# 3DR Radio Manual

The 3DR Radio (version 2) is the easiest way to setup a telemetry connection between your APM/Pixhawk and a ground station. This article provides a basic user guide for how to connect and configure your radio.

3DR Radio v2

Contents

 1 Overview

 2 Status LEDs

 3 Connecting the radios

o 3.1 Connecting to Pixhawk

o 3.2 Connecting to APM2.x

o 3.3 Connecting to a PC

o 3.4 Connecting to an Android tablet

 4 Configuring using the Mission Planner

 5 Expected range

o 5.1 Diagnosing range issues

 6 Improving the range

 7 Support for different countries/regions

 8 3DR Radio Discussion Forum 

# Overview

The 3DR Radio is the easiest way to setup a telemetry connection between your APM/Pixhawk and a ground station. It is small, light and i nexpensive, and typically allows ranges of better than 300m “out of the box” (the range can be extended to several kilometres with the use of a patch antenna on the ground). The radio uses open sour ce firmware which has been specially designedto work well with MAVLink packets and to be integrated with the Mission Planner, Copter,

Rover and Plane.

The radios can be either 915Mhz or 433Mhz and you should purchase the model which is appropriate for your country/region

.
The main features of the 3DR Radio are listed below (see the Advanced Config uration for more information):

 Very small size

 Light weight (under 4 grams without antenna)

 Available in 900MHz or 433MHz (v2 only) variants

 Receiver sensitivity to

- 121 dBm

 Transmit power up to 20dBm (100mW)

 Transparent serial link

 Air data rates up to 250kbps

 MAVLink protocol framing and status reporting

 Frequency hopping spread spectrum (FHSS)

 Adaptive time division multiplexing (TDM)

 Support for LBT and AFA

 Configurable duty cycle

 Built

- in error correcting code (can correct up to 25% data bit errors)

 Demonstrated range of several kilometres with a small omni antenna

 Can be used with a bi

- directional amplifier for even more range

 Open source firmware

 AT commands for radio configuration

 RT commands for remote radio configuration

 Adap tive flow control when used with APM

 Based on HM

- TRP radio modules, with Si1000 8051 micro

- controller and Si4432 radio module 

# Status LEDs

The 3DR Radios have 2 status LEDs, one red and one green. The meaning of the different LED states is:

 Green LED blinki ng

– searching for another radio

 Green LED solid

– link is established with another radio

 Red LED flashing

– transmitting data

 Red LED solid

– in firmware update mode 

# Connecting the radiosThe 3DR Radio v2 has interchangeable air and ground modules, meanin g that you use them as a

pair but it does not matter which one goes on the vehicle and which remains on the ground.

The radio has a micro

- USB port, and a DF13 six

- position port. The following sections explain how to connect these to flight controllers and ground stations.



## Connecting to Pixhawk

Use the 6 pin DF13 connector that should have come with the radio to connect the 3DR radio to your Pixhawk’s “Telem 1′′ (“Telem 2′′ or “Serial 4/5′′ can also be used but the default recommendation is “Telem1′′).

## Connecting to APM2.x

Use the 6

- to

- 5 pin DF13 co nnector to connect the 3DR radio to your APM2’s Telem port. Because of the limited number of seria l ports on the APM2.x, the telemetry radio cannot be used while the board is also plugged in with the micro USB port.



## Connecting to a PC

Connecting the 3DR radio to your Windows PC is as simple as connecting the micro USB cable (which should have been included with the radio) to your PC. The necessary drivers should be installed automatically and the radio will appear as a new “USB Serial Port” in the Windows Device Manager under Ports (COM & LPT ). The Mission Planner’s COM Port selection drop

down should also contain the same new COM port.To c onnect the radios:

 Select the new COM port, set the baud rate drop down (which appears between the COM port and Connect buttons) to 57600.

 Press the Connect button and if the two radios connect successfully you should be able to lean your vehicle left and right and see it’s attitude update on the MP’s Flight Data screen’s artificial horizon. 

## Connecting to an Android tablet

Connecting the 3DR radio to an Android tablet using the L shaped micro USB cable (which should have been included with the radio). Then follow the directions in your preferred Ground Station app

.



# Configuring using the Mission Planner

APM Mission Planner supports configuring your 3DR radios using a simple GU I interface.

Tip: Many users will not need to configure their radios! One case where you might do so is when you use your vehicle with others

— in which case you will need to specify different radio channels (Net ID).

To make changes:

 Connect one of the 3D R radios to your computer using the micro USB cable.

 Power the radio attached to the vehicle by plugging in the vehicle’s battery.

 Open the Mission Planner and go to the Initial Setup >> Optional Hardware >> 3DR Radio page.

 Select the correct COM port and set the baud rate to 57600. Ensure the “Connect” button is in a disconnected state as shown in the image below..

 Press the Load Settings button and both the Local and Remote areas should fill in with values including the firmware Version The most common entry to change is the Net ID . The default is 25 for all 3DR radios but

if you plan to fly in an area with other pilots who may be using the same radio it is best to change this to another number.

 After making changes, click the Copy Required Items to Remote and press Save Settings

Other parameters you may choose to update:

 Baud (default 57) : the rate at which the mission planner or vehicle communicates with the local radio. “57” = 57600 bits per s econd.

 Air Speed (default 64) : the rate at which the two radios will communicate with each other. “64” = 64kbps (kilobits per second). Setting a lower rate will increase the range of the radio but reduce the rate of data (i.e. the amount of data that can be sent in a given time) across the link.

 ECC (default is “on”): controls whether error correction is on or off. When on “12/24 Golay error correcting code” is used which involves sending a 16 bit CRC byte along with the data to ensure that bad data is thr own away. Unfortunately this also halves the data rate across the link but it is recommended to leave ECC on especially when when the vehicle is far from home base because transmission errors increase greatly with distance.

 MAVlink (default is “MAVLink”) : this controls whether the transmission is optimised for MAVLink packets or not. Set to “Low Latency” if using a joystick or an android tablet’s virtual joystick to manually fly the vehicle. Note that information on the radio signal strength (rssi) and err or rate is only sent if this parameter is set to it’s default, “MAVLink”.

 Tx Power (default 20) : the transmission power where 1=1.3milliWats, 2=1.5mW, 5=3.2mW, 8=6.3mW,11=12.5mW, 14=25mW, 17=50mW, 20=100mW. This should be set to conform with your local re gulations. Some per

- country information is below

.

 Duty Cycle (default 100) : the maximum percentage of time that the radio will transmit packets. Some regions of the world allow for higher transmit power or more frequencies if you have a duty cycle below a given threshold. So for example in Europe you can transmit on a wider range of f requencies in the 433 band if your duty cycle is below 10%.Telemetry traffic is quite ‘bursty’, so the average transmit time is not generally high.

When you set a duty cycle below 100% then your available bandwidth will be reduced, so you will find it wil l only work well for telemetry at higher air speeds. A radio can be set to receive only by setting it’s Duty Cycle to zero.

 Max Window (default 33) : ensure the GCS can send a packet to the vehicle ever 33msec. This should be kept as a low number (like 33) when the “MAVLink” setting is “Low Latency”

 LBT Rssi (default 0) : holds the threshold used for “listen before talk” which allows it to comply with some country’s regulatory requirements. When non

- zero the radio listens for quiet period of time where no s ignals from other radios are received before transmitting. This parameter holds the receiver signal strength below which the airwaves are considered “quiet”. If this param is set to zero then LBT is disabled. Setting this to 25 (the min) is

- 121 dBm. Each increment above 25 raises the threshold by about 0.5dB so for example 40 equals a signal strength of 7.5dB. The full formula is:

signal_dBm = (RSSI / 1.9)

- 127

The LBT implementation in the 3DR radio uses a minimum listen time of 5ms, plus randomised lis ten time as per the European 9.2.2.2 rules. Note that in many regions you need to implement LBT in conjunction with AFA (Adaptive Frequency Agility). The 3DR Radio implements AFA as long as you have NUM_CHANNELS set to more than 1. 

# Expected range

Typical r ange achieved with the 3DR radios using standard configuration and antenna is around 500m, but the range varies a lot depending on noise sources and antenna setup. 

## Diagnosing range issues

The first thing you should do when diagnosing range issues is the “o ne meter test”. Setup the two radios one meter apart and look at the local and remote RSSI. You should get a value of over 190 for a standard 3DR radio. If you don’t then your antennas may be faulty or your radios may have been damaged. If you have ever ru n the radios without an antenna attached them the radio may have been damaged.

If that test passes then have a look at your local and remote RSSI and noise from a flight. See the advanced setup page for detailed information on diagnosing range issues using telemetry logs. 

# Improving the range

The range can be i mproved by:

 Using a small “patch antenna” on the ground like this flat patch antenna or this Yagi
antenna perhaps mounted on an Antenna Tracker Replace at least one of the two 3DR radios with a higher powered RFD900

 Reduce the AirRate parameter which will increase range but at the expense of the rate of the data tr ansfer.

The graph below shows the ground and remote receiver strength vs distance from home (in meters) for a test flight of a 3DR radio on a SkyFun plane. The ground based radio was attached to a 3.5dB flat patch antenna. The SkyFun had a small ‘wire’ ant enna. The graph shows the vehicle reached a distance of nearly 3km and the link was completely maintained throughout the flight.

Although anecdotal, another user provided a Tlog showing a good link kept while the vehicle was 4.5km from the base station, using default radio settings for a 3DR 900 radio. The plane used a small omni antenna, and a 8dB patch antenna on the ground station. 

# Support for different countries/regions

It is very important that you configure your 3DR Radios to comply with your regional/country
reg ulations for frequency, hopping channels and power levels. The table below provides links to the applicable standards for users without any special license. If you are have an application specific license or have a HAM license then you should know what rul es are applicable to you.

Note: Compliance is your responsibility. The 3DR radio is a ‘DIY’ radio part and you need to ensure what whatever you build meets local regulations. Please check your local rules carefully.
Region Radio

Model Settings Standard

USA 3DR

900 MIN_FREQ: 902000 MAX_FREQ: 928000 NUM_CHANNELS=50 FCC 15.247

Canada 3DR MIN_FREQ: 902000 RSS

- 210 Annex 8.1900 MAX_FREQ: 928000 NUM_CHANNELS=50

Australia 3DR

900 MIN_FREQ: 915000 MAX_FREQ: 928000 NUM_CHANNELS >=20 LIPD

- 2000 item 52

Australia 3DR

433 MIN_FREQ: 433050 MAX_FREQ: 434790 TXPOWER<=14 LIPD

- 2000 item 17

Europe (most countries) 3DR

433 MIN_FREQ: 434040 MAX_FREQ: 434790 TXPOWER<8 NUM_CHANNELS>30 ETSI EN300 220 7.2.3

Europe (most countries) 3DR

433 MIN_FREQ: 433050 MAX_FREQ: 434790 TXPOWER< 8 DUTY_CYCLE 10 ETSI EN300 220 7.2.3

United Kingdom 3DR

433 MIN_FREQ: 433050 MAX_FREQ: 434790 TXPOWER<8 DUTY_CYCLE 10 IR2030/1/10

New Zealand 3DR

900 MIN_FREQ: 921000 MAX_FREQ: 928000 Notice 2007, Schedule 1

New Zealand 3DR

433 MIN_FREQ: 433050 MAX_FREQ: 434790 Notice 2007, Schedule 1

Brazil 3DR

433 MIN_FREQ: 433000 MAX_FREQ: 435000 TXPOWER<=8 ANATEL

– Resolução no 506/2008

Brazil 3DR

900 MIN_FREQ: 902000 MAX_FREQ: 907500 NUM_CHANNELS>=11 ANATEL

– Resolução no 506/2008

Brazil 3DR

900 MIN_FREQ: 915000 MAX_FREQ: 928000 NUM_CHANNELS>=26 ANATEL

– Resolução no 506/2008

Argentina 3DR

900 MIN_FREQ: 902000 MAX_FREQ: 928000 Comisión Nacional de Comunicaciones

South A frica 3DR

433 MIN_FREQ: 433050 MAX_FREQ: 434790 TXPOWER<=10mW 2008 RR 5.138, Government Gazette No 31127,Notice No 713 of 2008 and Government Gazette No 31290,Notice No 926 of 2008 refer