Hi Nigel, I have two distributors of frequency, one to be mounted in a rack where I have all my frequency reference and the other one in my laboratory to distribute the FX to the measuring instruments.
I will limit myself to the described modification for the laboratory one, while in the rack that I'm going to completely replace the power supply with another constructed by me, always well a switching psu but well filtered and in a small metal box that helps shielding interference. One additional note and that the original PSU also generates a lot of interference to the external power source. My goal 'to have a noise output of less than 1 mV pp measured without input signal. This' to avoid amplitude modulation that would increase the uncertainty of measurement for the phase noise and TIC. I have the operating manual of the Rapco. I think will be very difficult to have the schematic diagrams of this equipment. For radio use, I will recommend this high dynamic amplifier http://yu1aw.ba-karlsruhe.de/bfg135aeng.htm (single +12 VDC) followed by a passive splitter (ex.: minicircuit). Ciao, Luciano Luciano P. S. Paramithiotti IZ5JHJ -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: domenica 24 ottobre 2010 2.14 To: [email protected] Subject: Re: [time-nuts] RAPCO 1882M-2 autochance over distribution amplifier In a message dated 22/10/2010 14:09:13 GMT Daylight Time, [email protected] 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. >From the description in the manual I guessed in advance these might be >wideband and took a gamble on that, once confirmed on my first one I bought a >couple more:-) Aside from frequency distribution I was also curious to try them as LF/MF antenna distribution units. I knew they were likely to be quite noisy at microvolt levels but there's quite a bit of noise at LF anyway and the op amp noise actually wasn't too bad. However, when feeding into a radio with a 30MHz wide spectrum display the effects of those switching regulators are immediately obvious. They're running at 100KHz and the harmonics generate a nice picket fence that's clearly visible up to at least 20MHz. I'd still like to get rid of those switching regulators altogether but could really do with a schematic before trying that. I assume you got a copy of the basic user manual from the seller? If not let me know and I'll send it to you. regards Nigel _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
