[time-nuts] Dual GPSDO - any advantage?

[John Green]

With regard to two GPSDOs, it is an interesting experiment. I have two
Tbolts, both 2.2 firmware, both fed from the same antenna, both with
factory default settings, and I see differences. They are about 2 feet
apart on my bench and everything is pretty stable, +/- 20 nS or so until
the heat kicks on. Then, the time difference between the two 10 MHz outputs
goes wild. Go figure.
Regarding eBay and deadbeat sellers, they are much better than in the past.
I got ripped off by an unscrupulous seller some years ago and eBay just
told me they had closed their eBay account. Today, If I don't get my item
fairly fast, I file a complaint right away. An unscrupulous seller will try
a delaying tactic to get you to wait until the time for eBay to do anything
has run out.  I had an issue with a Chinese seller once and PayPal told me
they couldn't issue a refund because they didn't have access to the
seller's bank account.
Yeah, sure. The worst abuse I have heard of by eBay/PayPal was a case where
a local guitar store owner sold a rather expensive, $4,000 + guitar to
someone in England. He got paid, then a few days later, he got an email
from eBay saying that the buyer had reported the item as fake and destroyed
it. They took the money back out of his bank account and wouldn't listen to
anything he had to say. Yes, there are unscrupulous buyers too.
Oh, I ordered one of those $9.50 GPSDOs too. I doubt I will ever see it. I
am not too optimistic about getting my money back either. We'll see.
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[time-nuts] Tbolt temperature sensitivity.

[John Green]

I don't use what LH says about temperature. I compare the 10 MHz output to
something else. With two Tbolts sitting about 2 feet apart on my bench,
both fed from the same antenna, both with factory settings, when the heat
kicks on, I see a change in the difference between the two. Comparing a
Tbolt to another, different GPSDO, the effect is even greater. Next step is
to compare the Tbolt to a rubidium source that has been adjusted to match
the Tbolt as closely as possible at a stable temperature. I suppose you
could say the the Tbolt stays *locked* to GPS since the difference never
gets to 100 nS, meaning they are always within 1 Hz. What I usually see
when comparing the Tbolt to another, different model GPSDO is that the time
difference between the two 10 MHz signals slips at a fairly constant rate,
going from zero past 100 nS, and then through zero, over and over. I also
tried comparing the 1 PPS and the time jumped around quite a bit. Since I
plan to actually use 10 MHz instead of 1 PPS, I decided to quit looking at
1 PPS.
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Re: [time-nuts] QRZed.... OT: 16 Khz VLF, Rugby, England

[John Green]

Fascinating! Thanks for posting.

On Fri, Apr 6, 2018 at 7:19 AM, D. Resor  wrote:

> I am sure some have seen this, however.
>
> 16 Khz VLF, Rugby, England
>
> https://www.youtube.com/watch?v=Unlg2gY2Zrs
>
>
>
>
>
>
>
> Donald R. Resor Jr. T. W. & T. C. Svc. Co.
>
> http://hammondorganservice.com
> Hammond USA warranty service
> "Most people don't have a sense of humor. They think they do, but they
> don't." --Jonathan Winters
>
>
>
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Re: [time-nuts] Environmental sensor recommendations.

[John Green]

Why has no one mentioned thermocouples?
I had some experience with thermistors a few years back designing thermal
attenuators and equalizers for CATV. NTC thermistors can have a large
change of resistance for a unit change in temperature. They aren't linear,
but there are formulas for computing resistance vs temp. PTC thermistors
have a much smaller change per unit change in temp., but are much more
linear. And, they are susceptible to self heating, which makes things
interesting. If I remember correctly, in my research something called an
RTD was supposed to be the king when it came to accuracy and repeatability.
As someone else has stated, the IC devices are supposed to be quite good,
but you have to interface with them.
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Re: [time-nuts] Looking for information on True Position GPSDO.

[John Green]

Mark,
Yes, I saw that. My main interest at the moment is just getting the thing
working properly. It isn't.

On Tue, Mar 20, 2018 at 11:39 AM, Mark Sims  wrote:

> When I dumped the flash rom from one of the TruePosition units, we found a
> couple of commands that seem related to OCXO learning.   They are discussed
> a little in the thread on EEVBLOG.
>
> 
>
> > If you *do* go swapping around OCXO’s (or whatever) on a GPSDO board,
> it’s very nice to be able to change the internal “magic numbers” to get the
> control loop running properly again.
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[time-nuts] RE; True Position GPSDO.

[John Green]

Thanks to all who replied. You pointed me to a wealth of good information.
Seems lately that I have been getting let down in my Google searches. I
didn't find any of the stuff you led me to, but I should have. Hmmm. it may
be because I have been using Ecosia for searches instead of actually using
Google. Whatever, I should have found that information without needing
help. But, I am glad I did have help. Thanks much.


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[time-nuts] Looking for information on True Position GPSDO.

[John Green]

There is a small, about 3.5" by 4.5", GPSDO board being offered by several
sellers on eBay. I bought one from what looks to be the only US based
source. It is identified as True Position, Inc., and had a small CTS OCXO
and Furuno GT8031 on board. I found hook up information in one of the Asian
vendor's ads. When it arrived, I hooked it up and waited for it to achieve
GPS lock. I left it over night, but it never locked. This morning, I sent a
message to the seller requesting to return it. I looked around on eBay to
see what the going price was and discovered that the US source was about
1/3rd the price of the Asian vendors. I also noticed in one listing where
the seller mentioned that it will not discipline the 10 MHz unless you
entered a command by RS232. If you buy one, he will tell you what the
secret command is. Does anyone, perchance happen to know the secret
command? And, would you be willing to share? This isn't a bad looking
little board. I was thinking of pulling the little CTS oscillator and
replacing it with something better. The fact that you have to tell it to do
its thing is something of a bummer, but I think I can live with it.


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Re: [time-nuts] While we are talking about Z3801's

[John Green]

When I removed it from storage, communication was gone. It took a very long
while to lock, but did so and maintained lock for a couple of weeks before
going into holdover. It then locked back for a while.
I definitely need to do more trouble shooting on it before I give up
completely. It was the best unit I have. I also have a couple of
Thunderbolts, but I don't consider them in the same class as the Z3801.
I see Z3801s for sale on eBay, but I am reluctant to buy one. They are at
an age where things are going to fail. Also, for my needs, a Thunderbolt
would suffice. I just like the Z3801 better and would really like to get it
going again.

On Sun, Mar 4, 2018 at 9:27 PM, Hal Murray  wrote:

>
> kb...@n1k.org said:
> > If still nothing, put a scope on the RX output of the serial chip in the
> > 3801. Do the same  for the TX input of the same chip.
>
> I think the Z3801A prints out a version string at power up.  Sometimes that
> helps debug the transmit path.
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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Re: [time-nuts] While we are talking about Z3801's

[John Green]

Hal, I can't communicate with it. That has been gone for a while now.

On Sat, Mar 3, 2018 at 9:05 PM, Hal Murray  wrote:

> > Mine has quit achieving lock.
> ...
> > After reading about someone else's trouble, i wonder if my OCXO has aged
> > out.
>
> Have you checked the status page?  Is the GPS unit seeing satellites?
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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[time-nuts] While we are talking about Z3801's

[John Green]

Mine has quit achieving lock. It goes back a ways. I had it in storage for
a while. When I got it out of storage, It took about 2 weeks to lock. It
would go into holdover sometimes for no reason I could ever discover. I
lost the ability to communicate with it. Then, one of the Lucent DC/DC
converters blew. After replacing that, it locked for a few days then
refused to lock again. In desperation, I changed out all the tantalum
capacitors with no effect. Next, I purchased a replacement Motorola GPS
receiver off eBay and tried that. Nothing. It has been back in storage
since. I plan on checking the 10 MHz output to see if it still has one and
to see just how far off it is. After reading about someone else's trouble,
i wonder if my OCXO has aged out.
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[time-nuts] Need Oncore connector info.

[John Green]

I need the part number of the connector that the Motorola Oncore series GPS
receiver plugs into.  Does anyone have that info at hand?
Thanks in advance.
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[time-nuts] Chinese made eBay antenna breakdown.

[John Green]

I didn't mean to imply that all Chinese made products are garbage. But,
some of them are. And, has been said, that is because people want to pay
the absolute lowest prices for stuff. The company I recently retired from
has a long history with Chinese competition. We had a product that had but
one American competitor. We thought, foolishly, that being a low cost item
with a modest annual sales volume, he wouldn't have to worry about foreign
competition. We didn't take into account our main customer who would slit
your throat over a tenth of a cent. It wasn't long before we began seeing
competing products from China. At first, they either did what was cheapest
without regard for RF concerns, or they copied us exactly. However, in
recent years, I have seen Chinese products that show the result of some
real engineering talent. In some cases, they are better than ours. These
are parts that are molded in plastic, and the foreign competition certainly
knows a lot more about molding than we do. Their parts are cosmetically
superior to ours in almost every instance. Lately, I have suggested that we
obtain some of these products and copy them. That is what it has come to.
I noticed that the enable input is tied to the voltage input. I thought
that it may have seen too high a voltage, but the specs say it should be
able to take 20 volts. So, I don't really see any reason it should have
failed. I will put a new 3.3 volt regulator in and see if I can get it to
work. I want to do comparisons to other antennas. The rest of the circuitry
looks OK to me.
There is one SAW bandpass filter per band. Not like the Trimble, but should
work fine for my purposes.
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[time-nuts] Teardown of Chinese made eBay GPS antenna.

[John Green]

For those who have been following the saga of the Chinese made, eBay
purchased antenna that failed, I may have an answer as to why it failed.
I had to destructively disassemble it. I just could not get it apart any
other way. I used a Chinese version of a Dremel tool with a metal saw
blade. After making a huge mess with plastic particles everywhere, it
revealed a circular FR4 board with two patch antennas mounted, one atop the
other. I assume the smaller one to be the L1, and the larger to be L2. This
part looks almost identical to the Trimble Microcentered antenna I worked
on recently. On the back side of this is a metal shield  about 3 by 3
inches soldered to the circular FR4 board. I switched to a abrasive wheel
and took off some of the solder holding the shield to the board. Then,
using a small screw driver, I went around the shield breaking the solder
loose. The shield off revealed that the coax goes to some capacitors that
couple RF out and through an inductor with some capacitors to ground and
finally to a SOT23-5 package labelled LK33. This appears to be a Micrel
MIC5203 3.3 volt regulator. It is shorted on the input side. I believe that
putting anything over 7.5 volts on the input exceeded the power dissipation
rating and caused it to fail. I plan on wiring up a more robust 3.3 volt
regulator in its place and trying again. It looks like I will be able to re
solder the shield back. The watertight integrity is gone for good. I think
I can find a plastic box I can mount it in so I can at least experiment
with it. I have sent a message to the seller detailing my findings. The
Micrel part lists a 20 volt maximum input voltage, so in theory at least,
this might have worked, and there might be some of these out there that
don't fail.
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Re: [time-nuts] Furuno GT-8031 breakout board

[John Green]

Maek Sims wrote:  I have several Motorola compatible GPS receivers... and
not one of them does a perfect emulation of the Motorola devices.  Some are
quite close and not likely to cause problems... others are superiorly
craptastic.

Are there any readily available boards that will substitute for the
Motorola board in a Z3801?
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Re: [time-nuts] eBay GPS antenna test.

[John Green]

Bob wrote:  Hi

Just so people don’t get to down on eBay antennas:

I have gotten some deals on eBay I just couldn't have gotten elsewhere.
That is a nice looking antenna. A bit pricey for my budget. I thought just
north of $100 for a used Leica choke ring job was about it. The Trimble
antenna I got recently had issues, so I got it cheap and fixed the
mechanical problems. I think I have one of those HP timing antennas I have
heard mentioned here. I need to dig it up. I think I also have a PC Tel
model around somewhere. I still haven't gotten the top off that Chinese
made one that bit the dust at 12 volts. I need to get it apart somehow. I
think it can probably be repaired. I can at least let the seller know what
went bad.


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[time-nuts] eBay GPS antenna test.

[John Green]

Bob wrote:  Sitting here casually reading the data sheets for some of the
modern Trimble
survey receivers - they have gone to 7.2V (just below your 7.5V trigger
point)
as an antenna supply voltage.

Who knows what that might imply relative to this antenna.

After getting my refund, I sent the seller a message saying that I would
buy another if he could assure me it would work at 12 volts. He replied
that he needed to get his hands on a couple and do some testing first. The
antenna that I received seems to be different to the one pictured in the
eBay listing. At least the labels are different. I get the feeling he is
kind of a third party dealing with someone in China who is wholesaling
antennas made by someone else. Who really knows what spec. these are made
to, or by who. In my former place of employment, we made an SMB terminator.
Basically, a 75 ohm resistor soldered across the pins of an SMB connector,
then molded in black plastic. We bought the connectors from a Chinese
supplier who supplied them in individual plastic bags. We had to cut the
parts out of the bags before processing, which added a labor step. We tried
to get the supplier to sell them to us packaged in bulk, but they refused.
We decided that they were actually buying them from someone else and just
doing a passthru. The connectors themselves would change from time to time,
which caused problems in molding, and sometimes caused the electrical
performance to degrade. Getting parts to reliably meet a specification from
China can be a problem. I can't even imagine the issues that could arise
when you try to source an assembly, or completed product.


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[time-nuts] eBay GPS antenna test results.

[John Green]

They have issued a refund. The seller said that my antenna was defective.
This is kind of a strange outfit. They are in Russia selling Chinese goods,
shipped from China.  Since I don't have to return it, I will disassemble it
to see what went bad. I replied that if he could assure me that it would
work on 12 volts, I might order another.
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[time-nuts] eBay GPS antenna test results.

[John Green]

I opened a "Not as listed" case and heard back from the seller. They said
that the antenna is definitely 3.3 to 18 volts and have sold several that
are in operation. They wanted to know specifically how I tested the
antenna, why I thought it shorted, and if I actually ever hooked it to a
GPS receiver. I answered as best I could but haven't heard anything
further. eBay seems to like pictures or videos. Though problematic, I
suppose I could take some pictures. I offered to do so in my response to
the seller. They do seem a bit more responsive to buyer complaints than in
previous years. I recently ordered a 64 Gb micro SD card from a US based
seller. I got a message from eBay stating that they had removed the listing
but that everything should be OK. I never received the SD card, and after a
month, checked PayPal and saw that I had been charged for it. I contacted
eBay and they refunded my money the next day.
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[time-nuts] eBay GPS antenna test results.

[John Green]

Bob wrote:
Is it labeled 3.3 to 18V on the antenna?

No, the writing on the antenna is all Chinese. The specs published on eBay
state that it is.
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Re: [time-nuts] eBay GPS antenna test results.

[John Green]

To those who doubted that the antenna was actually a 3.3 to 18 volt design,
it seems you were correct. Today, I hooked it up to a variable power supply
and slowly raised the DC voltage fed to the antenna. It began to pull
current at about 2.9 volts and at 3.3 volts, took about 40 mA. I continued
to slowly raise the voltage. At about 7.5 volts, the current suddenly
dropped to 10 mA. At just below 12 volts, it suddenly increased to 80 mA
and the supply went into current limit. I increased the current limit to
130 mA and repeated the exercise. Everything went as above until I reached
12 volts and the current went to 130 mA and the supply went into current
limit. Lowering the voltage didn't lower the current. I disconnected it,
waited a minute, and tried again. Yep, shorted. It would have worked well
with the T bolt, but would have blown anyway if I tried to use it with my
12 volt supply and bias T. I guess I will get inside it somehow to see if
it can be repaired. My first attempt ended in failure. I guess I need a
bigger screwdriver with which to pry the top off. I am going to contact the
seller and tell them it was not as advertised. I kind of doubt that will
get me anything, but it won't hurt to try. There is a saying about
experience being a cruel teacher. You get the results first, and the lesson
after. Oh well.
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Re: [time-nuts] eBay GPS antenna discussion.

[John Green]

Dr. David Kirkby wrote:
Another RF engineer, who I don't know from working with antennas, said to
me that antennas are a still a charlatan's paradise.

Those words rang true to me. I have yet to see a yagi type antenna that, in
practice actually produced the gain it was specified to produce. True, I
don't have a proper chamber in which to test antennas. I can only do real
world comparisons. I have a pretty large collection of various 900 mHz
antennas and on occasion, I set up my home made antenna test range and do
measurements. This consists of a 900 MHz handie talkie with power turned
down as low as it will go and PTT fastened down with a rubber band. Several
hundred feet away, on a deck attached to my house at a height of about 10
feet, I have an HP 8924C to measure levels. First, I measure a home made
groundplane for reference. Then the antennas to be tested are attached and
measured. I realize that there are multiple places where error can and does
creep in. But, I have found that when I actually try to use the antennas
tested, the results are pretty accurate for real world conditions. I
haven't found a good way just yet to test GPS antennas. There are just too
many things besides gain to be considered. Many of which are beyond my
capabilities.
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Re: [time-nuts] eBay GPS antenna.

[John Green]

I kind of have to believe the specs. The two survey grade antennas I
already have, a Leica and a Trimble, both have regulators in the preamp
sections. The Leica has an 8 volt one and the Trimble has a 5 volt one. I
intend to hook it up to a variable supply and watch the current as I
increase voltage. If it has a regulator, the current should stabilize at an
input voltage just above what the internal preamp operates at. If not, it
should continue to rise. I am tempted to pry it apart, even if it risks
damage just so I can see for myself what they are using for the preamp
stages.
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Re: [time-nuts] eBay GPS antenna.

[John Green]

It should work with a T bolt since its range is 3.3 to 18 volts. I also
have a good bias T and GPS type splitter that only passes power to one port
that I can also use. I hope the gain isn't a problem. I live in the
country, so local RF shouldn't be an issue. I can scrounge up some pads if
need be. I plan on starting out with the Leica if I can retrieve it from
its present location. Then, I will probably compare that to the Trimble and
later the Chinese made one. I also have a couple of the type they use at
cellsites, one of which is a Motorola. Something tells me that the Leica
will be the eventual winner. It is the only one that is a choke ring type.
I keep looking on eBay for a reasonably priced unit that will work with the
new L5 civilian band birds. Nothing so far.
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Re: [time-nuts] eBay GPS antenna.

[John Green]

Thanks for the responses. It looks similar to but not exactly like the two
antennas referenced. They say the preamp is 3 to 5.5 volts, whereas the
eBay antenna says its preamp is good from 3.3 to 18 volts, indicating I can
run it off 12 volts. Regarding the internals, I must have somehow missed
the photo which clearly shows it to be a patch antenna. It looks pretty
similar to the Trimble I asked about recently, inside, that is. That
Trimble had been dropped from a great height. The nylon screws that hold
the actual antenna assembly had all been broken. I ordered new ones and
replaced them. Disassembly was easy, reassembly not so much. Mine was made
to have the groundplane, but doesn't have it. I suspect that since I am not
doing surveying, it won't matter all that much. I bought an adapter for the
5/8 by 11 thread it uses and have a pvc pipe mount ready to go up. My
location is not ideal. It will be atop a 40 foot Rohn 25 tower, but there
are tall trees nearby. Since my Z3801 died, I don't have much of a GPSDO to
use the antenna with. Just a couple of T bolts and some kind of postcard
sized unit I need to build a housing and power supply for. Still, enough to
experiment with.
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[time-nuts] Anyone have experience with this antenna?

[John Green]

https://www.ebay.com/itm/High-Precision-L1-L2-GNSS-GPS-GLONASS-BeiDou-RTK-CORS-survey-antenna/162718512935?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

Listed on eBay as a L1/L2 antenna with decent specs. They seem to indicate
it is as good as a choke ring antenna. I suspect it is just a patch in a
fancy package. That is what the Leica and Trimble survey grade antennas I
have contain anyway. I bought one but haven't had the chance to do any
testing. I couldn't figure out how to get to the insides to take a peek
without damaging it. My antenna testing abilities are pretty feeble.
Mostly, I will just compare it to the Leica and Trimble to see how many
satellites it sees and look at position wander of the uBlox. Is there any
simple way to judge the quality of a GPS antenna?
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[time-nuts] Looking for information regarding Trimble 33429-00 microcentered GPS antenna.

[John Green]

I have been gone for a good while, but now that I am officially retired, I
thought I would get back into the time/frequency hobby. I recently bought a
Trimble 33429-00 antenna off eBay. I can't seem to find much on the
internet about it. Google has not been my friend. First, I assume the
"micro centered" refers to the phase center being located with precision.
Mine was meant to be used with the ground plane, which did not come with
it, so the marks indication the part to be pointed north are missing. It
doesn't matter in my use since I won't be surveying anyway. Can someone
tell me what voltage it takes? I decided that the Leica choke ring antenna
I got a while back took 12 volts because the power input went to an 8 volt
regulator, and I figured 12 volts should work ok. On this one, the power
goes to a 2951 adjustable regulator, leaving me a bit in the dark. I will
probably try hooking an adjustable power supply to it and slowly raising
the voltage until the output of the regulator stabilizes. They seem to have
made two versions of this antenna. One with groundplane, and one without.
Since I will be feeding a GPSDO, would a groundplane be of benefit? In
looking through the archives, it seems I have missed a lot of good
discussions. Good to be back.
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Re: [time-nuts] Meaning of MTBF (was: Reliability of atomic clocks)

[John Green]

We make some thick film, plastic molded , plug in attenuators for the cable
TV industry. We have been asked on several occasions to provide MTBF data.
Being a small company with limited resources, we have never been able to
provide that data. The parts we make will easily outlast the equipment they
are used in, because such equipment is frequently upgraded. We tell our
customers that very few, if any, parts have ever been returned for being
defective. While true, it is somewhat misleading. The plug in attenuator is
an inexpensive part that is carried in a tech's belt bag by the handful. If
he encounters a bad one, he simply removes it, tosses it on the ground, and
installs a new one. In recent years the Chinese have taken most of the
market away from us with lower cost products. A lot of them use FR4 and
chip resistors. I have heard that some OEMs are going away from those
because of reduced reliability. I have been seeing some Chinese products
that are actually thick film. Most are either copies of ours, or they
didn't spend any time to optimize the RF performance. Sometimes, I do see
parts that out perform our own. The Chinese also make plug in, molded
equalizers, but I have yet to see one that works well. I must say to their
credit though, that they have gone from cheap imitations to parts that are
actually well designed and built. AT least some of them are.

On Mon, Mar 28, 2016 at 6:04 AM, Florian Teply  wrote:

> Am Mon, 28 Mar 2016 01:32:03 +0200
> schrieb Attila Kinali :
>
> > Yes, the MTBF is a very simplicistic measure and there are a couple
> > of assumptions in its calculation which do not hold generally (or
> > rather, it's rather seldom that they hold). Yet it gives a number to
> > something that is otherwise relatively hard to measure and the number,
> > even though flawed, makes it possible to compare different devices
> > on their reliability. As this is more a rule of thumb comparison,
> > you shouldn't read too much into a 10% difference. Yet a 100%
> > difference is significant, no matter which of the assumptions do not
> > hold.
> >
> Umm, well, even a 100% difference still might mean nothing if the
> derivation of MTBF between different devices is based on different
> assumptions. That both these derivations might be seriously flawed does
> not help at all.
> Yet, even MIL-Spec parts documentation does rarely contain sufficient
> detail to assess the validity of the numbers in a certain application.
>
> At the very least, one would need to know acceleration factors for the
> different failure mechanisms, and shape parameters of the
> failure-vs-time plot. This kind of data I wouldn't expect to find
> outside the manufacturers premises, and even there it's not likely to
> be accessible if it exists at all.
>
> Best regards,
> Florian
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Re: [time-nuts] Z3801A recovering

[John Green]

Joe, I'd be interested in knowing what you find out. My Z3801 is acting a
lot like yours. It is currently locked, but.

On Thu, Mar 17, 2016 at 8:15 AM, Joseph Gray  wrote:

> Dave,
>
> I power cycled it about 20 days ago, which did no good. That is the
> 496 hours holdover time. This time, I did just the survey once
> command. I'll try your suggestion before attacking the hardware. I'm
> currently using Z38xx.exe.
>
> Joe Gray
> W5JG
>
>
> On Thu, Mar 17, 2016 at 4:30 AM, Artek Manuals 
> wrote:
> > Joe
> >
> > I am confused by the fact that it shows the unit has been in HOLDOVER for
> > 496 hours if you did a fresh survey
> >
> > Did you do a SYSTEM:PRESET: and GPS:POS:SURVEY:ONCE commands to initiate
> the
> > new survey or just the survey command or  What software are you
> running?
> >
> > I would power the unit down and let it sit for 24 hours and then do the
> two
> > commands above.
> >
> > What software are you running?
> >
> > Dave
> > NR1DX
> >
> >
> >
> >
> >
> > On 3/16/2016 7:38 PM, Joseph Gray wrote:
> >>
> >> As I mentioned a while back, my trusty Z3801A, which has worked well
> >> for several years, went into holdover some time ago and stayed there.
> >> Until recently, I haven't had time to look into this. About 20 days
> >> ago, I did power cycle it to see if that made a difference. It did
> >> not.
> >>
> >> In the middle of the night, last night (couldn't sleep), I decided to
> >> see what initiating a new survey would do. Since the unit doesn't lock
> >> to as many satellites as my Lucent with the newer Oncore, it took
> >> quite a while for the survey to finish.
> >>
> >> I just got home from work and this is what I am seeing:
> >>
> >> https://dl.dropboxusercontent.com/u/19599147/Z3801A.png
> >>
> >> The good news is that the unit no longer telling me the PPS is
> >> invalid. It looks like it will be another long while before it comes
> >> out of Recovery (assuming the PPS stays locked).
> >>
> >> I'm not the best at interpreting these graphs. At this point, should I
> >> be concerned abouth the spikey nature of the EFC graph, or will things
> >> calm down eventually? I assume that the PPS graph won't show until
> >> Recovery is done?
> >>
> >> If this unit loses PPS lock again, or otherwise acts up, then I would
> >> assume it is a hardware problem, and I'll have to put it on the bench.
> >>
> >> Joe Gray
> >> W5JG
> >> ___
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> >> and follow the instructions there.
> >>
> >
> >
> > --
> > Dave
> > manu...@artekmanuals.com
> > www.ArtekManuals.com
> >
> > ---
> > This email has been checked for viruses by Avast antivirus software.
> > https://www.avast.com/antivirus
> >
> >
> > ___
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Re: [time-nuts] Instrument BASIC

[John Green]

The one we have was part of a big DOCSIS rack that came from Scientific
Atlanta.

On Wed, Mar 2, 2016 at 11:57 PM, Gerhard Hoffmann  wrote:

> Am 02.03.2016 um 19:04 schrieb John C. Westmoreland, P.E.:
>
>> Magnus,
>>
>> This was the best answer I got so far - I am sure this isn't what you're
>> looking for:
>>
>>
>> http://www.ebay.com/itm/HP-89441A-Vector-Signal-Analyzer-Opt-1C2-AY9-UFG-AY7-AYA-/252278222960?hash=item3abcf43070:g:uRMAAOxyNo9SojsE
>>
>> I have one more person that I am waiting for an answer/suggestion from - I
>> am not sure if there are any 3rd parties out there supporting this other
>> than what you might find on eBay.
>>
>> Interesting aside is some of these are selling for more than they were
>> being let go for after the first dot-com-bomb.
>>
>> The market for these was quite small, mostly cell phone developpers,
> and they have made the jump to LTE already a long time ago. The 89441A is
> not
> good enough for LTE, so they probably have discarded their surplus stuff
> long ago. Mine was pre-owned by Motorola I was told.
>
> Dynamic range  < 10Hz is severely degraded by 1/f noise. It took me
> 60 to 80 dB preamp gain for my noise measurements to hide that.
> Then there is not much dynamic range left over.
>
> It was easy to put on the network with a €25 BNC to Western plug
> adapter from Amazon. But you still need both BNC terminations even
> if there is no real Ethernet coax cable. Works much better.
>
> Controlling is as easy as opening port 5000-something on 192.168.1.123
> and and dumping GPIB commands. I have done a program to do FFT
> analysis over 7 decades (Linux, gcc, gnuplot...). Source is available.
> Ooohps, I'm not supposed to think about that ;-)
>
> regards, Gerhard
>
>
> I really like that 89441A!
>
>
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Re: [time-nuts] SoftMark USB to GPIB converter

[John Green]

I noticed some US made ones on the auction site for cheap. They say they
offer a 30 day money back guarantee. Hmmm

On Thu, Mar 3, 2016 at 12:27 AM, gonzo .  wrote:

> No - Please don't.
> No more of us need be burnt by that POS.
>
> Once you've bought it, you discover all you can do is send one command at
> a time until you buy additional software to get the DLL needed to do
> anything even remotely interesting.
> The documentation is terrible to the point the 'free' DLL has the same
> name as the 'paid' version, so it took me several emails (if you get a
> reply, you're doing well) to workout why why it didn't work as described.
>
> By far the best 'affordable' GPIB to USB adapter on the market is the
> Prologix (http://prologix.biz/).
> If you are interested in building your own, have a look at  Anders take on
> an open design (http://www.dalton.ax/gpib/).
>
> Cheers,
> ian
>
> --
> I have a desire to do some data collection and storage from my Racal 1992,
> and I need a USB to GPIB converter. We have a National Instruments
> converter at work, but I want to do this at home. The SoftMark unit is
> considerably less expensive than the NI one. Does it work? Specifically,
> would it work with my 1992? I seem to remember some discussion from way
> back that they don't play well with a lot of HP/Agilent/Keysight stuff. Has
> anyone with a 1992 used it with a SoftMark converter?
>
>
> --
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[time-nuts] SoftMark USB to GPIB converter

[John Green]

I have a desire to do some data collection and storage from my Racal 1992,
and I need a USB to GPIB converter. We have a National Instruments
converter at work, but I want to do this at home. The SoftMark unit is
considerably less expensive than the NI one. Does it work? Specifically,
would it work with my 1992? I seem to remember some discussion from way
back that they don't play well with a lot of HP/Agilent/Keysight stuff. Has
anyone with a 1992 used it with a SoftMark converter?
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Re: [time-nuts] I am a nut

[John Green]

I don't think I would go messing with it just yet. If the reference is
powered as long as it is plugged in, leave it plugged in for a couple of
weeks and then check it. I adjusted the reference on an 8920 once, and best
I remember, it moves in steps. I don't think I ever got it dead on. It
might also depend on who did the cal. Back when we were still ISO9000, we
contracted with some folks who won't be named for calibration services.
After watching them work, I decided we were just paying for a cal sticker
and not for a real calibration.

On Tue, Mar 1, 2016 at 8:58 PM, Joseph Gray  wrote:

> I just got an HP 8920B service monitor to replace what I had before.
> It has the High Stability oscillator option. After running the self
> tests, I was doing a quick check of the internal reference. With my
> frequency counter locked to a GPSDO, I see that the 8920B reference is
> 0.2 Hz high. OMG! I'd adjust it, but this thing came calibrated and I
> don't want to mess with it quite yet.
>
> Just thought I'd share my obsession :-)
>
> Joe Gray
> W5JG
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[time-nuts] Small Symmetricom GPSDO

[John Green]

I have been playing with one of those small, 2.75"by 4.5" GPSDOs that are
being sold on that auction site. Most of the ones I have seen any
discussion about have been Trimble, but this Symmetricom one looks similar
but is about half price. I have hooked it up a few times to see how fast it
can find satellites and how the LEDs work. Yesterday, I hooked it up and
compared the 10 MHz output to my Z3801 which has been running for about a
month now. I am using my Racal 1992 counter in time difference mode. It has
a resolution of 1 ns. The 10 MHz isn't present until it has "locked"on
satellites. Or at least I presume that is it. I didn't get any 10 MHz for
about the first 10 minutes. At first, it looked pretty stable. Then, I
decided it wasn't.  Now, I'm not sure. It acts differently to the Tbolt I
tested in the same manner before. While the Tbolt would sit steady on some
arbitrary time difference for maybe a half hour and then move 30
nanoseconds or so in a minute only to settle down again for a while, this
thing just slowly drifts back and forth. After thinking about it, I think
that is how it was meant to operate. It seems to have been an internal
piece of some other, larger piece of equipment. In that role it was most
likely meant to provide either 1 PPS, 10 MHz, or both at pretty good
accuracy pretty quickly after getting power. It isn't as good as say a
Z3801, but then I don't think it was meant to be either. It certainly isn't
nearly as big. I may put it in a case with a power supply and a buffer amp
and use it for an everyday standard. I certainly think it is good enough
for that. It seems happy running on 6.3 volts at around 600 ma. after warm
up. Has anyone else had any experience with one of these? What did you
think of it?
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Re: [time-nuts] HP Reliability

[John Green]

We have had mixed results with HP/Agilent/Keysight over the years. Our
experience with their repair and customer service has been less favorable.
One area where my experience has been unfavorable has been with the Genesys
software. We bought it back when it was still owned by Randy Rhea, and I
thought it was well worth what it cost. Since, we have upgraded to a newer
Agilent version and it rarely gets used. Their customer support hasn't been
helpful at all. We lost the new USB dongle and they want $1500 to replace
it. I think they, like a lot of other test equipment manufacturers, have
faced pressure from other, lower cost competitors and to maintain sales and
profit margins, they have cut corners. We have several 8712 network
analyzers that are nearing end of life. Management wants to find a cheaper
alternative. We bought a Chinese network analyzer for around $13K. It was
so weird and difficult to use, it just sat on the bench. Eventually, the
owner took it home.

On Sun, Feb 14, 2016 at 7:31 AM, Adrian Godwin  wrote:

> HP built their reputation for quality and reliability with test equipment.
> Computers were always considered a bit weird (in a nice way, in the case of
> handheld calculators) but printers have followed the consumer race to the
> bottom.
>
> It's sad to hear that the instrument division are no longer focused on
> keeping that reputation - perhaps that's why the medical division moved to
> separate the names.
>
> On Sun, Feb 14, 2016 at 11:28 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <
> drkir...@kirkbymicrowave.co.uk> wrote:
>
> >On 14 Feb 2016 09:04, "Perry Sandeen via time-nuts" <
> time-nuts@febo.com
> > >
> > wrote:
> > >
> > > Hi,
> > > It is rather depressing to me to hear RK and others remark about the
> > unreliability of HP test equipment.
> > > There is one area where they had outstanding equipment.
> >
> > I have a friend with a fairly large lab. He must have 50 signal
> generators,
> > 15 spectrum analyzers, plus plenty of other stuff. Mainly RF. Most is
> > HP/Agilent, but he has Rohde & Scwarz and Anritsu too. He finds the HP
> the
> > most reliable.
> >
> > Also Anritsu seem to charge a lot for calibration.  A recent repair to a
> > modern 6 GHz Anritsu signal generator resulted in the repair bill plus
> > £1200 GBP (around $1800) for calibration. That particular sig gen, which
> > was sold for mobile phone use, has an electronic attenuator that will
> blow
> > up if a mobile phone is transmitted into it.
> >
> > He used to think he preferred R signal generators to Agilent,  but the
> > reliability of the R has been poorer so his mind has been changed on
> > that.
> >
> > I am sure every company has some products that have been very reliable
> and
> > some less so, but I would dispute that HP is in general less reliable
> than
> > other decent makes.
> >
> > Support on HP is generally good, with the forums which are answered by
> > Keysight staff. (An annoying exception seems to be LCR meters and
> Impedance
> > analyzers developed in Japan. The Japanese engineers hardly ever visit
> the
> > forums so questions on LCR meters and impedance analyzers generally get
> no
> > response.)
> >
> > There are instrument ranges where other manufacturers seem better (e.g.
> > Keithley for electrometers), but overall HP/Agilent seem the best choice
> to
> > me.
> >
> > I know someone who is looking for a 20.GHz VNA. He just lost out on a
> > Windows based R VNA that sold on eBay for a bit over $7000. There's no
> > way a 20 GHz Windows based Agilent VNA would fetch so little.  This is
> > reflected in their higher resale values.
> >
> > At least with the older stuff,, service manuals for HP are useful,
> though
> > modern service manuals are less so.
> >
> > Just my opinion.
> >
> > Dave.
> > ___
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Re: [time-nuts] Cheap GPSDO's

[John Green]

That last one sure looks interesting. I have one that is similar to the
Trimble units that have been discussed, but was made by Symmetricom. About
all I can say right now is that it *seems to work. I'll know more after I
have compared it to the Z3801.*

On Thu, Feb 11, 2016 at 1:13 AM, Joseph Gray  wrote:

> I searched the list archives and found some discussion mid-to-late
> last year about several inexpensive GPSDO's made by bg7tbl. It seems
> that all of the better models (according to discussion on the EEVBlog
> forum) are gone.
>
> I do find two similar units currently listed:
>
> http://www.ebay.com/itm/252162780444
>
> http://www.ebay.com/itm/181948031179
>
> If these have already been discussed, please point me in the right
> direction. Otherwise, does anyone know anything about these particular
> units?
>
> Then, there is this listing, which looks like factory-made and not
> homemade:
>
> http://www.ebay.com/itm/181389532308
>
> Comments on this one?
>
> Thanks,
>
> Joe Gray
> W5JG
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Re: [time-nuts] Z3801 misbehaving

[John Green]

Charles,
 The OCXO has always been pretty warm to the touch. Except now, it is
barely warm.  I tried the antenna first with a card sized Symmetricon GPSDO
and it locked up OK. I have a small uBlox GPS that gives the signal levels
of the satellites it sees. I need to hook that up and check. The Antenna is
a Leica AT503 up 40 feet on a Rohn 25G tower. It is on top and seems to
have a pretty good view of the sky. It is fed 12 volts from a wall wart
power supply through a Pasternack bias Tee. I couldn't find any info on the
AT503 but I took it apart and the preamp has a 7808 voltage regulator in
it, so I think 12 volts should work alright. The cable is LMR400 from an
actual HP cable intended to work with GPS. I have a lot of checking to do
before I can narrow things down.

On Tue, Feb 2, 2016 at 1:06 PM, Charles Steinmetz 
wrote:

> John wrote:
>
> I am now thinking it may be an OCXO outer oven failure. It normally
>> runs quite warm. But now, it seems it may be body temperature or maybe a
>> little less.  The 10811 is different to a stock one but, is the outer oven
>> voltage the same? I would think the inner oven should keep it warm enough
>> to achieve lock and hold it. The outer oven is mostly to make the inner
>> oven's job easier.
>>
>
> Typically, the outer oven of a DO 10811 is on a thermostat.  It receives
> power only when the OCXO is warming up from cold, and is switched off when
> the inner oven gets close to its operating temperature.  So, the outside of
> the OCXO package is warm during warmup from cold, then less warm during
> normal operation.  If the outer oven does not heat, for any reason, the
> inner oven will eventually (~30 min.) get the crystal to operating
> temperature and it will work normally after that.
>
> The symptoms you have described all suggest very strongly that something
> is wrong with the antenna feed to the 3801:
>
> --  bad antenna location (needs to be outdoors with a clear view of at
> least the southern half of the sky, assuming you are in the Northern
> hemisphere)
>
> --  bad antenna
>
> --  no DC power reaching antenna
>
> --  bad antenna cable
>
> --  bad antenna cable connector(s)
>
> It's possible something is wrong with the 3801, but if it worked properly
> when it was taken out of service, it is *much* more likely that the problem
> is one of the items listed above.
>
> Best regards,
>
> Charles
>
>
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Re: [time-nuts] Z3801 misbehaving

[John Green]

Pete, I am now thinking it may be an OCXO outer oven failure. It normally
runs quite warm. But now, it seems it may be body temperature or maybe a
little less.  The 10811 is different to a stock one but, is the outer oven
voltage the same? I would think the inner oven should keep it warm enough
to achieve lock and hold it. The outer oven is mostly to make the inner
oven's job easier.

On Mon, Feb 1, 2016 at 11:23 AM, Pete Lancashire <p...@petelancashire.com>
wrote:

> I have a long shot.
>
> If you really do not think it is not anything to do with not getting a
> signal into the 3801, antenna, cable, connectors etc. I may have a
> replacement GPS module but will have to be confirmed by the group.
>
> The module is a 8 Channel Motorola Oncore
>
> http://petelancashire.com/gallery/main.php?g2_itemId=5249
>
> I'll send you one if you want to try it out. Only 'cost' I ask is it work
> let me know.
>
> -pete
>
>
>
>
>
>
>
>
>
> On Mon, Feb 1, 2016 at 6:52 AM, John Green <wpxs...@gmail.com> wrote:
>
> > After a couple of days of GPS lock, it went into holdover. I briefly
> > powered it down and it attained lock again in about 15 minutes. But, a
> > while later, it was back in holdover. I finally coaxed that Sager laptop
> > into working and after connecting to it with genuine RS232, I still can't
> > communicate with it. I get zip with Satstat. And, it isn't locking again
> > either. So, while it will achieve GPS lock, it doesn't seem to want to
> stay
> > locked. And, there is that troubling lack of communication. I am
> > considering trying a different GPS receiver module. I understand that
> > probably isn't smart unless I try one similar to the one in it. I
> > understand that the internal processor talks to the GPS module and
> anything
> > with a different command set will cause it to think the GPS has gone bad.
> > At this point, it looks like my options are limited to buying a new, used
> > one off eBay for $500, or going to the Thunderbolt, which I don't trust.
> I
> > have an old desktop PC I am going to try just in case the laptop RS232
> > voltages weren't up to snuff. And, I am going to try a different cable,
> > just in case. It probably wouldn't hurt to exercise the RS232 jumpers
> > either. Anything else I should try?
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Re: [time-nuts] Z3801 misbehaving

[John Green]

After a couple of days of GPS lock, it went into holdover. I briefly
powered it down and it attained lock again in about 15 minutes. But, a
while later, it was back in holdover. I finally coaxed that Sager laptop
into working and after connecting to it with genuine RS232, I still can't
communicate with it. I get zip with Satstat. And, it isn't locking again
either. So, while it will achieve GPS lock, it doesn't seem to want to stay
locked. And, there is that troubling lack of communication. I am
considering trying a different GPS receiver module. I understand that
probably isn't smart unless I try one similar to the one in it. I
understand that the internal processor talks to the GPS module and anything
with a different command set will cause it to think the GPS has gone bad.
At this point, it looks like my options are limited to buying a new, used
one off eBay for $500, or going to the Thunderbolt, which I don't trust. I
have an old desktop PC I am going to try just in case the laptop RS232
voltages weren't up to snuff. And, I am going to try a different cable,
just in case. It probably wouldn't hurt to exercise the RS232 jumpers
either. Anything else I should try?
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Re: [time-nuts] Z3801 misbehaving

[John Green]

Charles,
The place isn't out of the way. In fact, it wouldn't surprise me if it got
a power interruption sometime.  In addition, the temperature isn't stable
either. It will be at least a couple of weeks before I am ready to attempt
to use it for anything, and then it won't matter so much about absolute
accuracy. The thing that had me going about this was that even from the
very first time I ever fired it up, it always found satellites very
quickly. Next will be to get some kind of monitoring program running. I
will have to interrupt the GPS signal soon to insert the splitter so I can
hook up another receiver at the same time.

On Thu, Jan 28, 2016 at 10:58 PM, Charles Steinmetz 
wrote:

> John wrote:
>
> Tonight I got a GPS Lock light. Bravo!
>>
>
> Patience is a virtue.   ;-)
>
> Remember this when it comes to all the other metrics -- settling to good
> stability, in particular, which may take quite a while (weeks to months)
> since the OCXO has been off for so long.  My suggestion is to put it in an
> out-of-the-way place where the temperature is stable and there is little to
> no risk of it being physically jostled, and forget about it for a month.
> Then see where you are.  (I mean, really forget it -- don't monitor it,
> don't look at the lights -- because those will tempt you to play with it,
> which will make it take even longer to settle.)
>
> Charles
>
>
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Re: [time-nuts] Z3801 misbehaving

[John Green]

Tonight I got a GPS Lock light. Bravo!
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Re: [time-nuts] Working with surface mount components

[John Green]

I have been reading the posts regarding working with surface mount
components with great interest. One thing I think I should caution against.
That is soldering capacitors with a soldering iron. Some years ago, when
the folks I work for were just changing over to surface mount from through
hole, I was making all my prototypes using a soldering iron. I used a
fairly low temperature and thought it was perfectly acceptable. That is
until one of my prototypes failed at a customer's location. They called,
returned the part, and demanded to know exactly why it failed. Plus, they
wanted a "corrective action." Those familiar with ISO 9000 will know what
that means. After a brief investigation, I found a capacitor that was
intermittent. I could flex the board and the thing would work. Let it go
and it failed. So, I un soldered the cap and called the manufacturer. I
didn't really expect them to do anything but I insisted on sending the part
back for them to look at. A week or two later, one of their engineers
called me and asked how I soldered the parts. I told him I used a soldering
iron. He said that was my problem. I was causing micro fractures by uneven
heating. He said never, ever solder a surface mount capacitor with a
soldering iron. I took his advice and we have had no more problems with bad
caps. Most of our products are injection molded and we do have a problem
with the plastic blowing inductors off the board during molding. That, and
the plastic drasticlly changes the RF characteristics of the circuit.
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Re: [time-nuts] Z3801 misbehavior

[John Green]

Thanks guys. I'll hook it up to the regular power supply and let it cook
for a while. I have a uBlox board I want to check for jitter, but I'll need
that '3801 to check it against. The fun part will just have to wait.
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[time-nuts] Z3801 misbehaving

[John Green]

After running continuously for about 3 years at work, I stored my Z3801 for
a little over a year. I recently took it out of storage and when I hooked
it up, all I get is a power on light. The front panel LEDs light in
sequence and the 6 inside blink red once and then the last one blinks
continuously as always. Thing is, it never locks on GPS. I even left it on
over night. When run on 27 volts, it starts out at about 1.1 amps, then
after about 10 minutes, goes up to 1.26 amps. Then, after about 30 more
minutes, it settles down to .88 amps and stays there. The OCXO gets warm. I
haven't checked for 10 MHz out, but I am pretty sure it is there. I hooked
it up to my netbook but I get no response from it at all. I am using one of
those USB to serial devices and it used to work. I am looking for a PC with
a real serial port to try. I know the antenna is good. It works with one of
those Symmetricom GPSDO cards.  Having heard about the evils of tantalum
capacitors for years, I replaced them all except for those on the GPS
receiver board itself. All the test points that call out a voltage read
correctly. I'm thinking of trying a new GPS board next. I have had this
thing a long time and it has always just worked. Any ideas what the problem
is?
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[time-nuts] TBolt interference

[John Green]

In reading the posts regarding a TBolt being interfered with by a close by
GPS antenna/preamp/receiver, I don't have experience with Tbolts and
interference but I do have some with the Z3801. I had my Z3801 running for
a couple of years here at work. The antenna was a marine antenna mounted
about a foot off a metal roof maybe 30 feet away and 20 feet up. Lousy
location, I know. I got interested in how most cellphones now have GPS
built in, even if they aren't user accessable. I was interested in building
a micro power GPS jammer to attach to my own phone to keep it from sending
GPS coordinates. Don't ask me why. I have no interest in interfering with
anyone else's GPS, just mine. Anyway, while looking at the complexity of
doing it, I noticed there was a GPS jammer available from a certain Chinese
based company. I ordered one. Seems like it was less than $20. When It came
in, I examined the innards. A small VCO and some form of sawtooth generator
feeding a single stage MMIC amp to a small rubber ducky antenna. I was
standing in the lab intending to look at the spectrum on a spectrum
analyzer. I pushed the on button and the Z3801 immediately went into
holdover. Wow, I thought. Doesn't take much for that. I had a Garmin GPS in
my car, so I went out, turned it on, let it find satellites, hit that on
button, and nothing. Huh? I held the rubber ducky from the jammer up
against the Garmin and it kept operating perfectly. Go figure. I tried to
see if I had any results with my cellphone, but since I had no direct
access to the GPS, I could never tell. The jammer is in a box in my storage
building and has never been turned on since. So, some GPS receivers are
very prone to interference and others, not so much. I do know the military
PLUGR is virtually immune.
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[time-nuts] Leica AT-303

[John Green]

I've been away for a long time. So, I guess that makes me the new guy, all
over again.
I have long coveted a choke ring GPS antenna. Oh, I have several so called
timing grade ones but I have always wanted a choke ring. After watching
them on eBay for a long time and seeing them in the $600 range, I recently
saw one up for bid starting at $99. I didn't get it, but did get a second
chance offer and bought it. Now, I have come to realize there isn't much
information available on them. Alas, Google is not my friend here. So, I
was wondering, do they have a built in preamp? I kind of think not since
they are supposed to be L1, L2 antennas. Besides, I wouldn't think you
would need long cables for surveying. I just want to put it on top of what
used to be my TV antenna tower and feed the Z3801 with it. Does anyone here
own one? What do you think of it? Is there some place where I can get more
information on it?
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[time-nuts] Info on Hamilton Railroad watch?

[John Green]

I know there are those who have a lot of knowledge about pocket watches and
railroad watches so, I know someone with a 992B Hamilton Railroad Special,
21 jewel, lever set, with a Montgomery dial. He seems to think this is a
special watch. Is it?
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Re: [time-nuts] 992B Hamilton

[John Green]

Thanks Chuck. That kind of information was exactly what I was looking for.
Special is in the eye of the beholder. It does sound like a watch he would
fancy because it would have probably been the kind of watch an engineer
would have carried. Plus, it is a pretty good watch. I saw it briefly.
Looked like most any old pocket watch to me. I believe it did have an
engraved, gold colored case.
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Re: [time-nuts] Am I the only Time Nut who doesn't wear a watch?

[John Green]

I haven't worn a wristwatch in maybe 30 years. I generally use my cellphone
or whatever timepiece that's handy. Or, I just guess. I don't wear my
wedding ring either. Jewelry of any kind bothers me.
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Re: [time-nuts] TV White Spaces and wasted spectrum

[John Green]

Quote:
That is the white space plan. It is still active. It is an attempt to use
wasted TV bandwidth.

TV bandwidth is a waste. It is not a growing business. However, the MS
scheme is kind of dumb. The gear would sniff the ether and automatically use
the spectrum. They should really just refarm the spectrum.

I think the broadcasters are just waiting for the right price for their
spectrum. Over the air broadcasting doesn't reach that many people any more.
When the switch to digital occurred, all the stations around here reduced
power. Most by 10 Db. Stations that used to have a good picture in analog
mode now either aren't at all or reception is spotty. I changed to
satellite. In my view, the switch to digital wasn't progress.
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[time-nuts] Light Squared, etc.

[John Green]

Yes, what about L5? I thought that was going to be the new civilian
frequency that was going to revolutionize GPS. If the FCC is hellbent on
approving Light Squared's request, L5 might be our only option. Of course
the transition would be very nasty and expensive. Regarding nuclear powered
satellites, I suspect that spy satellites are nuclear powered but since they
are classified, who knows. Perhaps future GPS satellites with higher powered
transmitters could be nuclear powered and classified. Perhaps some
surveillance equipment could ride aboard getting them under the secret
umbrella. Or, the FCC could use some common sense for a change and deny
Light Squared. If I had to choose between a functional GPS system and
wireless internet, GPS would win hands down. This kind of reminds me of the
whole IDEN fiasco where the FCC took Motorola's word that the emission mask
for IDEN would allow adjacent channel operation without interference. Nextel
ended up paying Billions to move all the other 800 MHz licensees to the
other end of the band to get rid of interference they caused. I can't see
Light Squared buying me a new, improved Z3801.
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[time-nuts] OT Interesting microwave assembly

[John Green]

Sorry for the Off Topic nature of this but things haven't been too on topic
of late. Anyway, I digress. I stumbled across an interesting microwave
assembly and I know there are some microwave nuts around here, I think some
of our European friends. It has a Delphi (I could find no trace of them)
DE127-02 Microwave source. I thought the output frequency was 12.7 GHz, but
it can't be. Perhaps the reference is 12.7 MHz. This feeds into a Milliwave
OS5PO amplifier which is labeled as 25.3 to 25.5 GHz. This feeds an assembly
I assume is a mixer. The other input to this mixer? is from another little
unlabeled block with power wires which feeds a waveguide isolator and
filter. I am assuming these last two. The output feeds a Trak 60A3001
isolator which is listed as 2 to 4 GHz. So, this would appear to be a 25 to
roughly 27 GHz downconverter. I have no way to test it, though I would love
to. If anyone is interested or has info, please contact me off list.
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[time-nuts] Another Frequency divider requirement

[John Green]

I recently bought an old EF Johnson 900 MHz repeater to try to convert to
Amateur frequencies. It uses, but did not include, a 1.25 MHz reference. I
need a divide by 8 circuit in order to use a LPRO as reference. Phase noise
isn't an issue so a regenerative divider is out. I am not sure if the old
reference was sine or square out but I do know that 0 dbM from a 50 ohm
source works. So, I guess the real questions are: Do I need to square up the
LPRO output before the divider, and DO I need a buffer or attenuator on the
output? My feeling is that I will have to build it and just see.
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Re: [time-nuts] Ovenaire OCXOs

[John Green]

Interesting. I have several Ovenaire OCXOs of differing models. I used to
think they were pretty stable until I compared them to my Z3801. Compared to
a '3801, they stink. But then, a rubidium stinks compared to a 3801. Most
have a voltage input for frequency adjustment but one has a trimmer cap for
coarse and a pot for fine. Over a period of several days, I would think it
had settled down only to come back and find it had suddenly shifted. As they
say, stable is a relative term. About all I can say after testing maybe a
half dozen from different manufacturers it that the specifications should be
taken with a liberal dose of salt. I have seen TCXOs do better than a lot of
OCXOs over the limited temperature range of my lab. I have a chamber and
keep saying I am going to do some temperature testing but work is always
getting in the way.
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Re: [time-nuts] FE-5680A

[John Green]

Interesting to read the comments of others who have these. I have one I got
years ago, gave up on. I knew it worked because I could see the 50 something
MHz inside moving around and then locking up. I finally found out how to
hook RS232 up to it and reset the frequency. It couldn't be set to exactly
10 MHz, much to my chagrin. I played with the two little buttons everyone
says not to touch and finally got it to within parts of 10 to the minus 10.
I had other things going on so I put it in a box for later. I want to set it
to 10 MHz plus maybe 100 Hz for a DMTD system at some point. Should be OK
for that. I also have a couple of LPRO 101's and it seemed about as stable
from the short amount of time I had to fool with it.
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[time-nuts] OT question Mini Circuits MAR-5?

[John Green]

Please excuse the off topic nature of this question, but I knew you guys
would know. Is there, or was there a MAR-5 mmic? I thought I had some but
when I look for specs, everything I am finding seems to skip over the MAR-5.
If not, I'll have to dig into my mmic repository to see just what I do have.
If I remember, it has pretty good S11, S22 plus a decent noise figure and a
+17 DBM 1 Db compression point. I was looking for something to drive the
L.O. port of a 17 level mixer at about a +13DBM level.
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Re: [time-nuts] MAR-5?

[John Green]

Doh! Never mind. It was the ERA-5SM I was thinking of. Boy, my age is
beginning to show. Apologies.
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Re: [time-nuts] TBOLT Power Supply

[John Green]

I use an International Power IHBCC512 which is overkill but I had it
handy. I also use a cheap switcher on another one that serves as a
reference for a ham repeater. Based on my somewhat limited experience,
they are a long way from a Z3801. They are much cheaper though.

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Re: [time-nuts] Lightsquared and the FCC

[John Green]

If the FCC weren't a government entity they would be called whores.
This reminds me of the time several years ago when it was taking a
year or more to get a grant for a 800 MHz license. The FCC granted
thousands, yes thousands of requests from the company that would
become Nextel all in one day. Quite often granting them a license for
a frequency that was already licensed at the same location by someone
else. All who objected were told to shut up and go away. Some years
later when interference to public safety systems by Nextel got bad
enough, the FCC made Nextel relocate those systems to different
frequencies less prone to interference. But, they granted them access
to the adjacent 900 MHz spectrum without having to file paperwork.
When the first plane crashes because of Lightsquared interference, I
hope the political s**t storm drowns those clowns.

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Re: [time-nuts] GPS receiver jamming

[John Green]

The timing grade receiver I have, a Z3801 absolutely lays down at the
least possible amount of on frequency signal. My automotive grade
Garmin is immune to even high levels. It may be that the slightest
degradation is unacceptable to the Z3801. More testing is needed. If
these anticipated transmitters are merely close in frequency with no
actual energy at GPS frequencies, this looks like an excellent
business opportunity for someone to make and sell GPS antennas with
aggressive filtering. If they actually emit energy at GPS frequencies,
we are pretty much done for. I have seen the Youtube video of a
military GPS resisting jamming but I seriously doubt they would become
common place.

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Re: [time-nuts] Chinese GPS jammer

[John Green]

Some time back, I posted my experiments with a cheap Chinese made GPS
jammer and Z3801. Since then, I have been able to check it on a
spectrum analyzer. It sweeps over about 30 MHz centered on GPS L1
frequency. Power looks like about -3 dbM. If I turn it on within 30
feet of the antenna, the Z3801 goes into holdover immediately.
Yesterday I tried it on my Garmin Nuvi and much to my surprise, the
Nuvi is totally immune. Even with the antenna of the jammer touching
the case of the Nuvi, it never lets on. I can only attribute this to
different signal processing methods. Next up, my HTC G1 phone GPS.

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Re: [time-nuts] Problems with Garmin Nuvi

[John Green]

Quote:
Maybe we should cut these cartographers a little slack.  When you consider
that Garmin will sell you a map update of the entire northern hemisphere for
eighty bucks, we perhaps shouldn't get too wadded up if they miss the exact
location of my little bungalow by a couple of hundred feet.  After all,
we're not talking about GPS error here, but address designation.  And there
are quite a few little bungalows in all of North America...

Bill
You and I look at that a little differently. If I pay $80 for a map, I
want the part that concerns me to be correct. I could care less about
the rest of the US, I want my little neighborhood to be right.
Sorry, no slack cutting here.
I think the problem arises because the GPS calculates the street
address. There is a standard way of assigning addresses but sometimes
counties deviate. My ex wife worked in that business a while and she
said there are 1000 addresses per mile, or one every 5.28 feet. But,
counties, who are legally correct even if they are wrong do things for
their own reasons. My ex said she re addressed an entire street once
because it was done by the developer and done incorrectly only to have
to restore the older, incorrect addresses after the residents
objected. There are a lot of rules concerning addressing but they are
not always followed. If the GPS looks at the end of a road and
calculates the address based on distance, I am surprised it ever gets
one right. Incidentally, Google maps has my address wrong about 100
feet in the other direction.

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[time-nuts] Speaking of problems with Garmin

[John Green]

I just bought a Nuvi 265WT and after I entered my home address, it
says home is .2 miles away. I know this is a map error, but the map
comes from Garmin. To me, this is unacceptable. I will complain, in
vain, I am sure, to Garmin.
Sorry to be off topic but when I saw Garmin, I couldn't resist
venting a little.

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Re: [time-nuts] Garmin Nuvi troubles

[John Green]

I downloaded a topo map from a source not connected with Garmin and
get the same thing. I understand that you get one free update and I
already got it. I have only had it a couple of weeks so this should be
the latest map.

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Re: [time-nuts] UBLOX GPS boards

[John Green]

Magnus Danielson wrote:I would let the low-frequency PPS act as start
and the 10 MHz as stop,
unless you want to measure the PPSes directly.

I tried that too. Seemed to work perhaps a little better. I ended up
using the 1 PPS from the Z3801 instead of the 10 MHz. I am going to
have to dig out that Tbolt just to verify that the test set up is OK.

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Re: [time-nuts] UBLOX GPS board testing

[John Green]

I tried substituting the 1 PPS output from the Z3801 and comparing it
to its own 10 MHz output and find the same jumpy behavior as I get
with the UBLOX boards. Well, not exactly the same but pretty much. Now
I am confused. I expected the 1 PPS to be in lock step with the 10
MHz.

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[time-nuts] Ublox GPS board

[John Green]

I recently bought 4 older UBLOX GPS boards on eBay for $15 with free
shipping. I hooked one up to my 1992 and comparing it with the Z3801,
I am seeing it jump all over the place. I am using the 10 MHz output
from the 3801 to start and the 1 PPS from the UBLOX to stop. I will
have to bring in a TBolt just to verify the test set up. Has anyone
here ever made any measurements on the UBLOX TIM-LF-0-000? These are
not timing grade, by the way. The spec. sheet says the accuracy of the
time pulse is 50 nSec. If that is +/- 50, then what I am seeing might
be OK.

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Re: [time-nuts] FEI-Zyfer GPS Time Frequency Module

[John Green]

They have all sold and all but one for over $100. Seems someone
thought they were worth something.

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[time-nuts] ny information regarding FEI-Zyfer GPS Time Frequency Module

[John Green]

A few of these are currently on eBay at pretty low prices. I have
never heard of them and was wondering if anyone here has had any
experience with them or knows where some information might be found.

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Re: [time-nuts] GPS jamming susceptibility

[John Green]

I read that Phrack article and their jammer is much more sophisticated
than mine. Mine is just a sweeper. I don't even know yet the sweep
rate. I was thinking more along the lines of theirs. Something that
actually put out a signal that contained at least some aspects of the
signal they were intending to jam. My next experiment will be to get a
clock oscillator that works at some submultiple of the GPS frequency
and see if one of its harmonics can jam a handheld GPS if held close
by.

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[time-nuts] GPS jamming susceptibility

[John Green]

Given that this is an extremely sensitive topic and completely illegal
also, let me just state at the outset that I have no interest in
jamming anyone's GPS. A while back, I was looking at one of those
Chinese discount electronics websites, I'm sure we all have, and
noticed a GPS jammer for sale. I had been wanting to do some jamming
susceptibility testing for quite some time but had never got around to
building a generator to test with. The thing was cheap so I ordered
it. After it arrived, I opened it up, first thing, to see how it was
made. It has a dual 555 oscillator, a couple of analog switches, a 1.9
GHz VCO, a single amplifier. It doesn't look capable of putting out
more than 50 milliwatts or so into a 2 inch antenna. I was somewhat
dubious that it would do anything, so I took it to the bench where the
Z3801 lives and turned it on. Within 2 seconds, the holdover LED lit.
I immediately turned it off and within a few more seconds, the
holdover LED was back off. The GPS antenna is perhaps 35 feet away
with a cinder block wall, a brick wall, and a metal roof in between. I
also put a 15 Db attenuator between it and the antenna with almost the
same result. I am going to do more testing with it wired into the GPS
downfeed an an adjustable attenuator in line just to see how much
signal it takes. That way, there will be little danger of messing with
anyone's reception. It is just a simple sweeper so it must do its job
by brute force. I am amazed that it took so little to shut my Z3801
down. Has anyone here had any actual experience testing GPS receivers
for susceptibility?

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Re: [time-nuts] Losing things

[John Green]

I don't believe there are such things as fairies, etc. Unless you
count the 4 foot 10 Filipino fairy that inhabits my house. I was bad
enough to take my glasses off to work on something only to spend an
hour afterward looking for them. Now, I have someone else to blame.
She puts her glasses in the exact same place every night at bedtime
and without fail asks where they are every morning. I have gotten in
the habit of telling her that they are da'on, Tagalog for there.
Every time I am looking for anything she will invariably say its over
dere which is meaningless since dere is anywhere in the whole world
except here.

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[time-nuts] Updated Shera controller

[John Green]

Bert,
I for one, would be interested in that.

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[time-nuts] Any CW12-TIM users?

[John Green]

I seem to remember someone saying they had actually tried one. I am looking
to put another repeater on the air and while I have another TBOLT, I like
the fact that the CW12-TIM takes a single supply. Of course, I'll have to
have 5 volts to power the antenna but I can get the 3 volts for the CW12
from that. The 10 MHz output doesn't have to be as stable as a TBOLT, it
just needs to be GPS locked. It doesn't have to have holdover. If it loses
GPS lock, it would be OK if it just stopped putting out 10 MHz. Also, do I
have to get special software to talk to it? Or, hopefully, it just does a
self survey automatically and I won't have to fool with it.
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Re: [time-nuts] Thunderbolt test results

[John Green]

The default parameters are a compromise. The thunderbolt was originally used
to provide time and frequency, though I understand not always frequency, for
cellsites. Though heated and air conditioned, I suspect they had pretty good
temperature swings. Also, the sky view was not always optimum. It was
supposed to lock on to as few as 1 SV, come up from dead cold and work.
Obviously, those settings can be improved upon when we stabilize the
temperature, voltages, use good antennas. I use one as a reference for an
amateur repeater and it works well for that. When I was trying to put the
repeater on the air, I changed the settings from default to what I had found
in the lab that worked better and the Tbolt went into holdover and wouldn't
come out. I changed back to the default settings and it worked fine. I am
not sure why they didn't work but I didn't have a lot of time to
investigate. Months later, it is still working great. There are people here
that have spent many hours optimizing the Tbolt. Search back and you will
find lots about how to get the most out of it.
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Re: [time-nuts] Agilent Flat Rate repairs

[John Green]

If you decide to let Agilent repair your instrument be aware that flat
rate doesn't necessarily mean what you think it does. We sent a network
analyzer to them under the flat rate repair program and we were told that
certain repairs, anything expensive, wasn't covered and that the repair
would be considerably more.
I used to think that HP/Agilent's repair service was first rate. The last
few times we used them changed my mind. Still, certain things can only be
successfully repaired by them because they have proprietary software.
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Re: [time-nuts] Tbolts

[John Green]

I have a couple of TBOLTs as well as a Z3801. If it were me, I would spend
the extra and get a Z3801 or something similar. There is a Z3805 on eBay
right now for $199. I didn't notice if it was an auction or buy it now.
Z3801s seem to vary widely in price. I have seen them for under $200 but
right now, they seem to be in the $400 to $500 range.
If I didn't have a Z3801 and got a TBOLT, I would probably think it was
great. But after comparing them I'd go with the Z3801. I am not putting down
the TBOLT. In use one for a frequency reference for a ham repeater and love
it in that application.
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Re: [time-nuts] Tight PLL method. Is it good enough?

[John Green]

I am a relative outsider to this fine group. I mostly just read the posts. I
have learned a lot since I have subscribed.
So, I don't have a dog in the fight over whether the tight PLL method is all
Warren says it is. I can understand that Warren
has researched this method, discovered its weakness and made advancements to
compensate. He has tested it against
a well known and respected piece of commercial gear and found good, though
not perfect agreement. An achievement to be
proud of. Bruce has also researched this method and sees that it has
weaknesses. Some of which he feels Warren has not
addressed. He is frustrated because Warren won't agree that there are
problems with this method.
As someone who merely wants to test some oscillators, I am mainly interested
in finding components I can buy and assemble
into something I can have a modicum of confidence in. I was looking at doing
a DMTD setup because I have most of the
necessary components. But Warren has gotten my attention. By testing it
against a piece of commercial equipment, he has
gotten me to believe that if I build a similar setup, I can achieve similar
results. The interesting thing is that his setup is relatively
simple. I could probably duplicate it pretty closely. Is it perfect?
Probably not. Would it do what I need done? Probably so.
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[time-nuts] And you thought you were old

[John Green]

Anyone remember the CK722 transistor? As I remember they were about $7.50, a
considerable sum.
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[time-nuts] Microphonic Inductor?

[John Green]

Said,
I assume you are using something like the Coilcraft 0603 LS series which
seem to have ferrite cores. You might want to try a 0805 size part since
that inductance is available in the CS series which are ceramic only. I
don't know if size constraints prohibit using an 0805 but you can try one to
see if the inductor is the problem.If you must use a 0603, you might try
massaging the filter impedance so you can use a 390 nH which is available in
0603 size with a ceramic core. Then, you will either have to put up with a
mismatch or include some impedance matching components. I use the LS series
0603s a lot and they are somewhat temperature sensitive if that could be an
issue. The ceramic cored CS series don't seem to be temperature sensitive.
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[time-nuts] For Brian Kirby

[John Green]

Going to Talladega? I am in Anniston, just a hop, skip away. If you get
time, drop by. I am at 1750 Coleman Rd. We don't have a Time Nuts quality
lab here but do have some interesting stuff.
John Green
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Re: [time-nuts] GPS Networking splitter

[John Green]

They work very well. I have a LDCBS1X2 I got off eBay for $15 or so. Do have
a look there befor you pay retail. The one I have has one port thru and the
other blocked. Also has a load on the blocked side so some receivers won't
whine about open antennas. There are lots of options, but these are so
simple and easy.
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Re: [time-nuts] Measuring frequency difference

[John Green]

Raj wrote:
I must again check with a newer GPS for better coordinate accuracy.
Initially only two SV's lit green, after I set the co-ordinates then all are
green. Now the 10MHz is jumping between 0.1 0.00 ppb. comparing
with a a FE5680.
I understand that is mostly due to using the default settings on the TBOLT.
There are several here who have devoted much time and energy to the fine art
of TBOLT manipulation. I decided against trying to use the TBOLT for timing
and dedicated it to be a frequency reference for a Ham repeater where it has
performed very well. Closer to its original use. If you want to use it as a
frequency standard for setting Rubidiums and OCXOs, it should be OK as those
time jumps will average out over the long term anyway.
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Re: [time-nuts] REFLOCK

[John Green]

Luis,
I noticed that TAPR shows the Reflock2 items as no longer available. Is
there another source?
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Re: [time-nuts] High voltage supplies

[John Green]

I worked for a brief spell for a company that made transformers. We had
several high voltage parts and I came to appreciate making high voltage
stuff is as much an art as a science. One of our products was a 7 kV ferro.
The usual way to test one was to grab the silicone output lead and get it
near the frame to see how far it would arc. We stress tested them at 10 kV
for 24 hours by running the frequency at around 70 Hz. You would get a nasty
surprise if there was a pinhole in the insulation of that silicone wire.
They were vacuum potted in epoxy and you could tell when the vacuum pump
wasn't pulling enough vacuum. All the parts would fail in a couple of hours.
I don't remember the exact vacuum but it was extremely low. Another product
went into electric fence chargers. Our customer had gone through literally
dozens of transformer people before he tried ours. He said that after going
to our parts, excepting lightning, he had not had a single field failure.
There was a lot of stuff about high voltage I though counter intuitive but I
learned the hard way that what works with high voltage doesn't always make
sense.
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Re: [time-nuts] Tbolt altitude error

[John Green]

I had a Tbolt and a Z3801 both fed from the same antenna and they indicated
26 meters differenence in altitude. The 3801 seemed closer to right. If
geoid error were the cause, it seems that both would indicate about the
same.
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Re: [time-nuts] Sparkfun

[John Green]

I was going to try to purchase a Prologix GPIB converter but I can't access
their site. I sent an e mail informing them but have not gotten a reply. Is
it just me?
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Re: [time-nuts] Sparkfun

[John Green]

I am at work so I couldn't commit the time to trying to get in. I did manage
to get something in my cart but could never check out. They didn't answer my
e mail yesterday complaining about their site but I am going to send them
another reminding them that wasting the time of people who are potential
customers isn't a good thing to do. My life will go on without that Prologix
adapter so I will just chalk this up as another of life's little
disappointments. If you are into frustration and wasted time, try dealing
with USCIS or the US Department of State.
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Re: [time-nuts] Beginner's Time Reference

[John Green]

As someone relatively new to the precision time/frequency game my viewpoint
is a little different to the more seasoned folk. Your statement that you
wanted to build your own atomic standard leads me to believe that this is
more of a learning experience for you. Even if you want to build it
yourself, at some point you will wonder Just how good is this thing? Is it
better than the last one I built? The cheap and easy way to answer that,
unless whatever you build is very good indeed, is with some kind of GPSDO.
Probably not as good as a cesium but much cheaper. If I did not have a
Z3801, I would still be just guessing about those OCXOs and eBay rubidiums.
I suggest that you visit James Miller's website. You can build a simple
divider/comparator that will let you either lock whatever source you have to
GPS or compare its frequency to GPS. The last LPRO I got off eBay was $59
including shipping. The last Tbolt was just over a hundred. HP 10811 OCXOs
are good but pricey. There are all kinds of rubidiums and quartz oscillators
out there to experiment with and learn from. If a learning experience is
what you want, read every post here for several months while exploring the
archives. Watch eBay closely for a month or so to see what things sell for.
Decide on what is achievable and affordable and start having fun. You will
find that it is highly addictive.
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[time-nuts] Would a Resolution T work?

[John Green]

I always thought the microprocessor in a Z3801 had to talk to the GPS
receiver for it to work. Guess not. Anyway, would a Resolution T work to
supply 1 PPS? Would it be better or worse than the existing Oncore? By the
way, my Z3801 is still stinky. I powered it off yesterday and I am going to
remove the upper board to see if I can locate the source of the odor. It has
been running continuously for about 4 months now and just started to smell
bad a couple of days ago.
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Re: [time-nuts] Stinky Z3801

[John Green]

I lifted the top board and after some sniffing I determined that the smell
is coming from the 10811 reference oscillator can. I don't know if I want to
open it up but I guess at this point, I don't have much choice. Unless it is
normal for them to smell bad. Anyone ever experienced stinky reference
syndrome?
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[time-nuts] Re; Stinky Z3801

[John Green]

I partially disassembled the reference and the smell is coming from the
inner oven. After looking at the website that shows a complete disassembly,
it looks like the only thing that could be generating the odor is the black
foam insulation between the oscillator can and the outer oven. Since the
oscillator/inner oven can is sealed, there isn't anything else to generate
the smell. Funny part is that it still works fine. Why did it wait 4 months
to start smelling? I am going to put everything back together and just see
what happens.
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Re: [time-nuts] Stinky Z3801

[John Green]

Since the oscillator/inner oven can is sealed, how can you smell it?

Bill Hawkins


The point I was trying to make, perhaps unsuccessfully, was that since the
can containing the inner oven was sealed, the smell had to be coming from
the insulation between the inner and outer ovens.
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Re: [time-nuts] Thunderbolt reception problems

[John Green]

Warren, Thanks for the Tbolt tips. The power supply was a good linear supply
so I doubt that was causing what I see. The room temp was cycling a degree,
maybe two, I did sometime see some quick shifts that were not coincident
with temperature but they were all less than 10 nS. The largest swings
always followed temperature excursions. Even after putting it in a box and
lowering the temp. drift to fractions of a degree, I would see swings if as
much as 30 nS in 5 minutes. I thought that this was just too much to fool
with and decided to use it as a reference for a 900 MHz ham repeater. It
will be interesting to see how it does in a room with no heat or air
conditioning. I hope to get on next week. I have another one and may, at
some time try putting a double oven oscillator to see how it does. I thought
about trying an LPRO but I think the Tbolt would just make it worse rather
than better.
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[time-nuts] Double oven ocxo's was Tbolt reception problems

[John Green]

Warren,
Perhaps I am being too hard on the Tbolt. If I never had a Z3801, I am sure
I would like the Tbolt a lot more. The Z3801 seems to just sit there and
work without having to assure either its voltage or temperature or anything
else for that matter. I do believe the things I am seeing are coming from
the Tbolt because I compared an LPRO to the Z3801 and saw only a very slow,
uniform slip in phase.  No jumping around at all. By slow, I mean that it
took several hours for it to slip 1 cycle.
As to the double oven OCXO, I have 2 I purchased off eBay in the last few
months. One is a Morion MV89 and the other a UCT 8663. I compared both to
the Z3801 over several days and was not impressed. They seemed no better
than a good single oven unit. Of course, I wasn't trying them over a large
temperature excursion but I expected them to be better than a single oven. I
wouldn't expect either of them to improve the Tbolt much. The only thing to
really impress me lately has been the LPROs. They do move but seem a lot
less picky about everything than a quartz oscillator.
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Re: [time-nuts] Thunderbolt reception problems

[John Green]

I have been following the discussion regarding Tbolt performance closely. I
have 2 of them and have not seen performance even close to what others
report. I don't seem to have sensitivity related issues that others have
reported. I am feeding Tbolt and Z3801 from a common antenna through a
purpose made GPS splitter. The Tbolt seems to see more sats quicker than the
Z3801. The Tbolts I have are extremely temperature sensitive. Even putting
them in a box to shield them from room temperature variations, they seem to
wander around a lot. This sounds crazy and is not in line with what others
have reported but when I changed the TC to 500 seconds, mine got a lot
worse. I found that a TC of around 10 seconds with a damping of 1 made for
the least amount of phase slip compared to a Z3801.
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[time-nuts] 80 MHz Crystal

[John Green]

Do you need 80 MHz exactly? I have a number of tcxos around that frequency
but I doubt any that are exactly 80 MHz. By the way, $12 for a good crystal
doesn't sound all that high. Seems the last ones I bought from ICM for
channel elements which aren't all that precise, were close to $20.
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[time-nuts] Speaking of 10544As

[John Green]

I have one that I bought at least 25 years ago. Never been turned on. I
believe it was brand new. It had the HP spec sheet with it. I keep saying I
am going to power it up and see what it does. Now that I have some equipment
that can actually do that, I'll give it a try. Maybe sooner than another 25
years.
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Re: [time-nuts] Trimble Z3801 look alike

[John Green]

I did find this: http://www.realhamradio.com/GPS_Trimble_Receiver.htm
Looks kind of like a Tbolt in a fancy case. Article says it doesn't work
with Satstat. I'll bet it does work with Tboltmon.
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[time-nuts] Trimble copy of Z3801

[John Green]

There is what appears to be a Trimble copy of a Z3801 on eBay. number
370234484785.
I can't seem to find any info. Is this really a Z3801 copy or just a Tbolt
in a fancy case?
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Re: [time-nuts] Conical inductors

[John Green]

Just so you know, Colicraft makes them too.
http://www.coilcraft.com/bcl-s.cfm#table

Probably quite a bit cheaper than Piconics and they are available either
with flying leads or surface mount. I don't believe they use any core
material but the specifications look like they would be suitable for a large
number of applications. I don't know about these particular parts but
Coilcraft is very liberal in giving out samples. I routinely get 20 at a
time of several values at a time. Our purchasing folks don't like to order
from  Coilcraft but I always list them as an approved source because their
parts always work, unlike some other vendors.
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