[DSP-10] 1296 RSU TX Works!

[Courtney Duncan]

I'm talking to myself on FM in the other direction, from the RSU1296  
to the HT!  Looks like it's all working.

Extrapolating from KA7EXM meter measurements, it looks like linearity  
is OK for drive levels from -15 dBm to +10 dBm.  Looks like it goes  
into compression around 0 dBm drive.  Using this meter I don't have  
absolute readings so I don't really know what's going out, just what's  
coming in.

Looking at the specs on the MAR-6 and ERA-5, it looks like the  
conversion gain should be
-  7 mixer
-  7 filter
-  3 splitter
+20 MAR-6
+19 ERA-5
+22 total

The ERA-5 is supposed to compress around +18 dBm.  This plus the gain  
calculation roughly agrees with a little plot of output power readings  
I made.

This implies I should be driving at -6 to -4 dBm.  These are 80 - 82  
settings on my DSP-10 .

Does this all sound right?  I vaguely remember seeing a drive level in  
one of the articles somewhere but am not finding it at the moment.

(I also recalculated the receive conversion gain from better  
information:

+23 SGA-3586Z
-  3  splitter
-  7  filter
-  7  mixer
+ 6  total)

Next:  figure out T/R switching, put in box.

Courtney, n5bf/6


"It's science. They don't know anything; they just make a lot of  
educated guesses."  -- Viannah Duncan

Courtney Duncan, n5bf/6
cbduncan at earthlink dot net
144.200, 7.040.
n5bf at amsat dot org