Just found a person selling several downconverters on Ebay that look like they could be used for AO-51 mode S. (with modifications) No Bias T or power supplies though. http://shop.ebay.com/the_consumer_rebellion/m.html?_nkw=&_armrs=1&_from=&_ipg=&_trksid=p4340 73 Matt W5LL