diff --git a/src/algorithms/observables/gnuradio_blocks/hybrid_observables_gs.cc b/src/algorithms/observables/gnuradio_blocks/hybrid_observables_gs.cc
index 48a1b1c14..0bfef7185 100644
--- a/src/algorithms/observables/gnuradio_blocks/hybrid_observables_gs.cc
+++ b/src/algorithms/observables/gnuradio_blocks/hybrid_observables_gs.cc
@@ -70,6 +70,7 @@ hybrid_observables_gs::hybrid_observables_gs(const Obs_Conf &conf_)
       d_smooth_filter_M(static_cast<double>(conf_.smoothing_factor)),
       d_T_rx_step_s(static_cast<double>(conf_.observable_interval_ms) / 1000.0),
       d_last_rx_clock_round20ms_error(0.0),
+      d_ref_channel(0U),
       d_T_rx_TOW_ms(0U),
       d_T_rx_step_ms(conf_.observable_interval_ms),
       d_T_status_report_timer_ms(0),
@@ -225,6 +226,7 @@ void hybrid_observables_gs::msg_handler_pvt_to_observables(const pmt::pmt_t &msg
                         {
                         case 1:  // reset TOW
                             d_T_rx_TOW_ms = 0;
+                            d_ref_channel = 0;
                             d_last_rx_clock_round20ms_error = 0;
                             d_T_rx_TOW_set = false;
                             for (uint32_t n = 0; n < d_nchannels_out; n++)
@@ -508,17 +510,20 @@ void hybrid_observables_gs::update_TOW(const std::vector<Gnss_Synchro> &data)
         {
             // int32_t TOW_ref = std::numeric_limits<uint32_t>::max();
             uint32_t TOW_ref = 0U;
+            uint32_t ref_ch = 0U;
             for (it = data.cbegin(); it != data.cend(); it++)
                 {
                     if (it->Flag_valid_word)
                         {
                             if (it->TOW_at_current_symbol_ms > TOW_ref)
                                 {
+                                    ref_ch = it->Channel_ID;
                                     TOW_ref = it->TOW_at_current_symbol_ms;
                                     d_T_rx_TOW_set = true;
                                 }
                         }
                 }
+            d_ref_channel = ref_ch;
             d_T_rx_TOW_ms = TOW_ref;
             // align the receiver clock to integer multiple of d_T_rx_step_ms
             if (d_T_rx_TOW_ms % d_T_rx_step_ms)
@@ -756,6 +761,9 @@ int hybrid_observables_gs::general_work(int noutput_items __attribute__((unused)
         {
             std::vector<Gnss_Synchro> epoch_data(d_nchannels_out);
             int32_t n_valid = 0;
+            std::vector<gr::tag_t> tags{};
+            get_tags_in_range(tags, d_ref_channel, nitems_read(d_ref_channel) - ninput_items[d_ref_channel], nitems_read(d_ref_channel), pmt::mp("extra_data"));
+
             for (uint32_t n = 0; n < d_nchannels_out; n++)
                 {
                     Gnss_Synchro interpolated_gnss_synchro{};
@@ -802,6 +810,12 @@ int hybrid_observables_gs::general_work(int noutput_items __attribute__((unused)
             // output the observables set to the PVT block
             for (uint32_t n = 0; n < d_nchannels_out; n++)
                 {
+                    for (const auto &tag : tags)
+                        {
+                            add_item_tag(n, this->nitems_written(n) + 1, tag.key, tag.value);
+                            // std::cout << "[ED TAG (TRK)] [" << std::to_string(tag.offset) << "] ";
+                            // std::cout << std::endl;
+                        }
                     out[n][0] = epoch_data[n];
                 }
             // report channel status every second
diff --git a/src/algorithms/observables/gnuradio_blocks/hybrid_observables_gs.h b/src/algorithms/observables/gnuradio_blocks/hybrid_observables_gs.h
index 96a83b733..f23e67795 100644
--- a/src/algorithms/observables/gnuradio_blocks/hybrid_observables_gs.h
+++ b/src/algorithms/observables/gnuradio_blocks/hybrid_observables_gs.h
@@ -102,6 +102,7 @@ private:
     double d_T_rx_step_s;
     double d_last_rx_clock_round20ms_error;
 
+    uint32_t d_ref_channel;
     uint32_t d_T_rx_TOW_ms;
     uint32_t d_T_rx_step_ms;
     uint32_t d_T_status_report_timer_ms;