diff --git a/src/core/libs/gnss_sdr_fpga_sample_counter.h b/src/core/libs/gnss_sdr_fpga_sample_counter.h
index f30bb78c0..1f5db0b2d 100644
--- a/src/core/libs/gnss_sdr_fpga_sample_counter.h
+++ b/src/core/libs/gnss_sdr_fpga_sample_counter.h
@@ -48,6 +48,7 @@ gnss_sdr_fpga_sample_counter_sptr gnss_sdr_make_fpga_sample_counter(double _fs,
 class gnss_sdr_fpga_sample_counter : public gr::block
 {
 private:
+    friend gnss_sdr_fpga_sample_counter_sptr gnss_sdr_make_fpga_sample_counter(double _fs, int32_t _interval_ms);
     gnss_sdr_fpga_sample_counter(double _fs, int32_t _interval_ms);
     uint32_t test_register(uint32_t writeval);
     void configure_samples_per_output(uint32_t interval);
@@ -76,7 +77,6 @@ private:
     bool is_open;
 
 public:
-    friend gnss_sdr_fpga_sample_counter_sptr gnss_sdr_make_fpga_sample_counter(double _fs, int32_t _interval_ms);
     ~gnss_sdr_fpga_sample_counter();
     int general_work(int noutput_items,
         gr_vector_int &ninput_items,
diff --git a/src/core/libs/gnss_sdr_sample_counter.cc b/src/core/libs/gnss_sdr_sample_counter.cc
index 954d5d674..a20032edd 100644
--- a/src/core/libs/gnss_sdr_sample_counter.cc
+++ b/src/core/libs/gnss_sdr_sample_counter.cc
@@ -65,6 +65,9 @@ gnss_sdr_sample_counter::gnss_sdr_sample_counter(
 }
 
 
+gnss_sdr_sample_counter::~gnss_sdr_sample_counter() = default;
+
+
 gnss_sdr_sample_counter_sptr gnss_sdr_make_sample_counter(double _fs, int32_t _interval_ms, size_t _size)
 {
     gnss_sdr_sample_counter_sptr sample_counter_(new gnss_sdr_sample_counter(_fs, _interval_ms, _size));
diff --git a/src/core/libs/gnss_sdr_sample_counter.h b/src/core/libs/gnss_sdr_sample_counter.h
index a20502b9f..af36ba869 100644
--- a/src/core/libs/gnss_sdr_sample_counter.h
+++ b/src/core/libs/gnss_sdr_sample_counter.h
@@ -51,6 +51,7 @@ gnss_sdr_sample_counter_sptr gnss_sdr_make_sample_counter(
 class gnss_sdr_sample_counter : public gr::sync_decimator
 {
 private:
+    friend gnss_sdr_sample_counter_sptr gnss_sdr_make_sample_counter(double _fs, int32_t _interval_ms, size_t _size);
     gnss_sdr_sample_counter(double _fs, int32_t _interval_ms, size_t _size);
     uint32_t samples_per_output;
     double fs;
@@ -68,7 +69,7 @@ private:
     bool flag_enable_send_msg;
 
 public:
-    friend gnss_sdr_sample_counter_sptr gnss_sdr_make_sample_counter(double _fs, int32_t _interval_ms, size_t _size);
+    ~gnss_sdr_sample_counter();
     int work(int noutput_items,
         gr_vector_const_void_star &input_items,
         gr_vector_void_star &output_items);
diff --git a/src/core/libs/gnss_sdr_time_counter.cc b/src/core/libs/gnss_sdr_time_counter.cc
index 2bf29fa77..1daabf071 100644
--- a/src/core/libs/gnss_sdr_time_counter.cc
+++ b/src/core/libs/gnss_sdr_time_counter.cc
@@ -52,6 +52,9 @@ gnss_sdr_time_counter::gnss_sdr_time_counter() : gr::block("time_counter",
 }
 
 
+gnss_sdr_time_counter::~gnss_sdr_time_counter() = default;
+
+
 gnss_sdr_time_counter_sptr gnss_sdr_make_time_counter()
 {
     gnss_sdr_time_counter_sptr counter_(new gnss_sdr_time_counter());
diff --git a/src/core/libs/gnss_sdr_time_counter.h b/src/core/libs/gnss_sdr_time_counter.h
index 7be810ec7..76a7e09ed 100644
--- a/src/core/libs/gnss_sdr_time_counter.h
+++ b/src/core/libs/gnss_sdr_time_counter.h
@@ -59,6 +59,7 @@ private:
     friend gnss_sdr_time_counter_sptr gnss_sdr_make_time_counter();
 
 public:
+    ~gnss_sdr_time_counter();
     int general_work(int noutput_items __attribute__((unused)), gr_vector_int &ninput_items __attribute__((unused)),
         gr_vector_const_void_star &input_items __attribute__((unused)), gr_vector_void_star &output_items);
 };
diff --git a/src/core/monitor/gnss_synchro_monitor.h b/src/core/monitor/gnss_synchro_monitor.h
index 632fa72ed..03c37ab28 100644
--- a/src/core/monitor/gnss_synchro_monitor.h
+++ b/src/core/monitor/gnss_synchro_monitor.h
@@ -35,6 +35,8 @@
 #define GNSS_SDR_GNSS_SYNCHRO_MONITOR_H
 
 #include "gnss_synchro_udp_sink.h"
+#include <boost/shared_ptr.hpp>
+#include <gnuradio/runtime_types.h>  // for gr_vector_void_star
 #include <gnuradio/sync_block.h>
 #include <memory>
 #include <string>
@@ -51,7 +53,9 @@ gnss_synchro_monitor_sptr gnss_synchro_make_monitor(unsigned int n_channels,
     const std::vector<std::string>& udp_addresses);
 
 /*!
- * \brief This class implements a block that computes the PVT solution with Galileo E1 signals
+ * \brief This class implements a monitoring block which allows sending
+ * a data stream with the receiver internal parameters (Gnss_Synchro objects)
+ * to local or remote clients over UDP.
  */
 class gnss_synchro_monitor : public gr::sync_block
 {
@@ -61,21 +65,17 @@ private:
         int udp_port,
         const std::vector<std::string>& udp_addresses);
 
-    unsigned int d_nchannels;
-
-    int d_decimation_factor;
-
-    std::unique_ptr<Gnss_Synchro_Udp_Sink> udp_sink_ptr;
-
-    int count;
-
-
-public:
     gnss_synchro_monitor(unsigned int n_channels,
         int decimation_factor,
         int udp_port,
         const std::vector<std::string>& udp_addresses);
 
+    unsigned int d_nchannels;
+    int d_decimation_factor;
+    std::unique_ptr<Gnss_Synchro_Udp_Sink> udp_sink_ptr;
+    int count;
+
+public:
     ~gnss_synchro_monitor();  //!< Default destructor
 
     int work(int noutput_items, gr_vector_const_void_star& input_items,
diff --git a/src/core/monitor/gnss_synchro_udp_sink.cc b/src/core/monitor/gnss_synchro_udp_sink.cc
index 2978537ea..23cb236c4 100644
--- a/src/core/monitor/gnss_synchro_udp_sink.cc
+++ b/src/core/monitor/gnss_synchro_udp_sink.cc
@@ -44,6 +44,7 @@ Gnss_Synchro_Udp_Sink::Gnss_Synchro_Udp_Sink(std::vector<std::string> addresses,
         }
 }
 
+
 bool Gnss_Synchro_Udp_Sink::write_gnss_synchro(const std::vector<Gnss_Synchro>& stocks)
 {
     std::ostringstream archive_stream;
diff --git a/src/core/monitor/gnss_synchro_udp_sink.h b/src/core/monitor/gnss_synchro_udp_sink.h
index d72b2f18a..bfaebf45d 100644
--- a/src/core/monitor/gnss_synchro_udp_sink.h
+++ b/src/core/monitor/gnss_synchro_udp_sink.h
@@ -35,10 +35,15 @@
 #include "gnss_synchro.h"
 #include <boost/asio.hpp>
 #include <boost/system/error_code.hpp>
+#include <cstdint>
 #include <string>
 #include <vector>
 
 
+/*!
+ * \brief This class sends serialized Gnss_Synchro objects
+ * over UDP to one or multiple endpoints.
+ */
 class Gnss_Synchro_Udp_Sink
 {
 public:
diff --git a/src/core/receiver/gnss_flowgraph.cc b/src/core/receiver/gnss_flowgraph.cc
index 5881a3c49..898461d16 100644
--- a/src/core/receiver/gnss_flowgraph.cc
+++ b/src/core/receiver/gnss_flowgraph.cc
@@ -1664,10 +1664,10 @@ void GNSSFlowgraph::init()
 
     if (enable_monitor_)
         {
-            GnssSynchroMonitor_ = gr::basic_block_sptr(new gnss_synchro_monitor(channels_count_,
+            GnssSynchroMonitor_ = gnss_synchro_make_monitor(channels_count_,
                 configuration_->property("Monitor.decimation_factor", 1),
                 configuration_->property("Monitor.udp_port", 1234),
-                udp_addr_vec));
+                udp_addr_vec);
         }
 }