ANTENNAS FOR A WORLD RECORD

by Circular Wireless. 0 Comments

Since Roberto Montiel presented in the forums its new Fascination (www.aeromodelismovirtual.com , www.rcgroups.com) I started mulling over an idea.

Considering that:

– In the 2011 63Km record he did not use the motor.
– With the solar panels installed on the Fascination, which in summer should be able to cover the electronics consumption on board, he has a virtually unlimited flight time (if the sun shines, of course).
– Using Yagis in the UHF transmitter RC link can easily exceed 100 km.
– In the video of his record of 2011 I noted that at 40 km he had video losses every time the plane banked to circle in a thermal, and video quality at 63Km was crap.

I concluded that the only thing limiting him to beat his own record was the video link, and I decided to contact him to explain my idea.

The configuration used for Roberto’s record of 63 Km with the Grafas was:

– Video Transmitter 1.3GHz, 1500mW.
– Standard dipole antenna in the video transmitter.

– 1.3GHz Video Receiver LawMate.
– Patch Antenna 14dB and vertical polarization in the video receiver.

Hence the possible areas for improvement were:

– Reducing the transmission power to 850MW, to reduce consumption on board.
– Change to circular polarization, to avoid losses when banking the plane as it approaches the range limits.
– Build a circularly polarized antenna for receiving with the highest possible gain, within practical limits (the size of my car …).

With this starting point we scheduled a day in Madrid to meet, see in detail his setup, and exchange ideas. It was a very nice meeting. As Roberto said when we first met: “What a pair of crazy guys!”

From there I started to work, I built a Skew Planar Wheel for the transmitter, and began to build the receiver antenna.

Obviously the first idea was “the bigger, the better,” so I bought a 100cm offset dish, along with a portable tripod, and built a feed with a 3.5-turn helical:

Subsequently I developed the helical now sold at Circular Wireless, 6.5 turns and 11.5 dBi gain, and Roberto is so happy about its performance that he hasn’t used the dish yet. I hope this summer he will keep increasing the range and end up using it!

With this configuration (SPW on the plane, transmitter 850MW, Helical of 11.5dBi on the receiver), Roberto has overcome his own record and set it to 71km, with a radically improved video quality:

2011: 63 KM, VERTICAL POLARIZATION, 1500mW

2012: 71 KM, CIRCULAR POLARIZATION, 850MW

I suspect that he will not stop here. He has actually invented a new discipline in model aircraft flying, as explained in the April issue of AEROTEC, which breaks with the classic limitations of radio controlled gliding: FPV Soaring.

Happy Flights!

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