Gareth's Downstairs Computer wrote on 8/5/2017 5:57 PM:
On 05/08/2017 22:24, rickman wrote:
Gareth's Downstairs Computer wrote on 8/5/2017 3:14 PM:
On 05/08/2017 20:06, rickman wrote:

Yes, because it *is* a PLL. In fact the problem most people have with it
is that it doesn't adjust the phase by adjusting the frequency of the
slave. It adjusts the *phase* so clearly it *is* a phase locked loop.

All pendulums have circular error where the frequency is determined by
the amplitude of swing,

All *uncorrected* pendulums have circular error. The Fedchenko clock has
a mounting spring for the pendulum that corrects for circular error.

Hadn't heard of that one. At the BHI lecture there was mention of
another correction of circular error by a colied spring attached
somewhere at the bottom, but I wasn't paying full attention at
that point.

There were also other means such as cycloidal cheeks around the
suspension spring.

so for the half cycle where the phase is adjusted by
abridging the swing by the hit of the hit and miss stabiliser, the frequency
of the slave is, indeed, changed.

This has nothing to do with the circular error.

It has everything to do with the circular error and the variation
in frequency that comes with varying amplitude of the swing.

You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error. It
is a good pendulum, but not a great one. It doesn't need to be great, it is
corrected every 30 seconds by the electromechanical escapement of the master
pendulum. It only has to be good enough to provide an appropriately timed
release of the gravity lever.

So the small circular error has no bearing on the slave pendulum.


The standard formula given for the cycle time of pendulums ..

2 * PI * root( L / G)

... is only valid for those small angles where sin( theta ) = theta,
and such angles are so infinitesimal that no visible movement
of a pendulum would be seen!

This equation is an approximation which ignores the higher terms of the
power series of the full equation. It is only truly valid for no swing at
all.

... which is virtually the range where sin( theta) = theta.

Exactly. This *is* the range where sin(theta) = theta. Anywhere other than
zero it is an approximation.

--

Rick C

On 05/08/2017 23:25, rickman wrote:
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular
error.

I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.

Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.

On 08/06/17 10:38, Jeff wrote:

You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.


Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.

It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.

Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.

Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.

Jeff



Might be easier to define a set entitled "Locked Oscillators, of which
the phase locked loop, injection locked and hit and miss synchronised
are all members.

Are there other candidates ?...

Chris

On 06/08/2017 12:24, Chris wrote:
On 08/06/17 10:38, Jeff wrote:

You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.


Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.

It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.

Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.

Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.

Jeff



Might be easier to define a set entitled "Locked Oscillators, of which
the phase locked loop, injection locked and hit and miss synchronised
are all members.

Are there other candidates ?...

From pre-war, the Goyder Lock?

Which raises an interesting point; before the 3-tier
coffer-filling fiasco was the spawn of the RSCB, the candidature
for the RAE tended to know all about the history of amateur radio
before getting their licence, but now they seem to know
sweet FA even after getting their licences, such as the
difference between sideband and sidetone.

On 06/08/2017 13:52, Gareth's Downstairs Computer wrote:
On 06/08/2017 12:24, Chris wrote:
On 08/06/17 10:38, Jeff wrote:

You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.


Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.

It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.

Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.

Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.

Jeff



Might be easier to define a set entitled "Locked Oscillators, of which
the phase locked loop, injection locked and hit and miss synchronised
are all members.

Are there other candidates ?...

From pre-war, the Goyder Lock?

Which raises an interesting point; before the 3-tier
coffer-filling fiasco was the spawn of the RSCB, the candidature
for the RAE tended to know all about the history of amateur radio
before getting their licence, but now they seem to know
sweet FA even after getting their licences, such as the
difference between sideband and sidetone.




House!

On 08/06/17 12:52, Gareth's Downstairs Computer wrote:
On 06/08/2017 12:24, Chris wrote:
On 08/06/17 10:38, Jeff wrote:

You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.


Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.

It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.

Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.

Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.

Jeff



Might be easier to define a set entitled "Locked Oscillators, of which
the phase locked loop, injection locked and hit and miss synchronised
are all members.

Are there other candidates ?...

From pre-war, the Goyder Lock?

Which raises an interesting point; before the 3-tier
coffer-filling fiasco was the spawn of the RSCB, the candidature
for the RAE tended to know all about the history of amateur radio
before getting their licence, but now they seem to know
sweet FA even after getting their licences, such as the
difference between sideband and sidetone.




Hadn't heard of that, so looked it up and found:

http://www.dxmaps.com/discuss/oven.html

Which was an interesting read, but not enlightening.

Some of the early scope timebases, puckle, for example sounded
interesting, but they were effectively injection lock, of course.
I guess a triggered timebase is a variation of the hit and miss model.

Couldn't grok the relevance of the following paragraph above :-)...

Chris

Gareth's Downstairs Computer wrote on 8/6/2017 5:26 AM:
On 05/08/2017 23:25, rickman wrote:
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.

I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.

Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.

What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the pendulum.
The correction of the phase is from the added spring resistance shortening
the time as well as the travel of the pendulum. The fact that the swing is
shorter and the second order circular error will create a tiny error in the
timing is pretty much irrelevant. The real change is from the added spring
constant changing the first order effect in the pendulum equation. The
coefficient of the gravitational constant is effectively changed by the spring.

Is that more clear?

--

Rick C

Jeff wrote on 8/6/2017 6:38 AM:

You are making pointless distinctions. A phase locked loop is not defined
by its mechanics but by the nature of its control. The Shortt clock
maintains the relative *phase* of the two clocks by brief adjustments to
the frequency via a spring. This is controlled by measuring the relative
*phase* of the two clocks.


Wrong! It does NOT measure the relative phase, it makes NO measurement of
the phase difference. All it does is detect if there is a phase lag of any
degree. It could be a fraction of a degree or 180 degrees, the same
correction is then applied regardless.

....and that is a measurement. It determines if the relative phase is plus
or minus, a binary measurement. This is exactly the same as the measurement
taken by a 1 bit ADC. Even though it is one bit it is still a measurement.


It's that simple. You are just making things more complicated by talking
about the details of how the adjustment works and the time function of the
frequency. NO PLL can keep the two clocks perfectly in sync.

Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to the
measurement. It may be binary, but the adjustment is controlled by the
measurement.

Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.

Totally wrong. The phase adjustment varies from a constant about to ZERO!
Again it is a binary adjustment.

If there was a three level range of measurement and adjustment +, 0, -,
would that be enough to constitute a measurement and adjustment so it
becomes a PLL? If not, how many bits are required? If any number of bits
can't do it are digital PLLs not PLLs?

--

Rick C

On 06/08/2017 15:27, Chris wrote:
On 08/06/17 12:52, Gareth's Downstairs Computer wrote:
On 06/08/2017 12:24, Chris wrote:
On 08/06/17 10:38, Jeff wrote:

You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.


Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.

It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.

Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.

Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.

Jeff



Might be easier to define a set entitled "Locked Oscillators, of which
the phase locked loop, injection locked and hit and miss synchronised
are all members.

Are there other candidates ?...

From pre-war, the Goyder Lock?

Which raises an interesting point; before the 3-tier
coffer-filling fiasco was the spawn of the RSCB, the candidature
for the RAE tended to know all about the history of amateur radio
before getting their licence, but now they seem to know
sweet FA even after getting their licences, such as the
difference between sideband and sidetone.




Hadn't heard of that, so looked it up and found:

http://www.dxmaps.com/discuss/oven.html

Which was an interesting read, but not enlightening.

Some of the early scope timebases, puckle, for example sounded
interesting, but they were effectively injection lock, of course.
I guess a triggered timebase is a variation of the hit and miss model.

Couldn't grok the relevance of the following paragraph above :-)...


It relates to the abysmal lack of technical acumen amongst those
who are today's would-br radio amateurs, most of whom are
really CBers-masquerading-as-radio-hams, identifiable by their
M3 and M6 callsigns past and present.

On 06/08/2017 17:18, rickman wrote:
Gareth's Downstairs Computer wrote on 8/6/2017 5:26 AM:
On 05/08/2017 23:25, rickman wrote:
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.

I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.

Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.

What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring
resistance shortening the time as well as the travel of the pendulum.
The fact that the swing is shorter and the second order circular error
will create a tiny error in the timing is pretty much irrelevant. The
real change is from the added spring constant changing the first order
effect in the pendulum equation. The coefficient of the gravitational
constant is effectively changed by the spring.

Is that more clear?


You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter
amplitude and hence instantaneous higher frequency exists.