Is it practical to do this directly at the RF receive frequency? I expect = to sub-contract the design work but looking for an opinion first about prac= ticality.=20

Requirement: Receive two CW carriers off the air in the 1.8 to 2.5 MHz ran= ge, and report their relative phase with at least 50 nsec accuracy.

Assumptions: The CW carriers' frequencies are precisely known in advance a= nd are assumed to be perfectly stable. Nominal C/No >50 dB/Hz each carrier= .=20

"Phase:" The carriers are at different frequencies. What we really want t= o know is how much one leads or lags the other in time, like measuring the = relative zero-crossing times of the two sinusoids. For measurement accurac= y it is acceptable to time-average each measurement over as long as 100 mse= c.

Regarding implementation, we'd like to start work by 1 September assuming t= his concept is practical. Any recommendations for someone to do the design= are appreciated. We are located in Southern Calif.