diff --git a/srsapps/radio/include/srsapps/radio/radio_uhd.h b/srsapps/radio/include/srsapps/radio/radio_uhd.h
index 9a1677414..22ae95756 100644
--- a/srsapps/radio/include/srsapps/radio/radio_uhd.h
+++ b/srsapps/radio/include/srsapps/radio/radio_uhd.h
@@ -72,6 +72,7 @@ namespace srslte {
       
     private:
       void *uhd; 
+      bool is_first;
   }; 
 }
 
diff --git a/srsapps/radio/src/radio_uhd.cc b/srsapps/radio/src/radio_uhd.cc
index a22168ff6..0ba16daf1 100644
--- a/srsapps/radio/src/radio_uhd.cc
+++ b/srsapps/radio/src/radio_uhd.cc
@@ -57,6 +57,7 @@ void radio_uhd::set_tx_rx_gain_offset(float offset) {
 
 bool radio_uhd::init_agc(char *args)
 {
+  is_first = true; 
   printf("Opening UHD device with threaded RX Gain control ...\n");
   if (cuhd_open_th(args, &uhd, true)) {
     fprintf(stderr, "Error opening uhd\n");
@@ -87,7 +88,8 @@ void radio_uhd::get_time(srslte_timestamp_t *now) {
 
 bool radio_uhd::tx(void* buffer, uint32_t nof_samples, srslte_timestamp_t tx_time)
 {
-  if (cuhd_send_timed(uhd, buffer, nof_samples, tx_time.full_secs, tx_time.frac_secs) > 0) {
+  if (cuhd_send_timed2(uhd, buffer, nof_samples, tx_time.full_secs, tx_time.frac_secs, is_first, false) > 0) {
+    is_first = false; 
     return true; 
   } else {
     return false; 
diff --git a/srsapps/ue/phy/include/srsapps/ue/phy/ul_buffer.h b/srsapps/ue/phy/include/srsapps/ue/phy/ul_buffer.h
index aff04a192..b08faecf7 100644
--- a/srsapps/ue/phy/include/srsapps/ue/phy/ul_buffer.h
+++ b/srsapps/ue/phy/include/srsapps/ue/phy/ul_buffer.h
@@ -59,7 +59,9 @@ namespace ue {
     bool     generate_data();   
     bool     generate_data(ul_sched_grant *pusch_grant, uint8_t *payload);   
     bool     generate_data(ul_sched_grant *pusch_grant, srslte_softbuffer_tx_t *softbuffer, uint8_t *payload);   
+    bool     send(radio* radio_handler, float time_adv_sec, float cfo, srslte_timestamp_t rx_time, bool normalize_amp);
     bool     send(radio* radio_handler, float time_adv_sec, float cfo, srslte_timestamp_t rx_time);
+    bool     send_zeros(radio* radio_handler, float time_adv_sec, srslte_timestamp_t rx_time);
     static const uint32_t tx_advance_sf = 1; // Number of subframes to advance transmission
 
   private: 
diff --git a/srsapps/ue/phy/src/phy.cc b/srsapps/ue/phy/src/phy.cc
index 1b22ddf4f..313d260d5 100644
--- a/srsapps/ue/phy/src/phy.cc
+++ b/srsapps/ue/phy/src/phy.cc
@@ -518,28 +518,41 @@ void phy::run_rx_tx_state()
     log_h->step(current_tti);
     float cfo = srslte_ue_sync_get_cfo(&ue_sync)/15000; 
 
+    bool tx_zeros = true; 
+    
     // Prepare transmission for the next tti 
     srslte_timestamp_add(&last_rx_time, 0, 1e-3);
-    
-    // send prach if we have to 
+
+    // Generate scheduling request if we have to 
+    if (sr_is_ready_to_send(current_tti+ul_buffer::tx_advance_sf)) {
+      get_ul_buffer_adv(current_tti)->generate_sr();
+    }
+
+    // Every subframe, TX a PRACH or a PUSCH/PUCCH
     if (prach_buffer.is_ready_to_send(current_tti)) {
+      // send prach if we have to 
       prach_buffer.send(radio_handler, cfo, last_rx_time);
       radio_handler->set_tx_gain(old_gain);
       srslte_agc_lock(&ue_sync.agc, false);
       Info("Restoring AGC. Set TX gain to %.1f dB\n", old_gain);
-    }
-    // Generate scheduling request if we have to 
-    if (sr_is_ready_to_send(current_tti+ul_buffer::tx_advance_sf)) {
-      get_ul_buffer_adv(current_tti)->generate_sr();
-    }
-    // send ul buffer if we have to 
-    if (get_ul_buffer_adv(current_tti)->is_released() || get_ul_buffer_adv(current_tti)->uci_ready()) {
-      // Generate PUCCH if no UL grant
+    
+    // If we don't transmit PRACH, check if need to transmit PUSCH/PUCCH
+    } else if (get_ul_buffer_adv(current_tti)->is_released() || get_ul_buffer_adv(current_tti)->uci_ready()) { 
+      // If the packet was not generated by a call from MAC, means it's PUCCH. Generate now the signal
       if (!get_ul_buffer_adv(current_tti)->is_released()) {
         get_ul_buffer_adv(current_tti)->generate_data();
       }
+      // And transmit
       get_ul_buffer_adv(current_tti)->send(radio_handler, time_adv_sec, cfo, last_rx_time);      
-    } 
+    } else {
+      // Transmit zeros to avoid transitions. 
+      // FIXME: This keeps the TX RF chain always on. Should transmit zeros only before a true transmission
+      get_ul_buffer_adv(current_tti)->send_zeros(radio_handler, time_adv_sec, last_rx_time);
+    }
+    
+    
+      // send ul buffer if we have to 
+      // Generate PUCCH if no UL grant
     
     // Receive alligned buffer for the current tti 
     get_dl_buffer(current_tti)->recv_ue_sync(&ue_sync, &last_rx_time);
diff --git a/srsapps/ue/phy/src/ul_buffer.cc b/srsapps/ue/phy/src/ul_buffer.cc
index 268c77283..7d55fa349 100644
--- a/srsapps/ue/phy/src/ul_buffer.cc
+++ b/srsapps/ue/phy/src/ul_buffer.cc
@@ -218,7 +218,18 @@ bool ul_buffer::generate_data(ul_sched_grant *grant, srslte_softbuffer_tx_t *sof
 
 int nof_tx = 0; 
 
+bool ul_buffer::send_zeros(srslte::radio* radio_handler, float time_adv_sec, srslte_timestamp_t rx_time)
+{
+  bzero(signal_buffer, sizeof(cf_t)*SRSLTE_SF_LEN_PRB(cell.nof_prb));
+  send(radio_handler, time_adv_sec, 0, rx_time, false); 
+}
+
 bool ul_buffer::send(srslte::radio* radio_handler, float time_adv_sec, float cfo, srslte_timestamp_t rx_time)
+{
+  send(radio_handler, time_adv_sec, cfo, rx_time, true);
+}
+
+bool ul_buffer::send(srslte::radio* radio_handler, float time_adv_sec, float cfo, srslte_timestamp_t rx_time, bool normalize_amp)
 {
   
   // send packet through usrp 
@@ -227,20 +238,24 @@ bool ul_buffer::send(srslte::radio* radio_handler, float time_adv_sec, float cfo
   srslte_timestamp_add(&tx_time, 0, tx_advance_sf*1e-3 - time_adv_sec); 
 
   // Correct CFO before transmission
-  srslte_cfo_correct(&ue_ul.cfo, signal_buffer, signal_buffer, cfo / srslte_symbol_sz(cell.nof_prb));            
+  if (cfo != 0) {
+    srslte_cfo_correct(&ue_ul.cfo, signal_buffer, signal_buffer, cfo / srslte_symbol_sz(cell.nof_prb));            
+  }
   
   // Compute peak
   float max = 0; 
-  float *t = (float*) signal_buffer;
-  for (int i=0;i<2*SRSLTE_SF_LEN_PRB(cell.nof_prb);i++) {
-    if (fabsf(t[i]) > max) {
-      max = fabsf(t[i]);
+  if (normalize_amp) {
+    float *t = (float*) signal_buffer;
+    for (int i=0;i<2*SRSLTE_SF_LEN_PRB(cell.nof_prb);i++) {
+      if (fabsf(t[i]) > max) {
+        max = fabsf(t[i]);
+      }
     }
+    
+    // Normalize before TX 
+    srslte_vec_sc_prod_cfc(signal_buffer, 0.9/max, signal_buffer, SRSLTE_SF_LEN_PRB(cell.nof_prb));
   }
   
-  // Normalize before TX 
-  srslte_vec_sc_prod_cfc(signal_buffer, 0.9/max, signal_buffer, SRSLTE_SF_LEN_PRB(cell.nof_prb));
-
   Info("TX CFO: %f, len=%d, rx_time= %.6f tx_time = %.6f TA: %.1f us PeakAmplitude=%.2f PKT#%d\n", 
         cfo*15000, SRSLTE_SF_LEN_PRB(cell.nof_prb),
         srslte_timestamp_real(&rx_time), 
diff --git a/srslte/lib/cuhd/src/cuhd_imp.cpp b/srslte/lib/cuhd/src/cuhd_imp.cpp
index adf7bd708..45305bf2a 100644
--- a/srslte/lib/cuhd/src/cuhd_imp.cpp
+++ b/srslte/lib/cuhd/src/cuhd_imp.cpp
@@ -71,7 +71,7 @@ bool cuhd_rx_wait_lo_locked(void *h)
 {
 
   double report = 0.0;
-  while (isLocked(h) && report < 3000.0) {
+  while (isLocked(h) && report < 20.0) {
     report += 0.1;
     usleep(1000);
   }