Can I know how did you get that number of 50Hz? Thanks.

Harold E. Johnson wrote:
wrote in message
ups.com...
I'm dealing with a DSSS current signal at 70MHz. Before I start
designing anything, I am calculating the signal amplitude. It's going
to be 5nArms. If I have a 50ohm resistor, it's -153dBm. I'd be happy to
know any solid proof that it's not doable because it's my job now.

In theory DSSS signal can work under noise level, but can it be so
much?

Well, I have no idea of what a DSSS signal is, so I can't be of much help.
Whatever it is, it better be in a very narrow bandwidth. At that signal
level, it will take a 50 Hz bandwidth to achieve minimum discernable signal
(MDS) with a front end NF of 2.4 dB.

If you're talking about using autocorrelation to bring it up out of the
noise, all bets are off depending on how much time you can sacrifice.

If you're planning on bringing this signal to -10 dBm, better prepare for a
lot of shielding and decoupling, not to mention filtering and frequency
stability at 70 MHz center frequency.

W4ZCB