From 673605896f832b95a754f6f3caad6b01a357b742 Mon Sep 17 00:00:00 2001
From: fenrir <fenrir.naru@gmail.com>
Date: Thu, 28 Sep 2023 17:40:02 +0900
Subject: [PATCH] Add comment for old ubx support

---
 tool/ubx_filter.rb | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tool/ubx_filter.rb b/tool/ubx_filter.rb
index 1be0038b2..0dc5def75 100644
--- a/tool/ubx_filter.rb
+++ b/tool/ubx_filter.rb
@@ -177,6 +177,7 @@ def run(&b)
       event,2100:2000,drop,GPS:03 
           # start dropping GPS 3 after GPS time 2100[week] 20000[s]
 
+    Note: For old ubx, just PRN number (without satellite system) like "1" (<-instead of "GPS:01") works well. 
 __STRING__
 
 options = {