W2HX wrote:
Hi all,
I am close to closing in on a video distribution amp for a GPSDO for use in
10 MHz reference signals for various test equipment and had a few questions.
2. Many of these amps have LOOP through connections to expand the
number of outputs (in ->loop->in). I often see 75 ohm terminators at the
end of the loop. Since we are mostly using 50 ohm sources (GPSDO) would
there be any benefit in terminating these loops with 50 ohm terminators? I
realize that the output of the DA's are still 75 ohm, but I am thinking if a
50 ohm source terminated in 50 ohms might have less distortion (question
above) going into the amp.
For precision applications this is perhaps one of the worst frequency
distribution techniques as the differential phase shift and instability
thereof depends on the number of loop through connections.
Such effects should be readily apparent when making precision phase
comparisons using a DMTD or equivalent.
For less precise applications such distribution techniques may be useful.
Distribution amplifiers that employ AGC tend to have high phase noise
floors and poor phase stability.
Bruce
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