void MainWindow::displayDialFrequency ()
{
Frequency dial_frequency {m_rigState.ptt () && m_rigState.split () ?
m_rigState.tx_frequency () : m_rigState.frequency ()};
// lookup band
auto const& band_name = m_config.bands ()->find (dial_frequency);
if (m_lastBand != band_name)
{
// only change this when necessary as we get called a lot and it
// would trash any user input to the band combo box line edit
if (!m_lastBand.isEmpty()) {
m_qsoHistory.init();
if(m_config.write_decoded_debug()) writeToALLTXT("QSO history initialized by band change from transceiver");
}