The PN floor is somewhat lower with a 15dBm rather than a 4dBm input http://www.ko4bb.com/getsimple/index.php?id=phase-noise-and-other-measurements-with-a-timepod
Bruce > On 27 March 2020 at 06:11 kb...@n1k.org mailto:kb...@n1k.org wrote: > > > Hi > > Ok so here's a "new" part as opposed to one that is many decades old. > Again > this is a part that has been talked about > more than once on the list. The demo board is an early one, but I assume > it > is representative of how the CMOS output > part you get today works. > > There are two runs. The first pretty clearly shows the part warming up. > The > second still shows temperature effects, > they just are not as obvious. If you *really* need to hit < 1x10^-15 at > 100 > seconds with this part, drafts are not a good thing. > > The part is being driven with 4 dbm at 5 MHz. Max input is rated as 10 dbm > so that's not as nutty as it sounds. 5 MHz ( or > even 10 MHz) is well below the design target for this part. There's not a > lot on the datasheet to compare to. As with the previous > part, ADEV is pretty good (out to 100 sec). Phase noise is not in the > 10811 > class wideband. If you need low wideband phase noise > as a logic signal at 5 MHz, you need to do something different. For ADEV, > this will do just fine. > > Bob > > -----Original Message----- > From: time-nuts <time-nuts-boun...@lists.febo.com > mailto:time-nuts-boun...@lists.febo.com > On Behalf Of Charles > Steinmetz > Sent: Wednesday, March 25, 2020 5:23 PM > To: time-nuts@lists.febo.com mailto:time-nuts@lists.febo.com > Subject: Re: [time-nuts] Noise Floor > > Taka Kamiya wrote: > > > > I've been playing around with Clifton amplifier as well. Mine, > input is > > > > > terminated with 50 ohm register, and rest is unmodified, so it has > > 6dB gain. > I have a 10dB pad on input side. I, too, noticed there will be a severe > clipping with driving it too hard. * * * I with there was a little > more room there.... > > Bob wrote: > >> Maybe there's some noise in those resistors > >> Well..... maybe not so much. > >> > >> If you drive this board so it has a couple db more output, it goes into > clipping. When that happens .... yuck. > >> Noise and ADEV both are massively impacted. > >> You very much do *not* want to overdrive this board. * * * > >> I would stick with 12 dbm or less > > You can buy some headroom by raising the supply voltage. There is an > on-card LM78L09 9v voltage regulator (U902) that can safely be raised to > 12v (LM78L12). This will get you cleanly to and a bit past the > traditional +13 dBm (1v rms) standard reference level. Of course, you > will need to make sure the raw supply voltage is >15v. > > As to noise, the 200 ohm resistor on the opamp's noninverting input > (R901) accounts for nearly 6dB of the amplifier noise (assuming an > effective source impedance of 50 ohms). Reducing this to, say, 33 ohms > will lower the noise floor a few dB. > > Finally, the state of CFB video amplifier development has advanced > dramatically in the 20 years since the AD8007 was introduced. New > amplifiers with supply voltage ratings up to 36v are available (allowing > about 10dB greater headroom than the 8007), and many of the newer opamps > clip much more gracefully than the 8007 when you do hit the limit (but > you really want not to do that in any measurement application). > > Many of these new CFB amplifiers have been discussed here on the list, > and each has its own fans. One I like that doesn't get mentioned much > is the LME49713. It is discontinued, but still available from Rochester > Electronics and others. But there are lots of good choices. > > Best regards, > > Charles > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > mailto:time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > mailto:time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.