Well check the frequencies that it can recieve?
3S 6S and 8s are the HF frequencies that Flight Service now Flight Watch use. 6541 is the N.T. one ie. 6.541 Mhz is the actual frequency. The Band for HF is 3 to 30mhz, generally there may be some variations outisde that but no Much.
Your Sony may only have this in Bands or can you select the exact Freq?
Hope this HELPS
May work better at night
Regards
SHEEP