diff --git a/src/demod/DemodulatorPreThread.cpp b/src/demod/DemodulatorPreThread.cpp
index 9a4d5db..1c9718f 100644
--- a/src/demod/DemodulatorPreThread.cpp
+++ b/src/demod/DemodulatorPreThread.cpp
@@ -108,7 +108,12 @@ void DemodulatorPreThread::run() {
             sampleRateChanged.store(false);
             audioSampleRateChanged.store(false);
             demodTypeChanged.store(false);
-        } else if (cModemKit && cModem && (bandwidthChanged.load() || sampleRateChanged.load() || audioSampleRateChanged.load()) && (newSampleRate && newAudioSampleRate && newBandwidth)) {
+        }
+        else if (
+            cModemKit && cModem &&
+            (bandwidthChanged.load() || sampleRateChanged.load() || audioSampleRateChanged.load() || cModem->shouldRebuildKit()) &&
+            (newSampleRate && newAudioSampleRate && newBandwidth)
+        ) {
             DemodulatorWorkerThreadCommand command(DemodulatorWorkerThreadCommand::DEMOD_WORKER_THREAD_CMD_BUILD_FILTERS);
             command.frequency = newFrequency;
             command.sampleRate = newSampleRate;
diff --git a/src/demod/DemodulatorWorkerThread.cpp b/src/demod/DemodulatorWorkerThread.cpp
index 46fdadb..fcf4276 100644
--- a/src/demod/DemodulatorWorkerThread.cpp
+++ b/src/demod/DemodulatorWorkerThread.cpp
@@ -72,6 +72,9 @@ void DemodulatorWorkerThread::run() {
             } else if (makeDemod) {
                 cModemKit = nullptr;
             }
+            if (cModem != nullptr) {
+                cModem->clearRebuildKit();
+            }
             
             float As = 60.0f;         // stop-band attenuation [dB]
             
diff --git a/src/modules/modem/Modem.cpp b/src/modules/modem/Modem.cpp
index 69adc7b..21fb816 100644
--- a/src/modules/modem/Modem.cpp
+++ b/src/modules/modem/Modem.cpp
@@ -55,3 +55,15 @@ Modem::Modem() {
 Modem::~Modem() {
     
 }
+
+bool Modem::shouldRebuildKit() {
+    return refreshKit.load();
+}
+
+void Modem::rebuildKit() {
+    refreshKit.store(true);
+}
+
+void Modem::clearRebuildKit() {
+    refreshKit.store(false);
+}
diff --git a/src/modules/modem/Modem.h b/src/modules/modem/Modem.h
index 7edb2d5..1ca1ece 100644
--- a/src/modules/modem/Modem.h
+++ b/src/modules/modem/Modem.h
@@ -4,6 +4,7 @@
 #include "IOThread.h"
 #include "AudioThread.h"
 #include <cmath>
+#include <atomic>
 
 class ModemKit {
 public:
@@ -108,9 +109,12 @@ class Modem  {
 public:
     static void addModemFactory(Modem *factorySingle);
     static ModemFactoryList getFactories();
+    
     static Modem *makeModem(std::string modemType);
+    
     virtual std::string getType() = 0;
     virtual std::string getName() = 0;
+    
     virtual Modem *factory() = 0;
 
     Modem();
@@ -126,6 +130,12 @@ public:
     virtual void disposeKit(ModemKit *kit) = 0;
     
     virtual void demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) = 0;
+    
+    bool shouldRebuildKit();
+    void rebuildKit();
+    void clearRebuildKit();
+    
 private:
     static ModemFactoryList modemFactories;
+    std::atomic_bool refreshKit;
 };
diff --git a/src/modules/modem/digital/ModemFSK.cpp b/src/modules/modem/digital/ModemFSK.cpp
index aad5bfd..38c9871 100644
--- a/src/modules/modem/digital/ModemFSK.cpp
+++ b/src/modules/modem/digital/ModemFSK.cpp
@@ -1,6 +1,7 @@
 #include "ModemFSK.h"
 
 ModemFSK::ModemFSK() {
+    // DMR defaults?
     bps = 9600;
     spacing = 7000;
 }
@@ -12,14 +13,42 @@ Modem *ModemFSK::factory() {
 ModemArgInfoList ModemFSK::getSettings() {
     ModemArgInfoList args;
     
+    ModemArgInfo bpsArg;
+    bpsArg.key = "bps";
+    bpsArg.name = "Bits per-symbol";
+    bpsArg.value = std::to_string(bps);
+    bpsArg.description = "FSK modem bits-per-symbol";
+    bpsArg.type = ModemArgInfo::STRING;
+    
+    std::vector<std::string> bpsOpts;
+    bpsOpts.push_back("9600");
+    bpsArg.options = bpsOpts;
+    
+    args.push_back(bpsArg);
+
+    ModemArgInfo spacingArg;
+    spacingArg.key = "spacing";
+    spacingArg.name = "Symbol Spacing?";
+    spacingArg.description = "Not quite sure yet :-)";
+    spacingArg.type = ModemArgInfo::STRING;
+    spacingArg.value = std::to_string(spacing);
+
+    std::vector<std::string> spacingOpts;
+    spacingOpts.push_back("7000");
+    spacingArg.options = spacingOpts;
+    
+    args.push_back(spacingArg);
+    
     return args;
 }
 
 void ModemFSK::writeSetting(std::string setting, std::string value) {
     if (setting == "bps") {
-        
+        bps = std::stoi(value);
+        rebuildKit();
     } else if (setting == "spacing") {
-        
+        spacing = std::stoi(value);
+        rebuildKit();
     }
 }
 
@@ -35,8 +64,8 @@ std::string ModemFSK::readSetting(std::string setting) {
 ModemKit *ModemFSK::buildKit(long long sampleRate, int audioSampleRate) {
     ModemKitFSK *dkit = new ModemKitFSK;
     dkit->m           = 1;
-    dkit->k           = sampleRate / 9600;
-    dkit->bandwidth   = 7000.0 / sampleRate;
+    dkit->k           = sampleRate / bps;
+    dkit->bandwidth   = double(spacing) / sampleRate;
 
     dkit->demodFSK = fskdem_create(dkit->m, dkit->k, dkit->bandwidth);