diff --git a/hdlc/hdlcsync.c b/hdlc/hdlcsync.c
index ff236ea..f33f53f 100644
--- a/hdlc/hdlcsync.c
+++ b/hdlc/hdlcsync.c
@@ -102,13 +102,21 @@ static int process_raw_hdlc(struct hdlc_proc *hdlc, uint8_t *data, unsigned int
 {
 	unsigned int i;
 	int out;
+	static int last_out;
 
 	for (i = 0; i < len; i ++) {
 		out = process_hdlc_bit(hdlc, data[i]);
-		if (out == -123)
-			printf("F ");
-		else if (out >= 0)
-			printf("%02x ", out);
+		if (out == -123) {
+			/* suppress repeating Flag characters */
+			if (last_out != out)
+				printf("\nF ");
+			last_out = out;
+		} else if (out >= 0) {
+			/* suppress 0xAA and 0x55 bit pattern */
+			if (out != 0xaa && out != 0x55)
+				printf("%02x ", out);
+			last_out = out;
+		}
 	}
 }