I wish to use one antenna with three Shure PA821A personal monitor RF signal combiners. My thinking would be an passive RF combiner with 4.5 dB loss or at most 6 dB. Any suggestions?
Consider the Mini-Circuits model ZB3CS-900-6W three port RF combiner. Its should meet your needs as well as the stated performance criteria (i.e. loss is very close to 5 dB per port). The device uses N connectors, so BNC-N adapters will be needed. Or, better yet - obtain jumper cables terminated with N connectors on one end and BNC on the other end.
Here is the product information: http://www.minicircuits.com/pdfs/ZB3CS-900-6W.pdf