Perhaps you should try some spelling variations:
"white voice communications directly" » "white mobile communications directly" (Expand Search), "white device communications directly" (Expand Search), "white line communications directly" (Expand Search), "white noise communications directly" (Expand Search)
"white burst communications directly" » "white rural communication directly" (Expand Search), "white b communications directly" (Expand Search), "white bfsk communication directly" (Expand Search), "white forest communications directly" (Expand Search)

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"white voice communications directly\") OR (\"white burst communications directly\"))~".
• Removing quotes may allow a broader search: (( white voice communications directly ) OR ( white burst communications directly ))~.
• Adding a wildcard symbol may retrieve word variants: (("white voice communications directly") OR ("white burst communications directly"))*.