Hi > On Jun 14, 2018, at 9:31 AM, gandalfg8--- via time-nuts <time-nuts@febo.com> > wrote: > > > Hi Julien, > > > > Earlier replies that discussed removing the DC supply from the 8140 outputs > gave me the impression your requirement was to connect directly the outputs > of the 8140 without line tap modules, which is what I was addressing with my > recent suggestion of a series capacitor, but can see now that's not the case. > > > > If you were to build your own termination the same principle would still > apply of course but perhaps another option for a reasonably compact solution, > aside from a coaxial DC block followed by a 50 ohm termination, might be a DC > blocking attenuator followed by a BNC shorting dust cap, as the latter are > generally quite small. > > > For example, current Ebay item 332461304064 is a DC blocked 20dB attenuator, > they are also available in pairs at a slight discount, and that fitted with a > shorting cap would give you a return loss of 40dB, which is probably as good > as you'd get from most 50 ohm terminations anyway and would save having to > build your own.
I would be very surprised if the original terminations did any better than 20 to 30 db return loss. They are not fancy devices. I’ve also seen a lot of attenuators that only make it to about 20 db of return loss ….. Bob > > > The VersaTaps phase lock an internal crystal, any frequency between 4 and > 20MHz, to the 10MHz input and then provide an output at the crystal frequency > or the crystal frequency divided by a fixed integer between 1 and 8,192, so > in that sense yes they're a synthesiser but the few I've seen were still > supplied preset for a specific frequency. > > > However, "versatile" does not necessarilly mean quick or convenient to > reprogram. > Aside from perhaps needing to change the crystal the division ratio needs to > be set by adding or removing links across pairs of holes in the circuit > board. Those holes are on a standard 0.1inch pitch so fitting headers that > would take shorting links should be straightfoward enough, and I suspect what > was originally intended, but the units I have were supplied preprogrammed > using resistor style wire ended zero ohm links mounted above the circuit > board and soldered from below. Reprogramming one of these would involve > unsoldering and perhaps removing all the connectors etc in order to remove > the circuit board, so I'd certainly make darn sure they had headers fitted > before being returned to the box! > > > > Nigel, GM8PZR > > > > > > > -----Original Message----- > From: Julien Goodwin <time-n...@studio442.com.au> > To: gandalfg8 <gandal...@aol.com>; Discussion of precise time and frequency > measurement <time-nuts@febo.com> > Sent: Thu, 14 Jun 2018 11:36 > Subject: Re: [time-nuts] Spectracom 8140T Line Tap Schematic > > I'm somewhat tempted to take the schematic and see if I can fit it in > the comparatively tiny Pomona boxes, although I have far too many side > projects already, enough 10MHz taps, and I still need to do the terminators. > > The VersaTaps are supposed to be an actual synthesizer IIRC. > > > > > > > > > > > > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
