diff --git a/gprMax/grid.py b/gprMax/grid.py
index 48f43439..84db0654 100644
--- a/gprMax/grid.py
+++ b/gprMax/grid.py
@@ -255,7 +255,7 @@ def dispersion_analysis(G):
                     # FFT
                     freqs, power = fft_power(waveformvalues, G.dt)
                     # Get frequency for max power
-                    freqmaxpower = np.where(power == 0)[0][0]
+                    freqmaxpower = np.where(np.isclose(power, 0))[0][0]
 
                     # Set maximum frequency to a threshold drop from maximum power, ignoring DC value
                     try:
diff --git a/tools/plot_Ascan.py b/tools/plot_Ascan.py
index 8b1609f9..cabeeb98 100644
--- a/tools/plot_Ascan.py
+++ b/tools/plot_Ascan.py
@@ -86,7 +86,7 @@ def mpl_plot(filename, outputs=Rx.defaultoutputs, fft=False):
             if fft:
                 # FFT
                 freqs, power = fft_power(outputdata, dt)
-                freqmaxpower = np.where(power == 0)[0][0]
+                freqmaxpower = np.where(np.isclose(power, 0))[0][0]
 
                 # Set plotting range to -60dB from maximum power or 4 times
                 # frequency at maximum power
diff --git a/tools/plot_source_wave.py b/tools/plot_source_wave.py
index 88a54c1b..7de50d56 100644
--- a/tools/plot_source_wave.py
+++ b/tools/plot_source_wave.py
@@ -105,7 +105,7 @@ def mpl_plot(w, timewindow, dt, iterations, fft=False):
 
         # Set plotting range to 4 times frequency at max power of waveform or
         # 4 times the centre frequency
-        freqmaxpower = np.where(power == 0)[0][0]
+        freqmaxpower = np.where(np.isclose(power, 0))[0][0]
         if freqs[freqmaxpower] > w.freq:
             pltrange = np.where(freqs > 4 * freqs[freqmaxpower])[0][0]
         else: