[time-nuts] Any reason not to use one power amplifier and splitter for distribution amplifier?

Charles Steinmetz csteinmetz at yandex.com
Tue Jan 6 18:42:14 EST 2015

Dave wrote:

>At 50 MHz, the loss from the common port is 12.8 dB, and the isolation
>between two ports sets of ports is either 38 or 48 dB

To get the worst-case output-to-output isolation, you need to test 
two output ports that are electrically adjacent (i.e., that share the 
same last 2:1 splitter, assuming that the 1:16 is a hierarchy of 1:2 
splitters -- which is the case with the multi-output splitters I'm 
familiar with).  You may already have found an electrically-adjacent 
pair (ports 7 and 8), but to be absolutely sure, you would need to 
repeat the test from one output to each of the 15 others (or find a 
full internal connection diagram, which does not seem to be on the 

If it is a hierarchy of 1:2 splitters, you are correct that it is 
effectively two, 1:8 splitters.  In that case, each output port on 
one of the 1:8 splitters is electrically equidistant from all of the 
output ports on the other 1:8 splitter.  But the same is not true of 
the output ports of just one of the 1:8 splitters.  In that case, 
there is one adjacent output port, two output ports at one remove, 
and four output ports twice removed.  The isolation is generally 
worst between adjacent outputs, and better at each remove.  It is 
logical to think that the adjacent output ports are 1-2, 3-4, ... 
7-8, ... and 15-16 -- but this may not be the case.

I wouldn't bother retesting with out-of-band signals, but when you 
test at 10MHz it is something to think about.

Best regards,


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