Magnus and Bob. I appreciate the comments and the suggestions are easily implemented. Technical term "Piece-O-cake". One other note the the Z3801 uses a more negative voltage to raise frequency while the Piezo and FRS use a positive voltage. Absolutely agree on the offset. Been trying to do that. However the FRS C I am using wants seems to require +.6V to be on frequency. So because of its age there may be a real issue. I have 3 others and may grab another to see how it behaves. Also have some EGGs and FEI 5680s. Though those as I recall are digital control. But back to the basics first. Regards Paul. WB8TSL
On Wed, Dec 28, 2016 at 6:32 PM, Bob Camp <[email protected]> wrote: > Hi > > Ummm ….. errrrr …. > > The 10811 that is used in the Z3801 has a *larger* electrical tuning range > than the standard > 10811 not a smaller one. It’s tuning range and the TBolt OCXO’s tuning > range are > very similar. > > Bob > > > On Dec 28, 2016, at 6:22 PM, Magnus Danielson < > [email protected]> wrote: > > > > Paul, > > > > We just want to help you with that curiosity, it sounds like a fun > little project. :) > > > > The FRS-C [1] has a range of +/- 1E-9 over 0-5V, so EFC sensitivity is > 4E-10/V. > > > > The Z3801A has a range of 5.20E-10 [2] over -5V to +5V [3], so EFC > sensitivity is 5.2E-11/V. > > > > So, it looks like you need to have a gain of 8 and raise the EFC 2.5 V. > > > > Cheers, > > Magnus > > > > [1] http://www.to-way.com/tf/frs.pdf > > > > [2] http://www.leapsecond.com/pages/z3801a-efc/ > > > > [3] http://www.realhamradio.com/joe-geller.htm > > > > On 12/28/2016 11:42 PM, paul swed wrote: > >> Magnus and Bob, > >> Thank you for your response. As far as the original HO 10811 oscillator > >> goes there is some well written details on it behavior and sensitivity. > It > >> was not the same as a standard 10811. A far smaller range as I recall. > But > >> the data is there. > >> Its funny on the RB I have the EFC range from the spec sheet. It really > >> tunes from 0-5V. But I find it interesting that the best alignment with > >> other references is sub 1V. Its an old FRS C and I have others that may > >> present a more centered range. > >> > >> I'll have to compare the detials that I have on the 10811 and FRS C. > But I > >> actually pulled out a 100:1 antenuator I was using on the Piezo crystal > >> that indeed does lock. > >> > >> Goal in all of this is nothing special simply curiosity. > >> Thanks again. When I have some real numbers to share I will. > >> Regards > >> Paul > >> WB8TSL > >> > >> On Tue, Dec 27, 2016 at 10:26 PM, Bob Camp <[email protected]> wrote: > >> > >>> Hi > >>> > >>> The loop gain (as Magnus mentions) needs to be “correct” for the Rb. > Since > >>> the firmware was written for an OCXO with a PPM(ish) trim range, > tacking it > >>> on to a PPB(ish) Rb will require everything to scale by 1000:1. That’s > 10 > >>> bits. > >>> You may (or may not) have enough resolution in the math to handle that > wide > >>> a range of gains. > >>> > >>> If it really locks, the next challenge is to get it to run out to ~ 4 > days > >>> or more on > >>> the loop. Again, the firmware may or may not be able to do this. > Unless it > >>> does, > >>> the Rb really will not lock as well as it could. > >>> > >>> With the Rb correctly locked, you still have the issue that the Rb is a > >>> 2x10^-11 > >>> device (ADEV) at 1 second and the OCXO probably is 2x10^-12 (or > better). > >>> For > >>> driving a counter with a normal gate, the Rb may not show much (if any) > >>> improvement. > >>> There is the slight chance the ADEV will get the firmware confused….. > >>> > >>> Since the firmware source is running around somewhere, you *could* dig > into > >>> all of this wonderful stuff :) > >>> > >>> Bob > >>> > >>> > >>>> On Dec 27, 2016, at 8:33 PM, paul swed <[email protected]> wrote: > >>>> > >>>> OK so could not resist. The replacement of the HP 10811 with a PIEZO > ocxo > >>>> went very well. So in for a penny in for a pound. Why not an RB. > Having a > >>>> few around. Choice efratom FRS-c. Lot of thought went into this > choice. > >>> Not > >>>> really it was there. It has a inverse frequency to EFC voltage just > like > >>>> the piezo and opposite the HP 10811. > >>>> Well it connects runs and locks using the simple 1 opamp level ofset > and > >>>> and phase inverter. > >>>> But locked is a funny comment. According to HPsatstat and LH. Its pll > is > >>>> locked. But both scope and the LH graph shows a very slow frequency > drift > >>>> that with the offset I can make positive or negative. A cycle at 10 ns > >>>> takes quite some time about an hour compared to a TBolt and another > non > >>>> modified Z3801. At this level of resolution some things start to > become > >>>> questionable. > >>>> > >>>> I almost wonder if the modified z3801 under some level of drift > assumes > >>>> everything is locked and fine. Can it be pushed beyond expectations. I > >>>> suspect it can. > >>>> Anyhow as I say a bit of GPSDO fun. > >>>> Regards > >>>> Paul > >>>> WB8TSL > >>>> _______________________________________________ > >>>> 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. > >>> > >> _______________________________________________ > >> 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. > > _______________________________________________ > 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.
