Magnus Are you changing or did you change and if you are how much time do you have. Bert In a message dated 10/22/2012 6:24:06 P.M. Eastern Daylight Time, [email protected] writes:
Bert, On 10/22/2012 04:46 PM, [email protected] wrote: > Tom > A good place to start is with a manual of the Austron 2055 delay if there > is real interest. Does any one have it in PDF form? > As to the disciplining a Rb or specifically a HP5065A, the filter part is > the challenge. Having worked on it for the last ten years always using > Brooks loop and developing work around's it will do every thing except > temperature control and barometric pressure. I have done temperature analog but rely > mainly on holding the Rb temperature stable within a tenth degree C. > Bob recently put things in perspective when there was talk about a 32 bit > DAC. On one side you have GPS and time averaging is required to get full use > of it. That is why a Rb is uniquely qualified for it. The original Shera > input implemented on a 1 $ G/A is more than enough for time capture wether > using a sawtooth corrected GPS receiver or a Tbolt. On the other end a > LTC1655 is again more than enough in an Rb application. You can use it 16 bit > direct or dither two or 4 bits. Filter is easy and do not forget that the > Rb has an additional filter between cell and OCXO. Brooks V402NE will do the > job, how ever others and I have not been able to buy some in the last nine > month. Any one knows what is going on? > What is needed is some one in the group be willing and able to step up to > the plate and develop the filter on a PIC with all the things learned, and > believe me, we are still learning as we adapt a M100/8600 via a Tbolt . > I will be willing to help with every thing except the PIC. > If you bring out the C field coil directly you have full isolation and do > not have to worry about ground loops. > A complete unit would cost less than $ 40 and more important be assembled > by any one. I brought it up before but no one responded. If no response I > will still be able to do every thing with the HP5065A RVFR that was given to > me. The needed loop filter isn't all that hard to achieve. Do read the Stanford Research PRS-10 manual. The core PI-filter can be formulated as: VI = VI + Vd * I VF = VI + Vd * P Where Vd is the phase detector value (may be in number of nanoseconds or whatever), VF is the output frequency control (EFC) value. The I and P values is the control parameters and VI is the integrator state. Adding a pre-filter for Vd values can be done as in the PRS-10: Vd = Vd + (Vi - Vd)* F where Vi is the raw input and F is filter control parameter. F can be set in power of 2 steps without too much loss of control, allowing for shift-steps, which is what the PRS-10 uses. The PRS-10 runs it all in a whopping 6805 if I recall things correctly, just your off the shelf 8 bit processor that felt right in the moment. You can then allow for some front-end processing to cook up the I and P values from more user-friendly parameters if you like. Tossing in a FLL functionality on top of it for improved lock-in performance isn't hard either. There is a few scaling issues and most things is about getting a stable timing and such, but it's not all that hard. If you want to do PPS there is a little more attention to lock-in details naturally. Cooking up an open "lock-it-all" isn't that hard thing to accomplish with a bit of knowledge and experience. One might even have a bit of fun and cook up a Kalman filter, which is essentially a self-tuning PI regulator. PS. Sorry for not making you aware in advance that I was changing planes in Miami this Friday. It was a busy week in Atlanta. Cheers, Magnus _______________________________________________ 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.
