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[time-freq] TADD-1 gain?

Christopher Hoover ch at murgatroid.com
Thu Sep 7 22:52:47 UTC 2006


 
All power measurements below are 50 Z referenced (i.e. they were
measured with a 50 Z power meter).
 
If I put +10 dBm @ 10 MHz from a 3325A (or Z3801A or FTS 4050) into my
TADD-1's with JP3 (50 Z term) installed and gain set for maximum, I get
~ +5 dBm on the outputs.
 
With a single TADD-2, +5 dBm on the outputs works well enough.  I didn't
even notice until I tried to chain one TADD-1 off of another: output
levels drop down to 0 dBm.  And that's too low for some of my gear.
 
If I pull the 50 Z termination, I can obtain unity gain plus a bit (~
0.5 dBm) more.  That's an unsurprising result -- getting rid of the 50 Z
/ 50Z voltage divider -- but now I've lost termination of the far end of
the coax.
 
This performance appears inconsistent with the manual.  Staring at
schematic, I'm not sure sure where the gain has gone.   It looks like I
should be able to get more than 10x gain (modulo clipping) from the
input stage.  The output stages obviously run at unity gain.
 
I'm relatively confident of the construction, but there's always a
chance I made mistakes (or, one identical mistake?) on all three boards.
 
Any help?
 
-- ch
 
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