diff --git a/CMakeLists.txt b/CMakeLists.txt
index df28a6ecb..fe0f20d8f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -586,14 +586,14 @@ endif()
 ################################################################################
 # Log4cpp - http://log4cpp.sourceforge.net/
 ################################################################################
-find_package(LOG4CPP)
-set_package_properties(LOG4CPP PROPERTIES
-    PURPOSE "Required by GNU Radio."
-    TYPE REQUIRED
-)
-if(NOT LOG4CPP_FOUND)
-    message(FATAL_ERROR "*** Log4cpp is required to build gnss-sdr")
-endif()
+#find_package(LOG4CPP)
+#set_package_properties(LOG4CPP PROPERTIES
+#    PURPOSE "Required by GNU Radio."
+#    TYPE REQUIRED
+#)
+#if(NOT LOG4CPP_FOUND)
+#    message(FATAL_ERROR "*** Log4cpp is required to build gnss-sdr")
+#endif()
 
 
 
@@ -607,7 +607,7 @@ if(NOT ENABLE_OWN_GPSTK)
         PURPOSE "Used in some Extra Tests."
     )
 endif()
-if(NOT (GNURADIO_VERSION VERSION_LESS 3.8) AND LOG4CPP_READY_FOR_CXX17)
+#if(NOT (GNURADIO_VERSION VERSION_LESS 3.8) AND LOG4CPP_READY_FOR_CXX17)
     # Check if we have std::filesystem
     if(NOT (CMAKE_VERSION VERSION_LESS 3.8))
         if(NOT GPSTK_FOUND OR NOT (GPSTK_FOUND AND GPSTK_OLDER_THAN_8))  # Fix for GPSTk < 8.0.0
@@ -628,7 +628,12 @@ if(NOT (GNURADIO_VERSION VERSION_LESS 3.8) AND LOG4CPP_READY_FOR_CXX17)
             set(CMAKE_CXX_STANDARD_REQUIRED ON)
         endif()
     endif()
-endif()
+#endif()
+message(ALERT " debugging CMake ..."
+"\n     GNURADIO_VERSION=${GNURADIO_VERSION}"
+#"\n     LOG4CPP_READY_FOR_CXX17=${LOG4CPP_READY_FOR_CXX17}"
+"\n     CMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}"
+)
 
 
 
diff --git a/src/algorithms/signal_source/adapters/ad9361_fpga_signal_source.h b/src/algorithms/signal_source/adapters/ad9361_fpga_signal_source.h
index 2e1c951a3..6ac364fe0 100644
--- a/src/algorithms/signal_source/adapters/ad9361_fpga_signal_source.h
+++ b/src/algorithms/signal_source/adapters/ad9361_fpga_signal_source.h
@@ -18,6 +18,8 @@
 #ifndef GNSS_SDR_AD9361_FPGA_SIGNAL_SOURCE_H
 #define GNSS_SDR_AD9361_FPGA_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "fpga_dynamic_bit_selection.h"
 #include "fpga_switch.h"
@@ -38,7 +40,7 @@
 
 class ConfigurationInterface;
 
-class Ad9361FpgaSignalSource : public GNSSBlockInterface
+class Ad9361FpgaSignalSource : public SignalSourceInterface
 {
 public:
     Ad9361FpgaSignalSource(const ConfigurationInterface *configuration,
diff --git a/src/algorithms/signal_source/adapters/custom_udp_signal_source.h b/src/algorithms/signal_source/adapters/custom_udp_signal_source.h
index fb3aa39b4..af85a4696 100644
--- a/src/algorithms/signal_source/adapters/custom_udp_signal_source.h
+++ b/src/algorithms/signal_source/adapters/custom_udp_signal_source.h
@@ -18,6 +18,8 @@
 #ifndef GNSS_SDR_CUSTOM_UDP_SIGNAL_SOURCE_H
 #define GNSS_SDR_CUSTOM_UDP_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include "gr_complex_ip_packet_source.h"
@@ -40,9 +42,10 @@ class ConfigurationInterface;
  * \brief This class reads from UDP packets, which streams interleaved
  * I/Q samples over a network.
  */
-class CustomUDPSignalSource : public GNSSBlockInterface
+class CustomUDPSignalSource : public SignalSourceInterface
 {
 public:
+  void fixme() final {}
     CustomUDPSignalSource(const ConfigurationInterface* configuration,
         const std::string& role, unsigned int in_stream,
         unsigned int out_stream, Concurrent_Queue<pmt::pmt_t>* queue);
diff --git a/src/algorithms/signal_source/adapters/file_signal_source.h b/src/algorithms/signal_source/adapters/file_signal_source.h
index 1ba059a0c..ab4a234fa 100644
--- a/src/algorithms/signal_source/adapters/file_signal_source.h
+++ b/src/algorithms/signal_source/adapters/file_signal_source.h
@@ -21,6 +21,8 @@
 #ifndef GNSS_SDR_FILE_SIGNAL_SOURCE_H
 #define GNSS_SDR_FILE_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include <gnuradio/blocks/file_sink.h>
@@ -45,9 +47,10 @@ class ConfigurationInterface;
  * \brief Class that reads signals samples from a file
  * and adapts it to a SignalSourceInterface
  */
-class FileSignalSource : public GNSSBlockInterface
+class FileSignalSource : public SignalSourceInterface
 {
 public:
+  void fixme() final {}
     FileSignalSource(const ConfigurationInterface* configuration, const std::string& role,
         unsigned int in_streams, unsigned int out_streams,
         Concurrent_Queue<pmt::pmt_t>* queue);
diff --git a/src/algorithms/signal_source/adapters/flexiband_signal_source.h b/src/algorithms/signal_source/adapters/flexiband_signal_source.h
index 4dca13e68..a63fc1de1 100644
--- a/src/algorithms/signal_source/adapters/flexiband_signal_source.h
+++ b/src/algorithms/signal_source/adapters/flexiband_signal_source.h
@@ -20,6 +20,8 @@
 #ifndef GNSS_SDR_FLEXIBAND_SIGNAL_SOURCE_H
 #define GNSS_SDR_FLEXIBAND_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include <gnuradio/blocks/char_to_float.h>
@@ -45,7 +47,7 @@ class ConfigurationInterface;
  * \brief This class configures and reads samples from Teleorbit Flexiband front-end.
  * This software requires a Flexiband GNU Radio driver installed (not included with GNSS-SDR).
  */
-class FlexibandSignalSource : public GNSSBlockInterface
+class FlexibandSignalSource : public SignalSourceInterface
 {
 public:
     FlexibandSignalSource(const ConfigurationInterface* configuration,
diff --git a/src/algorithms/signal_source/adapters/fmcomms2_signal_source.h b/src/algorithms/signal_source/adapters/fmcomms2_signal_source.h
index 1038548cb..7d35629c5 100644
--- a/src/algorithms/signal_source/adapters/fmcomms2_signal_source.h
+++ b/src/algorithms/signal_source/adapters/fmcomms2_signal_source.h
@@ -20,6 +20,8 @@
 #ifndef GNSS_SDR_FMCOMMS2_SIGNAL_SOURCE_H
 #define GNSS_SDR_FMCOMMS2_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "gnss_block_interface.h"
 #include <gnuradio/blocks/file_sink.h>
 #if GRIIO_INCLUDE_HAS_GNURADIO
@@ -41,7 +43,7 @@
 
 class ConfigurationInterface;
 
-class Fmcomms2SignalSource : public GNSSBlockInterface
+class Fmcomms2SignalSource : public SignalSourceInterface
 {
 public:
     Fmcomms2SignalSource(const ConfigurationInterface* configuration,
diff --git a/src/algorithms/signal_source/adapters/gen_signal_source.h b/src/algorithms/signal_source/adapters/gen_signal_source.h
index 42cff5237..c75d02526 100644
--- a/src/algorithms/signal_source/adapters/gen_signal_source.h
+++ b/src/algorithms/signal_source/adapters/gen_signal_source.h
@@ -20,6 +20,8 @@
 #define GNSS_SDR_GEN_SIGNAL_SOURCE_H
 
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include <pmt/pmt.h>
@@ -37,16 +39,13 @@
  * \brief This class wraps blocks that generates synthesized GNSS signal and
  * filters the signal.
  */
-class GenSignalSource : public GNSSBlockInterface
+class GenSignalSource : public SignalSourceInterface
 {
 public:
     //! Constructor
     GenSignalSource(std::shared_ptr<GNSSBlockInterface> signal_generator, std::shared_ptr<GNSSBlockInterface> filter,
         std::string role, Concurrent_Queue<pmt::pmt_t> *queue);
 
-    //! Virtual destructor
-    virtual ~GenSignalSource() = default;
-
     void connect(gr::top_block_sptr top_block) override;
     void disconnect(gr::top_block_sptr top_block) override;
     gr::basic_block_sptr get_left_block() override;
diff --git a/src/algorithms/signal_source/adapters/gn3s_signal_source.h b/src/algorithms/signal_source/adapters/gn3s_signal_source.h
index 01ab5bc2c..2081b9da5 100644
--- a/src/algorithms/signal_source/adapters/gn3s_signal_source.h
+++ b/src/algorithms/signal_source/adapters/gn3s_signal_source.h
@@ -18,6 +18,8 @@
 #ifndef GNSS_SDR_GN3S_SIGNAL_SOURCE_H
 #define GNSS_SDR_GN3S_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include <gnuradio/blocks/file_sink.h>
@@ -38,7 +40,7 @@ class ConfigurationInterface;
 /*!
  * \brief This class reads samples from a GN3S USB dongle, a RF front-end signal sampler
  */
-class Gn3sSignalSource : public GNSSBlockInterface
+class Gn3sSignalSource : public SignalSourceInterface
 {
 public:
     Gn3sSignalSource(const ConfigurationInterface* configuration,
diff --git a/src/algorithms/signal_source/adapters/labsat_signal_source.h b/src/algorithms/signal_source/adapters/labsat_signal_source.h
index f93f55570..b2ab00161 100644
--- a/src/algorithms/signal_source/adapters/labsat_signal_source.h
+++ b/src/algorithms/signal_source/adapters/labsat_signal_source.h
@@ -18,6 +18,8 @@
 #ifndef GNSS_SDR_LABSAT_SIGNAL_SOURCE_H
 #define GNSS_SDR_LABSAT_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include <gnuradio/blocks/file_sink.h>
@@ -38,9 +40,10 @@ class ConfigurationInterface;
 /*!
  * \brief This class reads samples stored by a LabSat 2 or LabSat 3 device
  */
-class LabsatSignalSource : public GNSSBlockInterface
+class LabsatSignalSource : public SignalSourceInterface
 {
 public:
+  void fixme() final {}
     LabsatSignalSource(const ConfigurationInterface* configuration,
         const std::string& role, unsigned int in_stream,
         unsigned int out_stream, Concurrent_Queue<pmt::pmt_t>* queue);
diff --git a/src/algorithms/signal_source/adapters/multichannel_file_signal_source.h b/src/algorithms/signal_source/adapters/multichannel_file_signal_source.h
index 2632777f5..caf467df0 100644
--- a/src/algorithms/signal_source/adapters/multichannel_file_signal_source.h
+++ b/src/algorithms/signal_source/adapters/multichannel_file_signal_source.h
@@ -21,6 +21,8 @@
 #ifndef GNSS_SDR_MULTICHANNEL_FILE_SIGNAL_SOURCE_H
 #define GNSS_SDR_MULTICHANNEL_FILE_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include <gnuradio/blocks/file_sink.h>
@@ -45,9 +47,10 @@ class ConfigurationInterface;
  * \brief Class that reads signals samples from files at different frequency bands
  * and adapts it to a SignalSourceInterface
  */
-class MultichannelFileSignalSource : public GNSSBlockInterface
+class MultichannelFileSignalSource : public SignalSourceInterface
 {
 public:
+  void fixme() final {}
     MultichannelFileSignalSource(const ConfigurationInterface* configuration, const std::string& role,
         unsigned int in_streams, unsigned int out_streams,
         Concurrent_Queue<pmt::pmt_t>* queue);
diff --git a/src/algorithms/signal_source/adapters/nsr_file_signal_source.h b/src/algorithms/signal_source/adapters/nsr_file_signal_source.h
index 642f692f4..afe7a1c99 100644
--- a/src/algorithms/signal_source/adapters/nsr_file_signal_source.h
+++ b/src/algorithms/signal_source/adapters/nsr_file_signal_source.h
@@ -21,6 +21,8 @@
 #ifndef GNSS_SDR_NSR_FILE_SIGNAL_SOURCE_H
 #define GNSS_SDR_NSR_FILE_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include "unpack_byte_2bit_samples.h"
@@ -42,9 +44,10 @@ class ConfigurationInterface;
  * \brief Class that reads signals samples from a file
  * and adapts it to a SignalSourceInterface
  */
-class NsrFileSignalSource : public GNSSBlockInterface
+class NsrFileSignalSource : public SignalSourceInterface
 {
 public:
+  void fixme() final {}
     NsrFileSignalSource(const ConfigurationInterface* configuration, const std::string& role,
         unsigned int in_streams, unsigned int out_streams,
         Concurrent_Queue<pmt::pmt_t>* queue);
diff --git a/src/algorithms/signal_source/adapters/osmosdr_signal_source.h b/src/algorithms/signal_source/adapters/osmosdr_signal_source.h
index a25aad183..442de26d0 100644
--- a/src/algorithms/signal_source/adapters/osmosdr_signal_source.h
+++ b/src/algorithms/signal_source/adapters/osmosdr_signal_source.h
@@ -19,6 +19,8 @@
 #ifndef GNSS_SDR_OSMOSDR_SIGNAL_SOURCE_H
 #define GNSS_SDR_OSMOSDR_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include <gnuradio/blocks/file_sink.h>
@@ -42,7 +44,7 @@ class ConfigurationInterface;
  * HackRF or Realtek's RTL2832U-based USB dongle DVB-T receivers
  * (see https://osmocom.org/projects/rtl-sdr/wiki)
  */
-class OsmosdrSignalSource : public GNSSBlockInterface
+class OsmosdrSignalSource : public SignalSourceInterface
 {
 public:
     OsmosdrSignalSource(const ConfigurationInterface* configuration,
diff --git a/src/algorithms/signal_source/adapters/plutosdr_signal_source.h b/src/algorithms/signal_source/adapters/plutosdr_signal_source.h
index e27d25c48..07534923d 100644
--- a/src/algorithms/signal_source/adapters/plutosdr_signal_source.h
+++ b/src/algorithms/signal_source/adapters/plutosdr_signal_source.h
@@ -19,6 +19,8 @@
 #ifndef GNSS_SDR_PLUTOSDR_SIGNAL_SOURCE_H
 #define GNSS_SDR_PLUTOSDR_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "gnss_block_interface.h"
 #include <gnuradio/blocks/file_sink.h>
 #if GRIIO_INCLUDE_HAS_GNURADIO
@@ -42,7 +44,7 @@ class ConfigurationInterface;
 
 /*!
  */
-class PlutosdrSignalSource : public GNSSBlockInterface
+class PlutosdrSignalSource : public SignalSourceInterface
 {
 public:
     PlutosdrSignalSource(const ConfigurationInterface* configuration,
diff --git a/src/algorithms/signal_source/adapters/raw_array_signal_source.h b/src/algorithms/signal_source/adapters/raw_array_signal_source.h
index f61342dc7..8fe4be6a4 100644
--- a/src/algorithms/signal_source/adapters/raw_array_signal_source.h
+++ b/src/algorithms/signal_source/adapters/raw_array_signal_source.h
@@ -18,6 +18,8 @@
 #ifndef GNSS_SDR_RAW_ARRAY_SIGNAL_SOURCE_H
 #define GNSS_SDR_RAW_ARRAY_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include <gnuradio/blocks/file_sink.h>
@@ -39,7 +41,7 @@ class ConfigurationInterface;
 /*!
  * \brief This class reads samples from a GN3S USB dongle, a RF front-end signal sampler
  */
-class RawArraySignalSource : public GNSSBlockInterface
+class RawArraySignalSource : public SignalSourceInterface
 {
 public:
     RawArraySignalSource(const ConfigurationInterface* configuration,
diff --git a/src/algorithms/signal_source/adapters/rtl_tcp_signal_source.h b/src/algorithms/signal_source/adapters/rtl_tcp_signal_source.h
index 27af99ac5..6dc5889c3 100644
--- a/src/algorithms/signal_source/adapters/rtl_tcp_signal_source.h
+++ b/src/algorithms/signal_source/adapters/rtl_tcp_signal_source.h
@@ -18,6 +18,8 @@
 #ifndef GNSS_SDR_RTL_TCP_SIGNAL_SOURCE_H
 #define GNSS_SDR_RTL_TCP_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include "rtl_tcp_signal_source_c.h"
@@ -42,9 +44,10 @@ class ConfigurationInterface;
  * I/Q samples over TCP.
  * (see https://osmocom.org/projects/rtl-sdr/wiki)
  */
-class RtlTcpSignalSource : public GNSSBlockInterface
+class RtlTcpSignalSource : public SignalSourceInterface
 {
 public:
+  void fixme() final {}
     RtlTcpSignalSource(const ConfigurationInterface* configuration,
         const std::string& role,
         unsigned int in_stream,
diff --git a/src/algorithms/signal_source/adapters/spir_file_signal_source.h b/src/algorithms/signal_source/adapters/spir_file_signal_source.h
index 0b7c11b9e..565b53ede 100644
--- a/src/algorithms/signal_source/adapters/spir_file_signal_source.h
+++ b/src/algorithms/signal_source/adapters/spir_file_signal_source.h
@@ -21,6 +21,8 @@
 #ifndef GNSS_SDR_SPIR_FILE_SIGNAL_SOURCE_H
 #define GNSS_SDR_SPIR_FILE_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
 #include "gnss_block_interface.h"
 #include "unpack_intspir_1bit_samples.h"
@@ -45,9 +47,10 @@ class ConfigurationInterface;
  * \brief Class that reads signals samples from a file
  * and adapts it to a SignalSourceInterface
  */
-class SpirFileSignalSource : public GNSSBlockInterface
+class SpirFileSignalSource : public SignalSourceInterface
 {
 public:
+  void fixme() final {}
     SpirFileSignalSource(const ConfigurationInterface* configuration, const std::string& role,
         unsigned int in_streams, unsigned int out_streams,
         Concurrent_Queue<pmt::pmt_t>* queue);
diff --git a/src/algorithms/signal_source/adapters/spir_gss6450_file_signal_source.h b/src/algorithms/signal_source/adapters/spir_gss6450_file_signal_source.h
index 2fe2e3962..00d9c0333 100644
--- a/src/algorithms/signal_source/adapters/spir_gss6450_file_signal_source.h
+++ b/src/algorithms/signal_source/adapters/spir_gss6450_file_signal_source.h
@@ -21,8 +21,9 @@
 #ifndef GNSS_SDR_SPIR_GSS6450_FILE_SIGNAL_SOURCE_H
 #define GNSS_SDR_SPIR_GSS6450_FILE_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
-#include "gnss_block_interface.h"
 #include "gnss_sdr_valve.h"
 #include "unpack_spir_gss6450_samples.h"
 #include <gnuradio/blocks/deinterleave.h>
@@ -50,13 +51,13 @@ class ConfigurationInterface;
  * \brief Class that reads signals samples from a file
  * and adapts it to a SignalSourceInterface
  */
-class SpirGSS6450FileSignalSource : public GNSSBlockInterface
+class SpirGSS6450FileSignalSource : public SignalSourceInterface
 {
 public:
+  void fixme() final {}
     SpirGSS6450FileSignalSource(const ConfigurationInterface* configuration, const std::string& role,
         uint32_t in_streams, uint32_t out_streams, Concurrent_Queue<pmt::pmt_t>* queue);
 
-    ~SpirGSS6450FileSignalSource() = default;
     inline std::string role() override
     {
         return role_;
diff --git a/src/algorithms/signal_source/adapters/two_bit_cpx_file_signal_source.h b/src/algorithms/signal_source/adapters/two_bit_cpx_file_signal_source.h
index 59987a623..25ba669ef 100644
--- a/src/algorithms/signal_source/adapters/two_bit_cpx_file_signal_source.h
+++ b/src/algorithms/signal_source/adapters/two_bit_cpx_file_signal_source.h
@@ -20,8 +20,9 @@
 #ifndef GNSS_SDR_TWO_BIT_CPX_FILE_SIGNAL_SOURCE_H
 #define GNSS_SDR_TWO_BIT_CPX_FILE_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
-#include "gnss_block_interface.h"
 #include "unpack_byte_2bit_cpx_samples.h"
 #include <gnuradio/blocks/file_sink.h>
 #include <gnuradio/blocks/file_source.h>
@@ -44,9 +45,10 @@ class ConfigurationInterface;
  * \brief Class that reads signals samples from a file
  * and adapts it to a SignalSourceInterface
  */
-class TwoBitCpxFileSignalSource : public GNSSBlockInterface
+class TwoBitCpxFileSignalSource : public SignalSourceInterface
 {
 public:
+  void fixme() final {}
     TwoBitCpxFileSignalSource(const ConfigurationInterface* configuration,
         const std::string& role,
         unsigned int in_streams,
diff --git a/src/algorithms/signal_source/adapters/two_bit_packed_file_signal_source.h b/src/algorithms/signal_source/adapters/two_bit_packed_file_signal_source.h
index c87a7759f..2be63790f 100644
--- a/src/algorithms/signal_source/adapters/two_bit_packed_file_signal_source.h
+++ b/src/algorithms/signal_source/adapters/two_bit_packed_file_signal_source.h
@@ -21,8 +21,9 @@
 #ifndef GNSS_SDR_TWO_BIT_PACKED_FILE_SIGNAL_SOURCE_H
 #define GNSS_SDR_TWO_BIT_PACKED_FILE_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
-#include "gnss_block_interface.h"
 #include "unpack_2bit_samples.h"
 #include <gnuradio/blocks/file_sink.h>
 #include <gnuradio/blocks/file_source.h>
@@ -46,9 +47,10 @@ class ConfigurationInterface;
  * \brief Class that reads signals samples from a file
  * and adapts it to a SignalSourceInterface
  */
-class TwoBitPackedFileSignalSource : public GNSSBlockInterface
+class TwoBitPackedFileSignalSource : public SignalSourceInterface
 {
 public:
+  void fixme() final {}
     TwoBitPackedFileSignalSource(const ConfigurationInterface* configuration, const std::string& role,
         unsigned int in_streams, unsigned int out_streams,
         Concurrent_Queue<pmt::pmt_t>* queue);
diff --git a/src/algorithms/signal_source/adapters/uhd_signal_source.h b/src/algorithms/signal_source/adapters/uhd_signal_source.h
index 8cc9e27ec..6394cbcc2 100644
--- a/src/algorithms/signal_source/adapters/uhd_signal_source.h
+++ b/src/algorithms/signal_source/adapters/uhd_signal_source.h
@@ -17,8 +17,9 @@
 #ifndef GNSS_SDR_UHD_SIGNAL_SOURCE_H
 #define GNSS_SDR_UHD_SIGNAL_SOURCE_H
 
+#include "signal_source_interface.h"
+
 #include "concurrent_queue.h"
-#include "gnss_block_interface.h"
 #include <gnuradio/blocks/file_sink.h>
 #include <gnuradio/hier_block2.h>
 #include <gnuradio/uhd/usrp_source.h>
@@ -38,7 +39,7 @@ class ConfigurationInterface;
 /*!
  * \brief This class reads samples from a UHD device (see http://code.ettus.com/redmine/ettus/projects/uhd/wiki)
  */
-class UhdSignalSource : public GNSSBlockInterface
+class UhdSignalSource : public SignalSourceInterface
 {
 public:
     UhdSignalSource(const ConfigurationInterface* configuration,
diff --git a/src/core/interfaces/signal_source_interface.h b/src/core/interfaces/signal_source_interface.h
new file mode 100644
index 000000000..c6ba1b079
--- /dev/null
+++ b/src/core/interfaces/signal_source_interface.h
@@ -0,0 +1,62 @@
+/*!
+ * \signal_source_interface.h
+ * \brief Header file of the interface to a signal_source GNSS block.
+ * \author Jim Melton, 2020. jim.melton(at)sncorp.com
+ *
+ * This header file contains the interface to an abstract class for
+ * signal sources. Since all its methods are virtual, this class
+ * cannot be instantiated directly, and a subclass can only be
+ * instantiated directly if all inherited pure virtual methods have
+ * been implemented by that class or a parent class.
+ *
+ * -----------------------------------------------------------------------------
+ *
+ * Copyright (C) 2010-2020  (see AUTHORS file for a list of contributors)
+ *
+ * GNSS-SDR is a software defined Global Navigation
+ *          Satellite Systems receiver
+ *
+ * This file is part of GNSS-SDR.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ * -----------------------------------------------------------------------------
+ */
+
+#ifndef GNSS_SDR_SIGNAL_SOURCE_INTERFACE_H
+#define GNSS_SDR_SIGNAL_SOURCE_INTERFACE_H
+
+#include "gnss_block_interface.h"
+
+/** \addtogroup Core
+ * \{ */
+/** \addtogroup GNSS_Block_Interfaces GNSS block interfaces
+ * GNSS block interfaces.
+ * \{ */
+
+/*! \brief This abstract class represents an interface to signal_source GNSS block.
+ *
+ * Abstract class for signal sources. Since all its methods are virtual,
+ * this class cannot be instantiated directly, and a subclass can only be
+ * instantiated directly if all inherited pure virtual methods have been
+ * implemented by that class or a parent class.
+ */
+
+class SignalSourceInterface : public GNSSBlockInterface
+{
+    virtual std::string role() = 0;
+    virtual std::string implementation() = 0;
+    virtual size_t item_size() = 0;
+    virtual void connect(gr::top_block_sptr top_block) = 0;
+    virtual void disconnect(gr::top_block_sptr top_block) = 0;
+
+    virtual gr::basic_block_sptr get_left_block() = 0;
+    virtual gr::basic_block_sptr get_right_block() = 0;
+
+    virtual void fixme() = 0;
+};
+
+
+
+#endif
+