[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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