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Saturday, April 23, 2011

Hitec Aurora 9 vs. Spektrum DX8

The Aurora 9 has two index finger rollers on sides (not visible
in photo).  The DX8 in photo shows larger aftermarket stick grips.
As I explore alternatives to replace my Spektrum radios, the first contender is a less expensive, but more technologically advanced Hitec Aurora 9.  This is not intended to be a complete Aurora 9 or DX8 review.  My Aurora 9 flight review will come later.  This article focuses on differences.

Aurora 9 flight page: Model number and name, Flight Condition, built-in motor battery voltage telemetry, Tx battery in % remaining or volts, signal type and strength, double clicking the model type icon acts as throttle suspend, custom functions folder shortcut, settings shortcut, trim percent offset and graphic position, digital trim adjustments to programmed mixes, Tx on/off air, two timers
DX8 flight page: Mode, model number and name, transmitter volts, timer, graphic trim positions (note: there is no way to display optional telemetry on the flight page)

Basic load-outs look something like this:

Hitec Aurora 9 (paid $392)
  • 9ch Transmitter
  • 6 cell NiMH power
  • Optima 9 - 9ch Rx w/triple-redundant power & built-in telemetry.  (Free coupon) Optima 7 - 7ch Rx w/triple-redundant power & built-in telemetry.  (Half price coupon) Optima 6 Lite, 6, 7, and 9 Rxs
  • 2048 Resolution with all receivers
  • Real time response with all receivers
  • 5.1" Backlit LCD 
  • Touchscreen control
  • Acro, Heli, Glider modes
  • 9 Wing types
  • 5 Tail types
  • 8 Programmable, separate and/or cumulative, Flight Conditions 
  • 8 Programmable mixes, 5 linear and 3 with seven point curves
  • 7 Point pitch, throttle, and mix curves
  • 30 model internal memory with wireless data xfer between radios
  • 24 rate capable via 3 point switches and 8 layered flight conditions
  • Custom user menus
  • Removable/switchable sticks without opening case
  • Servo overdrive protection
  • Password protection
  • Two programmable timers
  • Adjustable motor voltage warning by model via built-in telemetry
  • Dedicated 4.8V or 6V Rx battery power module
  • NiMH charger for Tx battery and Rx switched battery power module
  • Updatable 2.4GHz module by USB connection (requires $23 HP-22 module)
  • Updatable transmitter software with above module
  • Updatable receivers with above module
  • Direct to laptop telemetry capable
  • Voice telemetry capable
  • 2.4GHz spread spectrum with adaptive frequency hopping 
  • 72 MHz digitally selectable, universally compatible  
Spectrum DX8 (paid $425)
  • 8ch Transmitter
  • 4 cell NiMH power
  • AR8000 - 8ch Rx 
  • 2048 resolution with AR8000; 1024 resolution with basic Rxs
  • Real time response with AR8000; slow response with basic Rxs
  • TM1000 with 4 function Rx telemetry including voltage sensor
  • 2.9" Backlit LCD 
  • Single axis roller control
  • Acro, Heli modes
  • 3 Wing Types
  • 5 point pitch and throttle curves 
  • 6 programmable linear mixes
  • 30 Model internal memory with SD card xfer
  • 3 rate capable via 3 point switches
  • Servo overdrive protection
  • Programmable Timer
  • NiMH charger for Tx
  • Updatable transmitter software by SD card
  • 2.4 GHz spread spectrum
Transmitters:

The Aurora immediately impresses the holder with a higher apparent technology level than the relatively stark DX8.  The most obvious difference between the two transmitters is the Hitec's huge touchscreen vs the relatively small DX8 screen & roller.  Despite being more compact, the Hitec Tx weighs about 20% more, at 33oz  vs. 28 oz, including the stock 6-cell vs. 4-cell batteries.  The Aurora 9 provides 4 switches on top, two index finger rollers on the sides, 4 switches on the front face, and 7 digital trim rockers.  The DX8 has 3 switches and one knob on top, 4 switches on the front face, and 6 digital trim rockers. 

Hitec's approach labels all switches generically (Sw A, Sw B, etc), while Spektrum labels their switches for the customer (Gear, Flaps, Elev, etc.).  I don't understand the latter, since the switches do not need to, and often don't correspond to the labeled functions.  This is an interesting difference because it quickly reveals the Nanny-State mindset of the Spektrum designers, who've embedded numerous, unrelenting annoyances and deficiencies (see my DX8 review for more).  This is more than an annoyance, it is a serious defect.  For example, if you want to mix your flaps to contribute to roll control, you can't, because Spektrum's "flap channel" logically connects both sides even though you never told it to so.

Hitec's design approach is backward compatible with a free people. They simply label and treat all servos on a receiver channel as independent Channels x thru n, so there are no artificial impossibilities forced on the user. Refreshing, and a lot easier to build ; you can always sort out what got plugged into where, later.

The Aurora has 7 point pitch and throttle curves and three 7 point mix curves.  The DX8 has 5 point pitch and throttle curves. 

Additionally, the Aurora includes more detailed features and customizations within virtually every menu and sub-menu, plus allows saving to a custom menus section to add user-specific features and configurations.
Note the C at the top left of the Aurora 9's expo graph.  That means this particular sub-feature within Flight Condition 1 will be "C"ombined, with other selected Flight Conditions unless overridden by that Flight Condition.
Flight Conditions are unique to the Aurora and allow you to customize entire sets of menu features then apply them in groups assigned to a single switch movement.  There are 8 programmable Flight Conditions available to every saved model, including the base setup which serves as Flight Condition 1, named "Normal."

For example, you might create 5 different helicopter Idle-Up modes with custom Pitch and Throttle curves, as well as custom rates, servo speeds, expo, sets of mixes, and different gyro gains for each one, then assign each of those comprehensive sets of Idle-Up customizations to its own switch. 

Each feature customization within every Flight Condition can be designated as a Combined or Separate change to any other selected Flight Conditions. This multiplies the number of features available since you can layer certain Flight Conditions on top of others in a cumulative way, while keeping other Flight Condition feature changes discrete.  This makes the potential number of available mixes and feature modifications for each model, effectively unlimited.

Updates:

Both the Aurora 9 and DX8 programming software can be updated, but only the Aurora can update its frequency hopping 2.4GHz module and its 72 MHz module with new software, as well as its receivers. In contrast, Spektrum charged customers for a new radio when they updated their 2.4Ghz DSM to DSMX, plus required customers to buy all new receivers to use the new standard.  You will need to buy a new transmitter and new receivers to take advantage of a frequency hopping or otherwise improved protocol if Spektrum ever introduces one.

Spektrum updates transmitter programming with downloads to an SD card which is then inserted into a slot in the radio, and they have been very aggressive in releasing update after update to squash numerous bugs, some quite dangerous.  You will need a computer based SD card reader/writer to download and save an update, they run about $10.  

To update Hitec transmitter programing, the 2.4GHz protocol and receivers you must buy an $23 plug-in HP-22 module.Hitec has released 2 updates as of this writing, mostly to add new features.  

Ergonomics:

You can read about Spektrums major ergonomics gaffs and annoyances in my full review linked above.  Another problem, not immediately apparent, became known after the Hitec equipment arrived for a side-by-side: the DX8 stick to hand-grip distance is wrong.  Despite having reasonably large hands, I cannot keep my palm on the hand-grip while moving either stick to the full up-and-over deflection point--corresponding to [full-throttle-right-rudder] or full [down-elevator-left-aileron].  This is another inexcusable error where Spektrum engineers failed to design the radio properly, forcing people to lose firm hold of the radio while flying.  The Hitec grip distance is perfect, allowing one to properly hold the radio and fly.

The Aurora has a nicer switch layout with quite a few more controls considering it only has one additional channel.  The index finger rollers with tactile and audio centering make finding any old flaperon/spoileron setting a breeze. I much prefer the positive feel of the Aurora's trim buttons.

Binding the Aurora is a bit of a hassle, as a button on the back must be pressed at the same time as making touchscreen inputs, not the easiest trick in the world.  Perhaps worse, the Spectrum radio won't bind to high line receivers without a hardware dongle. 

Both radios feature stick tension adjustments through rubber plugs on the back face.  But only the Aurora lets you swap sticks without opening the radio box.  Both radios have rubber hand grips, the A9 box's smaller more contoured profile allows the grips to be tighter and more compact.  The A9 also has a lighter more easily manipulated stick feel.  For example, it is easy to make a circle with either A9 stick, the DX8 sticks are too firm to do so without substantial ratcheting.

Receivers:

There are several Rx differences that jump out:  Most obvious, the Optima Rx has two longer antennas which are claimed to outperform any dual receiver setup.  Another huge Optima advantage are the triple redundant power inputs:
  1. ESC
  2. Dedicated Batt pack (an AA pack with switch and NiMH charger are included) - If you want to add a dedicated battery to keep the Rx awake and also power your servos (extending motor flight time), you can plug into the Batt port with supplied AA harness/charger.  Or, connect a 6V LiFe.  No need to consume a channel port or add a Y connector to inject dedicated batt power to the Rx and servos.
  3. SPC - a direct Rx power line from any battery that is under 35Vs (voltage is regulated down but not up, so 5V+ is required).  You can use the motor LiPo, making this port function a little like a built-in switching BEC, but an added benefit of using SPC port is that it only powers the Rx electronics, not the servos, so if you use a dedicated battery, like a 2S+ LiPo, you can keep it very small and lightweight. Another benefit is SPC battery Voltage telemetry displayed on the Tx LCD even without the telemetry module--V telemetry is built-into every Rx. 
Or, you can use all three at once.  Wonderfully thought out; bulletproof.

Spectrum Rx's gain power only through the ESC port.  If either the battery or ESC so much as glitches, the plane generally crashes (100% of the time in my way too-frequent experience) while the reciever takes its sweet time rebooting, even my quick connect Rx has been too slow to avoid a dirt pancake.  You can enhance the Rx by purchasing a dedicated Rx AA (or similar) pack and charger and plugging it into any empty channel or Y harness, but that costs more and is not supported by the manufacturer.  If you do so, it is recommended that you snip the ESC power lead, so that is still not a redundant solution so it fully relies on a single battery.  It takes the ESC out of the failure loop, but it puts a battery pack in.  The same goes for buying a dedicated switching BEC, still recommended to run single source power to avoid charging/discharging/shorting issues.   Low end reliability, to say the least.

Hitec makes four compatible Optima Rxs, a 6 and 6 lite, a 7, and a 9 channel, plus a Minima line for micros and profiles, all are 2048 resolution with built in Voltage telemetry and programmable fail safe modes (= servos and throttles go to your selected pre-programmed positions if the link is lost).   Street price is about, $45, $50, $85 (minus 10-20% if you are a Towerhobbies club member--no affliation).  All of them are software updatable and updates have been released.

Horizon charges 30%-50% more for the same number of channels, with lower reliability, a less sophisticated link, slower response time, less resolution, no fail safe mode, delayed re-links, and no built-in Rx telemetry.   None of them are software updatable. Spektrum's low technology level and poor value falls off the bottom of the chart.

Hitec Rxs are sold in even more cost-effective 3-packs and multiples with this and other radios, Spektrum Rxs are not.

This video (not mine) is a nice demonstration of Aurora 9 receiver boot time and re-link performance, although the servo motor is slow:

Airborne Operation and Response:

Great news!  I'm a heckuva lot better rc flier than I thought.  I had no idea how much the vagueness of the Spectrum standard had been holding me back.  Perfectly straight horizontals, verticals, quicker snaps, double  the hover stability, supreme glide path control, dancing wheel landings...WOW, this is fun!!!

I could go on and on about the gross superiority and shear dominance of the Aurora system over Specktrum, but int he interest of charity and brevity, I will limit it to a few quick observations:

From the instant of takeoff, the difference was blatant. Throttle response is quicker and step-by-step more accurate.  No more roll, trim trim, roll trim trim--roll, stop, rock stable, roll, stop, rock stable--straight lines with no centering drift whatsoever.  Faster servo movement.  New level of precision.  Easier spot landings.  I love the left index finger roller with center-detent (and beep) to allow the immediate selection of any flap position, or for 3D aircraft, any double-servo aileron position from full flaperons to full spoilerons--a programmable elevator position follows, both up and down.

This radio will save me money daily, through less wear and tear, outstanding control, and Rx power redundancy, link speed, and link reliability.  I would have saved so much and had so much more fun if I went with with the Aurora from the beginning.  Painful.

The great news for those who may disagree is that I'll be selling off my perfectly good (as in, perfectly good shape and fully functional) collection of Spectrum Rxs and also my transmitters (DX5e, DX6i, but not the defective DX8 unless someone wants to buy it knowing that (a) it is no different than any other DX8 new or used, and (b) that it is a horrible radio).  I'll be listing the Spektrum equipment I have for sale in the comments section of this post, or in a separate post as I replace it.  Please zap me an email or leave a comment if you wish to make an offer.

Head-to-Head fly-off:
For the H2H, I flew off the razor sharp Great Planes Electrify 41" Edge 540 in full DX8/AR8000 regalia against the Great Planes Electrify 41" Yak-54 3D in Hitec garb.  The GP Edge is an amazingly preceise 3D/pattern spaceship with near infinite pull.  The GP Yak-54 is a 3D scalpel that floats like blimp and hauls ass as fast as its 10K RPM, 3.8 pitch prop can chop air.  By any estimation, this should be a heckuva shoot out.

It wasn't.

The Aurora 9 decisively beat the DX8.  The difference in feel, responsiveness, programming features, and safety features was night and day.  Thank you Hitec for an amazing product selling at lower than reasonable prices.  The switch is on.

Side note: One thing that could be more clear in the A9 manual  is how the SPC (direct Rx power) connector works.  So here is how it actually works - The SPC port pin-out is the same as any servo connector as far as where the positive wire needs to connect (middle pin of 3) and where the negative wire goes (same orientation as any servo's black wire within its female connector plug).   The third pin of the receiver's SPC port, which would normally correspond to the servo control signal wire, stays unconnected.    You can modify any old servo extension cord to connect the SPC port to the battery (the Rx comes with one that only has a black and red wire, the third pin is empty).  Run the black wire to the black battery terminal, run the red (middle) wire to the red battery terminal.  The best place to connect these two wires is on the ESC-side of your airplane ESC battery connector, then to the SPC port, that way it stays connected and ready as part of the airplane's electronics.  Once you have this connection in place, the LCD touchscreen of the A9 transmitter will read out battery voltage via telemetry.  If you do not connect the SPC port, that field will show Rx voltage, or around 5V no matter what the battery's voltage state.

While it is bit inconvenient to have to solder-in your voltage telemetry, the A9 solution is no different from Spektrum's same requirement, but it is far less expensive since Hitec does not  mandate the purchase of a dedicated telemetry module (e.g. a Spektrum TM1000) which costs as much as the receiver itself.   Hitec packages free V telem with every Rx, as well as 2048 resolution.  The result is a Hitec cost savings of approx $150 per airplane over Spektrum ($130 for a 2048 resolution Rx, $56 for a TM1000 module, minus the cost of a Hitec Rx) to obtain these two critical features.

Final weighted scoring:

Spectrum DX8:  49.4
Hitec Aurora 9:   92.0 

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