Jason is spot on! Most all servos have a mechanical limit stop under the output shaft gear. That said the stop limits travel at about 180* or so. Pretty much; all servos can rotate stop to stop at 120-150* given adequate pulse width control signal. Servos work with 900-2100usec pulse width or 600usec either side of center. As a quasi standard most radio systems offerings work with 450usec either side of center, limiting you to about 90* total travel arc. If your Transmitter is capable you can turn up/down the adjustable travel volume, in your case the Spectrum DX is pre-set at 100% BUT can be turned up to 150%. This will drive the servo with greater pulse bandwidth garnering a 120-150* travel. arc.
If you really need 180* travel arc, Hitec sales inexpensive small programmable digital servos that can provide same. They can be ordered from Servo City programmed for speed, direction, travel volume and more, its your choice. Or Hitec sales a programmer for DIY. I have a programmer if you or someone else is in need of programming.
Last edited by Michael Glavin; 07-07-2015 at 05:21 AM.