I read in sci.electronics.design that john jardine
 wrote (in 
k) about 'Diode and very small amplitude high frequencies signals', on
Sat, 5 Feb 2005:
Test on a 1N4148.
ForwardV DiodeR
+50mV    8megs.
+30mV    9megs.
+20mV    10megs.
+10mv    12megs.
+5mV     21megs.
ReverseV
-5mV     21megs.
-10mV    30megs.
-30mV    270megs.
How did you measure the resistance? Is it an incremental resistance
(slope of the V/I curve at the data point) or the slope of a line
joining the origin to the data point on the curve.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see 
http://www.isce.org.uk