Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

On Thursday, September 22, 2016 01:37:02 AM Gerhard Hoffmann wrote: > Am 22.09.2016 um 00:24 schrieb Bruce Griffiths: > > Another issue is the requirement to trim the current sink for low output > > offset. > > And _that_ FET is made from Unobtainium. > > > If one takes advantage of the fact

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Am 22.09.2016 um 00:24 schrieb Bruce Griffiths: Another issue is the requirement to trim the current sink for low output offset. And _that_ FET is made from Unobtainium. If one takes advantage of the fact that the PLL imposes a low frequency cutoff to the PN measurements, the amplifier input

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Am 22.09.2016 um 00:24 schrieb Bruce Griffiths: For the later, Bruce commented that an jFET input stage would probably be more quiet. Gerhard Hoffman has designed a similar I must insist in my second "n" Hoffmann :-) system[3] that uses a couple of paralel low noise opamps instead of a

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

On Wednesday, September 21, 2016 08:59:18 PM Attila Kinali wrote: > On Wed, 21 Sep 2016 09:16:18 -0700 > > Dan Rae wrote: > > On 9/21/2016 9:01 AM, David C. Partridge wrote: > > > Yes, I fear a timepod is a bit out of my budget (I can dream tho'). > > > Over here in the UK

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

On Wed, September 21, 2016 1:59 pm, Attila Kinali wrote: > On Wed, 21 Sep 2016 09:16:18 -0700 > Dan Rae wrote: >> Pretty much all there, but the FET is hard to find now. > > If you want to build such an amplifier, then the first stage (aka the > jFET input and the first

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

On Wed, 21 Sep 2016 09:16:18 -0700 Dan Rae wrote: > On 9/21/2016 9:01 AM, David C. Partridge wrote: > > Yes, I fear a timepod is a bit out of my budget (I can dream tho'). Over > > here in the UK PN measurement kit is a bit thin on the ground too. > > > > So I looked at

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

On 9/21/2016 9:01 AM, David C. Partridge wrote: Yes, I fear a timepod is a bit out of my budget (I can dream tho'). Over here in the UK PN measurement kit is a bit thin on the ground too. So I looked at but that seemed a little thin

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

On 9/21/2016 8:01 AM, David C. Partridge wrote: Looks like all I've managed to do is measure the baseline noise of the analyser. Ho-hum looks like I need something a *lot* quieter to do these measurements. Indeed Dave, yes. I made the same mistake a few years ago when I tried to compare

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Yes, I fear a timepod is a bit out of my budget (I can dream tho'). Over here in the UK PN measurement kit is a bit thin on the ground too. So I looked at but that seemed a little thin on details. Or were you referring to something

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Looks like all I've managed to do is measure the baseline noise of the analyser. Ho-hum looks like I need something a *lot* quieter to do these measurements. Dave -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of David C. Partridge Sent: 18 September

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Worn out aluminum electrolytic capacitors usually improve in performance lowering ripple and noise as they warm up. On Sun, 18 Sep 2016 12:27:38 +0100, you wrote: >Now that's interesting I just re-ran the measurement, and got a quite >different result which is attached. The spurs have GONE. >

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Hi If you are measuring the OCXO, you should be getting around -155 to -160 dbc / Hz at 100 Hz offset. Depending on the particular board you have, and how it is powered, the numbers out of the TBolt can be quite a bit worse than this. With a good supply, you should get within 5 db. There are

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

On 9/18/2016 5:42 AM, David C. Partridge wrote: I've just redone the measurement without the external attenuator and with 10dB attenuation set internally to the analyser. The results are attached. I suspect that you are measuring the analyser phase noise, but it's rather early in the

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Assuming a nonlinearity, a distortion or partly clipping of only one halfwave, would result in a massive even harmonic, as the 200Hz in the example. From this point of view "as expected", but a different distortion could as well result in any other even harmonic. Peter Am Sonntag, 18. September

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Even harmonics are caused by asymmetrical nonlinearities, odd harmonics by symmetrical nonlinearities. Peter Am Sonntag, 18. September 2016 schrieb Magnus Danielson : > Hi, > > On 09/18/2016 12:26 PM, David C. Partridge wrote: > >> The local power is 50Hz, so I can understand the 100Hz spurs,

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Still way above what it should be.Whats the noise floor of the measurement system? Bruce On Monday, 19 September 2016 12:43 AM, David C. Partridge wrote: I've just redone the measurement without the external attenuator and with 10dB attenuation set

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

What is the specification for the Spectrum analyzer? They don´t tend to be useful for OCXO measurments so is this especially good? Or is it only the Analyzer phase noise we see? Lars Från: David C. Partridge Skickat: den 18 september 2016 14:43 Till:

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

I've just redone the measurement without the external attenuator and with 10dB attenuation set internally to the analyser. The results are attached. Dave -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: 18 September 2016 12:52

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Yes, it's through a 20dB attenuator. I'll redo the measurement w/o the attenuator. Dave -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: 18 September 2016 12:52 To: Discussion of precise time and frequency measurement Subject: Re:

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Using John Miles PN.exe and Agilent E4406A -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: 18 September 2016 12:47 To: time-nuts@febo.com Cc: mag...@rubidium.se Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Indeed, now I see it. As we expect around +10 dBm, the noise-floor might be raised by about 20 dB. I was more considering what is the reference noise here, is there a single oscillator as reference? Can a quieter reference oscillator be used? Can a cross-correlation setup be done? Cheers,

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Peter, Take a peak here (scroll down to the graphs): http://dsp.stackexchange.com/questions/5959/add-odd-even-harmonics-to-signal The full-wave rectifier creates a symmetric distortion, which causes even harmonics. Each half-cycle has the same output structure, so the resulting signal has

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

The signal level is also very low. Brue On Sunday, 18 September 2016 11:47 PM, Magnus Danielson wrote: The phase-noise still looks fairly high. How do you measure this? Cheers, Magnus On 09/18/2016 01:27 PM, David C. Partridge wrote: > Now that's

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

The phase-noise still looks fairly high. How do you measure this? Cheers, Magnus On 09/18/2016 01:27 PM, David C. Partridge wrote: Now that's interesting I just re-ran the measurement, and got a quite different result which is attached. The spurs have GONE. My only guess right now is that

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

The PN should be considerably lower than that even with the noisy output buffer the PN floor should be considerably lower (>40db lower). The OCXO by itself should have somewhat lower PN. Bruce On Sunday, 18 September 2016 11:14 PM, David C. Partridge wrote:

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Now that's interesting I just re-ran the measurement, and got a quite different result which is attached. The spurs have GONE. My only guess right now is that the E4406A power supply is getting quieter as it has been on for longer (I've only had it powered for short periods before now). Dave

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Thanks, that makes sense. Is the PN plot much as expected, or is it "could do better"? Thanks again Dave -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: 18 September 2016 11:56 To: time-nuts@febo.com Cc: mag...@rubidium.se

Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Hi, On 09/18/2016 12:26 PM, David C. Partridge wrote: The local power is 50Hz, so I can understand the 100Hz spurs, but I don't quite "get" where the 200Hz spurs are coming from. Or is that just BAU harmonics? Consider full-wave rectification of 50 Hz, the power consumption load on the