Introduction

An ULRS user has achieved 40 km distance with telemetry, and says he was only limited by his plane’s autonomy. His setup is the following :

ULRS Modules

Normal Orange 1W modules without increased power (3.3V operation, about 400 mW power)

Antennas

RC

DIY 4 elements Yagi antenna on the ground – DIY Vee antenna on the plane What certainly contributed to the range is that the antennas are precisely tuned with professional equipment :

Video

For the video, he’s using well tuned vee antennas in the plane, and a patch antenna on the ground :

Where to find these antennas ?

Have a look at this site,you can also find them on ebay here.

If you want to go still farther

Antennas

Have a look at this 10 elements yagi. Or this 7 elements yagi Or this $75 12 elements 14 dBd (=16.15 dBi) yagi

Calculations

Given that the user did 40 km with a 4 elements yagi (something like 7.6 dBd = 9.75 dBi), using this last 12 elements yagi would provide a gain of 14-7.6=6.4 dB or more than double the distance (80 km).

In addition, running the RFM module at 5.5V would go from 400mW (26dBm) to minimum 800mW (29dBm), which gives 3 dB, or 40% more distance.

So it should go to 80 * 1.4 = 112 km. And given that the user said 40 km was not the system’s limit, but his plane limit, the maximum distance is still more…