https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=FL-52A&_sacat=0
https://www.ebay.com/itm/ICOM-FL-44A-455kHz-SSB-Filter-2-4kHz-6dB/183878363145?hash=item2ad0012809:g:~G8AAOSwqzJdJzd7