RadioLink F121 User manual

Radiolink Electronic Ltd
www.radiolink.com
F121
Mini Racing Drone
Altitude Hold by Inertial Navigation
User Manual
* Please be kindly noted that this manual will be updated regularly and please visit RadioLink
official website to download the latest version：www.radiolink.com
V 1.0

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Thank you for purchasing RadioLink mini racing drone F121.
To fully enjoy the benefits of this product and ensure safety, please read the manual carefully and set up the device
as instructed steps.
If any problems found during the operation process, either way listed below can be used as online technical
support.
1. Send mails to [e-mail] or [e-mail] and we will answer your
question at the earliest.
2. Send message to us on our Facebook page or leave comments on our YouTube page
3. If purchased from an approved dealer or distributor, you can contact them directly for support.
All manuals and firmwares are available on RadioLink official website www.radiolink.com and more tutorials are
uploaded. Or follow our Facebook and YouTube homepage to stay tuned with our latest news.
⚫Never operate models during adverse weather conditions. Poor visibility can cause disorientation and loss of
control of pilots model.
⚫Never use this product in a crowd or illegal areas.
⚫Always ensure the trim levers at 0 and battery properly charged before connecting the receiver.
⚫Always check all servos and their connections prior to each run.
⚫Stay at a certain distance from the aircraft during flight to avoid getting hurt by the components of high-speed
rotation (eg. Props, brushless motors)
⚫After landing off, make sure the aircraft is disarmed and props have stopped moving before getting close to touch
the aircraft.
⚫Always be sure about turning off the receiver/powering off the aircraft before the transmitter.
⚫Follow the instructions of props installation in case of dropping during flight.
⚫To ensure the best radio communication, please enjoy the flight at the space without interference such as high
voltage cable, communication base station or launching tower.
This product is not a toy and is NOT suitable for children under the age of 14. Adults should keep the product out of
the reach of children and exercise caution when operating this product in the presence of children. Water or moisture
may enter the transmitter inside through gaps in the antenna or joystick and cause model instability, even out of control.
If running in the wet weather(such as game) is inevitable, always use plastic bags or waterproof cloth to cover the
transmitter.
This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions:
This device may not cause harmful interference, and Prevents external wireless interference, including interference that
may cause undesired operation.
Any Changes or modifications not expressly approved by the party responsible for compliance could void the user's
authority to operate the equipment.
WARNING
SAFETY PRECAUTIONS

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CONTENT
Chapter 1 Features of F121................................................................................................................................1
Chapter 2 Before Flight.......................................................................................................................................1
2.1 Power Supply.........................................................................................................................................1
2.2 Remote Controller..................................................................................................................................1
2.3 F121 .....................................................................................................................................................2
2.4 Joysticks & Flight Movements ...............................................................................................................3
Chapter 3 Get Ready to Flight ..........................................................................................................................5
3.1 Motor Installation....................................................................................................................................5
3.2 Propellers Installation ............................................................................................................................5
3.3 Power On F121......................................................................................................................................7
3.4 Flight Note..............................................................................................................................................7
3.5 Setup Compatible Transmitters .............................................................................................................7
3.6 Binding...................................................................................................................................................9
3.7 Arm and Disarm F121............................................................................................................................9
Chapter 4 Flight at Different Flight Modes............................................................................. 错误!未定义书签。
4.1 At Altitude Mode: Rise/Descend ..........................................................................................................11
4.2 At Altitude Mode: Hover .......................................................................................................................11
4.3 At Altitude Mode: Forward/Backward/Right/Left ..................................................................................11
4.4 At Altitude Mode: Clockwise/Anticlockwise Rotation ...........................................................................11
4.5 At Stabilize Mode.................................................................................................................................11
4.6 Low Voltage Alarm...............................................................................................................................11
Chapter 5 Image Transmission of F121............................................................................................................11
Specification ....................................................................................................................................................13

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Chapter 1 Features of F121
As the mini racing drone that can fly at high speed at Altitude Hold Mode, F121 is very easy to master for drone
freshman. The inertial navigation system technology blending Kalman filtering, gyro, accelerometer and
barometer makes F121 possible to flight through narrow space with accuracy and hold altitude even it’s less
than one-meter height to the surface or at high speed. With three flight modes Alt-Hold at low speed, Alt-Hold at
high speed and Stabilize, beginners can flight stably at the first trial.
F121 is monitored by RadioLink mini racing drone flight controller CS360, which is different from other flight
controllers with PID needs to be set before use,will tune automatically. The software noise reduction technology
not only enables a more pleasant flight but also makes the motors more responsive and more efficient than
traditional 8520 coreless motors.It can be thrown and start to fly at any angle even under high-speed and
remains stable even facing with sudden airflow fluctuations such as during takeoff, under braking, or after
extended flying. Without compass locking, F121 always automatically modify angles during flight .
Chapter 2 Before Flight
2.1 Power Supply
Power for transmitter T8S: Make sure the transmitter is fully charged.
Power for F121: The voltage of 1S LiPo battery packed with F121 by default is not fully charged so the battery
needs to be charged with the charger CM120 before flight.
The LiPo battery charger CM120, specially designed for 1S LiPo battery, sharing the professional development
and high precision of CB86PLUS, ensures safer charging and battery life span.
Charging current can be set as 1A or 2Aby toggling the switch at the side of the charger.
Red LED indicates the battery is under charging and green LED indicates the battery is fully charged.
CM120 applies general USB connector, both computer and power bank for mobile phone can be used with
CM120.
Note Voltage output of power supply should be NO higher than 5V.
2.2 Remote Controller
The two joysticks of T8S correspond to the four basic channels respectively . The below example takes
RadioLink radio T8S Mode 2 (Throttle on the left stick) .
Left joystick
Make the F121 rise or descend by toggling the left stick vertically upward or downward and rotate clockwise or
anticlockwise by toggling the left stick to the left or right.
Right joystick
Make the F121 fly forward or backward by toggling the right stick vertically upward or downward and turn left or
right by toggling the right stick to the left or right.

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Note If it’s the transmitter from other brands used with RadioLink F121, make sure that the receiver should be
SBUS signal output supported. Once the receiver is installed on the mini drone, the phase of the throttle should
be reversed while the other three channels normal and the CH5 should be set with a 3-way switch.
2.3 F121
Assembled as building block makes the RC students exercise their DIY ability and free from lengthy mobile
games.Learning knowledge of science and technology when assembling, setting parameters and flight.
2.4 RC Joysticks & Flight Movements
A. Throttle: Upward/ Downward/Hover
Push the Throttle Stick (on the left) vertically upward and F121 will rise while if push the Throttle Stick (on the left)
vertically downward, then the F121 will descend.
If at Alt-Hold Mode, push the Throttle Stick vertically upward till the F121 flight at the preferred height , then toggle the
Throttle stick back the center position and release , the F121 will remain at this height.
Note Hovering is also called Altitude Hold, which can be only realized under the Alt-Hold Mode both either at low
speed or high speed. BUT NOT STABILIZE MODE.
65mm prop(CW)
8520 motor(CCW)
Prop protector
Motor
Protector
65mm prop
(CCW)
8520 motor
(CW)
Prop
protector
Motor
protector
65mm prop(CW)
8520 motor(CCW)
Prop protector
Motor protector
65mm prop(CCW)
8520 motor(CW)
Prop protector
Motor protector
Camera
Camera protector
CS360 flight controller
Fiber
Frame
Cable(receiver& flight controller)
Battery frame
R8SM receiver
PA1.7*8
Screws
F121 cover
* CW: Clockwise
* CCW: Counter Clockwise
ROLL
Make F121
turn left/right
PITCH
Make F121
forward/backward
THROTTLE
Make F121
rise/descend
YAW
Make F121
clockwise/anti
clockwise
MODE 2

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2.4 Joysticks & Flight Movements
A. Throttle: Rise/ Descend/Hover
Toggle the throttle stick (on the left) vertically upward and F121 will rise and vertically downward, then descend.
If at Alt-Hold Mode, toggle the throttle stick vertically upward till the F121 rises to the preferred height, then
toggle back to center position and release, the F121 will remain at this height.
Note Hovering is also called Altitude Hold, which can be only realized under the Alt-Hold Mode either at low
speed or high speed. BUT NOT STABILIZE MODE.
B. Yaw: Clockwise/Anticlockwise
Toggle the rudder stick (on the left) to the left and F121 will turn anticlockwise and to the right, then clockwise.
Rudder stick to the left , F121 rotates anticlockwise
1m
2m
Rise
Descend
Hover

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C. Pitch: Forward/Backward
Toggle the elevator stick (on the right) vertically upward and F121 will flight forward and vertically downward,
then backwards.
D. Roll: Right/Left
Toggle the sileron stick (on the right) to the left and F121 will turn left and to the right, then turn right.
Elevator stick upward, F121 moves forward
Elevator stick downward, F121 moves backward
Rudder stick to the right, F121 rotates clockwise
Aileron stick to left, F121 turns left

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Chapter 3 Get Ready to Flight
3.1 Motor Installation
To make the aircraft fly, motors usually rotate clockwise(CW)/counterclockwise(CCW) with the propellers. The
rotation direction of F121 motors can be identified by the cable colors. That is, red/blue means motor of
clockwise(CW) while black/white means that of counterclockwise(CCW). It is very important to make sure about the
rotation direction as below when installing motors. Otherwise, the drone would fail to take off.
3.2 Propellers Installation
F121 is installed with propellers protector by factory default. To ensure a safety flight, it’s strongly advised to
check if the protector are well installed .
(1) Find the two notches respectively on the motor protector and propeller protector.
Aileron stick to right, F121 turns right

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(2) Put on the propeller protector from the bottom and adjust the position of the notches correspondingly.
(3) Stabilize the frame with left hand and buckle the notch of one side with right hand. Then buckle the notch of
the other side with left hand. A“DA”sound will be heard if the installation is done with success.
Note After the installation of the four propeller protectors, double confirm if they are leaning or slightly shake
F121 to see if they drop. If they are crooked or drop, repeat the above steps to ensure the well installation.
If the default propellers get worn and needs to be replaced after a period of flight, it is important to well
identify the rotation direction of propellers. If installed incorrectly, F121 can’t take off even the throttle is pushed
to max.
In order to identify the propellers rotation, take a propeller and observe there’s a radian at both sides of the
small cylinder in the middle. The higher part (also called windward side) of the right propeller is at the front and
the rotating motor will make propeller rotate counterclockwise(CCW). On the contrary, that is clockwise(CW)
rotation. For the 65mm GEMFAN propellers used on F121, there are two marked with a letter R, meaning they
should be installed on the motors of clockwise.
When the installation is done, make sure the four motors are vertical to the aircraft frame. Adjust them to
vertical positions if necessary, otherwise F121 may not flight successfully.

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3.3 Power On F121
Before powering on F121, fully charge the 1S LiPo battery first. Plug the PH2.0 end of the battery into the F121,
then insert the battery into the battery frame under at the bottom of F121..
(1) Put F121 on a level surface and do not move it when the green LED is flashing. NEVER power on F121 by
putting on hand as it’s not leveled.
(2) Orange propellers indicates the head of F121 by default. make sure they point to the same direction as the
pilot when powering on and be ready to fly, to ensure safety.
(3) The green LED of F121 will begin flashing when powered on. When it’s off, it means F121 finishes
calibration.
Note Head direction is determinate. If F121 is calibrated with the direction different from the default, it will turn
back to the default direction automatically when starts flying, That’s what we called Head Front Forward Point
Without Compass.
3.4 Flight Note
If it’s the first time of flying drone, flight mode of Altitude Mode-Low Speed is strongly advised to set. At the
altitude mode, when toggle the throttle upward till the drone reaches a certain height and release, F121 will
remain at this height. It’s simpler because pilots only need to toggle the other joystick to make the F121 move
forward/backward or turn left/right. If it’s the Stabilize Mode chosen, try to toggle the joysticks slightly to correct
the flight and avoid the drone having sudden moves.
If F121 drops by hitting something, toggle the throttle joystick to the bottom position immediately to stop motor
rotation.
Make sure the signal output of receiver is SBUS to ensure normal operation of F121. For RadioLink
receivers(R8SM/R6DSM) installed on F121, the led indicator is blue/purple when it’s SBUS working mode.
3.5 Setup compatible Transmitters
F121 is compatible with all RadioLink transmitters AT10/AT10II/AT9/AT9S/AT9S Pro/T8FB/T8S and transmitters
of other brands that support SBUS output.
There are two different receivers optional by factory default, R6DSM or R8SM. R6DSM is compatible with
RadioLink AT10/AT10II/AT9/AT9S/AT9S Pro while R8SM is compatible with RadioLink T8FB/T8S.
T8FB/T8S
RadioLink 8-channel transmitter are well set by factory default with the flight modes. To control F121, binding is
the only thing needs to be done.
There are three flight modes for F121 including Altitude Mode- Low Speed, Altitude Mode- High Speed and
Stabilize Mode. It can be changed by pressing the three-way switch on the right of T8FB- SWB or of T8S- CH5
as below
A
*Press forward is to the front side of T8S
Press backward is to the back side of T8S

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T9S Pro/AT9S/AT9/AT10/AT10II
①Enter BASIC MENU, select MODEL TYPE and choose MULTIROTOR
②Return to BASIC MENU, select REVERSE and set CH3 Throttle as REV .
③Enter ADVANCE MENU, select ATTITUDE and set the CHANNEL as CH5, SW3 as SWC with up
position as Alt-Hold Mode(Low Speed), middle position as Alt-Hold Mode(HIgh Speed) and low position as
Stabilize Mode.
Alt-Hold M.
(Low Speed)
Alt-Hold M.
(High Speed)
Stabilize M.
Alt-Hold M.
(Low Speed)
Alt-Hold M.
(High Speed)
Stabilize M.

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3.6 Binding
If it’s the RTF version( whole pack including T8S+F121+bag) purchased, there’s no need to bind because the
binding is complete by factory default. However, if it’s only the aircraft F121 is purchased, binding between the
transmitter and F121 needs to done first.
By default, F121 is equipped with receiver R8SM, which is compatible with Radiolink transmitter T8FB and T8S.
①Place the T8FB and F121 close to each other within 50 centimeters.
②Power on the T8FBand F121.
③There is a black binding button(ID SET) on the side of R8SM, press it for more than 1 second. When
the LED of R8SM starts flashing, meaning binding process has started.
④The binding is complete when the LED is always on.
⑤Make sure F121 is armed (Details in next section). Gently push the throttle of transmitter to see if
motors move. If doesn’t, retry binding again.
Note
⚫F121 currently supports SBUS signal output only, always make sure the LED of R8SM/R6DSM is
blue/purple, meaning SBUS signals output. If the LED is red, press the binding button twice in 1 second and
release to change it to purple/blue.
⚫If it’s the transmitter of AT9S Pro/AT9S/AT10/AT10II used, channel quantity needs to be set first in order to
be compatible with receiver R6DSM. Long press MODE to enter BASICE MENU, select SYSTEM and
modify CH-SELECT as 10CH. Otherwise, F121 won’t be able to be armed.
3.7 Arm and Disarm F121
A. How to arm
Throttle on left(Mode 2): Toggle the left joystick to the lower right corner and hold this position for 3 seconds till
the green LED of F121 is on.
Binding button of receiver
Always-on green led means F121 is
armed with success.

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Throttle on right(Mode 1): With right joystick at bottom, toggle the left stick to the right and hold this position for 3
seconds till the green LED of F121 is on.
B. How to disarm
When the flight is finished, always make sure F121 is disarmed when get close and try touching it to avoid
unexpected harm.
Throttle on left(Mode 2): Toggle the left joystick to the lower left corner and hold this position for 3 seconds till the
green LED of F121 is off.
Throttle on right(Mode 1): With right joystick at bottom, toggle the left stick to the left and hold this position for 3
seconds till the green LED of F121 is off.
Chapter 4 Flight at Different Flight Modes
It’s strongly advised for beginners to start from Altitude Hold Mode (Low-speed) to Altitude Hold Mode
(High-speed) then to Stabilize Mode.
It’s better to keep the direction of F121 head same as pilot in order to easily judge the flight direction. Otherwise,
F121 may flight towards pilot and get him/her hurt. If the aircraft head is changed unexpectedly and different
from pilot’s direction, pull the throttle stick to the lowest position to land F121.
Channel 4 to right
The green LED of F121 off means
it is disarmed with success.
Channel 4 to left

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4.1 At Altitude Mode: Rise/Descend
Press the CH5 switch of T8S backward, which makes F121 fly at Altitude Hold Mode (Low-speed). Make sure
the orange propellers at front when powering F121 on. Then arm F121 and push the throttle joystick vertically
upward higher than center position, then the F121 will rise while if push it vertically downward, then the F121 will
descend.
4.2 At Altitude Mode: Hover
Push the throttle joystick vertically upward till the F121 rises to a height as wish, then toggle it back to center
position and release , the F121 will hover at this height.
4.3 At Altitude Mode: Forward/Backward/Right/Left
At Altitude Mode, F121 is able to fly forward/backwards or towards to right/left by toggling the right stick at the
certain height .
For beginners, make sure to push the stick gently because being a racing drone, F121 is very responsive. It’s
advised to release the stick as soon as toggle to one direction so that F121 will back to level automatically.
Otherwise, F121 will keep flying to the toggled direction with accelerated speed.
4.4 At Altitude Mode: Clockwise/Anticlockwise Rotation
When get familiar with the above flights, try flight clockwise/anticlockwise because the yaw practice is more
difficult to judge the flight direction. Clearly knowing the direction will quickly help master drone flight. Try imagine
sitting on the drone could be a better way to practice.
Toggle the rudder joystick to the left and F121 will flight anticlockwise while if to the right, then the F121 will flight
clockwise.
4.5 At Stabilize Mode
Press the CH5 switch of T8S backward and it keeps F121 work in Stabilize Mode.
When at Stabilize Mode, F121 will flight faster than when at Altitude Mode. Toggle joysticks as gentle as possible
to avoid drastic movements, which may possibly hurt the pilot. Make sure that the battery is fully charged before
enjoying the flight.
4.6 Low Voltage Alarm
When the green LED on F121 starts flashing during flight, it means the voltage of F121 is lower than 3.7V as this
value is default for 1S battery. It’s advised to stop flying to avoid battery over discharging.
Chapter 5 Image Transmission of F121
The image transmission device of F121is 5.8G 200mW all-channel camera integrated image transmission. If it’s
the image transmission version purchased, the binding between F121 and the FPV screen has been done by
factory default. Pilots only need to power both on before flight. If it’s the standalone version of F121, an FPV
screen or a goggle with integrated 5.8G image transmission receiver is needed and setup by following its
instructions.
The default transmission power is 200MW. Available power among 25MW,100MW and 200MW can be changed
by pressing the button on the camera.

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Note As device of image transmission includes transmit and receive, the distance could be influenced by the
gain of transmit and receive.
Definition of the image transmission led indicator
①RED and BLUE(and YELLOW) always on means normal working status.
②If RED(and YELLOW) is always on while BLUE is off, meaning it’s at PitMode. That is, transmission off.
The transmission distance is 1-2m. It’s advised to choose this mode if there are many people switching channels
simultaneously at the same space so that channels won’t get mixed.
Customize the power and the channel frequency
After powering on, wait for 10 seconds to initialize, red and blue(and yellow) always on means normal working
status. Long press the channels/power switching button, the channel frequency, the channel team and the
transmit power will recycle.
Table of Band/Frequency
Frequency Selection: Long press the channels/power switching button for 5 seconds, the RED led flashes
once means entering the frequency selection mode. Then short press the button again, the frequency changes
each time the button is pressed once. The blue led flashes 1 time means Frequency 1, 2 times means
Frequency 2, 3/4/5/6/7/8 etc.
Band Selection: Long press the channels/power switching button for 5 seconds, the RED led flashes twice
means entering the band selection mode. Then short press the button again, the band changes each time the
button is pressed once. The blue led flashes 1 time means Band A, 2 times means Band B, C/D/E/F etc.
Power Selection: Long press the channels/power switching button for 5 seconds, the RED led flashes three
time means entering the power selection mode. Then short press the button again, the power changes each time
Band/Freq
1
2
3
4
5
6
7
8
A
5865M
5845M
5825M
5805M
5785M
5765M
5745M
5725M
B
5733M
5752M
5771M
5790M
5809M
5828M
5847M
5866M
C
5705M
5685M
5665M
5645M
5885M
5905M
5925M
5945M
D
5740M
5760M
5780M
5800M
5820M
5840M
5860M
5880M
E
5658M
5695M
5732M
5769M
5806M
5843M
5880M
5917M
F
5362M
5399M
5436M
5473M
5510M
5547M
5584M
5621M
Channels/Power Switching Button
*The cover of F121 needs to be removed when pressing the button

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the button is pressed once. The blue led flashes 1 time means 25mA, 2 times means 100mW and 3 times means
200mW.
Turn on/off the transmission: When at the normal working status(with red/blue led on), quickly press the
button twice and the working mode will change. When the red(yellow) led is on and blue led is off, it means it’s at
Pitmode(Low power mode). When red(and yellow)/blue leds are on, it means the normal transmission mode.
When all parameters set, long press the channels/power switching button, the red and blue leds always
on means setting saved, then normal working status. Otherwise, the setup mode remains and all the
parameters set above can’t be saved with success.
Note
①When installing the image transmission, make sure the heat radiation is considered. Otherwise, the
transmission power will decrease even turn off as the protection of over heating is activated.
②It’s normal that the camera will get heated during usage. DO NOT touch it directly with hands in case of
getting burnt.
③If the transmission antenna is broken or not well welded, the transmission distance will be impacted.
Replace the antenna as soon as possible.
④The detailed instructions of setting FPV screen and goggle, please refer to its corresponding manual.
⑤If there’s interference during the usage, try switching the camera channel first, then search for a new
channel on FPV screen or goggle.
Specification
Name: F121(Altitude Hold Micro Racing Drone）
Weight: 47.5g(Drone only)
Drone Size: 121*55mm(with antenna; 41mm without antenna）
Package Size: 170X210x113mm(RTF bag)；210x163x67mm(Standalone box）
Transmitter Frequency: 2.4G
Image Transmission Frequency: 5.8G
Material: Carbon Fiber(Frame), Plastic(Cover, Bases for Image transmission/battery, Prop protector)
Motor: 8520 coreless with software to reduce noise
Propeller: GEMFAN props with diameter of 65mm
Transmitter: RadioLink 8-channel handle transmitter T8S
Receiver: RadioLink 8-channel mini receiver R8SM
Flight Controller: RadioLink flight controller CS360
Battery: FULLYMAX 3.7V 660mA 25C LiPo Battery
Charger: USB Charger (1A/2A)
Flight Time: 10 minutes, suitable for Indoor and outdoor
Low Voltage Alarm: Green led flashes quickly when lower than 3.7V
Control Distance: 2KM in the air(Maximum range is tested in an unobstructed area free of interference)
Thank you again for choosing RadioLink products.