[time-nuts] RAPCO 1882M-2 autochance over distribution amplifier

Paramithiotti, Luciano Paolo S luciano.paramithiotti at hp.com
Fri Oct 22 13:07:31 UTC 2010

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).

Hope to help someone,

Luciano P. S. Paramithiotti

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