Hi
> On Jul 19, 2015, at 9:27 AM, Dr. David Kirkby (Kirkby Microwave Ltd) > <[email protected]> wrote: > > On 19 July 2015 at 10:56, Charles Steinmetz <[email protected]> wrote: > >> Dave wrote: >> >> Some time ago I mentioned I'd bought a couple of Minicircuits 16-way power >>> splitters with the intention of making a 10 MHz distribution amplifier >>> * * * >>> Here are the ISOLATION results. >>> * * * >>> CONCLUSIONS >>> * * * >>> 6) Despite the Minicircuits data sheets imply there are two isolation >>> figures for "adjacent" and "opposite", I measure 3 different values for >>> each splitter, not 2. >>> >> >> As I posted on January 8, there are actually four different cases in a >> 16-way splitter. You have found that the port-to-port isolation of two of >> the four cases are indistinguishable in practice in the MCL splitters. >> >> The datasheets do not imply that there are only the two cases. MCL simply >> specified the best ("adjacent") and worst ("opposite") cases, without >> specifying the intermediate cases. >> > > Minicircuits don't say "best" or "worst" but the data sheet does say > "adjacent" and "opposite". But I'm not disputing there are 4 different > isolation figures, but I could only measure 3. > > >> >> Good luck with your DA system. For simple distribution of a frequency >> standard, it should work very well. I use a similar system with a suitable >> ULN/HDR preamp to feed antennas to multiple receivers, and it performs >> superbly. >> >> For an output at the typical instrumentation level of 1Vrms (13dBm), you >> will need an amplifier with a 50 ohm output impedance that puts out ~26dBm >> (=400mW, =4.5Vrms, =6.3Vpk, =12.6Vp-p). The peak output current is >>> 125mA. If you are going to realize the 50 ohm output impedance with a low >> impedance amplifier and a 50 ohm buildout resistor for back-termination, >> the amplifier will need to put out over 25Vp-p into 100 ohms. If you want >> the outputs at the same level as the original source, the amplifier will >> need to have a bit more than 12dB of gain. Have you decided what you are >> going to use? >> > > I wont say I have decided for sure, but an obvious candidate is a > Minicircuits ZHL-2-8, since I have one here sitting around doing nothing. > The specs on that are: > > Gain min 31 dB, typical 36 dB > 1 dB compression point minimum +29 dBm. > > That has plenty of gain, and in fact would need an attenuator around 24 dB > if the typical gain is realized. It would also be running it a few dB below > the 1 dB compression point. But someone (perhaps even yourself) mentioned > phase noise increases as you get near the 1 dB compression point. That > amplifier does not have a great deal of headroom - just 3 dB. > > I was also considering the possibility of using a discrete transistor, > where it could be run well below the 1 dB compression point, rather than 3 > dB below it. > > All I need to find is a 24 V linear power supply of 600 mA or more. I > suspect I have one of them lying around too. > Be very careful about some of the packaged amplifiers. Many of the designs do *not* hold their noise performance when driven to within 20 db of the compression point. Phase noise dégradation of > 20 db is not at all uncommon with some of the designs out there. Bob > > >> Best regards, >> >> Charles >> > > Dave > _______________________________________________ > 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.
