[time-nuts] SMD TADD-1 distribution amplifier - seeking comments and suggestions?

Chris Caudle chris at chriscaudle.org
Thu Dec 17 20:23:36 EST 2015


On Thu, December 17, 2015 3:47 pm, John Miles wrote:
> Those spurs are reminiscent of what happens when you lift the ground of a
> coax cable at one end and turn it into an antenna, in my experience.

This came up several weeks ago, I don't remember whether an original
TADD-1 or some other distribution amp, where I pointed out that the
measurements provided were with the board connectors run on two short
pigtails to panel mount connectors which were mounted side by side on a
metal enclosure.  I think the question was why was there so much more
noise on the measurements done with the cables just hanging off the PCB.

With the layout of the new board shown any shield currents are going to
flow right across the PCB from the input connector to the output
connectors, causing voltage fluctuations across the ground plane.
A better layout would be to have the power and input connectors on the
same side of the PCB as the output connectors, and make  provision for all
of the connectors to be snugged down tight to a metal enclosure, or at
least a metal plate, so that any parasitic currents flowing on the shields
can stay on the shields and won't be forced across the PCB.
-- 
Chris Caudle





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