[TowerTalk] Rotator Choice for Larger Yagi

[Paul Christensen]

>"Oh, by the way... There is a Green Heron controller especially for the K7NV prop Pitch conversions."

It's a very capable controller.   The M2 PP controllers can be easily modified to equal, and even exceed the performance of the K7NV RT-21 units.   Like the RT-21, the M2 controllers also have PWM speed control that pulse the gate of a power MOSFET.  However, that device is subject to failing in a condition that keeps the rotator turning out of control if the MOSFET drain and source leads fail shorted.  By adding a pair of inexpensive Russian vacuum relays, a 2N7000 FET driver, and a ceramic MOSFET insulator, that problem is completely averted.  There's ample room inside M2 controllers to add these components.  

Like the K7NV RT-21 unit, the M2 controller is now mostly vulnerable only during a turning event.  The modified GH RT-21 units have relay isolation, but I think a pair of vacuum relays offers better circuit protection.  Now, if the MOSFET shorts in the M2 controller, the PWM ramping is certainly lost but the vacuum relays limit PP rotator travel, allowing the M2 controller to continue to function if necessary until the MOSFET is replaced.

Paul, W9AC