 | 5.5 | ||
| RG213/U | 50 | 10.3 | 0.66 | 0.62 | 2.6 | Polythene dielectric |
| RG214/U | 50 | 10.8 | 0.66 | 0.76 | 2.9 | Double screened, silver plated copper wire |
| RG223/U | 50 | 5.5 | 0.66 | 1.58 | 5.4 | |
| UR43 | 50 | 5 | 0.66 | 1.3 | 4.46 | |
| UR67 | 50 | 10.3 | 0.66 | 0.66 | 2.52 | Similar to RG213/U |
| UR74 | 51 | 22.1 | 0.66 | 0.33 | 1.4 | |
| UR76 | 51 | 5 | 0.66 | 1.7 | 7.3 | Similar to RG58C/U |
| UR79 | 50 | 21.7 | 0.96 | 0.17 | 0.6 | |
VHF / UHF / GHz Attenuation Chart
- dB loss per 100 ft
| Cable Type | 144 MHz | 220 MHz | 450 MHz | 915 MHz | 1.2 GHz | 2.4 GHz | 5.8 GHz |
| RG-58 |
6.2 |
7.4 |
10.6 |
16.5 |
21.1 |
32.2 |
51.6 |
| RG-8X |
4.7 |
6.0 |
8.6 |
12.8 |
15.9 |
23.1 |
40.9 |
| LMR-240 |
3.0 |
3.7 |
5.3 |
7.6 |
9.2 |
12.9 |
20.4 |
| RG-213/214 |
2.8 |
3.5 |
5.2 |
8.0 |
10.1 |
15.2 |
28.6 |
| 9913 |
1.6 |
1.9 |
2.8 |
4.2 |
5.2 |
7.7 |
13.8 |
| LMR-400 |
1.5 |
1.8 |
2.7 |
3.9 |
4.8 |
6.8 |
10.8 |
| 3/8" LDF |
1.3 |
1.6 |
2.3 |
3.4 |
4.2 |
5.9 |
8.1 |
| LMR-600 |
0.96 |
1.2 |
1.7 |
2.5 |
3.1 |
4.4 |
7.3 |
| 1/2" LDF |
0.85 |
1.1 |
1.5 |
2.2 |
2.7 |
3.9 |
6.6 |
| 7/8" LDF |
0.46 |
0.56 |
0.83 |
1.2 |
1.5 |
2.3 |
3.8 |
| 1 1/4" LDF |
0.34 |
0.42 |
0.62 |
0.91 |
1.1 |
1.7 |
2.8 |
| 1 5/8" LDF |
0.28 |
0.35 |
0.52 |
0.77 |
0.96 |
1.4 |
2.5 |
RG-58
Used for low power signal and RF connections. The cable has a characteristic impedance of either 50Ω or 52Ω. RG-58 CB coaxial is an affordable choice for basic CB installations. RG-58 (CB cable) has a high loss factor in VHF and UHF frequencies, so it really only is useful in runs less than 50 feet for frequencies above 100 MHz, and 20 feet for frequencies above 400 MHz.
Commonly used for Citizens Band radio.
RG-8/U
This cable is suitable for 50-75 foot runs in the VHF/UHF range. The cable is considered by some to be obsolete. The cable has a characteristic impedance of 50Ω.
RG8x is 50 Ohm cable that is about the same physical size as RG6. It is fairly high loss however and is not that well suited for 70cm except in short runs, however, is suitable for longer runs in the VHF 2m band. RG8 (RG213) is larger 50 Ohm cable that has less loss than RG8X.
RG-213
- thick, 50Ω, low loss
Considered to be a replacement to RG-8 and much better suited for both VHF and UHF operation. The cable has a characteristic impedance of 50Ω. The specifications for RG-213 are tight as compared to RG-8, increasing the consistency from one manufacturer to the next. RG213 is low loss cable with a non-contaminating jacket.
UR-67
LMR-400
There are different forms of Times Microwave LMR400. Standard LMR400 has a copper covered solid aluminum center conductor. LMR400/UF has a stranded copper center conductor, designed to replace Belden 9913. Standard LMR 400 Coax will have .7 dB loss at 30 MHz, with a length of 100 Feet.
Belden 9913
His similar attenuation characteristics to LMR-400. People tend to prefer LMR-400 as a replacement for Belden 9913. Some reasons include that Belden 9913 has a solid center conductor making it less flexible and Belden 9913 is more moisture prone. The 9913 dielectric is somewhat more fragile than the cellular polyethylene LMR400 dielectric, however, Belden 9913F also has a polyethylene foam dielectric.
- .405" diameter with a #10AWG center conductor
