Antenna & Length Calculator

Choice and location of antenna can make all the difference in your installation.  XL Provide a range of standard antenna for most circumstances, however - should you need something out of the ordinary - please don’t hesitate to ask! Please remember to check the local regulations before installing any gain antenna.

Here is a brief summary of some of the antennas most commonly used for radio data modem installations along with hyperlinks to their data sheets. XL are always pleased to discuss your application and to offer advice on which antenna is the most suitable for your application.  Remember if you need range, you will need to sight the antenna as high as possible to get it into free space. Always check that you are complying to local regulations regarding transmission power.  If you require something not listed then please ask, it is more than likely that we can help you.

  • Standard 1/4 wave is suitable for direct connection to the radio modem for internal use and for the attachment to a waterproof housing for external use. 
  • 1/2 Wave Omnidirectional  (YA0103)
  • Folded dipole (KG-2208) - radiates down as well as outwards
  • Magnetic Mount (KG-MAG) can be supplied with a surface mounting
  • Omnidirectional Dipole (KG-2208) marine quality, this is unity gain and very rugged - ideal for most situations.
  • 3DB Collinear dipole (KG-2216) This will double the power of a 10W Epic - 
  • 6dBd Collinear dipole (KG-222) this would take a 10W signal and convert it to around 4W 
  • 869 Base Station antenna 6dBd (KG2223 or 5dBi (KG-2226)
  • Ground Plane independent antenna  (KG-058) ideal for vehicles with glass fibre roofs

Antenna Cables 

In order to place your antenna in the prime location i.e as high as possible and in free space, XL can provide low loss cable with suitable connectors to your specification.

This is a useful too to calculate loss incurred from long cable runs


Simple explanation of DBD V DBI

If you can imagine looking at an antenna from the side and ‘seeing’ the RF field that is generated it would look like the patterns shown below.

You can see the (Gain) difference in dBi verses dBd. Also you can see the pattern shape when using a Yagi and the gain in one direction.


Antenna Length Calculation

300 divided by the transmit frequency in Megahertz will give you the wave length at the transmit frequency.

Divide the wave length by four and you will arrive at a quarter wave antenna.

Get out your digital calculator!


300/458.5MHz = 0.654 Metres or 654mm /4 = 0.163 Metres or 163mm

Thus a ¼ wave whip at 458.5MHz is 163mm

Remember to measure the ACTUAL antenna minus any base it may have.


Rule of thub formula for calculating watts versus distance is that every 10dB adds 3 times more distance:

5mW     =     7 dBm  =  1,1km

50mW   =   17 dBm = 3,3km

500mW  = 27 dBm = 10km

This be effected when channel is clear and line of sight

© XL Systems 2019