Place LO offset to sprate /2

uhd_cpp/uhd_spectrum/qtgui/freqctrl.cpp

@@ -58,7 +58,7 @@ CFreqCtrl::CFreqCtrl(QWidget *parent) :
     m_DigitColor = QColor(0xFF, 0xFF, 0xFF, 0xFF);
     m_HighlightColor = QColor(0x5A, 0x5A, 0x5A, 0xFF);
     m_UnitsColor = Qt::gray;
-    m_freq = 146123456;
+	m_freq = 0;
 	setup(0, 1, 6000000000U, 1, FCTL_UNIT_NONE);
     m_Oldfreq = 0;
     m_LastLeadZeroPos = 0;

uhd_cpp/uhd_spectrum/specwidget.cpp

@@ -118,6 +118,8 @@ void specWidget::setBookmarksEnabled(bool enabled){
 	ui->plotter->setBookmarksEnabled(enabled);
 }
 void specWidget::setCenterFreq(quint64 f){
+	if (f<=0)
+		return;
 	f = set_center_freq(f);
 	ui->plotter->setCenterFreq(f);
 	if (ui->doubleSpinBox_center->value() * 1e6 !=ui->freqCtrl->getFrequency())

uhd_cpp/uhd_spectrum/uhd_device.cpp

@@ -224,8 +224,9 @@ quint64 uhd_device::set_center_freq(const quint64 freq_in_hz)
 {
 	if (usrp)
 	{
+		double rate = usrp->get_rx_rate(m_channel);
 		using uhd::tune_request_t;
-		tune_request_t tune_request_rx = tune_request_t((double)freq_in_hz);
+		tune_request_t tune_request_rx = tune_request_t((double)freq_in_hz,rate/2);
 		usrp->set_rx_freq(tune_request_rx,m_channel);
 		return (quint64)(usrp->get_rx_freq(m_channel));
 	}

uhd_cpp/uhd_spectrum/uhd_device_win32.cpp

@@ -252,15 +252,18 @@ quint64 uhd_device::set_center_freq(const quint64 freq_in_hz)
 {
     if (!usrp)
         return freq_in_hz;
-   fprintf(stderr, "Setting RX frequency: %f MHz...\n", freq_in_hz/1e6);
+	double srate = 0;
+	UHD_DO(uhd_usrp_get_rx_rate(usrp, m_channel, &srate));
+
+	fprintf(stderr, "Setting RX frequency: %f MHz...\n", freq_in_hz/1e6);
     uhd_tune_result_t rx_tune_result;
     uhd_tune_request_t rx_tune_request =
     {
         /*.target_freq =*/ (double)freq_in_hz,
         /*.rf_freq_policy =*/ UHD_TUNE_REQUEST_POLICY_AUTO,
         /*.rf_freq =*/ 0,
-        /*.dsp_freq_policy = */UHD_TUNE_REQUEST_POLICY_AUTO,
-        /*.dsp_freq =*/ 0,
+		/*.dsp_freq_policy = */UHD_TUNE_REQUEST_POLICY_MANUAL,
+		/*.dsp_freq =*/ srate/2,
         /*.args =*/ 0
     };
     UHD_DO(uhd_usrp_set_rx_freq(usrp, &rx_tune_request, m_channel, &rx_tune_result));