I don't know what sort of scientific level this contest is geared for,
but would guess that for middle-school level, extreme numbers-oriented
analysis of esoteric, time-nutty things may not dazzle, but bore the
participants, judges, and audience.
It may be best to relate to more hands-on,
If it's just to set for the initial setup or aging, just do it the
old-fashioned way, with a trimmer pot to run the Vt - simple, easy to
program, and it remembers the setting.
Ed
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Before adding complexity of parallel devices or external passing, why
not just try the old parallel-resistor trick? If the load takes a
certain minimum current under all conditions, provide less than that via
a resistor from the raw source to the regulated output, likewise under
all
One thing I forgot to add - if you must use the 4-40 screw size for some
reason, you can save a lot of grief by using a slightly larger bit than
the standard tap drill. You're not really too concerned with optimal fit
and strength here - it's more about being able to make a whole lot of
usable
This is the first time I've looked at time-nuts in about a month, and I
noticed the run about this project. I'm very late to the party, but have
a few suggestions that may help - if it's not too late. I quickly
scanned many of the posts, and agree with many of the ideas. Please
forgive if my
If you make a variable delay by adding external RC (varicap) circuits,
the edges will be slower, and the amplitudes will be affected. This will
tend to complicate the detection and reshaping of the clock by the
LTC6957. Pay particular attention to page 24 and Fig 8 in the datasheet,
regarding
Even presuming this system is for clocking within a single-board
environment, that seems like a fairly tall order for setting resolution
and long-term stability. It could be tough to keep these numbers with
temperature and supply variations in all the circuitry involved,
including the parts
I had a reference problem on my Z3801A years ago, and ultimately found
that the opamp that controls the 10811 oven temperature was bad. I think
it turned out there was a bad batch of certain date codes. Replacing the
IC with an equivalent type fixed it right up, with no other changes or
It would be helpful to give some specific info about the circuit and
regulators used for these experiments, such as operating voltage, load
current, and regulator type. I may have missed some points in the
discussion on this, but I think the following things are the case:
1. The circuit
Wow. Nice job of dissection, and good pictures - very informative. No
wonder those things are so expensive.
It's a shame that they're not built in such a way that just the wear-out
parts could be replaced, and not wasting all the rest of the design and
craftsmanship that's probably just fine.
I should mention that the input supply filtering to the DC-DC converter
should have good attenuation at the switching frequency, but not at low
frequencies, so there's no need to get carried away with the size of the
filtering at the converter input. Too much filtering, especially
inductance,
Yes, for best quietness, you definitely should "can it up" in a metal
box, and use feed-through caps for all the I/O, including the commons or
grounds. You have to figure out also where all the currents flow, and
contain the loops. With sufficient L-C filtering on the input and output
(all
I'm kind of late to the party on this one, but I think the simplest
approach with the least disturbance to the operation of the original
system would be to form a VCXO and PLL.
Good old 4000 series CMOS stuff should be plenty fast enough. Two pieces
should be sufficient. For example, a CMOS
For high-drive outputs, my favorite is the 74AC541 octal bus driver,
which is very nice for paralleling outputs through small series Rs. If
you look at the pinout, you'll see why.
BTW with any of these high-drive circuits, it is essential to provide
good bypassing of the supplies, and be sure
You may have seen this before, but there is a nice writeup on how to
disassemble the whole thing, with pictures and all.
http://www.realhamradio.com/GPS-oven-journey.htm
I had to take mine apart quite a few years ago to replace the opamp in
the inner oven temperature regulator circuit. If
This may be totally ridiculous, but maybe there's another way to get a
balance wheel signal. The X-band Doppler type microwave motion detectors
can pick up various object signals in free air from quite a distance, so
maybe up close there would be enough resolution and penetration of the
metal
I don't want to muddy the water too much, but I'd second going
all-digital, along the lines of what Bob L. recommended earlier. It
seems like you just need to make some specific delay times, so various
logic counting or shifting circuits should be just fine - and
well-defined and understood.
Problem solved - one missing connection was fixed, and it now runs just
fine. Symmetry looks good on a scope, and the toggle rate is plenty
enough. It runs OK to beyond 120 MHz input.
Ed
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After studying the various divide by 3 circuits, I decided to try
designing one that would be simpler in terms of package count, using
available ECL DIPs on-hand. Instead of the JK-FF version followed by
duty cycle-fixing circuitry, I opted for two 10131 dual D-FFs to provide
the state
I found I have some 10135 dual JK FFs on hand, so will try a version
based on JK, that needs no extra gates, with a 10116 triple line
receiver for I/O. If it turns out that symmetry is needed, I'll add a
10131 D FF, and the 10116 already provides both clock edges. Either way,
it should be
Thanks guys - good info. Some of these circuits must be the ones I've
seen before, and some are new to me, so I'll keep them too (until I lose
them again).
I'm not sure if I will need symmetry in the output, but it seems better
to have it for cleaning up if necessary. The resulting signal
I need to build an ECL divide by 3 circuit to run at about 50 MHz input.
I know there are lots of examples out there, but I vaguely recall years
ago I stumbled upon one or more that also provided more of a symmetrical
output nearly 50 percent duty factor, by using both input edges, or
I have rediscovered what I need, so no problem anymore. Ed
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It could be that the inner oven temperature regulation is off a bit, or
even failed. There was a report at one of the popular time-nuts oriented
websites (I forget which one, but it's the one that had extensive
coverage of the Z3801A) about inner oven problems a few years ago. I
took mine
Yes, I think those were from the era when service info became sparse -
treated as modules or black boxes - unlike the products from the good
old days, which had much more info available. I believe the SD26 is to
fit in the Tek 11801B or other 11000 series sampling scope setups. A
quick look
One thing I want to clarify - it is not a Jupiter GPS module - it
just uses the chipset, presumably hooked up as in the application
info. The board is proprietary, and there seems to be no standard
electrical or operational interface as would be expected in an OEM
GPS module. So, the only way
Actually, the core saturation depends on how much voltage is applied
at a given frequency. Most power transformers are run partly into
saturation at rated line, to get the most from the copper and iron
available, in exchange for heat and less efficiency. The magnetizing
current and losses will
I opened it up and found a 4 by AA cell battery holder for power, and
a single module that looks pretty proprietary. One side of the module
has a patch antenna, and the other has the brain. I assume there's an
RF board in between, but cannot open it further without possible
damage - the
It seems to me that a low voltage secondary should be OK by using a
fast comparator IC rather than a transistor to decide - the gain of
the IC allows for much smaller detection levels, so the equivalent
zero-crossing velocity could be the same. An IC tripping in a 10 mV
band should provide the
I peeled open the shield can without too much deformation, so it can
be restored. I found that it's a single board, with the DSP on one
side, and the RF section on the other. It is a Rockwell chipset, with
11577-11 DSP, and 6732-13 RF. On searching I found that this seems to
be called their
I just picked up an old DeLorme Tripmate GPS receiver for cheap, and
am wondering if it can be used for getting a 1 PPS signal. I looked
online a little and found it's pretty common, but didn't see anything
about getting deep into the guts. Most hacks seemed to be about
getting it powered up,
I investigated those 10b-t isolation modules a while back, and have
saved every module from every network card and router/hub/switch that
I have junked out. The very old 10b-t stuff is the best for getting
LPFs and individual per-channel (port) type parts. When they started
making 10/100
If the plan is to use a three-terminal regulator after all, I'd
suggest not using a low-dropout (LDO) type if the raw input supply is
noisy - the LDOs usually have PNP output transistors (for positive
regulators), so may tend to have poorer HF input ripple rejection
than equivalent ones with
I was just looking at various modern LDOs, and I see that they are
greatly improved wrt PSRR - I think the older style PNP passers have
been supplanted by new topologies that also even include MOSFETs, so
there should be plenty of choices out there.
So, I'm changing my recommendation - to
There are a number of ways to multiply-up the 10 MHz, but what about
just changing things around to make the 20 MHz VCTXO phase-locked to
the 10 MHz OCXO, and then discipline the 10 MHz. There will be phase
noise issues, whether doubling one thing, or dividing the other by
two, but overall, I
I'd recommend going with what Bob Stewart mentioned, using separate
gates as buffers, operated from a better-grade reference, to shift
from the noisier and driftier logic supplies, into the more critical
circuits. It's simple, and can be powered from a modest reference circuit.
If the logic
A signal like that coming from a dish makes some sense to me. I
vaguely recall from about ten years ago investigating how the
satellite receivers work, that a fairly strong control signal of
around 20 kHz was used in some to select the various LNBs and their
polarizations in more complicated
Maybe it's leakage from another time-nut's experiment in the
neighborhood, or some commercial equipment. There's probably lots of
stuff going on in that area. It's not necessarily a broadcast
carrier, but just a frequency that happens to be generated somewhere
and getting out big enough -
The Ta caps in old HP gear should last virtually forever, especially
if they have already lasted for decades. What you are referring to as
wet slug Ta caps are mostly dry solid ones in hermetically sealed
cans. There can be some actual wet slug types, but only in certain
spots where their
Of all device types, I think gas tubes are the best for this sort of
application - very low C, and high surge current rating. I'm
picturing the kind that are used in power supplies and such for
limiting line transients - about 1 cm dia and length with axial
leads. I don't know what kind are
I have this nice little thermoelectric 12-bottle wine cooler (about
one cubic foot inside) that I've fixed twice already, and it just
crapped out again. It's always the same thing - bad caps in the
switching power supply - they're just too small to take the necessary
ripple current. So, I
It could be a combined time display with a channel number and
measured value, from some kind of data logging instrument. LN was
big in thermocouple measurements and the like. With those digits you
could show temperature at three digits resolution, selected channel
00-99, and hours and minutes,
The best solution depends on the situation. Is this to build into the
unit? Is it to be permanently applied? Is a DIY solution acceptable,
and if so, at what level of complexity?
If you happen to have a synthesized VHF generator, just run it from
the same reference and set for 200 MHz -
I agree with Tim - a common 10.7 MHz IF can is close enough, and will
provide a nice tuned circuit that you can rough-in with an extra cap,
and also fine-tune with the coil slug. If you want a fairly wide BW,
then an IF can may be too narrow as-is - but it can be broadened with
a little extra
I agree with Tim - a common 10.7 MHz IF can is close enough, and will
provide a nice tuned circuit that you can rough-in with an extra cap,
and also fine-tune with the coil slug. If you want a fairly wide BW,
then an IF can may be too narrow as-is - but it can be broadened with
a little extra
I have three of these units, and have been looking for the right
manual for years. Thanks for this part, but I believe the SPTB is
different from the FRK in the schematics and some of the construction
detail - for example, since it's 5 MHz vs 10, that circuit is
different, not just the crystal
I recently acquired a Fluke 6071A, and have found some pieces of the
service and operating manuals, but not the schematics. Does anyone
know where the schematics can be found? This unit looks pretty good
except the FREQ and UNCAL indicators are flashing. I managed to
decipher enough of the
Paul,
If the 10811 is that far off, are you sure the oven is working? A
few years ago mine had a failure of a particular date code range of
the opamp that controls the oven, that were prone to failure.at high
temperature. The symptom in the Z3801A was that the outer oven seemed
bad - it did
NiCd batteries should have the lowest noise for their size due to low
resistance, but if you look at ever-lower frequency, the Hg should be
superior since it has the most stable voltage with time and
temperature. Drift (including self-discharge) and temperature
variation response can appear as
Second attempt at emailing again:
NiCd batteries should have the lowest noise for their size due to low
resistance, but if you look at ever-lower frequency, the Hg should be
superior since it has the most stable voltage with time and
temperature. Drift (including self-discharge) and
Third attempt at emailing again:
NiCd batteries should have the lowest noise for their size due to low
resistance, but if you look at ever-lower frequency, the Hg should be
superior since it has the most stable voltage with time and
temperature. Drift (including self-discharge) and
I have been experimenting with three mixing devices: an RF
double-balanced mixer (MCL SRA-1B), a DFF (74AHCT74), and an EXOR
(74ACT86). The mixer and EXOR give similar results - the sum and
difference frequencies, and a slew of various other products that
need to be filtered out. What was
Here we go again - the first send didn't seem to get through. This is
the second attempt.
This talk of Costas loops reminded me of something I wanted to
investigate some day. I read somewhere a while back about
carrier-phase measurements, and various methods for recovering the
GPS carrier
This talk of Costas loops reminded me of something I wanted to
investigate some day. I read somewhere a while back about
carrier-phase measurements, and various methods for recovering the
GPS carrier frequencies, including the Costas loop, and something
with carrier-squaring. Nothing I found
Hal Murray said:
They make 74xU04 for many values of x. The U is for Unbuffered. They have
lower gain in the linear region.
I thought they were intended to be used for things like this, but I don't
understand that area. Can anybody give me a quick lesson or point me at a
good URL?
I always
I am revisiting that tracking generator reference I brought up here a
while back, and trying to get my head around how a DFF can take the
difference between two frequencies. I have studied and thought about
the various topologies and conditions, and searched online for good
explanations, but
I presume you used the regular 74HC04 or 74HCU04 inverter, not the
74HC14 Schmitt trigger input type?? If the '14 is actually used, that
may explain the problems around setting the feedback biasing resistor
value - you may be overriding the built-in hysteresis to get it in
the linear region.
I believe the original problem was that the raw unregulated voltage
may be marginally too high for a conventional three-terminal to take
safely. I have often encountered this problem, which is due to the
wide input range possible considering the worst-case line voltage
tolerance, transformer
topic. I'm using an old version of Eudora (7.1.0.9), if that matters.
Ed
Ed strange no body and you sent it 3 days ago.
On Thu, Jun 27, 2013 at 12:13 AM, ed breya
https://www.febo.com/cgi-bin/mailman/listinfo/time-nutseb at
telight.com wrote:
I presume you used the regular 74HC04
Still having email problems - here we go again. This is second try,
please excuse if both show up.
Hal Murray said:
They make 74xU04 for many values of x. The U is for Unbuffered. They have
lower gain in the linear region.
I thought they were intended to be used for things like this, but I
Email still seems to not be getting through - it seems like sending
twice works sometimes. Here this one goes again - sorry if it shows up twice:
I presume you used the regular 74HC04 or 74HCU04 inverter, not the
74HC14 Schmitt trigger input type?? If the '14 is actually used, that
may
I still can't tell if my email is messed up. Last time the second
attempt went right through. I'm trying again now. Please excuse if
the redundant original shows up too.
Original message:
I am revisiting that tracking generator reference I brought up here a
while back, and trying to get my
I sent this on the 18th, but it didn't show up, so here goes another
try. I don't know if something's wrong with my email. Please excuse
if the redundant original shows up too.
Original message:
At low frequency, the HC parts should take very little dynamic
current - the big current draw is
Since the actual crystal frequency appears to be 19.2 MHz rather than
19.5, my original suggestion of injection locking it would have to be
modified. For example, you could divide the 10 MHz by 25 ( a single
74HC390 could do it) to make 400 kHz, so 19.2 MHz could sync to the
48th harmonic.
Since short-term stability is no problem, and you already have the
right frequency in the 19.5 MHz oscillator, you can try
injection-locking it to the 10 MHz. Just divide the 10 MHz by 20, and
feed the 500 kHz edges into the original oscillator section, and lock
to its 39 th harmonic.
Ed
Before you tear into the OCXO, have you checked to be sure it is
properly connected and set up, and its working conditions are right?
There must be a BNC jumper on the back to connect the 10 MHz, and the
reference selector switch set to internal.
Furthermore, the power to the XO section is
When the unit is up and running, you won't be able to tell if the
oven is working from touch - the fan blows right at it. If you open
it up and run in standby for a while (an hour or so), it should feel
a little warm. Also, of course, check the oven power supply, which
should always be on
Does anyone know what 50.791095 MHz was used for? I assume it was
some sort of telecom clocking rate - perhaps obsolete. I
serendipitously discovered that I have some VCXO modules of this
frequency, that will likely solve a problem on one of my projects.
I'm now curious about what they may
You don't save these kinds of synthesizers for high frequency
coverage, but for their 10 to 11 digit frequency resolution. If you
anticipate needing that, then of course they should be kept and
fixed. The long-obsolete telecom standard connectors and ranges are
pretty much useless - sacrifice
If there are plenty of them, I'd recommend dissecting one to see how
well they're made, and what sort of components are inside. If the
crystal is hermetically sealed, it's probably OK. If there are any
aluminum electrolytic caps in there, they may be no good. Most other
parts from that era
I assume the question is about going from 10 Mhz to 500 MHz. The
possible solutions depend on how clean the result has to be. For
counting grade use, this has been done in a number of test
instruments like the HP5345A and HP5370A that I'm familiar with, and
certainly others. If you look at the
I'm interested in these improvements too, and hope some can be
applied to other models. I don't have a 5065A, nor do I expect to
ever get one, but I do have three identical old Efratom units.
Whether it's worthwhile to modify any Rb units also depends on
whether it's possible to rejuvenate
I don't think that you can effectively directly mix two laser
wavelengths in a semiconductor light detector and get a useable IF -
it's hard enough just to get the tens of GHz modulation signals out
above the noise floor, let alone a tiny difference signal between
hundreds of THz. You need an
sizes to baseband. The
size of the scattering particles can be inferred from the shape of the
resultant frequency spectrum.
An interferometer of itself (without a detector) is a linear device that
merely superimposes optical fields and will of itself produce no
difference frequency output.
Bruce
ed
I recently acquired a junker Trimble 4000S GPS surveying unit. It's
mid-1980s technology, so very big, but nice to salvage various RF and
signal processing goodies from. I have no plan to get it working, and no
need for the function - it's just for parts/subsection use. I found that
this unit
If you only need cardiac pulse rate, an optical pulse-oximeter type
interface - but without the oximetry part - would be much simpler than
an ECG system, and it doesn't need galvanic connection. If you need more
than that, then ECG methods should suffice.
Back in the 1970s, there was a lot of
How do you know that the frequency range is incorrect for the function?
Assuming this is for calibration of wristwatches, maybe the idea is to
set them to some nominal value at room temperature, then expect them to
drift to the right frequency at skin temperature or so. There would
have to
If you meant to say the frequency starts out too high when the oven is
cold, then I think it's AT cut.
Ed
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I tried to send this message on Sunday, but for some reason it didn't go
through, so here it is again. Please excuse any redundancy if the
original shows up. I will have an update of the project soon.
Hi Bob L.,
Your suggestion of the 300/953 scheme was inspiration for what hopefully
will be
Yes Robert, the 59. kHz is effectively added to the 10. MHz, but
not by direct mixing. The 1 or 10 MHz reference drives a D-flop flop,
which samples the 10.059444 MHz, leaving the difference frequency
59. kHz, the feedback signal in the second PLL. The direct way to do
it would be
Bob, please tell me more about cascading the DFFs. I was only using one
half of the '74, with the other inactive, so both are available for the
task. From your description it sounds like I just run the Q from the
first DFF to the D of the second, clock them together from the 1 or 10
MHz, and
I've got to make a very clean 10.0594... MHz VCXO for a redo of one
of my old circuits. I previously used a 10 MHz ceramic resonator, which
was easy enough to push around in frequency. Of course, I have a couple
dozen of those somewhere, but can't find them now that I need them
again. I
Bob, are you saying they have 10.059 MHz crystals? I've never seen
one anywhere, or anything even close.
Ed
Hi Mouser shows 16 items tighter than +/- 20 ppm accuracy. Six of them
are in stock and less than $1 in single piece quantities. The cheapest
is 39 cents. Bob
Maybe I should clarify what I meant by pushing the crystal frequency. I
meant only using various topologies and electronic components in the
associated circuitry, that would detune it from its natural resonance
far enough to reach the new frequency, and still have it be sort of a
Thanks all, for the feedback on this issue. In summary, I got these
points out of the discussion on crystals:
1. The correct terminology is pulling the frequency.
2. Getting beyond about a few hundred ppm from the nominal frequency
ranges from very difficult to pointless.
3. It's easier to
Since you measured the same R on opposite ends, it appears to be a
center-tapped inductor. Since there's no input signal other than power
in the schematic, it must be a low frequency oscillator. If you draw in
the inductor on the schematic, it should make more sense. It could be
that they used
I just noticed one more thing - if the NTC thermistor in the schematic
is the actual one that senses the oven temperature, then the oscillator
and bridge are one in the same. If this is the case, then the oscillator
amplitude could be proportional to bridge imbalance - if the NTC is
being
Is it manually adjusted right at the oscillator? If so, just opening it
up and sticking a screwdriver in there gives it a thermal shock, and the
adjusted element will have mechanical stress that has to settle out too
- the value can change for a while.
Ed
I want to modify an old HP XTL oven for remote voltage tuning. The HP
part number is 0960-0079-1, made by Ovenaire (model OSC 49-14). These
were used in HP8443A tracking generators and probably other models too.
It puts out 1 MHz, and is powered from +24VDC wrt the case ground. On
opening it
Sure enough, the XO runs at 3 MHz. The fine tuning pot runs from ground
to about +6.8 V, which appears to be the main regulated supply. I just
have to add some feedthroughs to connect up the new stuff.
Ed
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Thanks Nigel,
The output comes right from the '140, via a small Ta cap and series R,
so it makes sense that they used a line driver - they got the drive
capability and the gate decoding for divide by 3 in one package.
Ed
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Can you completely swap the Vectron crystal oscillator modules between
the Datum units? Maybe the fault lies in the other part. If they are
GPSDOs, each must have a DAC somewhere driving the tuning control line
to the VCXO, The 10 kHz may be the DAC serial data rate, or a PWM rate
for fine
Oops - regarding that capacitance test on the tuning line, I meant to
say up to several uF or more. You can start small to see if there's
any effect. It all depends on the impedance of the tuning line
circuitry, and the existing amount of filtering - you may need quite a
bit of C to swamp it
It should have virtually no effect.
Ed
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Yes, that's true, Simon, but remember the initial goals of simplicity
and long term phase coherence, while jitter doesn't matter so much. The
longer term average frequency ratio should be right on, while comparing
at any particular cycles it would be awful.
Ed
I'm kind of late to the party on this one, and don't want to reopen and
send it off on a tangent. I agree with the injection-lock method, but
just want to suggest that since most uPs and uCs have their own CMOS
oscillator built in, the simplest solution would be to just use that as
intended,
Actually, I was referring to an RC and Diode network in anticipation of
the possible need for more signal shaping flexibility, depending on the
signals and circuitry. The built-in oscillators are usually self-biased
CMOS inverters intended to go with crystals, and usually a couple of
small
Yes, something must supply the minimum magnetic field to activate the
oscillator - but the current determines the field, so it's
necessarily part of the drift characteristic. It also depends on
whether the YIG sphere is heated - usually to 80 deg C or so, to help
stabilize it.
Without any
That would certainly provide good distance capability and isolation,
but there may be a severe penalty in signal to noise ratio (and some
non-linearity) due to converting to optical and back. It may be
worthwhile considering the specs of the overall E-O link versus the
extra gain and SNR or NF
I recently picked up an interesting early 1970s vintage WWVB
receiver, Model 630, made by Specific Products of Monrovia, CA -
that's what the adhesive sticker on the front says, and the name 1
MHz Time Base Calibrator (Utilizes WWVB accuracy of 2 parts in
10^11). There's also a pair of banana
1 - 100 of 165 matches
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