Bad Ass FLARM dipole antenna

Home Youtube-Channel About Shop
dipole antenna 868mhz
In the winter of 2017/2018 I did a small project to improve the range of my FLARM. The result was that I built this new antenna for it as I identified the antenna being the biggest problem regarding better range. This is the result from changing the antenna:

Before with original 'toothpick' antenna: Flarm range before
After with new BA-dipole antenna: Flarm range after

The new antenna is a dipole antenna which have been tuned exactly for 868mhz. What makes it special is that it's etched on a PCB card and actually TUNED (not just theoretically dimensioned). This makes them very good and it easy to produce them with high precision/low cost. PLEASE note that I'm not the designer/tuner of this antenna, all info can be found at the lowpowerlab.com forum

The antenna cable is also an important part of the antenna system. It should be as short as possible to reduce losses but also be tuned to the frequency. The tuning is done by making sure the length from the antenna to the receiver is in even divisions of half wavelength, corrected for the cables velocity factor.

Example: 868mhz wavelength is 34,5cm, half 17,25cm. RG316 cable velocity factor is 0,7.
0,7x17,25=12cm.
So the cable (or feed line as it's called) should be either: 12,24,36,48 etc cm long. This is measured from the board edge to the tip of SMA connector.

Build it

First you need to order the antenna element. Download the board files and send it to your preferred producer: Download board files

The cable I order from a random seller on eBay. I order a 50cm cable with the same contacts(SMA male) in both ends. This way I just cut it in the middle and can use one 50cm cable for two antennas (24cm cable each).

Putting it togheter is very straight forward just soldering the centerpin of the cable to the marked solder pad on the antenna element. The shield of the cable is soldered to the other solder pad marked GND. Done. Please buy one from me to help support this site.

Installation in glider

Don't let anything touch the antenna element, all fixation is done by the cable/feedline. It's a dipole and should be mounted vertically. Also put the antenna as far away from any metal/carbon fiber as possible. Moving the Flarm transceiver and getting an external display is better than utilising a long antenna cable. This is how the installation looks in my Standard Cirrus (glasfiber fuselage). I've used zip ties and epoxy super glue to fixate it.
Flarm range after

Support me

I build and maintain this site to help you. I do it in my spare time and it's not free. I DON'T WANT ADVERTISEMENT on this site. Help me to help you:

Buy me a beer!

© 2018 Niklas Löfgren