[time-nuts] RAPCO 1882M-2 autochance over distribution amplifier
GandalfG8 at aol.com
GandalfG8 at aol.com
Sun Oct 24 00:13:41 UTC 2010
In a message dated 22/10/2010 14:09:13 GMT Daylight Time,
luciano.paramithiotti at hp.com writes:
I bought a distribution amplifier Rapco model 1882M-2 auto changeover on
ebay. This distribution amplifier was intended to be used in conjunction
with a GPSDO to distribute 5MHz and 1PPS.
It has two inputs for 5MHz and and two for 1PPS, and have nr14 5Mhz
outputs and two 1PPS. Switching between the two couple of input is automatic.
Normally each master input works, when the the master drop,the input source is
switched to the second input.
This equipment uses wideband amplifiers with ft100 MHz and I verified
that it works perfectly with no attenuation at 10 Mhz. The gain of the Rapco
is 1 and is not adjustable.
I noticed, however, that without the input signal, at the exit, there is
noise due to the two internal switching regulators that generate -6 and +11
volts from +24 vdc input. The noise at the 5 Mhz output is 60mV pp(sum of
the two switching noise).
I reduced the noise to 10mVpp, cuttingin two tracks on pcb, from power
output from the switchings and inserting an inductance 300uH (.8 A)than
putting an electrolytic 470UF 16V. from inductance to ground (respecting their
polarity).
---------------
Hi Luciano
Thanks for the information, I'd been planning on replacing those two
switching regulators with linear but that's not so straightforward for the
negative supply so might experiment with your suggestion.
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