[hpsdr] Diversity measurements

[wully]

Hi Joe, hi all

On tuesday, I have made some measurements for diversity. Using an RF 
generator, a splitter and two 6dB-attenuators into two mercuries, the 
clock of the second one driven by the LVDS-Signal (122.88MHz) from the 
first one, by adjusting the phase and amplitude relation to a minimum on 
different frequencies, I got the following results:

freq[kHz]        phase        amplitude        in[dBm]    minimum[dBm] 
    RF-Gen[dBm]    suppression
7160        175.5                0.5                -58            
-110                        -50                        52
7150        -163.5                0.5                -65            
-114                        -50                        49
7150        -163.5                0.5                -47            
-104                        -40                        57
7150        -93                    0.5                -37               
-96                        -30                        59
14180        175.5                0.5                -38            
-95                        -30                        57
14181        28.5                0.5                    -37            
-98                        -30                        61


Sorry, if the table does not fit good into the mail.

1) suppression is near to 60 dB!
2) when changing the frequency and going back to the same frequency, the 
phase for minimum is not reproduced
3) the Input signal has to be big enough, so as to avoid the noise floor 
(see second line)

In practice, using a dipol on the first mercury and a lying loop on the 
second, both antennas about 5 m from each other (no place to make 
spatial separation), I can adjust phase and amplitude such that the 
background noise might be reduced, but it depends very strongly on the 
current conditions.

Comments are welcome.

73, Alfred, hb9epu