Randy
In August you asked
First off, what I am about to do is ask a REALLY STUPID question, but
more and more of the GPS stuff I do is drifting towards the precision
timing end of things, so I thought I should ask.
I have been seeing a lot of traffic concerning making 10MHz frequency
Hal Murray wrote:
Suitable TDC chips are available from [1]http://www.acam.de/ [2]http://
www.acam.de/ In particular the TDC-GP1 has a resolution of better
than 250picosec with a range of 200 millisec, which should be more
than adequate for measuring the time delay between GPS and local
Yet another high resolution time interval interpolation technique is to
sample a pair of quadrature sinewaves at the leading edge of the pulse
to be time stamped.
When sampling a pair of 10MHz sinewaves in quadrature with a 12 bit ADC
a timing resolution of better than 50 picosec is possible.
Brian O'Connor [1]vk4gtw at bigpond.com wrote:
I note that Shera's QST article refers to using the 1 MHz
output from a HP5328A. Is there any degradation of
performance or increased thermal sensitivity due to the use
of a HP marked 7490 (ripple counter) to divide down to 1 MHz?
Would use of
Dr Bruce Griffiths wrote:
Brian O'Connor [1]vk4gtw at bigpond.com wrote:
I note that Shera's QST article refers to using the 1 MHz
output from a HP5328A. Is there any degradation of
performance or increased thermal sensitivity due to the use
of a HP marked 7490 (ripple counter) to divide
Dr Bruce Griffiths wrote:
Brian O'Connor [1]vk4gtw at bigpond.com wrote:
I note that Shera's QST article refers to using the 1 MHz
output from a HP5328A. Is there any degradation of
performance or increased thermal sensitivity due to the use
of a HP marked 7490 (ripple counter) to divide
Another way of determining the the arrival time of a pulse with high
resolution is to use centroid timing techniques.
The input pulse is converted to a short pulse using a delay line timed
monostable then the resultant pulse is low pass filtered by a discrete
component RLC Gaussian low pass
Hal in July you asked
/ With the fibre-based two-way time transfer. For shorter distances you
// can do well on coax, but for the distance range you require you really
// want to go fibre. That world is a bit different but can be made sense
// off.
/
How do I setup 2 clocks so they are
Hal Murray wrote:
Another way of determining the the arrival time of a pulse with high
resolution is to use centroid timing techniques. The input pulse is
converted to a short pulse using a delay line timed monostable then
the resultant pulse is low pass filtered by a discrete component RLC
Glenn wrote:
Brooke Clarke wrote:
I'm interested in automatically measuring the earth's period by looking
close to straight up with a fixed telescope.
This sounds like an interesting project. I've been looking for something
to do with the Meade 4455D telescope I just got.
Glenn wrote:
Brooke Clarke wrote:
I'm interested in automatically measuring the earth's period by looking
close to straight up with a fixed telescope.
This sounds like an interesting project. I've been looking for something
to do with the Meade 4455D telescope I just got.
Data Delay Devices quote 1-2% typical variation in delay for their all
silicon delay lines over the -40 to + 85C operating temperature range.
These devices have built in temperature compensation.
They claim a residual tempco of 200ppm/K
Maxim/Dallas don't specify this parameter for their
Passive delay line has a much lower tempco than active delay lines.
Typical tempco is 100ppm/K.
Just add you own active devices and line termination.
Bruce
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Dr Bruce Griffiths wrote:
David Forbes wrote:
Bill Hawkins wrote:
Tom Van Baak wrote,
2) Instead of a fixed base, gnomon, and slowly moving shadow like
almost all sundials, you put a stepper or servo motor/encoder on the
base. Then place matched photodiodes on either side
Tom Van Baak wrote:
The scheme probably needs three photocells to be sure that the one
in the middle is darker than the others. Might be able to mask it
with a slit and use a fine wire gnomon, in a coarse/fine servo.
Could use a variable frequency motor and precision reduction, like
a
of a
reflecting (e.g. cassegrain) telescope. A index sensor gives you your
phase reference.
Robert G8RPI.
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Dr Bruce Griffiths
Sent: 29 September 2006 01:09
To: Tom Van Baak; Discussion of precise time
Tom Van Baak wrote:
Accuracy still won't be much better than1% of the solar diameter or
about 1 second of time nowhere near the o.1 sec or better hoped for.
Bruce
Bruce,
Can you show us how to derive the accuracy number?
I would have guessed that with fractional degree Al-El
Bill Hawkins wrote:
OK, there are serious sources of error in making a one-time
solar transit measurement.
What I propose is a differential method, a favorite of
instrument makers to reduce errors. This is possible
because the equation of time makes a correction of only
one percent or so.
Poul-Henning Kamp wrote:
In message [EMAIL PROTECTED], Ulrich Bangert writes:
Hello Paul-Henning,
www.tmo.jpl.nasa.gov/progress_report/42-121/121G.pdf
definitely uses no FFT but uses a theoreme from geometry to estimate the
signal's frequency and the rest is a two dimensional non-linear
Magnus Danielson wrote:
From: [EMAIL PROTECTED]
Subject: Re: [time-nuts] On some pitfalls of the dual mixer time
differencemethod of h...
Date: Sun, 1 Oct 2006 13:53:57 EDT
Message-ID: [EMAIL PROTECTED]
Hello Ulrich,
Ulrich and Said,
the latest generation of TSC
M. Warner Losh wrote:
In message: [EMAIL PROTECTED]
Dr Bruce Griffiths [EMAIL PROTECTED] writes:
: The Allan deviation of current state of the art cryogenic sapphire
: oscillators is more than an order of magnitude lower than the noise
: floor of these instruments.
I'm
Dean Weiten wrote:
Hi there,
Having worked with the folks who operate the power utilities (I designed
protective relaying and recorder electronics for several years), I can
advise that they do take the long-term accuracy of their power
seriously. However, the short-term is not a big
Bill Hawkins wrote:
Dr Bruce Griffiths said,
Some generators are kept continuously spinning and
synchronised to the mains but generating little power.
These spinning reserve generators are necessary to
stabilise the grid against load fluctuations, they can
very quickly supply power when
Tom Van Baak wrote:
Interesting as the techniques employed may be, the resultant performance
is still inadequate for characterising state of the art oscillators.
The instrument phase noise floor is higher than that specified for
current low noise (but not necessarily low drift) crystal
Poul-Henning Kamp wrote:
In message [EMAIL PROTECTED], Bill Hawkins writes:
Think of the incredible amount of energy stored in many
rotating generators linked by the synchronous network.
This is actually far less than you seem to think.
If the load suddenly increased 10%
David McGaw wrote:
The 10811 is the newer SC cut crystal oscillator. The 10544 would be
the older AT cut oscillator.
At 09:43 PM 10/14/2006, you wrote:
I got an HP 5370A from eBay which did not work at power up (display was
messed up). After resetting all the ROMs and the CPU in their
Robert Atkinson wrote:
Hi Chuck,
I'd agree on the use of connector wipes, but doubt that they have
silicone as a lubricant. Silicone oil or grease is not generally
suitable as a lubricant on electrical contacts as it can form an
insulating layer that is virtually impossible to remove. This is
Dave Brown wrote:
Interested in any comments on this GPSDO -
http://www3.sympatico.ca/b.zauhar/GPS_Std/GPS_Std.htm#GPS_Receivers
DaveB, NZ
Why anyone would bother to create something like this escapes me.
Just another example of unintelligent engineering.
If one is foolish enough to
John Miles wrote:
I think it'd be great to see Dr. Griffiths' list of issues in a letter to
QEX, sans a couple of the more, er, editorial comments. This would give
the author a chance to respond, and alert other builders of opportunities
for improvement.
Some of the concerns may not be
Tim Shoppa wrote:
John Miles [EMAIL PROTECTED] wrote:
Some of the concerns may not be major issues (e.g., it seems safe to say
that the FLL action will correct for drift caused by the 7805's tempco,
unless you plan to dump a can of R134a on it), but others are worth bringing
to the
) fine tune the phase lock parameters and estimate the quality of the
end product
Any further information and guidance (with practical tips) would be
greatly appreciated.
Didier KO4BB
Dr Bruce Griffiths wrote:
Tim Shoppa wrote:
John Miles [EMAIL PROTECTED] wrote
Didier
If you are going to use a PPS divider to divide the oscillator frequency
down to 1Hz, you will need to measure the inherent jitter of the divider
to ensure that it doesn't degrade the measurement resolution. It may be
necessary to resynchronise the divided output using a fast D flipflop
Tim Shoppa wrote:
Dr Bruce Griffiths [EMAIL PROTECTED] wrote:
Most GPS receivers with higher frequency outputs than 1Hz, phase
modulate the high frequency output in this way and the datasheets
explicitly indicate this.
Thus there would appear to be little advantage in phase locking
John Ackermann N8UR wrote:
Dr Bruce Griffiths said the following on 10/22/2006 07:33 PM:
Didier
If you are going to use a PPS divider to divide the oscillator frequency
down to 1Hz, you will need to measure the inherent jitter of the divider
to ensure that it doesn't degrade
John Miles wrote:
You can do a lot worse than straight TTL. Some useful graphs on pages 102
and 103 of Rohde's Microwave and Wireless Synthesizers: Theory and Design.
Hint: Look it up at www.amazon.com and you can view those two pages, if you
search within the book for the phrase 170 dB.
Didier Juges wrote:
Dr Bruce Griffiths wrote:
In principle this measurement could be made with a time interval counter:
PPS - START
delayed 10KHz - STOP
Vary the delay and watch the jitter jump when the leading edge of the
PPS signal occurs during the 10KHz burst which was phase
Didier Juges wrote:
Dr Bruce Griffiths wrote:
In principle this measurement could be made with a time interval counter:
PPS - START
delayed 10KHz - STOP
Vary the delay and watch the jitter jump when the leading edge of the
PPS signal occurs during the 10KHz burst which was phase
Didier Juges wrote:
Dr Bruce Griffiths wrote:
In principle this measurement could be made with a time interval counter:
PPS - START
delayed 10KHz - STOP
Vary the delay and watch the jitter jump when the leading edge of the
PPS signal occurs during the 10KHz burst which was phase
Didier Juges wrote:
Dr Bruce Griffiths wrote:
Didier Juges wrote:
Dr Bruce Griffiths wrote:
In principle this measurement could be made with a time interval counter:
PPS - START
delayed 10KHz - STOP
Vary the delay and watch the jitter jump when the leading
to reuse the divider for my frequency
standard.
Thanks
Didier
Dr Bruce Griffiths wrote:
Didier
If you are going to use a PPS divider to divide the oscillator frequency
down to 1Hz, you will need to measure the inherent jitter of the divider
to ensure that it doesn't degrade
to reuse the divider for my frequency
standard.
Thanks
Didier
Dr Bruce Griffiths wrote:
Didier
If you are going to use a PPS divider to divide the oscillator frequency
down to 1Hz, you will need to measure the inherent jitter of the divider
to ensure that it doesn't degrade
Didier Juges wrote:
Dr Bruce Griffiths wrote:
Didier Juges wrote:
Dr Bruce Griffiths wrote:
Didier Juges wrote:
Dr Bruce Griffiths wrote:
In principle this measurement could be made
Tom Van Baak wrote:
Didier,
I've been out of town and I see a flurry of postings to
your original query about Allan deviation. It sounds
like your goal is to measure the stability of various
oscillators that you have lying around?
First, your 5370 or any other TIC (Time Interval Counter)
As a first submission to a collection of pathological PPS divider
designs where the input clock to output delay is so large that its
jitter and more particularly its tempco are significant I suggest that
the following:
Input stage HEF4017 with 10V power supply
clock to output delay 110 ns max
Magnus
The drawback with a CPLD is that most have a relatively high dc supply
current.
I have a couple of CPLD designs that work the way you advocated.
A CMOS divider has the attraction that its power supply current can be
relatively small even when the (small duty cycle) output drives a 50 ohm
There is a potential problem, particularly with the 5370A and possibly
the 5370B which may not be generally known.
1) Crosstalk between the microstriplines from the Schmidt trigger
outputs (XA4: U1, U2) to the arming board amplifier inputs (XA22: U19, U20)
2) Cross talk between the
Didier Juges wrote:
Hi Ulrich,
comments are embedded:
Ulrich Bangert wrote:
the Datum LPRO User's Guide / Installation Guide discusses some methods
of sine to square wave conversion in terms of lowest phase noise.
This is good to know. Do you have any suggestion how I might
Didier
Did you get my comment on HP5370A differential linearity errors.
It made it to the list but I didn't receive a bounced copy.
Bruce
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Didier Juges wrote:
Here are my $0.02...
Magnus Danielson wrote:
From: Dr Bruce Griffiths [EMAIL PROTECTED]
Subject: Re: [time-nuts] How to measure Allan Deviation?
Date: Tue, 24 Oct 2006 10:52:21 +1300
Message-ID: [EMAIL PROTECTED]
Tom
Hi Bruce
Didier Juges wrote:
I do not understand the signal on the rear trigger outputs. At the
moment, I have a single 10 MHz sine signal fed to the START channel, and
the 5370 is set to TI, MEAN, SAMPLE SIZE 1, + TI ONLY, START channel
triggers on rise and STOP channel triggers on fall, and START
Didier
START and STOP selection is even more complex than I indicated.
START SOURCE STOP SOURCE REAR PANEL START TRIGGER REAR
PANEL STOP TRIGGER
Front panel START Front Panel STOP Front Panel START
Front Panel STOP
Front panel STOP
Didier Juges wrote:
Dr Bruce Griffiths wrote:
Didier Juges wrote:
I do not understand the signal on the rear trigger outputs. At the
moment, I have a single 10 MHz sine signal fed to the START channel, and
the 5370 is set to TI, MEAN, SAMPLE SIZE 1, + TI ONLY, START channel
Didier Juges wrote:
Hi Bruce,
Dr Bruce Griffiths wrote:
Didier Juges wrote:
Dr Bruce Griffiths wrote:
Didier Juges wrote:
I do not understand the signal on the rear trigger outputs. At the
moment, I have a single 10 MHz sine
Stephan Sandenbergh wrote:
Hi All,
Can anyone give me the low-down on logic standards for clock distribution in
digital systems?
It seems that ECL, PECL and LVDS are the most widely used. After a quick
glance at the specs for the above mentioned standards I noted the following
Didier Juges wrote:
I have downloaded and installed Plotter, and found it easy to setup and use,
at least for basic functionality. The menu threw me off a little bit (no
simple File-Open dialog), but I am sure I will get used to it.
I have ran my spare HP10811 overnight (twice), against the
Stephan Sandenbergh wrote:
Hi Bruce,
Thank you for the elaborate answer covering different logic types. Funny
enough, I have just read the excellent book you recommended cover to cover -
probably the origin of many of my questions.
As I said in reaction to Said's response - I am not
Didier
It would be useful if you describe in some detail your measurement setup.
Which signals are connected to which inputs on the 5370A?
How long are the cables? etc.,
Also given your source selection problems with the 5370A it may be
instructive to run a simple test.
Connect a low frequency
The positive supply connection to A22:U7 (LM339 quad comparator) is
shown as ground in the circuit diagram.
This is surely incorrect as the inputs of U6B and U6C are connected to
TTL(+5V VCC) signals.
Surely this is not the designers intention
The positive supply of A22:U7 should be +5V.
Is
Correction to previous post. (typed U7 instead of U6 VVC connected too
ground OK for U7 as inputs are ECL levels. )
The positive supply connection to A22:U7 (LM339 quad comparator) is
shown as ground in the circuit diagram.
This is surely incorrect as the inputs of U6B and U6C are connected to
Fix for yet another typo, I really should check the text more carefully.
The positive supply connection to A22:U6 (LM339 quad comparator) is
shown as ground in the circuit diagram.
This is surely incorrect as the inputs of U6B and U6C are connected to
TTL(+5V VCC) signals.
Surely this is not
Dr Bruce Griffiths wrote:
Correction to previous post. (typed U7 instead of U6 VVC connected too
ground OK for U7 as inputs are ECL levels. )
The positive supply connection to A22:U7 (LM339 quad comparator) is
shown as ground in the circuit diagram.
This is surely incorrect as the inputs
Dr Bruce Griffiths wrote:
John Miles wrote:
In the 5370B manual (2940A prefix), it looks like they are running U7
from
+5 on pin 3 and -5.2 on pin 12. Probably a drafting error in the -A
manual.
-- john, KE5FX
Dr Bruce Griffiths wrote:
Correction to previous post. (typed U7
Stephan Sandenbergh wrote:
Hi Bruce,
You mentioned that locking to a crystal at the receiving end as an option.
Does this mean that signal transmission is primarily plagued by short term
noise?
I have never really touched the topic of optical fibre, but I realise that
it is superior to
Robert Atkinson wrote:
Hi,
Have a look at,
http://www.wenzel.com/pdffiles/diodedbl.pdf
Also http://www.wenzel.com/documents/hints.htm indicates that the NIST
design uses JFET's but I can't find any more details.
Robert G8RPI.
-Original Message-
From: [EMAIL PROTECTED]
Christopher Hoover wrote:
Hey 'nuts,
I'm looking for a good design for a 5 MHz frequency doubler.
The Wenzel Blue Tops HF doubler is said to be based on a low phase
noise, public-domain NIST design:
http://www.bluetops.com/Modules/lnhd.htm
Christopher Hoover wrote:
Dr Bruce Griffiths wrote:
The design is probably a pair of low noise n channel JFETs
configured as a push push doubler.
Inputs driven in antiphase so that each FET conducts ffor
opposite 1/2 cycles with the 2 FET drains connected in parallel.
A bypassed
Christopher Hoover wrote:
Dr Bruce Griffiths wrote:
The design is probably a pair of low noise n channel JFETs
configured as a push push doubler.
Inputs driven in antiphase so that each FET conducts ffor
opposite 1/2 cycles with the 2 FET drains connected in parallel.
A bypassed
Didier Juges wrote:
Magnus Danielson wrote:
Look at the AD8561 datasheet first. The 74HC4046 is much slower than the
AD8561 and the higher output slewrate of the AD8561 is certainly good to keep
jitter down. The 74HC4046 is worse for that aspect.
What I would rather critize Didiers
kd7ts wrote:
Didier Juges wrote:
There are sudden increases in noise (bursts that last from seconds to
minutes) on the plots I posted.
I believe the sudden and drastic increase in noise at times comes from
the GPS loosing lock. At the moment, I cannot hook up the computer to
the GPS
Eric Haskell wrote:
I purchased this item to ebay to play with the YIG. Can anyone help with
proper voltages to apply to this unit and which pins they go to?
Eric Haskell
KC4YOE
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Didier Juges wrote:
Dr Bruce Griffiths wrote:
Good timing antennas have built in ceramic or equivalent bandpass
filters to minimise the effect of interference.
A patch antenna is not as satisfactory as a quadrifilar helix or a choke
ring ground plane antenna for accurate timing
Didier Juges wrote:
Dr Bruce Griffiths wrote:
Good timing antennas have built in ceramic or equivalent bandpass
filters to minimise the effect of interference.
A patch antenna is not as satisfactory as a quadrifilar helix or a choke
ring ground plane antenna for accurate timing
Didier Juges wrote:
That's the impression I am getting. I do not know if any of the GPSDO
that I have seen described in recent literature take care of this properly.
It seems when the GPS goes nuts, the 1 PPS goes quite a bit out of
normal range, so it should not take too much
Didier Juges wrote:
Dr Bruce Griffiths wrote:
Didier
Alternative GPSDO solution
Divide the 10MHz reference by 32 resync the output to 10MHz with a fast
D flipflop and then divide the D flipflop output by 4 using a 2 bit
switchtail ring (Johnson) counter.
Low pass filter the outputs
Didier Juges wrote:
Dr Bruce Griffiths wrote:
Didier Juges wrote:
That's the impression I am getting. I do not know if any of the GPSDO
that I have seen described in recent literature take care of this properly.
It seems when the GPS goes nuts, the 1 PPS goes quite a bit
Rob Kimberley wrote:
Back to good ol' UTC here in the UK this morning!!
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Bill Hawkins
Sent: 29 October 2006 05:42
To: Discussion of precise time and frequency measurement
Subject: [time-nuts]
Didier Juges wrote:
Dr Bruce Griffiths wrote:
Didier
Alternative GPSDO solution
Divide the 10MHz reference by 32 resync the output to 10MHz with a fast
D flipflop and then divide the D flipflop output by 4 using a 2 bit
switchtail ring (Johnson) counter.
Low pass filter the outputs
be measured in term of lowcheap parts count
as seems to be a quite common opinion.
Best regards
Ulrich Bangert
-Ursprüngliche Nachricht-
Von: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Im Auftrag von Dr Bruce Griffiths
Gesendet: Samstag, 28. Oktober 2006 23:46
An: [EMAIL
of it??
Best regards
Ulrich Bangert
-Ursprüngliche Nachricht-
Von: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Im Auftrag von Dr Bruce Griffiths
Gesendet: Sonntag, 29. Oktober 2006 14:37
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] Allan Deviation
John Miles wrote:
Definitely an interesting chart. I don't know how much stock I'd put in it,
though. The figures cited are, in some cases, much worse than those
published elsewhere and observed personally.
I didn't look at all of the test circuits, but there are more things wrong
with the
The article below describes how the local oscillator frequency is
distributed to the antennas of the Atacama millimeter array.
The techniques used to stabilise the local oscillator frequency and
phase at each antenna may be of some interest to anyone considering
fibre optic distribution of
Brooke Clarke wrote:
Hi Tom:
Thanks for the lab test report on the earth frequency standard. Since
there are a number of frequency/time standards that have much better
performance I'd like to find a way to directly measure the performance
of the earth standard. I've thought about a
Jack Hudler wrote:
Sheeesh!
Actually I use the 5501B for its intended purpose... I'm a bit of a precision
nut. Never seen an Allan variance plot of one.
I prefer 473.6057788309637 THz :)
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of Robert
---BeginMessage---
Magnus Danielson wrote:
From: Dr Bruce Griffiths [EMAIL PROTECTED]
Subject: Re: [time-nuts] HP 10811A/B OCXO OP/SRV manual is
onlineathparchive.com AND HP 5501B manual.
Date: Wed, 08 Nov 2006 11:25:44 +1300
Message-ID: [EMAIL PROTECTED]
To measure the Allan variance you
Subject: Re: [time-nuts] HP 10811A/B OCXO OP/SRV manual is
onlineathparchive.com
AND HP 5501B manual.
From: Dr Bruce Griffiths [EMAIL PROTECTED]
Subject: Re: [time-nuts] HP 10811A/B OCXO OP/SRV manual is
onlineathparchive.com
AND HP 5501B manual.
Date: Wed, 08 Nov 2006 13:56:38 +1300
Ulrich Bangert wrote:
Hi folks,
first i would like to announce a new version of PLOTTER which can be
downloaded from
www.ulrich-bangert.de
The new version can classify data and compute new data columns from
existing ones using a formula interpreter in that you may input a
formula of your
A resolution of 1E-15/T has been achieved (at JPL) by measuring the
period of a 1Hz beat signal produced by mixing a pair of 100MHz
sources, the zero crossing detector used requires heroic measures to
combat the high phase shift temperature coefficient (~60us/K with
polypropylene capacitors,
Magnus Danielson wrote:
Hi!
I have a HP G-69B-2 Z-235 Crystal Oven 100 kHz lying around. I'm considering
heating it up and run it (just for fun). Operating temperature is 65 C.
Anyone care to share any information on this device? I have no clue which box
it ever was in or anything. Also,
Dr Bruce Griffiths wrote:
Magnus Danielson wrote:
Hi!
I have a HP G-69B-2 Z-235 Crystal Oven 100 kHz lying around. I'm considering
heating it up and run it (just for fun). Operating temperature is 65 C.
Anyone care to share any information on this device? I have no clue which box
Magnus Danielson wrote:
Hi!
I have a HP G-69B-2 Z-235 Crystal Oven 100 kHz lying around. I'm considering
heating it up and run it (just for fun). Operating temperature is 65 C.
Anyone care to share any information on this device? I have no clue which box
it ever was in or anything. Also,
David Forbes wrote:
Jason Rabel wrote:
A good initial buffer chip for all the TTL signals would be an IDT QS3384
with 10 inputs/outputs.
Jason,
The only problem with that part is that it's not a buffer! It's a
switch. It has no drive capability at all.
There are useful buffer
David Forbes wrote:
Jason Rabel wrote:
A good initial buffer chip for all the TTL signals would be an IDT QS3384
with 10 inputs/outputs.
Jason,
The only problem with that part is that it's not a buffer! It's a
switch. It has no drive capability at all.
There are useful buffer
Hal Murray wrote:
Driving a full 5V TTL signal into a 50 ohm load is another matter -
you need a lot of DC power (1/2 watt) to do that. I was just using a
Liner Tech LT1010 for a similar job - it would get the job done, but
folks here might complain about the phase noise.
Where does
David Forbes wrote:
Jason Rabel wrote:
A good initial buffer chip for all the TTL signals would be an IDT QS3384
with 10 inputs/outputs.
Jason,
The only problem with that part is that it's not a buffer! It's a
switch. It has no drive capability at all.
There are useful buffer
Jason Rabel wrote:
Jason,
The only problem with that part is that it's not a buffer! It's a
switch. It has no drive capability at all.
There are useful buffer chips for this task, but their names escape me
just now. Perhaps the 74FCT245 or equivalent would work.
Driving a full 5V TTL
I may have asked this before, but do you happen to have a few references on
the extensions to Leeson's theory?
Cheers,
Magnus
References are:
/A General Theory of Phase Noise/ /in Electrical Oscillators/
Ali Hajimiri, Student Member, IEEE, and Thomas H. Lee, Member, IEEE
IEEE JOURNAL OF
Tom Van Baak wrote:
Brooke,
Maybe this helps. The clock prediction into the future
is based on the past history and the current point. If
the measured ADEV for a clock is, say 1e-13, for a
measurement interval of 1 day (tau), then the prediction,
within one standard deviation, is that
Tom Van Baak wrote:
On the subject of Brooks Shera's design, the one thing that troubles me is
the
use of a 24 MHz oscillator to count the width of the 1PPS signal.
This yields a precision of 4.16e-8, but does it really?
No, with averaging it's much better than that.
[EMAIL PROTECTED] wrote:
On Thu, December 14, 2006 23:07, Dr Bruce Griffiths said:
Thus devising inexpensive phase detectors/TICs with subnanosecond
performance allows one to take advantage of improvements in GPS timing
receiver performance when they occur.
The possibility of utilising
[EMAIL PROTECTED] wrote:
On Thu, December 14, 2006 23:07, Dr Bruce Griffiths said:
Thus devising inexpensive phase detectors/TICs with subnanosecond
performance allows one to take advantage of improvements in GPS timing
receiver performance when they occur.
The possibility of utilising
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