Bad Ass FLARM dipole antenna
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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:
After with new BA-dipole antenna:
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's easy to produce them with high precision/low cost. 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
Simply order from here:
Antenna
Installation in glider
Equally important to which antenna to use is the installation. 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.
last update: 14 December 2020
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© 2018 Niklas Löfgren
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