On an Airtronics radio dual rate, brake and throttle percentages can go beyond 100 percent. Why go beyond 100 percent?

What is the advantage or disadvantage of this?

Any help would be appreciated!

Thanks.

I don't know about all of them but my Futaba 2PL does this also. I'm assuming it's for servos that actually have more throw than the radio can recognize at 100%.

I'm not positive, but I think the main reason for it is to make it more adjustable(more electronical steps) such as reducing items like braking on gas cars. The gaps between the (%) are smaller and more accurate.

Thats the way I see it.

Robmaxx is correct!!!

Thanks for the replys. I was talking with the friend who got me to ask this and that is what I got to thinking. More "steps" as Robmaxx said. Thanks for confirming Fl Flash.

That is not true. Increasing your EPA (End-Point Adjustment) on a radio does nothing to the 'steps' you are referring to. Those steps are actually the resolution properties of the servo (and in some cases the LACK of resolution of the radio type, FM, PCM, etc.) High-end servos are much more accurate than an AM radio. Since the number of steps a servo travels is directly related to the distance you can turn the wheel on the transmitter or pull the trigger, you cannot remove or add steps in the sense you are talking about. While you may still say it's the same thing, it isn't. Your radio doesn't know how many steps is in 60 degrees, but your servo does.

To understand why you can have 150% (or more on some radios) when adjusting the EPA, you have to look at how your linkages are moving. Most RC linkages are based on the servo arm you use. If you go back to geometry days in school, you can quickly understand that a servo arm that is perpendicular to the long axis of a servo will travel at a decreasing linear rate as the servo arm turns. In other words, if you measured from the outside hole on the arm, then moved the servo arm 60 degrees from perpendicular, you may end up with 0.75" of linear travel (the line you measure must stay parallel to the long axis of the servo). However, if you measure from the inside hole on the arm, you may find the linear distance to be only 0.6". So, how would you compensate for the lack of distance? You adjust the EPA on the radio until you get the required linear travel. Again, your radio doesn't know where the servo is in relation to how far you've pulled the trigger, it just knows to send a signal to move the servo. The EPA you can change adjusts the voltage depth that is understood by the receiver, which is sent to the servo's 'signal' lead. A deeper voltage depth tells the servo to move farther, while a shallower depth is less. In most radios, there is no feedback protocol, so again your radio has no idea how far the servo actually moves. Hence, why you have EPA.

Another way to look at it:
If the wheel on your transmitter rotated 60 degrees either way (a total of 120 degrees travel) and the radio had 1,240 steps of resolution per 60 degrees; and your servo for steering had 1,240 steps of resolution per 60 degrees; and the servo and radio were designed to understand the SAME voltage change per step, then when you turned the wheel a full 60 degrees, the servo (in theory) would also rotate 60 degrees. That's great, but so what? A car's steering may only require the servo, using a 1" arm, to turn 45 degrees before the wheels are lock-to-lock. You would then have to turn the EPA down on the transmitter, so the servo doesn't turn as far. Vice versa, the car may require 75 degrees before the wheels are lock-to-lock, so you would turn the EPA above 100%.

To take it a step further, the change in linear distance as a servo arms turns is exponential, and why higher-end radios have exponential, so you can adjust the radio to compensate and you could get a true linear FEEL through the trigger or wheel. Although the algorithm the radio performs is very complex.

I know it sounds a little confusing, but that's the truth. I'm not always the best at explaining complex things in simpler terms. Once your radio is set correctly, you rarely have to change it. Do not confuse EPA with Dual Rate (D/R). Dual Rate should ONLY be used AFTER a radio is set correctly, and should always be set to the MAXIMUM BEFORE you setup the radio for the car. You can then use the D/R (which is usually accessible via a grip switch or dial so you can change it during racing) to dial-in/out steering. A high-grip track usually requires less steering than a low-grip track. D/R is the quick, efficient, and easy way to change that on the fly.

Hope this helps...don't want to start an argument here or ?*() anyone off, but try reading your Radio manual. Most of them explain this very clearly (EPA, D/R, etc).