Tutorial

Here is short Tutorial with video materials about how to increase range of toy-grade quadcopter as is for example Bayangtoys X8. It is not limited to his particular quadcopter, but may be applied to any other quadcopter as well. Plus, there is way to install buzzer – which may serve mainly two purposes: LVC (Low Voltage Controll), which sounds alarm when battery on quadcopter is low, and second – maybe most important thing, buzzer helps you to find lost quadcopter.

I think this one is better than old ‘cloverleaf’ antenna.

The case

Someone who followed this tutorial, and increased range of the drone:

But, then it happened

Nikola said: “After removing too heavy cover of the quad-copter, my flight was very long, but little bit unstable (without cover). But, there is no way back, just rising drone up to prevent treetops and begins to fly back, but then it happened:
Too small to be visible, just distant sound – but no more drone in sight. Trying to keep it in air for some time, but end result is… well, lost drone. Got to suspected crash location, wander for a while, but no much luck. Now, I know that I need buzzer… or perhaps GPS tracker.”

The other story, my personal

My first record was 550 meters, second one 800, and third one is 1100 meters. Or click to video below to watch whole video, or chose navigation times to watch exactly part you want. Don’t forget to share, comment, rate and subscribe to my YouTube channel if you found it useful. Thanks.

Navigation through this long video tutorial:
00:00 Antenna modification on remote
14:08 Antenna modification on drone
26:02 Installing buzzer for lost drone and battery alarm
37:31 Flying with modified antennas

Picture below showing how it looks when installed. If you click on the picture, you will get magnification. It opens in new tab.

On the transmitter (Remote), it looks different. While on receiver it is good to receive signal from every dirrection, on transmitter it is good to have somewhat directed signal:

Note that according to math, center frequency of 2450 MHz (on 2.4 GHz band), Lambda is: 300/2450= 0.12245 m, or 122.45 mm. And then 1/4 lambda (1/4 wavelength) is then 122.45/4= 30.6 mm, but this working only for ultra-thin wire. As long as you have thicker wire, there is some so called “Shortening Factor“, similar to “Velocity Factor“. I am opened few WiFi antennas, and found that for this type of wires, it is about 29 mm, and “Sleeve” part, which serve as BALUN (Balanced-Unbalanced) is 26.4 mm (let’s round it to 26 mm).

This part serves important role in balancing RF signal from unbalanced (not “symmetric”) signal from coaxial cable into balanced 1/2 lambda dipole (very “symmetric”). All residual unbalanced RF signal goes over this 1/4 lambda sleeve and back over it to initial point, but now in proper phase so that bottom part of the dipole getting maximum possible signal.

Recommended coaxial cables for this antenna are: RG316 or thinner “cousin”: RG178. Thicker is better (less attenuation), but also this cable is heavier and can’t be bent easily if needed. My recommendation to use RG316 if possible. Both cables has PTFE (Teflon) insulation inside, which works great on high frequencies. Also, PTFE is heat resistant, so it is not easy to burn center of this cable by soldering iron. Only trouble is that this cable is though, not easy to cut, which is actually good in external application as is this antenna, but pain in the… to cut and manipulate. Yet, it is worth to mess with it, because it is very durable.

The reason why this antenna extending that far from the body of the Quadcopter is two fold: First and mostly important is put dipole as far as possible from noise sources (microcontroller, switching MOSFETs, motors), and second is odd multiplication of 1/4 lambda. Thus, maximum signal is feed to antenna with minimum SWR (Standing Wave Ratio). For both coaxial cables mentioned above, VF (Velocity Factor) is 0.7 or 70% of speed of light. This means that 1/4 lambda is 30.6 mm * 0.7 = 21.42 mm. This is first “odd multiplication”, or 1/4 * 1. Second one is 1/4  lambda * 3, where 21.42  * 3 = 64.26, or roughly 64 mm. Antenna is made from piece of coaxial cable 64 mm (3 * 1/4 lambda) + 29 mm (1/4 lambda dipole element).  Note that on opposite end of the dipole, you should to make cable so that can be soldered to the receiver board inside Quadcopter. Since you need about 5 mm for that, and then velocity factor and shortening factors changed slightly,  lets do it from 66+29= 95 mm. Cut coaxial cable exactly that long, then stripe insulation from 29 mm from one end, and 5 mm from another. Sleeve part may be done by removing braided wire and soldering 26 mm piece of braided wire from the same piece of coax, or from another one. Or, you may do it as is shown on following video:

Before complete whole tutorial, here is video of my record in range flight: 1100 meters with Bayangtoys X8 quadcopter, which had maximum range of 50-80 maybe maximum 100 meters. So, this is incresing range by tenfold!

For long ragne quadcopters, you need some FPV goggles.

Note that this video is on my second YouTube channel, completely dedicated for video and photo recordings from above, or aerial photo and video. You may subscrive on this channel too if you wish to enjoy my aerial videos. Thanks.

Compadre, did you forgot buzzer? Yes gringo, yes… I forgot it. But in the meanwhile, please take look at this beautiful nature from the above (thanks to extended range, I can fly very far):

Tutorial about installing buzzer

The buzzer is relatively easy to install. Sorry for hand drawing, I have no brain currently to search for some schematic program that can draw it nicely.

 

Note that I am using white LEDs, which has different properties than stock green and red LEDs. I found that for my setup, 27 kOhm is okay, but someone from RCGroups reported that in order to work properly, resistor should be down to 900 Ohms, or less. Please check it experimentally. This buzzer can save your lost quadcopter, and can indicate low battery, also known as LVC (Low Voltage Cutoff).

Note that it works only when LEDs are off, and it is silent while LEDs are on and glowing. If some quadcopter has button on remote that allow to switch off LEDs as is JJRC1000, then it can be done differently.:

On this quadcopter, if LEDs are off, buzzer is off as well, but when LVC begins to blink LEDs, buzzer also sounds with intermittent sound. Since, there is 5V voltage booster , no need for any additional electronic, just connect 5V buzzer +ve (positive) to cathode of the boost converter, and -ve (negative) wire of the buzzer to the MOSFET as is shown on this video.