Attenuation versus
Frequency

Attenuation versus frequency for some coaxial cables
The graph sheet shows the attenuation of 100 m cable in various cable types with frequencies up to 5 GHz.

Cable loss is an unavoidable factor that one should consider when choosing cable. In the above left corner of the graph you will find a conversion table from dB/100m to both Neper/km and dB/100 ft. This conversion is necessary if the attenuation demands have not been stated in dB/100m.

Cable types stretch from RG 174/U-LL-PROCOM, the thinnest and most flexible cable, to CELLFLEX LCF ½” which is a strong and rigid cable.

Large drawing: Attenuation vs. Frequency

Type of cable is chosen among others on the basis of the following:

• Which frequency it is going to be used for (car radio, GSM-band, UMTS and so on)
• Which length is needed (5 m in a car, 50 m for a base station mast and so on)
• Where are the cables going to be mounted (car with min. space, yacht where weight has to be taken into consideration, base station mast with lots of space and so on)

It is important to use a low loss cable in the given frequency range, therefore the frequency range which is of interest is found on the x-axis first. All the cables, that are shown as curves within this range, can be used. If attenuation is needed the y-axis is of importance - here the attenuation, which fits the application, is found. Consequently you will know exactly which cable to choose.

Example 1:
If a 900 MHz mobile phone is to be installed in a car and a 5 m cable has to be used the graph will show that the cable RG 58A/U-XLL PROCOM has an attenuation of 29 dB per 100 m which corresponds to 1.45 dB on 5 metres. If the same 900 MHz mobile phone is installed with a RG 174/U-LL-PROCOM cable this type of cable will have an attenuation of 62 dB per 100 m corresponding to 3.1 dB on 5 metres.

Example 2:
If a cable has to be found on 50 MHz, it has to be 200 m and the power inserted is 100 W. The antenna at the other end of the cable needs 10 W. Max. attenuation is 10 dB on 200 m meaning max. 5 dB/100 m. After having looked at the table at 50 MHz and 5 dB/100 m you will see that the cables RG 213/U or RG 214/U can be used.