diff --git a/background.npy b/background.npy
new file mode 100644
index 0000000..c3d18da
Binary files /dev/null and b/background.npy differ
diff --git a/rfg_adc_plotter/gui/matplotlib_backend.py b/rfg_adc_plotter/gui/matplotlib_backend.py
index e7f737f..b936a22 100644
--- a/rfg_adc_plotter/gui/matplotlib_backend.py
+++ b/rfg_adc_plotter/gui/matplotlib_backend.py
@@ -12,7 +12,7 @@ from rfg_adc_plotter.constants import FFT_LEN, FREQ_SPAN_GHZ, IFFT_LEN
 _IFFT_T_MAX_NS = float((IFFT_LEN - 1) / (FREQ_SPAN_GHZ * 1e9) * 1e9)
 from rfg_adc_plotter.io.sweep_reader import SweepReader
 from rfg_adc_plotter.processing.normalizer import build_calib_envelopes
-from rfg_adc_plotter.state.app_state import CALIB_ENVELOPE_PATH, AppState, format_status
+from rfg_adc_plotter.state.app_state import BACKGROUND_PATH, CALIB_ENVELOPE_PATH, AppState, format_status
 from rfg_adc_plotter.state.ring_buffer import RingBuffer
 from rfg_adc_plotter.types import SweepPacket
 
@@ -204,6 +204,24 @@ def run_matplotlib(args):
             state.set_calib_enabled(bool(calib_cb.get_status()[0]))
             fig.canvas.draw_idle()
 
+        ax_btn_bg = fig.add_axes([0.92, 0.27, 0.08, 0.05])
+        ax_cb_bg = fig.add_axes([0.92, 0.20, 0.08, 0.06])
+        from matplotlib.widgets import Button as MplButton
+        save_bg_btn = MplButton(ax_btn_bg, "Сохр. фон")
+        bg_cb = CheckButtons(ax_cb_bg, ["вычет фона"], [False])
+
+        def _on_save_bg(_event):
+            ok = state.save_background()
+            if ok:
+                state.load_background()
+            fig.canvas.draw_idle()
+
+        def _on_bg_clicked(_v):
+            state.set_background_enabled(bool(bg_cb.get_status()[0]))
+
+        save_bg_btn.on_clicked(_on_save_bg)
+        bg_cb.on_clicked(_on_bg_clicked)
+
         ymin_slider.on_changed(_on_ylim_change)
         ymax_slider.on_changed(_on_ylim_change)
         contrast_slider.on_changed(lambda _v: fig.canvas.draw_idle())
diff --git a/rfg_adc_plotter/gui/pyqtgraph_backend.py b/rfg_adc_plotter/gui/pyqtgraph_backend.py
index ed76229..97aa872 100644
--- a/rfg_adc_plotter/gui/pyqtgraph_backend.py
+++ b/rfg_adc_plotter/gui/pyqtgraph_backend.py
@@ -10,7 +10,7 @@ import numpy as np
 from rfg_adc_plotter.constants import FREQ_SPAN_GHZ, IFFT_LEN
 from rfg_adc_plotter.io.sweep_reader import SweepReader
 from rfg_adc_plotter.processing.normalizer import build_calib_envelopes
-from rfg_adc_plotter.state.app_state import CALIB_ENVELOPE_PATH, AppState, format_status
+from rfg_adc_plotter.state.app_state import BACKGROUND_PATH, CALIB_ENVELOPE_PATH, AppState, format_status
 from rfg_adc_plotter.state.ring_buffer import RingBuffer
 from rfg_adc_plotter.types import SweepPacket
 
@@ -225,6 +225,32 @@ def run_pyqtgraph(args):
     calib_cb.stateChanged.connect(_on_calib_toggled)
     calib_file_cb.stateChanged.connect(lambda _v: _on_calib_file_toggled(calib_file_cb.isChecked()))
 
+    # Кнопка сохранения фона + чекбокс вычета фона
+    bg_widget = QtWidgets.QWidget()
+    bg_layout = QtWidgets.QHBoxLayout(bg_widget)
+    bg_layout.setContentsMargins(2, 2, 2, 2)
+    bg_layout.setSpacing(8)
+
+    save_bg_btn = QtWidgets.QPushButton("Сохр. фон")
+    bg_cb = QtWidgets.QCheckBox("вычет фона")
+    bg_cb.setEnabled(False)
+
+    bg_layout.addWidget(save_bg_btn)
+    bg_layout.addWidget(bg_cb)
+
+    bg_container_proxy = QtWidgets.QGraphicsProxyWidget()
+    bg_container_proxy.setWidget(bg_widget)
+    win.addItem(bg_container_proxy, row=2, col=0)
+
+    def _on_save_bg():
+        ok = state.save_background()
+        if ok:
+            state.load_background()
+            bg_cb.setEnabled(True)
+
+    save_bg_btn.clicked.connect(_on_save_bg)
+    bg_cb.stateChanged.connect(lambda _v: state.set_background_enabled(bg_cb.isChecked()))
+
     # Статусная строка
     status = pg.LabelItem(justify="left")
     win.addItem(status, row=3, col=0, colspan=2)
diff --git a/rfg_adc_plotter/state/app_state.py b/rfg_adc_plotter/state/app_state.py
index 229b273..0530fb4 100644
--- a/rfg_adc_plotter/state/app_state.py
+++ b/rfg_adc_plotter/state/app_state.py
@@ -15,6 +15,7 @@ from rfg_adc_plotter.state.ring_buffer import RingBuffer
 from rfg_adc_plotter.types import SweepInfo, SweepPacket
 
 CALIB_ENVELOPE_PATH = "calib_envelope.npy"
+BACKGROUND_PATH = "background.npy"
 
 
 def format_status(data: Mapping[str, Any]) -> str:
@@ -54,6 +55,10 @@ class AppState:
         # "live" — нормировка по текущему ch0-свипу; "file" — по огибающей из файла
         self.calib_mode: str = "live"
         self.calib_file_envelope: Optional[np.ndarray] = None
+        # Вычет фона
+        self.background: Optional[np.ndarray] = None
+        self.background_enabled: bool = False
+        self._last_sweep_for_ring: Optional[np.ndarray] = None
 
     def _normalize(self, raw: np.ndarray, calib: np.ndarray) -> np.ndarray:
         if self.calib_mode == "file" and self.calib_file_envelope is not None:
@@ -96,6 +101,43 @@ class AppState:
         """Переключить режим калибровки: 'live' или 'file'."""
         self.calib_mode = mode
 
+    def save_background(self, path: str = BACKGROUND_PATH) -> bool:
+        """Сохранить текущий sweep_for_ring как фоновый спектр.
+
+        Сохраняет последний свип, который был записан в ринг-буфер
+        (нормированный, если калибровка включена, иначе сырой).
+        Возвращает True при успехе.
+        """
+        if self._last_sweep_for_ring is None:
+            return False
+        try:
+            np.save(path, self._last_sweep_for_ring)
+            return True
+        except Exception as exc:
+            import sys
+            sys.stderr.write(f"[warn] Не удалось сохранить фон: {exc}\n")
+            return False
+
+    def load_background(self, path: str = BACKGROUND_PATH) -> bool:
+        """Загрузить фоновый спектр из файла.
+
+        Возвращает True при успехе.
+        """
+        if not os.path.isfile(path):
+            return False
+        try:
+            bg = np.load(path)
+            self.background = np.asarray(bg, dtype=np.float32)
+            return True
+        except Exception as exc:
+            import sys
+            sys.stderr.write(f"[warn] Не удалось загрузить фон: {exc}\n")
+            return False
+
+    def set_background_enabled(self, enabled: bool):
+        """Включить/выключить вычет фона."""
+        self.background_enabled = enabled
+
     def set_calib_enabled(self, enabled: bool):
         """Включить/выключить режим калибровки, пересчитать norm-свип."""
         self.calib_enabled = enabled
@@ -140,6 +182,7 @@ class AppState:
                 self.save_calib_envelope()
                 self.current_sweep_norm = None
                 sweep_for_ring = s
+                self._last_sweep_for_ring = sweep_for_ring
             else:
                 can_normalize = self.calib_enabled and (
                     (self.calib_mode == "file" and self.calib_file_envelope is not None)
@@ -153,6 +196,14 @@ class AppState:
                     self.current_sweep_norm = None
                     sweep_for_ring = s
 
+            # Вычет фона (в том же домене что и sweep_for_ring)
+            if self.background_enabled and self.background is not None and ch != 0:
+                w = min(sweep_for_ring.size, self.background.size)
+                sweep_for_ring = sweep_for_ring.copy()
+                sweep_for_ring[:w] -= self.background[:w]
+                self.current_sweep_norm = sweep_for_ring
+
+            self._last_sweep_for_ring = sweep_for_ring
             ring.ensure_init(s.size)
             ring.push(sweep_for_ring)
         return drained