On 6 August 2013 09:37, Raj <[email protected]> wrote: > Found this on Hack-a-day > > http://www.youtube.com/watch?v=chrzrod3tQY > > Cheers > > -- > Raj, VU2ZAP
Interesting video. I decided to but one of the distribution amps. I already have the rubidium. There were a few things that struck me in the video. 1) Having a PIC to control an LED seems a bit OTT. Personally I'd just stick a second LED - one as a power indicator, the other as a lock indicator, rather than make it flash when warming up, and solid when locked. 2) If one does have a flashing LED, it would be better if it is slower, in case there are any epilepitcs about. As someone who suffers from photosensitive epilepsy, I would not want it flashing any faster than 1 Hz. He should just about be ok, but I'd feel a bit happier if it was slower. 3) I'm not really convinced there is a need to change the output impedance from 75 to 50 Ohms. The impedance mis-match is pretty small. 4) More concerning to me would be the fact the output connectors are 75 Ohm, and so would be damaged with the larger male pin of a 50 Ohm connector. I guess one might get away with it given one is not going to be disconnecting this a lot, but I think I'd buy 75 Ohm BNC plugs to put on one end of the cable, and 50 Ohm BNC plugs on the other end, sticking a bit of heatshrink on the 75 Ohm end of the cable so I know they are not standard BNC cables. 5) I wondered if there is enough cooling air there? What size heatsink would be optimal? I think unlike most electronics, one does not want to cool the rubidiums too much, so "bigger is better" might not apply here. 6) Is the use of a SMPS a good idea? I thought the Rb oscillators should be powered from a linear supply. I don;t suppose it is possible to get a linear power supply in there. 7) He scrapped the BNCs configured as digital lines. I would have thought it worthwhile bringing out a 1 pps output, which I think those Rb oscillators have. 8) I wonder if one could fit a GPS locking module in that box and antenna connector on the box. 9) It will look very odd to have the heatsink as the front panel !! But I guess that is a small price to pay for getting a reasonably sized box and 10) I suspect the box will be hard to keep in place, since with a dozen or so BNCs on the rear, that is going to go where the cables tell it to go, rather than the other way around. Perhaps a heavy heatsink will mittigate that. 11) If I recall correctly, there is a way of adjusting the freqency of those rubidiums, though I guess for the intended application, a Rb is plenty good enough. I know it is for me, but perhaps not for a dedicated time-nut. Dave, G8WRB _______________________________________________ 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.
