I had to switch to HDMI to get it to work, as it didn't run on the RCA. It goes to a RF modulator so its definitely the STB doing the decoding.
Here is the one I bought:
http://www.ebay.ca/itm/391004471164?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
Sorry I only have KU here, so can't...