Issue creating a template class for the first time

Question

I have been reading up on creating template classes and I think I have it.. well, apart from one annoying bug I can't figure!

this is what I have so far:

template<class T>
class CStateMachine
{
public:
    // Constructor
    CStateMachine(QByteArray smName);

private:
    QByteArray _smName;
};

// Here is the constructor implementation
template <class T>
CStateMachine<T>::CStateMachine(QByteArray smName):
    _smName(smName)
{
    qDebug() << "New statemachine:" << _smName << endl;
}

// Now here is the usage called from normal class CRpeComms:
#include "cstatemachine.h"
...
CStateMachine<CRpeComms> rpeSm("test");
...

This generates an error:

unidentified reference to CStateMachine<CRpeComms>::CStateMachine(QByteArray)

Note: I am using Qt so if you are not familiar with that then think of qDebug() and std::out or similar and QByteArray as CString or similar.

I have looked at lots of example and mine seems identical. If I move the implementation of my constructor into the header file (like below) then it works no problem...:

CStateMachine(QByteArray smName):
    _smName(smName)
{
    qDebug() << "new statemachine:" << _smName << endl;
}

So I am not sure what I am doing wrong here...

Any help much appreciated!