MAVLinkSettingsWidget::MAVLinkSettingsWidget(MAVLinkProtocol* protocol, QWidget *parent) :
    QWidget(parent),
    protocol(protocol),
    m_ui(new Ui::MAVLinkSettingsWidget)
{
    m_ui->setupUi(this);

    connect(m_ui->paramRewriteSpinBox, SIGNAL(valueChanged(int)), protocol, SLOT(setParamRewriteTimeout(int)));
    ...
    connect(m_ui->droneOSComboBox, SIGNAL(currentIndexChanged(QString)), this, SLOT(setDroneOSHost(QString)));
    ...
}

a = new MAVLinkSettingsWidget(...);
...
b = new MAVLinkSettingsWidget(...);