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Today's Topics:
1. Re: Wilkinson TDC (David)
2. Re: General Technology Corp model 304b (paul swed)
3. Re: Antique Rb Standard - Thanks, Pictures, Parts Request,
Question (Magnus Danielson)
4. Re: General Technology Corp model 304b (Ed Palmer)
5. Re: Antique Rb Standard - Thanks, Pictures, Parts Request,
Question (Cliff Sojourner)
6. Re: PICDIV for 1 min pulses (Bob Camp)
----------------------------------------------------------------------
Message: 1
Date: Sun, 29 Apr 2012 18:17:10 -0500
From: David <davidwh...@gmail.com>
To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Subject: Re: [time-nuts] Wilkinson TDC
Message-ID: <mr9rp7lgruccve3eaq954sr1og26575...@4ax.com>
Content-Type: text/plain; charset=us-ascii
On Mon, 30 Apr 2012 06:51:37 +1200, Bruce Griffiths
<bruce.griffi...@xtra.co.nz> wrote:
The circuit for the Tek 2440 is in the manual.
However, it isnt that well executed.
I like using the 2440 as an example because the design and theory are
readily available online. Its execution only had to be good enough
for 40ps equivalent time sampling and less than 50 measurements per
second. Unfortunately the self calibration logic is obfuscated inside
of a Tektronix black box custom ASIC.
Relying on the overload recovery of an unclamped jfet input opamp limits
the recovery time and performance as does the unisolated input
capacitance of the opamps used to control the current source transistor
emitter currents, the Wavecrest interpolators which incorporate several
refinements to improve the transient response of the current sources are
far better in this respect.
By unclamped JFET input opamps do you mean U590B and U590C which are
used to adjust the ramp start to zero volts and operate open loop
during the measurement? With such a slow measurement rate, that
feedback loop has at least 20ms to complete settling. I notice that
they attenuated the open loop gain by a factor of 6. I wonder if that
was to lower the noise or to add phase margin to the control loop.
The Wavecrest interpolators also have sub picosecond resolution although
their noise is around 3-6ps.
Is there a published schematic and theory for the Wavecrest other than
the patent? The best information I have found through Google is from
your own posts here.
Bruce
paul swed wrote:
Do you have an actual circuit?
It looks a lot like the old hp5360 counter interpolator.
Regards
Paul
On Sun, Apr 29, 2012 at 3:51 AM, Bruce
Griffiths<bruce.griffi...@xtra.co.nz
wrote:
The essentials of a Wikinson TDC can be simplified to the attached
circuit
which only requires the addition of a zero crossing comparator to
monitor
the voltage across the capacitor C1.
A few refinements to improve the capacitor charging current switching
transitions and the addition of an upper voltage clamp together with
the
use of faster transistors may be useful.
Apart from level shifting to drive the npn and pnp longtailed pairs
only a
2 bit shift register is required for the synchronisers reducing the
number
of external (to an FPGA or CPLD) logic packages required.
The jitter of the count logic etc., isn't critical and can be
implemented
in an FPGA or CPLD.
With a 100MHz synchroniser and counter clock a resolution of 10ps can
be
achieved with a 1000:1 ratio between charge and discharge currents.
------------------------------
Message: 2
Date: Sun, 29 Apr 2012 19:18:13 -0400
From: paul swed <paulsw...@gmail.com>
To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Subject: Re: [time-nuts] General Technology Corp model 304b
Message-ID:
<CAD2JfAi67wi3c9Ea4p+Qcx=daowx-28JNAuw_q5cA_ZY+TDr=q...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Curious is the manual online?
Would be interesting to look at.
On Sun, Apr 29, 2012 at 6:33 PM, Ed Palmer <ed_pal...@sasktel.net> wrote:
Hi Don,
On 4/29/2012 2:54 PM, Donald Henderickx wrote:
On 4/29/2012 1:36 PM, Ed Palmer wrote:
Thank you Ed,Paul,and Marco for the reply's
The foam I was referring to is or was around ceramic base were the
igniter wire goes . Yes my wire also broke loose however I do not want
to
disassemble any more than I have to. I think that just inserting it back
in
to the hole and securing in some way should work. I do not know what the
potential is but I have seen a spark jump at least an eight of an inch.
The igniter wire has to be connected to the base of the lamp. The patent
explains it quite well. Just inserting it into the hole in the ceramic
is
unlikely to work. I don't know what the voltage is, but the capacitor
that
stores the voltage is rated for 400V.
Does the foam look original? It definitely isn't on mine so I wasn't
sure
if it was supposed to be there or not. The patent describes how the base
is the coolest part of the bulb. I don't know if a foam covering is
appropriate.
Tell me about the lamp voltage test point. My manual has no mention of
it? Were is it located?
All the test points are described on page 5-3 of the manual. The lamp
heater test point is the sixth one from the top. Ground is the seventh
point.
In you first posting I think you mentioned some grounding problems. On
this unit there is a three pin amp connector on the rear on mine the
bottom
pin -20 must be grounded or the unit will not work. The red light will
come
on very bright but nothing else works.I believe you can also ground the
+20
this allows this to work in various ground polarity systems IE telco
systems +ground. Perhaps I am wrong.
Do you mean the 3 pin round connector on the back? That's for an
external
DC power supply. It has no other function and grounding the bottom pin
(which is ground) shouldn't make any difference.
Ed
I have Hp113,Hp115 that caution you on the ground polarity of the
systems
you are installing them in. I think all the -20 floats from chassis
ground
until they get to that rear plug.
Thanks for foam an fiberglass suggestions.
Hi Don,
You know that we're going to be swapping many emails, don't you? :-)
On 4/29/2012 11:16 AM, Donald Henderickx wrote:
After following Ed Palmer's thread on 304b restoration,I was inspired
to get my GTC (tracor) 304b ser#279 going. It seems that the failure
of
this unit was the break down of the foam that was wrapped around the
vcxo
located inside the control box. The vapors or the moisture the foam
collected corroded the steel fasteners and caused the switches to
become
intermittent.
The foam around my OCXO is still in great shape. Still spongy and
providing lots of holding force for the OCXO. My unit is serial #449.
The replacement of the foam in the control box is not that much of a
problem,what I need help with is what to use around the Rb lamp base.
The
foam has turned to powder.
Do you mean foam around the back end of the lamp where the wire lead
comes out or the foam that surrounds the reflector (#16 in the picture
in
the patent that describes the lamp (3311775))? My #16 foam is really
solid.
Should I try Home foam sealant? The cell's ,of this seem about the
same
as the old foam.Will it take the heat?Should I make a fiberglass
cocoon to
put around the lamp base.
Read the fine print on the can. It may list the maximum temperature
rating. I'd try a fiberglass cocoon first just because it's easily
reversible if it doesn't work. When your unit is running is the lamp
test
point voltage correct?
Ed
The unit now achieves lock in about an hour. The only other thing I
did
was to replace the caps in the main supply.
Any thoughts on the insulation?
Don H
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------------------------------
Message: 3
Date: Mon, 30 Apr 2012 01:21:24 +0200
From: Magnus Danielson <mag...@rubidium.dyndns.org>
To: time-nuts@febo.com
Subject: Re: [time-nuts] Antique Rb Standard - Thanks, Pictures, Parts
Request, Question
Message-ID: <4f9dccf4.3090...@rubidium.dyndns.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hi Ed,
On 04/29/2012 05:46 PM, Ed Palmer wrote:
Hi Magnus,
Second, pictures. If anyone is interested, check out
http://s701.photobucket.com/albums/ww18/edpalmer42/Tracor%20304-B/ .
Nice photos. Thanks. GAS building up.
What does GAS mean?
Gear Acquisition Syndrome.
GAS is a diagnose which I think no time-nut would admit to. ;-)
that talks about cavities in general, but the calculations don't work.
I'm guessing that the Rb cell is changing the resonant frequency of the
cavity.
The glass pulls the cavity resonance somewhat, yes. A TE111 resonance
mode is typically used, allowing light to enter and leave at the ends
of the cylinder.
TE011 was used before, but it much larger.
Todays modern cells use a "loaded" cell (dielectrum added) to move the
resonance frequency down, which allows much smaller physical cells.
This unit is TE011 No dielectric, plain brass - not silver-plated, 2.495
inch diameter @ room temperature, length tunable from ~0.9 to 1.07
inches.
Not surprising, and actually I think I've read that during the day.
W.J.Riley "Rubidium Frequency Standard Primer" is a good
starting-point, but following the references should help.
I think just searching for "TE111 mode rubidium" cranks out a few
interesting things, such as:
http://dspace.thapar.edu:8080/dspace/bitstream/10266/968/1/Satyendr_Thesis.pdf
Thanks for that link. I have been searching, but it's like panning for
gold - lots of sand and dirt and a very few nuggets of gold.
Indeed. I have a few more hints on where it can be worth panning, as I
have gathered a few books on the subject.
Reading Riley's book (as I mentioned above) today has given much more
body to the subject. Learning things quickly. While his book isn't heavy
on the deep stuff, he summarize it so you get an overview and then gives
several hundreds of references.
Cheers,
Magnus
------------------------------
Message: 4
Date: Sun, 29 Apr 2012 17:27:04 -0600
From: Ed Palmer <ed_pal...@sasktel.net>
To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Subject: Re: [time-nuts] General Technology Corp model 304b
Message-ID: <4f9dce48.3010...@sasktel.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Yes, there's a partial copy of the manual online. It's missing a few
schematics, but is otherwise complete.
http://sundry.i2phd.com/ServiceManual_304b.pdf
Ed
On 4/29/2012 5:18 PM, paul swed wrote:
Curious is the manual online?
Would be interesting to look at.
On Sun, Apr 29, 2012 at 6:33 PM, Ed Palmer<ed_pal...@sasktel.net> wrote:
Hi Don,
On 4/29/2012 2:54 PM, Donald Henderickx wrote:
On 4/29/2012 1:36 PM, Ed Palmer wrote:
Thank you Ed,Paul,and Marco for the reply's
The foam I was referring to is or was around ceramic base were the
igniter wire goes . Yes my wire also broke loose however I do not want
to
disassemble any more than I have to. I think that just inserting it
back in
to the hole and securing in some way should work. I do not know what
the
potential is but I have seen a spark jump at least an eight of an inch.
The igniter wire has to be connected to the base of the lamp. The
patent
explains it quite well. Just inserting it into the hole in the ceramic
is
unlikely to work. I don't know what the voltage is, but the capacitor
that
stores the voltage is rated for 400V.
Does the foam look original? It definitely isn't on mine so I wasn't
sure
if it was supposed to be there or not. The patent describes how the
base
is the coolest part of the bulb. I don't know if a foam covering is
appropriate.
Tell me about the lamp voltage test point. My manual has no mention of
it? Were is it located?
All the test points are described on page 5-3 of the manual. The lamp
heater test point is the sixth one from the top. Ground is the seventh
point.
In you first posting I think you mentioned some grounding problems. On
this unit there is a three pin amp connector on the rear on mine the
bottom
pin -20 must be grounded or the unit will not work. The red light will
come
on very bright but nothing else works.I believe you can also ground the
+20
this allows this to work in various ground polarity systems IE telco
systems +ground. Perhaps I am wrong.
Do you mean the 3 pin round connector on the back? That's for an
external
DC power supply. It has no other function and grounding the bottom pin
(which is ground) shouldn't make any difference.
Ed
I have Hp113,Hp115 that caution you on the ground polarity of the
systems
you are installing them in. I think all the -20 floats from chassis
ground
until they get to that rear plug.
Thanks for foam an fiberglass suggestions.
Hi Don,
You know that we're going to be swapping many emails, don't you? :-)
On 4/29/2012 11:16 AM, Donald Henderickx wrote:
After following Ed Palmer's thread on 304b restoration,I was inspired
to get my GTC (tracor) 304b ser#279 going. It seems that the failure
of
this unit was the break down of the foam that was wrapped around the
vcxo
located inside the control box. The vapors or the moisture the foam
collected corroded the steel fasteners and caused the switches to
become
intermittent.
The foam around my OCXO is still in great shape. Still spongy and
providing lots of holding force for the OCXO. My unit is serial #449.
The replacement of the foam in the control box is not that much of a
problem,what I need help with is what to use around the Rb lamp base.
The
foam has turned to powder.
Do you mean foam around the back end of the lamp where the wire lead
comes out or the foam that surrounds the reflector (#16 in the picture
in
the patent that describes the lamp (3311775))? My #16 foam is really
solid.
Should I try Home foam sealant? The cell's ,of this seem about the
same
as the old foam.Will it take the heat?Should I make a fiberglass
cocoon to
put around the lamp base.
Read the fine print on the can. It may list the maximum temperature
rating. I'd try a fiberglass cocoon first just because it's easily
reversible if it doesn't work. When your unit is running is the lamp
test
point voltage correct?
Ed
The unit now achieves lock in about an hour. The only other thing I
did
was to replace the caps in the main supply.
Any thoughts on the insulation?
Don H
------------------------------
Message: 5
Date: Sun, 29 Apr 2012 16:36:22 -0700
From: Cliff Sojourner <c...@employees.org>
To: time-nuts@febo.com
Subject: Re: [time-nuts] Antique Rb Standard - Thanks, Pictures, Parts
Request, Question
Message-ID: <4f9dd076.2070...@employees.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 2012-04-29 16:21, Magnus Danielson wrote:
Hi Ed,
On 04/29/2012 05:46 PM, Ed Palmer wrote:
Hi Magnus,
Second, pictures. If anyone is interested, check out
http://s701.photobucket.com/albums/ww18/edpalmer42/Tracor%20304-B/ .
Nice photos. Thanks. GAS building up.
What does GAS mean?
Gear Acquisition Syndrome.
GAS is a diagnose which I think no time-nut would admit to. ;-)
hey GAS happens to musicians too. the reason I have 12 guitars is
because I have really held back on buying more. anyways the wife has
three guitars and 4 keyboards, my daughter has two pianos and three
flutes and two piccolos.
let's not talk about my radios :)
------------------------------
Message: 6
Date: Sun, 29 Apr 2012 20:20:54 -0400
From: Bob Camp <li...@rtty.us>
To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Subject: Re: [time-nuts] PICDIV for 1 min pulses
Message-ID: <c59777c6-8676-4aca-93c2-ccfc372bc...@rtty.us>
Content-Type: text/plain; charset=us-ascii
Hi
The problem is a bit more complex than simply getting a pulse at the
second / minute. At least back when I last got into this - the pulses need
to be the proper width. In some cases you need pairs of pulses in the
right order.
Simple solution - feed the Rb 10 MHz into the clock input on a PIC (or
what ever) and write some simple code to generate exactly what is needed
for the specific stepper or escarpment. Since the Rb is a power hog
there's no advantage to low power in this case. For the 5680's you need
some outboard "stuff" anyway. Just drop the PIC onto the board with the +5
regulator and DB-9 connector on it.
Bob
On Apr 28, 2012, at 6:29 PM, Magnus Danielson wrote:
Fellow time-nuts (and Tom in particular),
I am now seeing the effects of the article a few days earlier. At least
two friends wants to play around. One of my friends wants to drive a
classic clock from a rubidium. I recommended him to take a look at the
PICDIV and he kind of liked it.
So, he would need a minute pulse and a second pulse. Wouldn't it be sweet
if the PICDIV was able to crank out these pulses?
As I recall from his brief discussion, there is two styles of
clock-drive.
I thought that this would be a little inspirational to others, so
therefore I toss it to the list than just Tom.
Cheers,
Magnus
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End of time-nuts Digest, Vol 93, Issue 152
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