Brian [email protected] wrote: > Bruce Griffiths wrote: > > >> Very few OCXOs and other frequency standards have outputs >> lower than +4dBm. Most have outputs in the +7dBm to +15dBm range. >> >> > And what happens to that +7 dBm source if you split it 8 ways and > add some padding for additional matching and isolation, plus some > input transformer and/or filter losses? > That is a very effective way of elevating the phase noise floor. Its usually far better to amplify the input and then split the output maintaining a gain to the splitter outputs of at least 0dB. > > Or what if the reference being distributed comes off a multiplier > chain or VCO at a lower output level? > > Again, its better where possible to ensure that the input to a multiplier is as high as is reasonably possible, most multipliers are more efficient with higher inputs. If one has a low level signal it is best to use a low noise buffer driving a > Is there room in your world view for a simple, low cost design > that doesn't reach the ultimate noise floor, but covers a wide > range of input frequencies with decent noise floor performance? > > None, where it severely compromises the phase noise floor of the reference frequency source. Even a Thunderbolt OCXO phase noise floor will be degraded by a system using this device (unless of course it is used to drive N of them in parallel and their outputs are recombined - however thats more expensive than implementing a good design in the first place). >> Using an unnecessarily wide band device in a frequency distribution >> system isn't usually a particularly good idea. >> >> > It isn't "unecessary" when the circuit needs to operate over > that wide of an input frequency range in its' intended range > of applications. > > Its almost always better to design the circuit to suit the operating frequency, often this just means using suitable output and input filters. >> The only way to find out what the close in phase noise characteristics >> are is to construct an amplifier using such a device and measure it. >> >> > Some data sheets contain this information at spot frequencies; > this one does not. > Very few datasheets from Maxim specify much about the noise characteristics of such devices. > > Unfortunately, I do not have access to a phase noise test system > at this point in time, hence my question to the list. > > > You can easily cobble one together using whatever sound card your PC has together with a mixer and a few inexpensive opamps, filters etc.
> Brian > > p.s. > > I deleted most of my original reply before posting this. > > Your posts contain many condescending remarks insinuating > misuse of the part, and how easy it is to do it properly, > yet you refuse to answer a simple question, to wit: > > Can you point to something, IC or discrete, that will > cover sources in the 10-200 MHz range with similar or > better reverse isolation at comparable size and cost ? > > > The criticism is aimed at the concept not the person. The question is largely irrelevant. The use of such a device in the way which you intend is far from optimum. But of course you are free to do that. However, I think that its important that the limitations of such an approach be clearly stated. Bruce _______________________________________________ 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.
