Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

It's been 20 years since I presented that paper in San Francisco at FCS and I had just about forgotten about it. It is flattering to realize that people are still reading it now. It might be useful for the discussion here if I explained why I wrote the paper. We had recently completed the

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

(ADEV of 4E-16 at tau of 1000 seconds is a typical state of the art requirement) …. and has been since the 1970’s when I first started talking with JPL people about this :)…. They've gotten a lot smaller and probably draw less power since then. There's also the testing problem: proving

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

On 12/8/15 3:31 PM, Bob Camp wrote: Hi Let’s see: EFC uses reference out of the OCXO. EFC comes on the OCXO at no added cost. 16 bit DAC costs ~$2 to $5 Total cost for EFC setup $2 to $5. Net result is a system with spurs that are how ever far down you wish them to be. (It’s all about

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

In message <56675da0.4050...@rubidium.dyndns.org>, Magnus Danielson writes: >> So, what did I miss? Why do people use DAC-EFC control instead of >> the DDS scheme? > >The main reason I would say is habbits, people have habbits and stick to >them. And I think right after that comes the

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

God eftermiddag, On Tue, 8 Dec 2015 23:45:52 +0100 Magnus Danielson wrote: > If you would setup essentially a micro-stepper design, such as those > being used for cesium and hydrogen masers, but maybe adapted to a > hobbyist needs and with straight-forward way of

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Hi > On Dec 8, 2015, at 11:20 PM, Jim Lux wrote: > > On 12/8/15 3:31 PM, Bob Camp wrote: >> Hi >> >> Let’s see: >> >> EFC uses reference out of the OCXO. >> EFC comes on the OCXO at no added cost. >> 16 bit DAC costs ~$2 to $5 >> >> Total cost for EFC setup $2 to $5.

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

On 12/9/15 4:37 AM, Bob Camp wrote: Hi On Dec 8, 2015, at 11:20 PM, Jim Lux wrote: On 12/8/15 3:31 PM, Bob Camp wrote: Hi Let’s see: EFC uses reference out of the OCXO. EFC comes on the OCXO at no added cost. 16 bit DAC costs ~$2 to $5 Total cost for EFC setup $2 to

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

A friend and I have been messing with a DDS replacement for the VFO in older radios. The odds runs between 5 and 5.5 MHz. There are some mixers that generate the final LO frequency. We found many many birdies (caused by spurs for the non-hams) over the tuning ranges. We had to put in a lo-pass

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Don, DDSes used to be very crude in terms of spurs. However, things have improved significantly and some of the chips you can get now is pretty impressive. It has even inspired some significantly different radio designs in the ham world. As for filters, yes, they can vary delay with

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

In message <566883d1.6050...@rubidium.dyndns.org>, Magnus Danielson writes: >Indeed. As any engineering time estimate, you need to multiply with pi. >At work, we engineers divide our estimates with pi before giving it to >the project managers, as they will multiply with pi before

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Hi > On Dec 9, 2015, at 9:34 AM, Jim Lux wrote: > > On 12/9/15 4:37 AM, Bob Camp wrote: >> Hi >> >>> On Dec 8, 2015, at 11:20 PM, Jim Lux wrote: >>> >>> On 12/8/15 3:31 PM, Bob Camp wrote: Hi Let’s see: EFC uses reference

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

God kväll, On 12/09/2015 11:47 AM, Attila Kinali wrote: God eftermiddag, On Tue, 8 Dec 2015 23:45:52 +0100 Magnus Danielson wrote: If you would setup essentially a micro-stepper design, such as those being used for cesium and hydrogen masers, but maybe adapted

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Poul-Henning, On 12/09/2015 09:24 AM, Poul-Henning Kamp wrote: In message <56675da0.4050...@rubidium.dyndns.org>, Magnus Danielson writes: So, what did I miss? Why do people use DAC-EFC control instead of the DDS scheme? The main reason I would say is habbits, people have habbits

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Some of the suggestions offered here are incorporated in the FE 205/405/505. We have done extensive work using a 405 with very good results. Tom did some tests on the 406 and we traced issues back to the temperature control. We disabled it and continue to have an excellent GPSDO. Tests are

[time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Moin, I've been digging through some stuff and stumbled (again) over Rick's paper on high resolution, low noise DDS generation[1] and got confused. The scheme is very simple and looks like to be quite easy and reliably to implement. If I understood it correctly, the critical points are the DDS,

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Something like good_100MHz_OCXO+DDS => same as a BVA? On Tue, Dec 8, 2015 at 5:32 PM, Attila Kinali wrote: > Moin, > > I've been digging through some stuff and stumbled (again) over Rick's > paper on high resolution, low noise DDS generation[1] and got confused. > The scheme is

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Given that until now good (maximum stability) OCXO are much less than 100MHz, from the OCXO we exploit its high stability and we impose accuracy from a coordinated source: the OCXO+EFC method uses the built-in stability and disciplines the accuracy. The DDS method virtually can start from any

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

On 12/8/15 8:32 AM, Attila Kinali wrote: Moin, I've been digging through some stuff and stumbled (again) over Rick's paper on high resolution, low noise DDS generation[1] and got confused. The scheme is very simple and looks like to be quite easy and reliably to implement. If I understood it

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

On Tue, 8 Dec 2015 17:32:17 +0100 Attila Kinali wrote: > The only > problem would be to get a narrow band 10.0MHz filter (I couldn't find > one within 5 minutes of googling). 5 stages should cost around 50-70USD) Correction: I should have looked at "Resonators" instead of

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Jim, On 12/08/2015 07:09 PM, Jim Lux wrote: On 12/8/15 8:32 AM, Attila Kinali wrote: Moin, I've been digging through some stuff and stumbled (again) over Rick's paper on high resolution, low noise DDS generation[1] and got confused. The scheme is very simple and looks like to be quite easy

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

God kväll Attila, On 12/08/2015 05:32 PM, Attila Kinali wrote: Moin, I've been digging through some stuff and stumbled (again) over Rick's paper on high resolution, low noise DDS generation[1] and got confused. The scheme is very simple and looks like to be quite easy and reliably to

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Ciao Azelio, On Tue, 8 Dec 2015 19:36:37 +0100 Azelio Boriani wrote: > Given that until now good (maximum stability) OCXO are much less than > 100MHz, from the OCXO we exploit its high stability and we impose > accuracy from a coordinated source: the OCXO+EFC method

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Azelio, You don't get BVA performance easily out of an oscillator being significantly less stable than a BVA. Some environmental aspects you can dampen, some you can compensate, but then as you hit the fundamental noise processes of the oscillator. Knowing how systematics affects the

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Hi Let’s see: EFC uses reference out of the OCXO. EFC comes on the OCXO at no added cost. 16 bit DAC costs ~$2 to $5 Total cost for EFC setup $2 to $5. Net result is a system with spurs that are how ever far down you wish them to be. (It’s all about grounding in this case). Bob > On Dec 8,

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

On Tue, 8 Dec 2015 10:09:44 -0800 Jim Lux wrote: > > What puzzled me is, why this has not been used more often to correct > > the frequency of OCXOs instead of using some DAC-to-EFC scheme? > > Heritage... if you have a design that works, and there's a lot of them > in

Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

Bar Giora Goldberg wrote a book on DDS Digital Frequency Synthesis Demystified see here: http://www.amazon.com/Frequency-Synthesis-Demystified-Bar-Giora-Goldberg/dp/1878707477 [· In-depth coverage of