diff --git a/csdr/__init__.py b/csdr/__init__.py
index 3e13453..1677fb8 100644
--- a/csdr/__init__.py
+++ b/csdr/__init__.py
@@ -41,7 +41,7 @@ from csdr.chain.demodulator import DemodulatorChain
 from csdr.chain.fm import NFm, WFm
 from csdr.chain.am import Am
 from csdr.chain.ssb import Ssb
-from csdr.chain.digiham import Dstar
+from csdr.chain.digiham import Dstar, Nxdn
 from csdr.chain.clientaudio import ClientAudioChain
 
 import logging
@@ -142,6 +142,9 @@ class Dsp(DirewolfConfigSubscriber):
             elif which == "dstar":
                 self.pycsdr_chain = DemodulatorChain(self.samp_rate, 48000, 0.0, Dstar(self.codecserver))
                 return self.pycsdr_chain
+            elif which == "nxdn":
+                self.pycsdr_chain = DemodulatorChain(self.samp_rate, 48000, 0.0, Nxdn(self.codecserver))
+                return self.pycsdr_chain
 
         chain = ["nc -v 127.0.0.1 {nc_port}"]
         chain += ["csdr shift_addfast_cc --fifo {shift_pipe}"]
diff --git a/csdr/chain/digiham.py b/csdr/chain/digiham.py
index c3c8a9b..110d8a5 100644
--- a/csdr/chain/digiham.py
+++ b/csdr/chain/digiham.py
@@ -1,31 +1,44 @@
 from csdr.chain import Chain
-from pycsdr.modules import FmDemod
-from digiham.modules import DstarDecoder, DcBlock, FskDemodulator, DigitalVoiceFilter, MbeSynthesizer, NarrowRrcFilter, NxdnDecoder
+from pycsdr.modules import FmDemod, Agc
+from pycsdr.types import Format
+from digiham.modules import DstarDecoder, DcBlock, FskDemodulator, GfskDemodulator, DigitalVoiceFilter, MbeSynthesizer, NarrowRrcFilter, NxdnDecoder
+from digiham.ambe import Modes
 
 
 class Dstar(Chain):
     def __init__(self, codecserver: str = ""):
+        if codecserver is None:
+            codecserver = ""
+        agc = Agc(Format.SHORT)
+        agc.setMaxGain(30)
+        agc.setInitialGain(3)
         workers = [
             FmDemod(),
             DcBlock(),
             FskDemodulator(samplesPerSymbol=10),
             DstarDecoder(),
-            MbeSynthesizer(codecserver),
-            DigitalVoiceFilter()
+            MbeSynthesizer(Modes.DStarMode, codecserver),
+            DigitalVoiceFilter(),
+            agc
         ]
         super().__init__(*workers)
 
 
 class Nxdn(Chain):
     def __init__(self, codecserver: str = ""):
+        if codecserver is None:
+            codecserver = ""
+        agc = Agc(Format.SHORT)
+        agc.setMaxGain(30)
+        agc.setInitialGain(3)
         workers = [
             FmDemod(),
             DcBlock(),
             NarrowRrcFilter(),
-            # todo: switch out with gfsk
-            FskDemodulator(samplesPerSymbol=20),
+            GfskDemodulator(samplesPerSymbol=20),
             NxdnDecoder(),
-            MbeSynthesizer(codecserver),
-            DigitalVoiceFilter()
+            MbeSynthesizer(Modes.NxdnMode, codecserver),
+            DigitalVoiceFilter(),
+            agc,
         ]
         super().__init__(*workers)