[time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Hal Murray]

davidwhess at gmail.com said:
> I looked at the TADD-3 design and it sacrifices back termination impedance
> for signal swing which results in ringing but I presume not too much if
> people were using it successfully.

If the far end (receiver) is terminated to match the coax, there will be no 
ringing and no reflection so the mismatch in back termination won't be a 
problem.  (I'm being sloppy when I say "coax".  It also works for PCB traces 
or any other transmission line.)


There is an approach that gets full height at the receiver and good back termination (and low power).  Digital geeks call it series termination.  The idea is to leave the far end (receiver) open and use good back termination to catch the reflection.

When switching, the wave will go down the coax at half height.  When it gets to the far end (open circuit), it bounces back.  The far end sees a clean switch to full height.  That's the sum of the original wave and the reflection.  When the reflection gets back to the transmitter, it sees a clean termination and doesn't generate any more reflections.

Note that this only works if you have a single receiver at the far end of the transmission line.  If you have a receiver half way down the line, it sees a half-height signal between the time the outgoing wave goes past and the time the reflection gets back.


The TADD-3 uses 3 AC drivers in parallel, each going through a 51 ohm resistor.  Changing those resistors to 150 ohms should work.  Maybe a bit lower to account for the impedance in the drivers.  I'd probably check it with a scope.


-- 
These are my opinions, not necessarily my employer's.  I hate spam.