So also, a "bad" Q story may resonate with the audience to reinforce the
concepts. There are events like buildings and bridges resonating and
collapsing.
Ed
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John, if you look back at the recent GPSDO discussion initiated by
"dandober" in hpaligent keysight group, you'll see a post by Leo Bodnar,
linking a Ublox model here
https://www.u-blox.com/sites/default/files/products/documents/LEA-M8F_DataSheet_%28UBX-14001772%29.pdf
I looked it up, and I
I just took a quick look. I have four of these ovens, definitely marked
for the HP5110A. One is partly disassembled so the crystal can be
pulled. It looks very much like the one in the picture that Jeremy put
up. There are two quite large mica caps mounted on a disc-shaped board
along with the
If you can open it up and get at and identify the crystal, you can
synthesize its ideal frequency from a GPSDO output, then run it in there
in place of the crystal.
Ed
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Haha - interesting pictures. It looks like they really do glow, but I
doubt it's from anything the crystal element is doing - it and the mount
structure may just serve as the electrodes for a gas discharge lamp. If
the envelope is filled with some relatively "inert" gas or mixture,
instead of
I have some similar, that came from some old HP OCXOs. They look like
they were built inside octal tube envelopes, without the pin bases. I'm
pretty sure they are 1 MHz, and came from some HP51110 (I think ?)
reference generators, part of one of their ancient synthesizers - it was
a two-piece
I didn't realize before that there was a picture attached in the OP.
That's a lot different from the HP ones. The crystal element looks more
like those in regular packages, but on the large side, due to the low
frequency. If it's a 1 MHz, then you should be able to find plenty of
Paul, from your description, it sounds like it's not an outer and inner
oven in the traditional sense, but that the extra heater is to improve
things at the weak spot in the Dewar system - the opening, where the
high-grade insulation is lost, and conductive things pass through. So
maybe it
Well, 40 C is fairly close to 110 F. Maybe this is a special model
intended only for indoor, controlled room conditions - or outdoor, cold
climate only. Why? I dunno, but I can guess. Having both heaters set to
the same temperature makes sense, so the open end being the same as
inside would
Hi Hal,
I have one of these big (maybe 14" dia) old office clocks, still
working, hanging on the garage wall at the farm, next to a modern WWVB
clock. I don't worry about what time it says, but I sometimes look to
estimate total power outage time (can be quite a lot up there) since the
last
Walter, for you Rb box, look for info on the common Efratom standards of
that vintage, and see if any look like what you have inside the plug-in.
I remember the FRK and M-100 (a variation of which I have). These are
the ones in about a 4 inch cube format. They may not exactly match
yours, but
Did you say there's a 1 mH choke at the LDO input? I gather that
overall, you're regulating 5 V in to 3.3 V out, running the IC that
takes a few mA DC, and loading the CMOS output with 50 ohms scope input
(or a 50 ohm terminator on a scope or probe setup). I'd recommend the
following changes.
to the address that shows in the email digests, not the one at
the archive site, so this is kind of an experiment. Hope it works. Ed
Forwarded Message
Subject:Re: [time-nuts] in-ground clock room
Date: Fri, 10 Sep 2021 12:48:41 -0700
From: ed breya
To: time
I have the 1 PPS circuit working just fine. The pulse width is around 27
uSec, nice and flat and strong regardless of the termination. I can't
discern the rise time or prop delay yet.
I discovered an interesting thing about the 1 PPS signals from the DB-25
connector. They are (or rather, one
The CR13 can be almost any small SCR, like in a TO-92 size. I happen to
know of one offhand, because I just yesterday used it in the Z3801A
project, for the same type of function - latching the state of the
indicator. I have a bunch of these in the thyristor department, and
looked up various
There should a number of types. I looked in the manual for my
Gigatronics 7200, which has VFDs and is probably from the same era, and
found they used NE594s.
Ed
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I assume you're talking about the RTC chip that runs off the CMOS BIOS
memory settings battery, to keep time whether the computer is on or off.
These are as you suspect, typically cheap items that get the basic job
done. You may be able to find better grade ones. It also depends on
whether the
Thank you Francis, for the info on the 1PPS interface. I like that TI
65ELT23 pECL to TTL converter - it looks ideal for the situation. For
now though, I'll be going with the LM311, then upgrade to the better
solution next time I do another round of wrapping things up.
I studied the Z3801A
If you look at the schematics of the C-field adjustment circuits, you'll
find where the tweaking is available for fine tuning the Rb system. I
think that's the only "frequency adjustment" spot to worry about. The
other is the tweak for the crystal oscillator to accommodate long term
drift
I was just looking at a HP8566, and found that it can reach the right
range, right on the hairy edge of its capability. It's specified range
is to 22 GHz, but you can tell it to go up to 24 GHz stop frequency -
beyond that it will ignore numeric entries, or adjust the other
parameters to limit it
Oops - in previous post I meant to say isolators, not directional
couplers, in describing the microwave plumbing. Isolators are
directional too, but different purpose.
Ed
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That's a fascinating article.
Regarding ammonia
Anhydrous liquid ammonia is a common commodity material, but probably
comes in many grades, depending on use. I'd break it into three basic
ranges. For something like this, you would want to look at reagent/lab
grade, to get it as clean and dry
I've been doing a bit more work on the far from finished Z3801A project,
trying to button things up. It has been sitting for years all opened up
(but running), with temporary pieces and cables and wiring hanging out
every which way. The next piece I want to get going is the 1 PPS
interface, to
My plan has been to go with it being a 50 ohm source. My go to driver
setup for these sorts of things is a 74HC/AC 500 series octal bus
device, so you get all the ins and outs across each row of pins - easy
to parallel.
For now, it's looking like a 74HCT541, with the outputs ballasted with
Andy wrote:
"... I too was surprised to see nothing more than a Zener being used in
one case, but bearing in mind this was in a temperature controlled
environment is not as bad as a Zener in open air."
In the OCXOs I've had opened up, they used a temperature compensated
Zener, typically in
I forgot to mention that the TCZD regulators are affected by the power
supply too, depending on the rest of the circuit. I think they typically
had a two-stage deal, with a regular Zener to make a higher voltage, and
provide a fairly stable supply to operate the reference regulator, but
of
Many of the older VTOCXOs have the internal reference voltage accessible
simply to use them stand-alone. A remote adjustment pot could be fed
from the reference, and set the fine tuning voltage, without needing any
other support from the system. Nowadays we typically tune from PLLs, and
such,
Yes, that non-hermetic C3 is a wet-slug Ta cap. These are quite special
(and expensive), and can be amazingly good, or cause lots of grief if
they leak. The key is in the seal around the Ta positive lead, and how
well it holds up over time. Ultimately, the cap either loses its
necessary
As Corby said, check for the 137 Hz signal first. If that's OK, I think
the simplest thing you can do before taking things apart, is to look at
the adjustment pot for the 274 Hz amplitude. Mark its position, then
tweak it end to end a number (like tens) of times, then back to its
original
BTW please don't toss any junker Oncore GPS RX units. I'm interested in
collecting any that I can find for parts - in particular, the 19.096 MHz
TCXO. I'd like to find some for experiments with my Z3801A system, and
would rather use junker Oncore units than risk damaging the two good
ones I
You say there's continuity from each VFD pin to the driver IC, but what
about to everything else? Check the problem line resistance to ground to
see if something's shorted or overloaded. As I recall, the VFD segment
(plate) lines want to go up to some positive voltage like 20-30 V, while
the
I actually have this kind of setup, with two "identical" GPSDO boards I
salvaged from some telecom gear long ago. I've yet to be able to
identify them by make or model. All I know is they use Oncore UT or GT
RX units, and seem to work, according to the LED indicators and the 10
MHz outputs.
Just an interesting observation. Last night, shortly after I wrote about
my dual GPSDO system, I decided to take a look at it, with the usual
scope setup looking at both 10 MHz outputs. It looked like one of those
reasonably good times, where the phase between them seemed very stable
during
I found a spare Oncore VP GPS RX unit in the parts department last week,
and tried it out in the Z3801A. It would not track, even after quite
some time in use. The original would pop right up almost immediately,
after warm up.This one had some slight differences from the original,
around the
Paul and Hal, I think there may be some confusion here. I modified the
Z3801A to RS-232 way back when I first got it. My recent post was just
discussing some of what's in this demo/testing unit thing. It's just a
translator for TTL/RS-232 for when the GPS RX board (TTL serial) is used
by
Aha, thanks John. I just saw your message after sending my previous reply.
That would explain a couple of things - first, that the TCXO needs a
workout, and may have been the entire cause all along, and second, that
those Flash parts (or is it something else?) are used for storing data
during
Paul,I'm using the old HP SatStat program. It's plenty good enough for
my simple needs. I also found I have a bunch of old stuff from over ten
years ago, while organizing the older PCs and consolidating backup
files. The original Motorola WinOncore program is included. This can
talk to the RXs
Last night I told it to do a survey, and let it slog through it
overnight. This morning it seemed to be working fine, and apparently in
position hold mode.
Then I shut it down for about 45 min to let things cool down to nearly a
fresh cold-start condition. On power up, it went through the
I think I finally fixed the date issue on the Z3801A, by some fooling
around with settings using SatStat, combined with experiments and lots
of power ups and downs.
The GPS RX unit now thinks it was installed 1 Jan 2006, and everything
starts tracking, and reports the right date within about
Gerhard, your info is a little confusing. I see several PLL parts
mentioned - 4046, 4096, 9046, and 8046. Only the 74LV4046 seems to have
a datasheet, according to my quick look on line. I can't tell yet if
these others exist, but if they do, and are supposed to be roughly
equivalent to the
That's quite a bit different from the PS in the Z3801A.
From the pictures, I'd guess that the "A" and "B" markings on the DIP
switch are for 24 or 48 V AC or DC Battery operation. I did a little
looking around, and found this:
http://www.realhamradio.com/GPS_Z3816A_Receiver.htm
It says that
Sam, I noticed in your last post that you're planning to use a printer
type PS. It may work if you luck out, but I suspect that it won't have
enough juice to get things up and running.
If it's anything like the typical ones I've seen, it's a small SMPS
brick, built for running ink-jet
I was curious and looked up the Datum unit. In the datasheet, there's
this option:
26B55144 HIGH GAIN GPS ANTENNA
This antenna supports an antenna cable loss of up to
35dB. It is required for Option 20D (400'/120 m) or
20E (500'/150 m) antenna cables.
So, 200' should be no sweat, if you
I suppose you could do a split type distribution of the conversion
functions, but it may be simpler to just add some more gain at L1 with
an in-line amplifier - preferably close to the far (antenna) end. You'd
have to work out how to provide the DC power for it, like taking some 5V
supply
I did a few more experiments on changing the initial date, hoping to get
it to accept more recent values, and still give correct date reports. It
seems like there's an absolute limit somewhere in 2007. 01 Jan 2007
seems to work, and during startup, it momentarily forces 28 Dec 2006,
but still
I just did another experiment with the new deal. I shut it down for
about an hour, to get fairly close to a fully cold start. Here's
approximately the sequence of events and timing:
T=0, power on
SatStat establishes com
GPS time 04:00:00 and counting
Date 01 Jan 2006
"OCXO warmup"
T+2 min
Just thought I'd report a little on my portable Rb reference source.
This has been shut down for a few years, due to a failure during some
experiments. I couldn't recall what the problem was, and now I remember
after running it recently. A little over a week ago, while doing some
other
I was curious and looked up this Red Pitaya SDR thing (which I had never
heard of - I would have guessed a poisonous snake, without the
internet), and the Abracom TCXO. It's getting a little confusing to keep
up with what's going on.
First, does the installed TCXO have EFC capability, or not?
Tom Holmes wrote:
"I am curious about one part of the warmup process. At around 7 minutes,
the power jumps up radically, which you attribute to
the outer oven kicking in. It has often been stated on this list that
the outer oven was intended for use during really cold
starts, which I would
I've been wrapping up the last major sheet metal parts, and found I had
no ground tie in for the box that holds the Z3801A's power supply. This
is the part that holds the PS board cantilevered up over the main board,
in its proper position that's necessarily different from original. The
whole
Sorry I haven't been proactive on this. My main PC crapped out last week
in a big way. I've been doing almost a total rebuild on it. Just got
internet and email working this morning, followed by printer problems.
Regarding the Z3801A date/rollover issue, it looks like there's no easy
fix, so
I've been doing some more cold start testing, and thought I'd share this
info, for any Z3801A owners who may be curious about the behavior. Some
aspects are probably well known since long ago. I've seen it all since
first starting work on this some 10-12 years ago, so I know
approximately what
The battery control system uses relays to ultimately control the
connect/disconnect operations. The front panel battery control switch
selects the external, off, or internal battery mode, mutually exclusive
(although they don't necessarily have to be).
The internal battery operation will be
Since back in October, I've been working on getting the Z3801A in a
5065A carcass project closer to completion. I mostly finished the clock
control board and other details, and moved on to the power system. I
decided to completely redo a lot of the mechanical arrangement, wiring,
and the line
I'd vote for going with a transformer too, but not just any old
transformer - I'll explain later.
You can indeed connect directly to line with an AC divider, and measure
the signal. In fact, you can even build a very broad band probing system
that can go all the way down to DC, and up to RF,
The new boost converter is working great for external DC power input.
Yesterday I put the Z3801A guts back into the carcass, after being out
of commission since October when I started the latest round of additions
and changes. The bench supply I've been using doesn't have enough oomph
to do
All this 1/f noise talk got me to thinking about some of my noise
measurement and generation projects over the years. One project that I
want to revisit is one for making "nearly-true" random white noise all
the way down to DC, for comparing and testing things in the very low
frequency 1/f
On 4/7/22 3:09 PM, Joseph Gwinn wrote:
>
> This BTULN OCXO looks very good. While they do mention that it
> contains its own regulator, no numbers are given, so it's hard to
> know what to make of that claim.
>
As far as I know, every OCXO and most everything else has its own
internal supply
It depends on context and your definition of low noise. I was picturing
ones commensurate with the 1/f discussion, trying to get down toward DC.
Many are spec'd for so many nV or uV p-p over 0.1 to 10 Hz. The OP-07 is
a good example of this class.
A lot of opamps are spec'd ok for their
Oops - pardon my part referencing error. I meant to say OP-27, not
OP-07, in the first paragraph.
It depends on context and your definition of low noise. I was picturing
ones commensurate with the 1/f discussion, trying to get down toward DC.
Many are spec'd for so many nV or uV p-p over 0.1
The low noise opamps are indeed designed for the feature, and they tell
you about it, and how and why. The trade-offs are usually input bias
current being quite high (due to bigger or paralleled transistors
running at fairly high currents), and only good for a low resistance
environment.
Ed
That's an interesting old machine - very cool.
One thing though, is that unless I'm missing something, I believe the
two available loop time constants are in minutes, not seconds, or that
it should be in many more (maybe 100X) seconds, if stated that way.
Since the unit can synchronize to a 1
Continuing on, the mixer's output looks amazingly good. The filter's,
not so much. I have the IF now going directly to the SA input - no pads,
no filters, no nothing, except some SMB cable/adapter stuff, and about
20 feet of BNC cable. It looks great, letting the SA do the filtering.
The low
Continuing on, the 70 MHz for the LO is tapped off at a leveled low
impedance point, that feeds the normal 70 MHz 0 dBm output on the front
panel. The tap off point is probably around +3 dBm, and I added a higher
R attenuator to get about -10 dBm for the power amp. This CATV amp is
made for
I'm a little confused now about what power supply is at issue. The
normal PS board in the Z3801A mounts on top of the main board, and
provides +/- 15V and +5V to it, to run everything. The PS board also
includes the outer oven control, run from a separate 5V DC-DC converter.
The two DC-DC
I'm wondering if anyone has dissected enough common canned RF mixers, to
know how symmetric they are, internal construction-wise, or knows of
available info, especially on specific models.
I have taken some apart over the years, and I believe they generally are
made highly symmetric wrt the
The noise converter project based on the Scientific Atlanta 4647 is
moving along nicely. Still no luck in finding any more info about this
unit, but I did quite a bit of digging in the guts, and figured out
enough to make progress.
The noise generator, to my surprise, is not a typical
Do you happen to know what's wrong with the PS? If you can figure this
out, you can probably fix it. AFAIK the DC-DC converters are still
commodity parts, under a number of brands, so the easiest is if one of
those crapped out. If the problem is in the "other" stuff, you'd need
some reverse
Thanks all, for filter info. For reasons that will become evident when I
describe the LF/DC situation, I plan to use an all-passive LC LPF. I
assume I'll be needing a fairly high-order (like 9 or so) Butterworth
type response for good flatness, and enough stop-band rejection for the
higher
Thanks Mike, for info on LCR alternatives. It's good to know of others
out there, if needed. I have an HP4276A and HP4271A. The 4276A is the
main workhorse for all part checking, since it has a wide range of LCZ,
although limited frequency coverage (100 Hz - 20 kHz). The 4271A is 1
MHz only,
I managed to build a filter, using the values for a 9th order
Butterworth, 50 ohms, 25 MHz fc. The caps were fairly straightforward to
get nearly right on in values, with one or two (paralleled) selected
micas for each spot. The chokes were tricky. I decided to use IF-can
style adjustable
Now that I have the "official" filter in place, I can wrap up the LF/DC
issues. This is the other extreme, so no SA here, just time domain view
with a Tek 7A22 vertical, which gets down to 10 uV/div, and has settable
BW steps from 100 Hz to 1 MHz. For very low f and DC, I use a HP3456A.
There
This may give some idea of how fast things can happen when the OCXO is
subject to drafts. I have this dual GPSDO box that usually is open for
experimenting, and have a setup comparing one of the 10 MHz outs to my
portable Rb reference. The 10 GHz multiplied output from the Rb is
indicated on a
All good comments about the isolation issues, but remember we're talking
about a desired 200 MHz amplifier system here, not a 10 MHz one, so RF
transistors are appropriate. This is a little different from the
original DIY PN test discussion, which is why I replied in a different
thread title.
Thanks Gerhard, for putting up the schematic. After a quick look, I'd
recommend trying the following changes. Of course, I don't know the fine
details, so this is just from a general circuit perspective - could be
all wrong versus the actual situation.
1. Delete the Q7 circuitry including R10
I've been following the thread about Erik's DIY PN analyzer, and
wondering if it might be easy enough to use a frequency discrimination
method. I'm opening this in a different thread to avoid muddying the
water on the original (and long) one.
What I'm picturing is putting the DUT's output
Hi Magnus,
I know what you mean about not needing a quadrature splitter - if you
have a very wide phase or delay tuning range - but I'm picturing getting
most of the way to quadrature with a fixed structure for a given
frequency, and only fine-tuning the phase over a narrow range, in order
Gerhard wrote:
"I have made a new isolation amplifier but I'm absolutely not happy with
the available transistors. Anything in sot-89 is either to slow (
Zetex/Diodes Inc, the 2N3904-alikes)
or is much too hot.
I want at least 200 MHz to have no phase shift at 100. BFQ19s gave me 1
GHz of BW.
Yes, that transformer sure looks burned out. It's hard to tell how big
it is from the pictures, but my impression is that it looks kind of
skimpy to run a FRK Rb plus whatever else is going on like a GPS RX and
uP system, and maybe battery charging too. You can easily estimate the
VA rating by
After more experimenting and measuring, I think the RF is done enough. I
found that the main 20 MHz and the 300 MHz LPFs were letting a lot of HF
above 1200 MHz straight through. I believe the choke I used in the 300
MHz LPF has a self-resonance in that range - it's a wire coil molded in
Continuing with experiments and spur measurements, I found that closing
the lid on the little filter box does seem to reduce the LPF's
effectiveness at the higher frequencies, but leaving it open reduces
effectiveness at the lower. I can sculpt it to a taller structure if
necessary, which
I've been working on final design cleanup, mainly in the RF. I found
quite a bit of spurious LO harmonic content up to almost 2 GHz, with
some quite strong (-75 dBm). It was time to clean up the experimental
wiring layout, so I simplified the cabling and consolidated the RF stuff
onto the LPF
I forgot to mention that you should also consider possible effects from
the RF present, on the LNA. This can be more significant than SMPS
frequencies getting where they don't belong, especially since the RF is
intentionally right at the opamp's input. Your LPF only reduces, and
does not
Erik, I'd really recommend that you use a real, "solid" ground reference
on the instrumentation side, with +/- large (12-20 V) supplies, as
others have suggested.
Your most recent setup diagram indicates that you're relying on the
"differential" input of the audio PC card etc analyzer to
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