diff --git a/projects/rfdsatt/attenuator.c b/projects/rfdsatt/attenuator.c
index bea3514..937df09 100644
--- a/projects/rfdsatt/attenuator.c
+++ b/projects/rfdsatt/attenuator.c
@@ -68,6 +68,10 @@ int attenuator_set(uint8_t channel, uint8_t stage, uint8_t val_qdb)
 	if (val > 0x1f)
 		return -ERANGE;
 
+	/* the DAT-31A-SP actually has a B0 which works in half-dB steps,
+	 * but according to the manual it must alsays be 0 */
+	val = val * 2;
+
 	/* The shift register should be loaded while LE is held low to
 	 * prevent the attenuator value from changing as data is
 	 * entered */