diff --git a/palps.rkt b/palps.rkt
index 811e862..d14fa70 100755
--- a/palps.rkt
+++ b/palps.rkt
@@ -1,6 +1,13 @@
 #! /usr/bin/env /usr/local/bin/racket
 #lang racket
 
+(define (call-valid? call)
+  (and
+   (<= (string-length call) 9)
+   (andmap
+    (or/c char-numeric? char-alphabetic? (curry char=? #\-))
+    (string->list call))))
+
 ;; get callsign, first thing passed by BPQ
 (define call (read-line (current-input-port) 'any))