BOOST_FOREACH(FGPositionedRef ref, stations) {
FGNavRecord* nav = static_cast<FGNavRecord*>(ref.ptr());
if ( f <= 0.0 || nav->get_freq() == f) {
BOOST_FOREACH(FGPositionedRef ref, stations) {
FGNavRecord* nav = static_cast<FGNavRecord*>(ref.ptr());
if ( f <= 0.0 || nav->get_freq() == f) {