Spektrum is a brand of 2.4GHz radio control equipment designed and manufactured by Horizon Hobby. Spektrum systems are available for all types of RC vehicles, including helicopter and airplane specific models. They also sell modules for most popular brands of radios. These modules allow the use of Spektrum receivers with other brands of radios.
DSM is an abbreviation for Digital Spectrum Modulation, which is a proprietary implementation of spread spectrum technology. This allows the radio to choose an available channel based on noise and other nearby radios transmitting in the 2.4GHz band. This technology effectively mitigates the risk of a shootdown due to two radios using the same frequency and helps in noisy RF environments. 2.4GHz DSM radios and receivers are not compatible with any other brand or implementation of 2.4GHz technology. More information is available in the Spektrum website FAQ.
DSM was updated and renamed DSM2 to differentiate it from the older technology. DSM2 has a more robust connection than DSM, creating a safer, more reliable experience. DSM2 has a higher bit rate, which equates to more precise control over the model. Most DSM2 radios are backward compatible with older DSM receivers, but older DSM radios such as the DX6 cannot be bound to newer DSM2 receivers.
DSM2 was updated in early 2011 with DSMX which adds frequency agility to the DSM system. DX6i, DX7 and DX8 transmitters can be upgraded to the newer standard, and new production units will ship with it. DSMX upgrades remove compatibility with the older DSM protocol, but there is forwards compatibility between DSM2 Txs and DSMX Rxs, and backwards compatibility between DSMX Txs and DSM2 Rxs. The DX10t ships with DSMX.
Some DSM2 receivers are equipped with two or more antennas. The receiver can automatically choose between the antennas based on signal strength and clarity to provide the best connection with the radio. This helps reduce signal loss in instances where a single antenna might be masked by part of the fuselage, affected my multipath issues, or otherwise oriented in such a way that signal strength is reduced or lost.
This low power DSM2 transmitter is only sold in RTF packages such as the E-Flite Blade MCX, Parkzone Vapor, Parkzone Ember 2. It is styled like a console "game pad", runs from 4 AA cells, provides access to dual rates on some models (via a 5th channel activated by pressing one of the control sticks in) but is not programmable.
This radio has been designed to be used with the mCP X and allows you to switch back and forth between flight modes, but these are not configurable. It has a switch to change mode 1 and mode 2. It has a trainer port that can be used to control a simulator.
This E-Flight-branded transmitter is only sold with the E-flite Blade CX and CX2. It is a low power DSM2 radio, suitable for micro helicopters and indoor planes but lacking the range for even moderate planes and not compatible with the AR6000 receiver. It is not programmable.
This E-Flight branded radio is sold with the Blade CP and CP Pro. It is 2.4GHz DSM2 compatible.
The DX5e is a 5-channel, full range, DSM2 radio designed with basic functionality for beginners and those who don't need a full feature set. This radio is marketed to the value segment, and is therefore missing many of the more advanced features of the DX6i or DX7. It has servo reversing switches, trim, delta (elevon) mixing and a dual-rate switch. It is not programmable.
The first transmitter released. This radio was labeled 'for park fliers only' but has been used at ranges of over half a mile. It is only compatible with the AR6000 receiver, which limits it's suitability when there are large metal objects in the model. The DX6 uses the older DSM technology.
The DX6 has all the functions common to entry level computer radios (dual rates and exponential on elevator and aileron, ATV, Sub trims, 7 standard mixes and 3 programmable mixes and 10 model memories. This is sufficient for the many pilots but there is no timer and it is a little limited for helicopters (only 3 point throttle and pitch curves, and 2 flight modes) and it's not possible to program crow brakes for gliders with 4-servo wings.
The improved version of the DX6 that is sold as 'Full Range', the DX6i has almost all the programming features of the DX7, and can use all the receivers. It also has a purpose designed case that balances correctly when hung from a neck strap (unlike the DX6 and DX7) and runs from 4AA batteries (a rechargeable pack can be used). It is a DSM2 radio.
The advantages of this transmitter over the DX6 are:
- Rudder dual-rate and exponential
- 5 point throttle and pitch curves and faster CCPM mixing for helicopters, like the DX7. (the DX6 CCPM mixing is considered 'slow' by some pilots and the servos do not move at quite the same time, leading to some undesired interaction during aerobatics).
There is a bug in the software of the DX6i that means that the mixes cannot be set up to use differential thrust for rudder control on a twin motor model.
The DX6i has been subject to a recall for the following date codes: 807E, 808E, 809E, 810E, 811E, 812E, and 901E. This relates to faulty potentiometers.
The DX7 was released a year after the DX6 and provides 'full range' for larger models and more powerful programming (especially for helicopters), 20 model memory, and Model Match (a feature that prevents you flying with the wrong model memory selected). It was sold with the AR7000 receiver as a 'full range' system suitable for large models. The DX7 uses DSM2 technology, and is also available in a Heli version that defaults to heli settings where applicable, and the three position switch is swapped with one of the two position switches, but is otherwise the same as a regular DX7.
The advantages over the DX6i are:
- 3 flight modes
- 6 programmable mixes (for aeroplanes, 3 for helis)
- 20 model memories
- 7 channels
- 5 point throttle curve
It is possible to program crow brakes with the DX7 but it is quite complex; there are several guides posted elsewhere.
The DX7se is a "special edition" version of the standard DX7. It incorporates a few minor changes including an updated interface and screen area, higher resolution and faster frame rate for more precise control. It is designed primarily for use with helicopters, and the advanced features are only available when it is paired with the higher-end Spektrum or JR receivers that are capable of interpreting the higher frame rates and resolution. The DX7se has no trainer port and therefore cannot be used for buddy-boxing or to control a simulator. The DX7se cannot be upgraded to DSMX.
The DX8 is a new transmitter similar in appearance to the DX6i. It has 8 channels, and has several new features such as telemetry, data log, throttle-activated timer, backlit display, selectable modes (1-4), SD card removable memory for extra storage and firmware updates. Release date is scheduled for 22 June 2010.
The DX10t is a tray-type transmitter expected to be available in Europe only.
Spektrum modules are available for JR and Futaba radios. This is very useful for those who have invested in a good radio and don't want to reprogram all their models when they switch to 2.4GHz, or who don't want to loose some of the more advanced features. For example, the DX7 does not have:
- Analogue sliders or knobs (for channels 5, 6 and 7)
- Built in mixes for 4-servo wings
- 7 (or better) point curves
- Adjustable trim steps
- Timer started by the throttle position
However there are a few limitations of the modules, because they only receive the output from the transmitter after it has been through all the mixing.
- The module does not know which model memory is selected, so there is no model match. It also cannot switch between DSM and DSM2 when you change model memory - you have to rebind.
- The module is limited to the data rate of the original radio, so it is slightly slower than the DX7. However this is probably only noticeable to quite advanced helicopter pilots.
- The Futaba modules only have 8 channels, even if you have a 9 channel Rx and a 12 or 14 channel Tx. The JR modules have 9 channels.
This receiver is commonly sold with the DX5e radio. It is a 5-channel, full range, DSM2 receiver. It has two connectors for the servo channel, removing the need for a y-harness. There are two aerials - one protrudes from the side of the Rx, the other is at the end of a length of coax, approximately 6 inches long. This allows for the 2nd aerial to be mounted at a distance and at 90 degrees to the other.
This full range receiver is similar to the AR500 except that it has six channels. It has replaced the AR500.
The first receiver released. It has 6-channels, two receivers, and uses DSM technology (and is therefore park flyer rated). It is compatible with the DX6, the DX7, but not the DX6i.
This DSM2 receiver has two bits of wire that make a single dipole aerial, and a single set of receiver electronics. However it receives both of the signals sent from the transmitter. It is designed for smaller, lighter models that cannot carry the larger receivers, and is rated as "park flyer" range, rather than full range.
This receiver is technically identical to the regular AR6100, but has the servo pins located on the end of the receiver, oriented 90-degrees from the standard model. This makes routing servo and ESC wires easier in some applications.
This update to the AR6100(E) has the two aerials mounted at 90 degrees and has new software that indicates the number of holds that occurred during flight via the LED. As with the previous model, the E indicates end pin format.
This DSM2 receiver is similar to an AR6100 with an additional 'satellite' receiver (similar to the AR7000) that can be positioned some distance from the main receiver. Both receivers receive both signals from the transmitter, giving 4 chances for the message to get through. It is commonly sold with the DX6i. It is rated as "full range"
The AR6250 is designed for planes with carbon fuselages. It is "full-range" unlike the 6100, and has two long antenna wires. Only the last 31mm need to be outside the carbon fuse, but the extra length gives you more mounting flexibility. It also has two LEDs for power and hold indicators. Otherwise it is a similar form factor to the AR6100E, with servo pins located on the end of the receiver
This is a lightweight version of the AR6100 for JST-ZH plugs, and is designed for use with very small, lightweight park flyer and indoor applications.
(See separate article) This ultra-micro 2.4GHz brick has a receiver, integrated servos, and brushed ESC. A 1.5g Linear Servo is also available. The AR6400L is a version with slightly longer servo throws.
This 7-channel, DSM2 receiver commonly sold with the DX7. It has two parts, the main receiver and a satellite receiver, each with a dipole aerial that receives both signals from the transmitter.
This receiver is designed for use with helicopters. It is similar to the AR7000 but includes a built-in 5.2V voltage regulator and two failsafe modes.
The AR7100R is identical to the AR7100 except that it includes a built-in rev limiter.
The AR76000 is a high resolution (2048,) compact, 7-channel, full-range receiver that comes with 1 satellite receiver. Designed for use with the DX7SE.
This looks similar to the AR7000 with a 'satellite' receiver and 9 channels, except that the two wires are actually two separate aerials - giving a total of 3 receivers and 6 chances to receive the signal. It also has a socket for an additional 'satellite' receiver, data recorder or (not yet released) telemetry module.
The AR9100 is a robust, 9-channel, DSM2 receiver that has dual power inputs and comes with 3 satellite receivers, with a plug for an optional 4th satellite receiver, and other features that increase safety in the event of a failure. It is designed for use with giant scale and jet models.
This is a version of the AR7000 sold for the robot market. The difference is that all channels have a fail safe.
OrangeRx receivers are inexpensive, Spektrum-compatible receivers marketed and sold by internet retailer HobbyKing. These receivers are not clones of actual Spektrum receivers but are claimed to be original designs built by state-of-the-art robotics. Range of the park flyer-sized receivers is similar to that of the AR6100 with some users on HobbyKing's discussion boards claiming range similar to that of a full-range receiver.