This patch might be useful for successful reception at 300 baud.

It uses longer RX filters and it also makes them supposedly more
robust against overflows.
---
 afsk/modem.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- afsk/modem.c	2012-03-03 19:14:53.748535161 +0100
+++ afsk/modem.c	2012-03-03 19:16:34.066638207 +0100
@@ -248,7 +248,7 @@ struct modulator afskmodulator = {
  * Rx FIR Filter length is normally equal
  * to 16.
  */
-#define RXFILTLEN       16
+#define RXFILTLEN       48
 
 /*
  * Rx FIR Filter length is normally equal
@@ -256,7 +256,7 @@ struct modulator afskmodulator = {
  * the minimum wordlength to avoid
  * overflow.
  */
-#define RXFILTOVERBITS	3
+#define RXFILTOVERBITS	5
 
 #define RXFILTOVER      (1<<(RXFILTOVERBITS))
 #define RXFILTFIDX(x)   (((x)>>(16-(RXFILTOVERBITS)))&(RXFILTOVER-1))