Stupid Programmable Transmitters

[Ran D. St. Clair]

Modern computer radios are stupidly designed. I'm talking about the way they are programmed. They try to make the programming easy, without sacrificing capability, but they end up doing just the opposite. They started with a paradigm that worked fine when radios could only reverse the servo’s, and maybe do simple elevon mixing, but as the capability grew the method became more and more unwieldy.

Allow me to demonstrate with a simple example. Lets say you have a 4 servo wing with 2 ailerons and 2 flaps. You want the ailerons to work like ailerons, but they should have a little more up than down to make the roles more axial. They should also go up slightly with up elevator, and down slightly with down elevator to improve stability in a harrier and make for cleaner walls. They also need to mix in a bit of opposite aileron from the rudder to counteract a bit of yaw/roll coupling. The flaps are setup on a slider (or pot if you prefer). When you drop the flaps the ailerons go up to create more drag (crow) and also to prevent tip stalling. The flaps move with the ailerons, but only about half as much.

I realize that most any top of the line, or even middle of the line, computer radio can do this and a lot more. My point is not that this somewhat simplified example is impossible, only that it is unnecessarily difficult to accomplish.

Some of you who are experts with your radio can bang this out in 5 minutes, but most of us are going to struggle for an hour or two before we get it all working just right. Lets walk through the process to see why.

You need to start by plugging your servo’s into the proper RX channels. Most radio’s have specific channels you will need to use to do something like this. If you pick the wrong channels you may never get there. You also need to tell the radio what kind of plane you have. Depending on your radio you may need to trick it a bit and tell it you have a glider. You might also need to tell it if you fly mode 2 (or mode 1).

Once you get all the servo’s moving, you need to get them moving in the correct directions. The left aileron might be correct, but the right aileron is backwards. So you invert the right aileron channel, but now the flap input on the right aileron is backwards. So you invert the flap input, and now the left and right flaps are moving in the wrong direction. So you invert the flaps back to where you started and try inverting just the travel on the right aileron servo, which seems to work. While you are there you set the right aileron to have more up than down travel and then find that the left aileron now has more down than up travel. Round and round you go like this until hopefully you find the right combination that does what you want.

It doesn’t need to be like this. You may love your radio, and love the fact that it can do this stuff, but that doesn’t make it the best way to get the job done. It only makes it the way that you are currently most comfortable with.

Now imagine a different kind of radio (that to my knowledge doesn’t exist). You plug your right aileron servo into any channel, it doesn’t matter which. You program that channel with a mixer to take inputs from the “right Stick Horizontal” (Aileron), “Right Stick Vertical” (Elevator), “Left Stick Horizontal” (Rudder), and the Flap Slider. You set the sign and mix percentage for both directions of these 5 inputs and you are done. If something works backwards you flip the sign and it fixes the problem without creating a new problem with some other channel/servo/surface.

Now that you have the right aileron working you copy the program to the left aileron which is on some other channel, it doesn’t matter which. Depending on your linkage it works perfectly, or its all backwards. You simply flip the signs as needed to fix it without any impact on the other aileron. You might find that it has more down aileron than up, so you flip the percentages, and you’re done.

You then copy the same program to the left flap. Depending on your linkage it now mirrors the left aileron, which isn’t what you want, but it’s a start. You flip the sign on the flap input, reduce the percentages on the aileron input, bring the rudder input down to zero, and it works perfectly.

You then copy the left flap program to the right flap, tweak it a bit, you get the idea.

At no point did you tell the transmitter you were flying a glider, in mode 2, or any other nonsense. At no point were you in danger of getting stuck in a seemingly endless loop of fixing one problem only to create another. At no point did you need to buy a different receiver that has more channels than you actually need because the radio is set up to only put certain functions on certain channels.

Radio manufacturers are you listening? Stop the madness!

None of this is meant to bash any particular brand of radio. Futaba, JR, Multiplex... As far as I know they all have these problems in one form or another. What I can't figure out is why the obvious simpler path is never taken.

[Edge 540]

Like on the 9c, why are the programming menus for the HELI and AIR modes DIFFERENT? haha

[ericb]

IMHO the 9C is the easiest one to program. In the time it took you to type this post, you could have programmed your radio.

[Edge 540]

Yes it is extremely easy, it just makes no sense to have different menus for different model types. Go program the dual rates EPA and expo in your plane then do it in a heli. Tell me what you notice....

[exeter_acres]

umm...because a Heli and airplane have totally different setups and mixes... it makes total sense to me

[JimC-MD]

Hi Randy,

I see you figured out how to post a new thread to the forum. I know you were having trouble with that the other night. Looks like we got you worked through it in chat. This technology stuff is fun, eh?

As far as the programming problems you mentioned, I guess I just do not see the level of problem you do. I find those types of things to be relatively simple on the radios I use. My suggestion to those that are challenged by this is RTFM. (read the freakin manual) If that does not do it, RTFMA. If that fails, get someone that understands the manual to help you. It really is not rocket science. To me it is very logical.

[pitviper51]

dx7 is cake to program,.. all those features you said,, moving the ailirons down when the eles go up ,, not many real ones do this except military,, so why cheat fly the plane the ways its meant to fly.. haha.. but you are right the programming can be a pian to get just how you want it.. oh well my .02
mike

[whirlyspud]

I did not know that a 4 wing servo setup was even an option with the DX7.

Mike

[pitviper51]

it better be i havent tryed yet, and i have a 4 servo husky to build,,, actually it will work , you may not have more then an on and off mode for the flaps hook on the gear ch. or 3 position switch. havent tryed it yet
mike

[JPrc]

With the JR 9X trying to program downline mixing is a PIA. Instead of having a function for downline mixing that is activated at the last 2 to 3 clicks of the throttle stick position you have to program an offset so it does not start kicking in down elevator right below half stick. This is not that bad but coupled with the fact that when you adjust your throttle trim it changes the amount of throw you mixed in for downlines it gets aggravating trying to get it dialed in just right.

[Cobra1]

Randy, I agree, they are hard to completly understand and EASY to forget. But then again I like the prices for these radios to be kept low also. I learned to program my 9C and you are right, it takes about 5 to 10 minutes. I also will not change brands because I don't want to have to learn it all again...

[Edge 540]

	Quote: Originally Posted by exeter_acres
	umm...because a Heli and airplane have totally different setups and mixes... it makes total sense to me

Do you know what I'm referring to?

What I was trying to say is that the expo/rates menu is displayed differently. It has nothing to do with what the servo is strapped to, its the display. Apparently one team of engineers setup the plane menus and another did the heli menus. There's a slight difference between the two and I found this funny. Probably just an oversight.