diff --git a/python/trx/radio_if.py b/python/trx/radio_if.py
index d2afcf6..407e724 100644
--- a/python/trx/radio_if.py
+++ b/python/trx/radio_if.py
@@ -4,7 +4,7 @@
 # GR-GSM based transceiver
 # Follow graph implementation
 #
-# (C) 2016-2017 by Vadim Yanitskiy <axilirator@gmail.com>
+# (C) 2016-2018 by Vadim Yanitskiy <axilirator@gmail.com>
 # (C) 2017      by Piotr Krysik <ptrkrysik@gmail.com>
 #
 # All Rights Reserved
@@ -29,6 +29,7 @@
 
 from math import pi
 
+from gnuradio import eng_notation
 from gnuradio import digital
 from gnuradio import blocks
 from gnuradio import uhd
@@ -59,6 +60,7 @@
 
 class radio_if(gr.top_block):
 	# PHY specific variables
+	freq_offset_hz = None
 	rx_freq = 935e6
 	tx_freq = 890e6
 	osr = 4
@@ -274,11 +276,21 @@
 		return self.ppm / 1.0e6 * 2 * pi * fc / self.sample_rate
 
 	def set_rx_freq(self, fc):
+		if self.freq_offset_hz is not None:
+			fc += self.freq_offset_hz
+			print("[#] Shifting RX freq. to %s (offset is %s)"
+				% (eng_notation.num_to_str(fc),
+					eng_notation.num_to_str(self.freq_offset_hz)))
 		self.phy_src.set_center_freq(fc, 0)
 		self.rotator_src.set_phase_inc(self.calc_phase_inc(fc))
 		self.rx_freq = fc
 
 	def set_tx_freq(self, fc):
+		if self.freq_offset_hz is not None:
+			fc += self.freq_offset_hz
+			print("[#] Shifting TX freq. to %s (offset is %s)"
+				% (eng_notation.num_to_str(fc),
+					eng_notation.num_to_str(self.freq_offset_hz)))
 		self.phy_sink.set_center_freq(fc, 0)
 		self.rotator_sink.set_phase_inc(-self.calc_phase_inc(fc))
 		self.tx_freq = fc