Been interesting. Did increase the gain to 8 and remove the attenuation 10:1 needed for the piezo ocxo. Not sure I would say the system locks but it certainly slows the drift down to 10ns/30 minutes. I also added an offset after the amplifier. This allowed the Z3801 EFC to set its range more towards 50%. Though the FRS manual says the range is 0-5V for EFC the FRS is clearly offset with age to the +1.7V for center. (The other FRS was +.6V)
Its interesting to see at the startup of the Z3801 the EFC range in the RB. Nice steps down towards a fairly low angle line according to Lady Heather. Have had to stop the experimentation late today to give a hand to a fellow on a HP 70-110GHz signal source. Till today I was a 10 GHz sort of guy. Regards Paul WB8TSL On Wed, Dec 28, 2016 at 6:51 PM, Magnus Danielson < [email protected]> wrote: > Hi, > > Well, that was the data I was able to find (and I referred to TvBs page > where I found it). If you have more accurate data, please share so we can > get the numbers right. > > The Z3801A will do a least square estimate of frequency error and then > translate that into an initial DAC setting assuming it knows the EFC > sensitivity, and the loop will work out the rest from there (hopefully). > Getting EFC in the right neighborhood is probably wise for this reason. > > Cheers, > Magnus > > > On 12/29/2016 12:32 AM, Bob Camp 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/m >>>> ailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to https://www.febo.com/cgi-bin/m >>> ailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/m >> ailman/listinfo/time-nuts >> and follow the instructions there. >> >> _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/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.
