really slow PLL

One might feel a little silly, having sent 14,000 commands to a box and then discovering that the power strip is off.

As far as crystals go, we have reached the end.

More on this:

< >

IIRC, Poseidon Scientific Inst. , a spin-off from that Australian univ belongs to the Microchip timing empire now.

< >

(shorten that ridiculous filenme) Driscoll seems to be everywhere it is interesting.

< >

The entire web site is most interesting, Alone the reference section! In this context:

< > < >

and so on. He is also into optical oscillators .

cheers, Gerhard

SVHS ran a higher bandwidth, unbalanced, over the 4 pin version. localtalk was only a few hundered kilobaud.

Shileded pair conectors are fairly common now, USB, HDMI, SATA all give multiple shielded pairs. (SATA is actully untwisted). Oh shit! I forgot "RJ45" is also used for STP.

I'm beyond my pay grade here, but summing jfets can be done with an ideal isolated n-port summer and the s/n improvement indeed goes as sqrt(n). But injection locking 10 oscillators is different. Each one pulls towards the mean of the other nine. They herd one another.

Yup. Inside the locking bandwidth, it's probably possible to make the phases chaotic at some level, so the close-in noise might even be worse.

Outside that, though, as long as the peak phase error is smallish, both amplitude and phase noise look additive, so the usual theorems apply.

For small epsilon,

sin(t + epsilon) = sin t cos epsilon + cos t sin epsilon

~= sin t + epsilon*cos t, (1)

so

(sin(t) + sin(t + epsilon))/2 ~=

sin t + (epsilon / 2) cos t. (2)

Using (1) backwards,

(sin(t) + sin(t + epsilon))/2 ~= sin(t + epsilon / 2).

With N different epsilons, you have a random phasor sum, which winds up with an average phase error going like 1/sqrt(N).

Cheers

Phil Hobbs

Of course the summing follows the usual linear equations AFTER the oscillators are locked. But the things being summed are changed by the phase locking, not independent sources any more.

If one oscillator is the big outlier, it gets all nine others pounding on it to get in sync. Injection locking is fundamentally nonlinear.

On a sunny day (Wed, 27 Jul 2022 12:12:42 +0200) it happened Gerhard Hoffmann snipped-for-privacy@arcor.de wrote in <tbr32q$qg7c$ snipped-for-privacy@solani.org:

No idea what you are doing, but in the old days of Ampex broadcast videotape recorders there were several loops on top of each other to get the color carrier to nano seconds precision in playback

1) slow one capstan tape speed 2) 4 head rotating scanning head to get the signal from tape 3) AMTEC (Automatic Time Element Compensator) a variable delay to get the video to micro second correct phase 4) Colortec a vaiable delay to sync the playback 4.43 MHz playback color carrier to the studio precision reference all this so they could cross-fade and edit and use effects, and people's TVs would sync. and display color.

Old tech... Slow PLL was not the way it worked, From tape speed variations to nano second precision. google Ampex AMTEC and Ampex Colortec sixties and seventies

Am 27.07.22 um 16:13 schrieb Phil Hobbs:

That was Andy Tanenbaum, either in his book "Structured Computer Organisation" or in a guest lecture i saw at TU Berlin. I was seldom more impressed by a prof.

He announced the "Free Univerity Compiler Kit", from the Free Univerity Amsterdam. :-)

Gerhard

Am 27.07.22 um 18:13 schrieb Gerhard Hoffmann:

:gs/Univerity/University/

I hate that keyboard.

Am 27.07.22 um 17:00 schrieb snipped-for-privacy@highlandsniptechnology.com:

No, they all follow the Lucent GPS timing receiver and its own MTI-260 oven by a dedicated PLL in my case

<snip>

My much older, late partner used to play saxophone in High School in the

1950s. He belonged to an Illinois union and said you had to sight read sheet music to join the union. It was the big band era. To keep costs down, the band's core, of say six musicians, would tour and then hire local union musicians for a one night stand in order to fill out the big band.

There's a Muscle Shoals studio interview somewhere out on the Inet. In it one of the sessions players talks about how he played by ear - at first. Until someone told him he needed to wise-up and learn how to sight read in order to earn the easiest money.

My church's two volume songbook contains 634 songs. And a different mix is played each weekend. It's best to simply sight read the songs, as needed.

Humble symphony orchestras work it about the same. Part-time musicians pick up their sheet music a day or two before a concert. There's simply not enough available time to "play a piece hundreds of times to get it right." Danke,

Well outside the lock bandwidth, they'd be pretty well independent, I should think.

Yes, and the math is very pretty, as I remember--all sorts of bifurcations and strange attractors and limit cycles and stuff. It gets more boring with weaker coupling, which is usually all you need.

Cheers

Phil Hobbs

Well, after all, it's more prestigious than the South Holland Institute of Technology.

Cheers

Phil Hobbs

I suspected that I've been taking too many pictures.

The issue with BNCs in phase-critical radar timing systems is that the delay through a BNC can jump by a few picoseconds from mechanical rattling. If the signal traversing the BNC is subsequently multiplied up into the GHz, the angular phase shifts can become intolerable. Especially in a high-vibration environment.

BNCs are also somewhat leaky, even in the precision grades.

So, BNCs are usually forbidden except for test outputs. Only threaded coax connectors, or mechanically stable blind-mate, or the like are allowed.

Joe Gwinn

For synthetic-aperture radars, I believe that--small phase transients are bad news. I had a similar experience long ago.

When I was a grad student, back around 1985-6, I built a heterodyne interferometric scanning laser microscope.

It had a 13-bit phase digitizer, which used a nulling technique to measure phase directly. There was an AM2504 successive-approximation register, driving an AD DAC80 12-bit DAC, driving a homemade linearized varactor phase shifter, with a MCL RPD-1 phase detector looking for a null. (All dead-bug construction.)

One extra SAR cycle (with an external d-flop) made sure it was shooting for the stable null, making 13 bits in all. It ran at the 60-MHz IF, and pi phase was about 6000 LSBs, so 1 LSB was equivalent to

dt = 1/(6000 * 60 MHz) = 2.8 ps.

It had an associated calibrator, based on two 60-MHz crystal oscillators locked together with a divide-by-360 counter on each. The counters had (iirc) 11C90 10/11 prescalers, and one of them had the appropriate logic for a pulse-swallower. That way the two outputs could be phase shifted in exact 1-degree increments. A whole lot of attention was paid to shielding and isolation amps and so forth, because any leakage of one signal into the other above the -80 dB level would cause measurable phase whoopdedoos.

Fortunately that was easy to verify by sitting on the pulse-swallowing button, which moved the frequency enough to see any spurs on the spectrum analyzer. (I borrowed an 8566A from another group for the purpose.)

Calibrating the phase shifter with 1-degree steps made it easy to run a cubic spline through the data to 1-LSB accuracy. Linearizing the phase shifter meant that the conversion of 1 LSB to delta phase didn't vary much across the range--it was always around 3 ps.

Jiggling coax cables during a measurement made for some very entertaining image artifacts there too.

Cheers

Phil Hobbs

(Taking today off because it's so nice out, and because I can.)

Yes, all threaded connectors need to torqued to the "inspection torque" value specified by the manufacturer, using a actual torque wrench.

Joe Gwinn

Oh yes. Must use only double-shielded or better coax - RG-58 need not apply.

Also must worry about power-frequency ground loops driving large currents through the coax shield.

Yes, exactly the same kinds of things bedevil phased-array radars.

Joe Gwinn

There are a small eternity of approaches. Line turnarounds are one.