Spektrum DX8 beside the boxSpektrum DX8 Review/Tips
last updated 10-20-2010

First off... do I like it? That would be a big YES. Going from the DX7 to the DX8 makes a lot of task much easier. And it has some features that I missed not having after switching from the Airtronics RD8000. Let's go over a few things that make this radio great.

Timer functionTimer - I switched to all electric helicopters in September 2009. With the DX7 and most radios you start the timer just before you lift off. Sounds simple, but in reality you sometimes forget to start the timer. With electric helis you depend on the timer so you can follow the 80% rule. Beginning with version 1.01 you can set the timer to work off of the throttle output. The problem with working off of the throttle stick is that the timer will stop when doing inverted climbouts and it will not stop when doing autorotations. With throttle output set for the timer, this makes the whole timer issue effortless. Now I do not start the timer, it takes care of itself. All I do is just go fly and the timer will let me know when it is time to stop. So easy!!! The timer will make one beep  near the end of flight to let you know you have one minute left. Then it will beep one per second for the last ten seconds. Then the timer will start counting up and beep once per minute. BTW: If you have trouble hearing the sound from the radio, just set the timer to vibrate instead (or do both). NOTE: The position value for the throttle output is based on the throttle output. So what does that mean, well it means that when you set the value do not expect 0% to be stick low and 100% to be stick high. It could very well be reverse of that depending on how you have the throttle channel set. The easy way to set this value is to start off at 50% and move the throttle stick up until you hear the beep that the timer makes. Now move the value to 35% and then move the stick until you hear the beep. Take note if the stick was below the middle or above. If above then you know you need to move toward 100%. If below then keep lowering the value until you hear the beep just as the stick is moved from the bottom.

Inactivity - This is a feature I really missed after switching from an Airtronics RD8000. It is not an often used feature, but when needed it really is nice to have. At times you could be doing a radio setup at home and get a phone call that takes longer then you expect or you finish flying and get into a conversation with your flying buddy's before turning off the radio. When this happens the radio will make a tone after ten minutes of inactivity.

Quick Model Change - Just like the Timer, this is an often used function so I really appreciate it. I usually fly one heli right after the other when I go out. As soon as one heli is done I let it cool while I fly my other heli. With my DX7 I would have to turn the radio off and hold two buttons while turning the radio back on. That would get me in the System menu. I go to Model Select and then set the radio to the next heli I want to fly. With the DX8, I do not have to turn it off and wait for the system screen. Instead I just press the two buttons on the left and it instantly goes to a list of the models I have. I select the next heli I want to fly. Another nice feature here is that after you select the model it goes to the System menu in case you want to make any changes. If not, just press the roller one time and you will be at the main screen ready to fly.

Updates - As new features or fixes become available you simply download the update to the SD card that came with the radio. Insert the card in the radio and turn the radio on. No need for any special button combinations or menu selections, just turn the radio on and it recognizes the update is there and installs it. It really is great knowing that a year from now my radio will still be just as up-to-date as one bought then.

Feel - The switches have a low threshold to flip. Some radios I have used (including expensive ones) require so much force to flip, it causes the radio to jerk. I was really glad the DX8 was just right. Another thing that was great to find out is the roller feels perfect. It has enough tension for the press direction that you will not accidently select a menu item while rolling through the selections. But at the same time it does not require an abnormal amount of force to press it. And as you roll it, there are distinct notches so you do not accidently rotate it while pressing down. This is something I have ran into often with the DX6i. Another thing that is nice is if you move the roller fast it will act like you spun a wheel that still rolls for a shot time after you let go. As an example, if I go in the menu and I want to go down to the timer function, which is next to the bottom of the list, I can do a single quick roll and it will make it all the way to the bottom of the function list. This also works when setting values such as servo end points. Another item that gives this radio such a good feel is the switch placement. The switches are layed out so they are easy to get to and the switches on the top have good spacing. Some radios have such close spacing that your fingers are squeezed between the front and back switches. The back switches on this radio are also inset toward the middle about a half inch. The case is wider then my DX7 but I quickly got use to it and like it more. Also the bottom of the case has a curve to fit those of us that do not have flat abs :) Another thing is the weight of the radio feels just right. It is not heavy like I consider the 9303 and 10X to be.

Backlight - I know some have said that is a waste of electricity because you fly in the daytime. First off it does not consume much. The stock battery will last a long time. And second, some people do night flying and very much appreciate this. And third, if you are in the house and need to use the radio you will be glad it has it. Even in my well light living room I have to angle the display of my DX7 to read it. But not the DX8, this backlight screen is great!!!

Hangs straight - Yes, it will hang level from the neckstrap. No more need to buy or make an extension for the hook. BTW: It comes with a neckstrap.

Throttle hold - On my DX7 the throttle hold is basically where the Rudder D/R switch is on the DX8. The Hold switch is behind this and inset toward the middle some. My first reaction was to change the switch setting in the radio so that Hold was using the Rudder D/R switch. I did several autos with it setup this way but between flights I was feeling what it would be like to use the switch labeled Hold. A few minutes later I decided I would like that better so I switched it back to the factory default and have kept it there ever since. It is nice that this radio will let you have a choice.

Servo Setup screenServo Setup function - The first time I got to look through the menu this function was one of the first things I noticed and liked about the DX8. I guess it means a lot to me because I have setup so many helis. A common setup with other radios goes like this: Elevator servo - go to the Reverse function, set the direction, go to the sub-trim function, install the servo arm and adjust the value to set the 90 degree angle, go to the travel adjust, set the end points,  go to next servo and repeat. So you end up hopping from one function to another all throughout the setup. With the DX8, most things you need are in this one screen. A picture of this is shown on the right. You have your monitor, travel, sub-trim, and reverse all in one screen. Now instead of working on one servo and hopping in and out of functions to get everything done, now you set the servo in the middle selection then scroll between the travel, sub-trim, and reverse functions at the top. The value is on the bottom. It is great having the monitor display in this all in one screen. A common task I would do is on a new setup of a 120 swash, I would lift into a hover and if the trim was off I would land, go to the heli and stop the blades, put my thumb on the servo that needs to be trimmed, go to the sub-trim function and guess a direction to adjust the servo and feel if that went the correct way. Now with the DX8, I just land and move the cyclic stick in the direction needed and watch the monitor. This will show me which way the servo needs to go. I then select sub-trim and adjust the value so that it moves the indicator on the monitor bar in the correct direction. BTW: With version 1.03, when adjusting the Travel, both values will adjust at the same time if the stick is in the center. However if you bump the stick off center then back, that one side will be selected and remain selected even though the stick is back in the center.

Cyclic Mixing - No more need for the sub-trim trick to prevent throttle binding with cyclic mixes. This radio has a cyclic to throttle mix that will not go past the end points you setup for the throttle. The mix will also let you set which flight modes for it to be active in.

gyro functionGyro Function - In the DX7 you could set two values then you could assign these to flight modes. In the DX8 you can set a different value for each flight mode. I use it for bank switching my VBar. It lets me set four modes. One for each flgiht mode, Norm, FM1, FM2, and Hold. This is great because I set the Hold bank in the Vbar for decreased cyclic agility. A common problem with autoing a flybarless system is the cyclic is touchy at the end of the auto compared to what you are use to with a flybar. As the head speed decreases with a flybar head, the controls get soft so you get use to adding a lot of cyclic at the end of the auto. But a flybarless unit does not care what the headspeed is, it will still maintain the roll rate you set it up to.

Trim Step  - This is a nice feature to have for radios with digital trims but it also provides a great function for heading hold gyros and flybarless controllers. With these units you do not want to move the trims off of center. So a nice feature this radio has is it will let you set the trim steps to zero. By placing these to zero you are essentially disabling them.

Warnings - First the best feature here is you can disable the Hold alarm. Why a radio would warn you the Hold is activated I do not know.That always annoyed me with the DX7 (and other radios). Especially with electrics you want it in Hold. I would rather it warn me if I did not have the Hold switch turned on. I hope Spektrum will make an update available that will give the option of warning you if the Hold switch is not engaged. And the Telemetry Warnings help add confidence in your helicopter. Now you will know when something is wrong and will likely have a chance to land and fix the problem instead of having one of those mysterious crashes. I have mine set to warn me if the receiver pack gets too low and the same for my flight pack (electric heli). A friend recently had a battery go bad in flight and did not realize it until the head speed was so low it ended up crashing. His spotter noticed the lower head speed and let him know but I feel like if he had telemetry then he would have know well before the head speed got low enough to notice.

Telemetry - I have mentioned some already in the Warning topic but another nice feature is that one of the Telemety screens will give you minimum and maximum values for things like your motor temperature and flight pack voltage. With a nitro helicopter this is a feature that can save an engine. I have seen many engines torn up from lean runs. A lean run can occur from many things, not just having the needle a few clicks too lean. Most people new to nitro engines do not know what to observe to recognize when the engine is too hot. So this feature will help a lot. Another nice feature of this Telemetry system is that it has X-Bus. This will be for upcoming sensors. One that was mentioned will measure the milliamps used from the flight pack. This will be great for electric helis. Imagine being able to set a fuel gauge of 2200mah for a 2650mah battery and have the radio let you know when you need to stop flying.

Tips/Notes -
-- tm1000 with color coded plugsColor code the Telemetry plugs - Unfortunately I know from experience what happens when you get the wrong plug in the RPM connector. The Data, RPM, and Volts/Temp plugs are all three JST-ZH (mini JST) (Japanese Solderless Terminals) connectors. I had all the wires tucked out of sight in the framset. The wiring job looked nice. But I was not satisfied with the Telemetry module location. I unstuck it from the frame and tried some other places. I ended up putting it back where it was. I reconnect the mini-JST plugs but unknowingly I ended up with the flight pack plug in the RPM connector of the TM1000. The next time I connected the Flight Pack, I heard multibple pops. The Cypress programmable IC inside the TM1000 was ruined. That chip was not expecting to be hit with 40 volts. So my tip here is to color code the connectors. I used a red and green marker on the new TM1000 I bought.
-- where to hook up the battery? - A common question is if you hook up the Telemetry module to the Batt. port of the receiver then where do you hook up the battery? You have a couple of options. One is to connect it to any open channel in the receiver. All of the positive pins of the AR8000 are connected to each other and the same goes for the negative pins. The same is true for most receivers including the AR7000 and AR6100. The second option is used if you have all of the channels filled up. You use a Y-splitter to connect the battery and Telemetry both to the Batt/Bind port on the receiver.
-- Frame Rate - When you setup a model, make sure you change the Frame Rate to 22ms if you have analog servos. By default the radio will be set for 11ms. This is too fast for analog servos and can damage them. Go to the System menu to change this.
-- tm1000 with binding tooltm1000 with binding toolBinding - With the Telemetry module attached you put it and the receivers in Bind mode by holding in a small button on the side of the Telemetry module. The TM1000 comes with a small plastic stick that fits tight in the binding hole. It is suppose to be tight enough you can leave it in place without holding in. One of mine will do that, but the other you have to hold it yourself while at the same time you plug the battery in. It can be done but it really needs two people.
binding switch not as easy with telemetry module
-- User Name - This is located in the System menu. You could put your name but it only has room for 10 characters. I put AMA followed by my AMA number. But a friend of mine, Jack Doherty, came up with a better idea, put your cell phone number. That way if you lost the radio they could call you directly. Each time the radio comes on, your phone number is displayed at the bottom of the screen.

Products/Features I would like to see:
--  "Quick Timer" From the main screen, hold the 'Clear' button and use the 'Roller' to set the timer. It would be for just that one session. If you start flying and a couple
of minutes realize you need to make a mechanical adjustment, you set the timer for a couple of minutes less when you continue to fly.
-- "Switch Check" For each model I would like to be able to position each switch where I want them and store this. Then when the radio is turned on it will warn me if any switch is out of place. This would of course include the throttle hold so I could have it warn me if throttle hold was not engaged. But this would function would not include sticks, trims, or the knob.
-- hand held display for telemetry - This would be a small unit with a display that would "listen in" on the data being transmitted from your telemetry module. Your spotter would hold it and could for example read out the engine temperature to you as you performed certain maneuvers to test the high and mid range needle settings.
--receiver and telemetry built into one unit for smaller helis.