Tom, OK - one question for now if that is OK - your video amp - is it base-band or broadband?
Regards, John W, On Thu, Sep 26, 2013 at 11:11 PM, Tom Minnis <tom_min...@att.net> wrote: > Thanks for all your thoughts on the subject. Let me play back what I have > learned and how it may apply to my challenge. One of my first applications > is to use a 10MHz output to phaselock a VCXO master clock in a radio > transceiver. The VCXO is the Christek CVHD-950 which has a noise floor of > -164dBc and is -86dBc at 10Hz. The source I want to use is the Jackson > Labs GPSTCXO which has a noise floor of -155dBc and is -73dBc at 1Hz and > 103dBc at 10Hz. i did a quick survey of the phase noise specs on various > Jackson products that claim to be ultra low phase noise and found similar > numbers. One was -100dBc at 1Hz but only -145dBc at 100KHz. Another was > down -90dBc at 1Hz and -160dBc at 100KHz. It would appear that even the > best parts I could find quickly would not merit the fancy analog gizmo and > that a good stiff logic buffer would work. Next I went to IDT to find the > best logic buffer I could find. I am looking at the IDT 74FCT38072 2 > channel clock driver for PPS. It can drive about 50mA if needed with 1nS > rise and fall times. The one I am looking at for 10MHz is the ICS553 4 > channel clock driver. This one is good for 25mA drive and they actually > give a typical output impedance spec of 20 Ohms. With a 3.3V supply, it > has 1nS rise and fall times and a little faster with a 5V supply, 0.7nS and > 35mA drive. To make a sine wave should I use one of the 4 ports on the 4 > port driver to input to the filter or should I try to hook the filter input > directly to the clock driver input? > Are there tried and true 10MHz filter circuits or is that a non issue? > After the filter would come the video amp set up for a 50 Ohm drive and > into a splitter. That sound simple enough. What am I missing? > > Tom > > > On 9/26/2013 3:05 PM, Bob Camp wrote: > >> Hi >> >> How clean is your clock source? If you have something that is -150 dbc at >> 1 Hz, then you probably need some fancy analog gizmos. If you can make do >> with "only" -110 to -120 dbc/Hz at 1 Hz, then properly driven LVC CMOS will >> do just fine. That's true for a square or a sine output. Since you pretty >> much can't find an OCXO better than -120 at 1 Hz, I'd bet you'll be ok. 5 >> volt logic will be a little more quiet than 3.3V. More or less faster is >> quieter as long as you stay with saturated silicon CMOS. Change materials >> and all bets are off. >> >> For square wave cable drive you can parallel up a couple of the '125 or >> '126 gates to get how ever much power you want to put into the cable. You >> can source or load terminate (or both). If you source and load terminate, >> your logic levels will be 1/2 the output. With either source only or load >> only termination you can get full swing logic levels. More drive will >> always be required with load termination (you are putting current into 50 >> ohms). >> >> Logic IC's are cheap, easy to use, and simple to find. A low voltage >> single supply drives them and they aren't current hogs unless heavily >> loaded. What's not to like? >> >> Bob >> >> >> On Sep 26, 2013, at 1:28 PM, Tom Minnis <tom_min...@att.net> wrote: >> >> I am looking into various degrees of craziness. The source is CMOS and >>> there are plenty of 1 in to N out parts designed to drive clocks on a PCB >>> but not much is said about driving clocks on to a random length of coax to >>> another piece of equipment and what additional precautions that might >>> warrant. I am also considering making a sine wave output and maybe other >>> frequencies. >>> Tom >>> >>> On 9/26/2013 4:34 AM, Bob Camp wrote: >>> >>>> Hi >>>> >>>> Standard high speed CMOS logic works pretty well. How crazy are you >>>> trying to get? >>>> >>>> Bob >>>> >>>> On Sep 26, 2013, at 1:48 AM, Tom Minnis <tom_min...@att.net> wrote: >>>> >>>> I am working on a small clock distributor and wanted to get some ideas >>>>> on what works best for 10MHz and 1PPS driver circuits. I remember sifting >>>>> through the archives a year or so ago and tripped on some discussion of >>>>> this but I can't find it anymore. >>>>> Tom >>>>> ______________________________**_________________ >>>>> time-nuts mailing list -- time-nuts@febo.com >>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/** >>>>> mailman/listinfo/time-nuts<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<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<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<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<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.