Signal loss in RF cable - what is the numbers?

When using Coax cable, the signal loss of the cable, and also the cable connectors needs to be taken into consideration, how long can I run a Coax cable from an access point to an antenna before I loss signal strength. As all cables will give some signal loss it\'s important to be able to calculate the losses and therefore know how this will affect the signal strength.

Which cable should I use ?
The distance that you need to run the Coax will be the main factor in deciding the cable to use, for short runs LMR/HDF 200 will be adequate but for longer runs then LMR/HDF 400 should be used. If we have a look at the specifications of the 2 cables :-

Losses in cable for 2.4Ghz Frequency.


HDF 200


Attenuation dB/M



Bend Radius



Overall Diameter



In the table above the attenuation is the amount of signal that will be lost through the cable, if we consider that for every 3dB the signal halves (as the decibel is a logarithmic unit – see here for more reading - ), with HDF 200 a run of 5M will half the signal strength, with HDF400 we can run 13M before the signal strength halves. This is why it's important to use HDF400 for longer runs.

Other factors that need to be considered are the size of the cable, and the bend radius, both factors make it easier to work with the thinner HDF200. Each connector that is added will also add some losses to the cable typically a N-type connector will add a cable loss of around 0.15dB at 5Ghz frequency.
For outdoor bridging and point to Multipoint networks keeping the cable lengths as short as possible is important, and using a dedicated bridge with a built in antennas will remove any losses at all.

Cable losses can be allowed for by increasing the transmit power of the radio, however the losses on the receiving antenna cannot be allowed for.

If you're unsure about the correct cable to use, than please contact us and we will be happy to discuss the available options with you.