[time-nuts] Distribution amp - Use a video amp unit ?
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Mon Mar 26 18:01:34 UTC 2012
Randy wrote:
>if one is distributing 10 Mhz, does it really
>matter what the circuit does at 300 and 900 Mhz??
That depends on what it is feeding and what noise
and other signals are getting to the DA
input. Some synthesized 10 MHz sources produce energy well above 10 MHz.
I consider nonmonotonic behavior to be a design
flaw in general (except where it is specifically
desired or you are up against the bleeding edge
of technology and it can't be avoided), so I
eliminate it at every opportunity as long as the
fix doesn't cause worse problems. In this case,
the nonmonotonicity is cured by replacing an 8¢
transistor with a 16¢ transistor, and some other
small benefits are realized at the same time, so
I say it's 8¢ well spent. Nearly a whole dollar
extra for a 12-output DA. The noise bump is
cured by restricting the 3 dB bandwidth to ~80
MHz, which does not affect the 10 MHz but may
help the receiving instrument if it is sensitive
to VHF noise (although the magnitude of the bump is not large).
I consider these good prophylactic design
measures. Practicing them keeps you out of
trouble that you might not even know was
threatening, whether or not it makes a practical
difference WRT a particular design.
Best regards,
Charles
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