Tony posted this catch and summary at his page here;
http://i56578-swl.blogspot.com/2020/06/50bd500-fsk-likely-cis-govmil.html50Bd/500 FSK (likely CIS Gov/Mil)
Ran the linked audio file thru K500 to see what it said and it triggered the KG84C parser;
[2020-06-13 19:38:59] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:00]
[2020-06-13 19:39:00]
[2020-06-13 19:39:00] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:01]
[2020-06-13 19:39:01]
[2020-06-13 19:39:01] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:03]
[2020-06-13 19:39:03]
[2020-06-13 19:39:03] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:04]
[2020-06-13 19:39:04]
[2020-06-13 19:39:04] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:05]
[2020-06-13 19:39:05]
[2020-06-13 19:39:05] Detected KG-84C SYNC with 93% confidence
[2020-06-13 19:39:06]
[2020-06-13 19:39:06]
[2020-06-13 19:39:06] Detected KG-84C SYNC with 92% confidence
[2020-06-13 19:39:08]
[2020-06-13 19:39:08]
[2020-06-13 19:39:08] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:09]
[2020-06-13 19:39:09]
[2020-06-13 19:39:09] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:10]
[2020-06-13 19:39:10]
[2020-06-13 19:39:10] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:11]
[2020-06-13 19:39:11]
[2020-06-13 19:39:11] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:13]
[2020-06-13 19:39:13]
[2020-06-13 19:39:13] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:14]
[2020-06-13 19:39:14]
[2020-06-13 19:39:14] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:15]
[2020-06-13 19:39:15]
[2020-06-13 19:39:15] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:17]
[2020-06-13 19:39:17]
[2020-06-13 19:39:17] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:18]
[2020-06-13 19:39:18]
[2020-06-13 19:39:18] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:19]
[2020-06-13 19:39:19]
[2020-06-13 19:39:19] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:20]
[2020-06-13 19:39:20]
[2020-06-13 19:39:20] Detected KG-84C SYNC with 100% confidence
[2020-06-13 19:39:22]
[2020-06-13 19:39:22]
[2020-06-13 19:39:22] Detected KG-84C SYNC with 90% confidence
[2020-06-13 19:39:32] Initialization vectors: 4443CF0683C041C0 43C3C3C3C3C3C3C3
[2020-06-13 19:39:33] C3C3C3C3F0F0C3C3C3C3C3C3C3C3C3C3C3C3C3C3F0F0C3C3C3C3C3C3C3C3C3C3C3C3C3C3F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0FFFFFFFFFFFFFFFF
[2020-06-13 19:39:44] End of message (idle pattern)
Mebbe not cis nav but fun anyway.