That was one of three receivers in our main arsenal when I was a Radioman in the Navy along with the RBB and RBC. It took all three to cover the spectrum. We actually did use it occasionally along with a VLF Transmitter that stood about six feet tall.
I found a RBA-2 in a local electronics shop. The guy says he doesn’t think it works & he doesn’t know what’s wrong. He wants $250 for it. What do you think? Is it worth that?
find noise source, fix noise at source, find out how you are receiving noise from antenna or from AC power, move antenna away from noise source, use coax feed line, try low noise antenna such a BOG, EWE, loop or short amplified whip, try noise blanker such as ANC-4 or MFJ noise reduction device,
