Steve . | 1 Dec 03:00 2011
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Re: Line Voltage frequency Interface morphed to batteries

Hal,

I don't know what I'd do if i had reliable power like that. Here at work
(the lab) It's normal to see outliers of anything between 58hz and upper
63. As I had commented before, this power distribution in this area is
terrible (South Western Pennsylvania)

Steve

On Wed, Nov 30, 2011 at 3:06 PM, Hal Murray <hmurray@...> wrote:

>
> > I hooked up a 47k resistor from line to the 50 ohm input of my 5334B and
> it
> > "just worked."
>
> That's something I wouldn't do.  It's too easy to forget to push the 50 ohm
> button.  I might do it if I had a handy 50 ohm terminator built into a BNC
> pass through.  That would be easy to verify with a quick glance.
>
>
> >  I am watching the 60 Hz drift all around as I type this (although not
> all
> > that far, seems to be holding within 0.01 Hz tonight).
>
> I'm surprised you are that close.  How long have you been watching?
>
> I think 0.1 Hz (low) is where the US power companies have to file paperwork
> so they try (very) hard to avoid getting that low.
>
(Continue reading)

Peter Bell | 1 Dec 04:13 2011
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Re: troubleshooting a FE-5680A (got two; only one works)

It does seem rather off frequency - the other thing that might be
worth checking is to verify that the PTC thermistor soldered to the
crystal is getting hot, since failure of that would seem likely to
induce frequency errors of about that magnitude.

Regards,

Pete

On Thu, Dec 1, 2011 at 2:01 AM, beale <beale@...> wrote:
>> [Peter Bell] ...check to make sure that the VXCO is actually sweeping through 10MHz - if not, you can try
adjusting C217 to centralise the sweep range.
>
> Thanks Pete, you are exactly right. As mentioned, the VCXO was sweeping from 9.999799 to 9.999994 MHz with
no lock. I found that the C217 trimmer was nearly at minimum C already, but a tiny tweak to move it to absolute
minimum C shifted up the center frequency 30 Hz, which (just) enabled a lock at 10.000000 MHz.  Given the
pre-existing C217 setting, I wonder if this unit was marginal even from the factory. I don't know what
minimum value C217 has, but I could remove C217 completely which might center it more. Or, maybe there is a
way to increase the VCO tuning range, no doubt at a cost in phase noise.
>
> Asking for a replacement unit is another option, but I'm just too impatient for that, so I'm taking it as an
opportunity to learn something.  (in fact I did send him a note, but I'm not expecting anything.)
>
> Thanks to Pete and the time-nuts list for the solution!
>
> -john
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@...
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
(Continue reading)

Peter Gottlieb | 1 Dec 04:19 2011
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Re: Line Voltage frequency Interface morphed to batteries

On 11/30/2011 3:06 PM, Hal Murray wrote:
>> I hooked up a 47k resistor from line to the 50 ohm input of my 5334B and it
>> "just worked."
> That's something I wouldn't do.  It's too easy to forget to push the 50 ohm
> button.  I might do it if I had a handy 50 ohm terminator built into a BNC
> pass through.  That would be easy to verify with a quick glance.
The unit is specified to be able to handle 200 volts DC + peak AC on the input 
in high impedance mode either X1 or X10.

I just tried it and it has no problem with it.

>
>
>>   I am watching the 60 Hz drift all around as I type this (although not all
>> that far, seems to be holding within 0.01 Hz tonight).
> I'm surprised you are that close.  How long have you been watching?
A couple of hours.

>
> I think 0.1 Hz (low) is where the US power companies have to file paperwork
> so they try (very) hard to avoid getting that low.
>
> Here is what I saw.  Each data point is averaging over 10 seconds.
>    http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-Jul11-12-freq.png
>
>

Peter Monta | 1 Dec 04:56 2011
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Re: Compensating phase differnces in dual frequency GPS receviers?

Hi Attila,

> [ L1 / L2 timing differences ]
> How do dual frequency receivers deal with that?

I've also been toying with the idea of an inexpensive dual- or
tri-band GPS SDR, especially since there are now quite a few
satellites emitting L2C, the civil L2 signal.  (Though I'd still like
to try my hand at the fancy L2 semicodeless schemes.)

I think that manufacturers calibrate out the timing differences
between channels (as well as group-delay variations within a channel).
 There must be some remaining error, though, e.g. over temperature,
depending on the filter technology.

ObTimeNuts:  There's an interesting recent thesis on GPS for time and
frequency metrology:

http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_4/4.4_zeit_und_frequenz/pdf/Feldmann_2011_Dissertation.pdf

Section 5.1.3 has a few words on exactly this channel-filter-delay
issue.  The author measures a coefficient of 20 ps per degree for a
pair of receivers.

Cheers,
Peter

Peter Monta | 1 Dec 05:09 2011
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Re: Compensating phase differnces in dual frequency GPS receviers?

Speaking of GPS's L2C signal, it turns out there's a timing difference
between L2C and L2, namely 90 degrees of phase (nominally).
Apparently there was some controversy over whether to include this
correction in the RINEX files.  The RINEX 3.0 document has details.

Even with all this complexity, it would be really nice for everyone to
have access to ~2 ns time, as a significant upgrade to present-day
inexpensive systems giving ~20 ns time using single-frequency
pseudorange.

Cheers,
Peter

Steve . | 1 Dec 06:05 2011
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Heated crystal? & Rb tube corrosion (FE-5680A)

I've been paying particular attention to the discussions involving the
FE-5680A frequency standards of recent attention. I do not have a FE-5680A
yet, but rather I am studying what is shared from the others prior to
buying. At the very least I want to know what I'm up against should I get a
DOA module.

It appears that these units use a heated crystal.(..i sure hope it's heater
and not an acoustic resonator). Has anyone performed sub 1degree c drift
testing against a known stable source? What are the performance gains by
using tighter temperature control? Also It appears that quite a few of
these have corroded Rb tube interfaces. My guess is the corrosion is a
tale-tale sign of small amounts of rb gas leakage in combination with the
raised temperatures of the tube oven?  If this is the case I suppose a
visual check of the tube interface for corrosion would yield a fair
approximation of the tube condition?

Lastly, is the Rb tube a quartz tube or is it a metal(silver
lined?)canister sealed with polymer tape?

Thanks,
Steve
WB6BNQ | 1 Dec 06:16 2011
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Re: Heated crystal? & Rb tube corrosion (FE-5680A)

HUH ?

What, exactly, do you mean by "corroded Rb tube interfaces ?"

bILL....wb6bnq

"Steve ." wrote:

> snip
>
> Also It appears that quite a few of
> these have corroded Rb tube interfaces.
>
> Thanks,
> Steve

Steve . | 1 Dec 07:00 2011
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Re: Heated crystal? & Rb tube corrosion (FE-5680A)

Bill,

I was starting to think i may have to crack open an instrument to get a
picture. But i found a reference online.
http://n1.taur.dk/fe5680a-2/IMG_1375.JPG

Note the corrosion around the cheaper metal parts (screws, spacers, shell).
I can't speak for the FE-5680A, but when i see something like this in the
instruments i maintain it's a tale-tale sign gas mitigation.

Steve

On Thu, Dec 1, 2011 at 12:16 AM, WB6BNQ <wb6bnq@...> wrote:

> HUH ?
>
> What, exactly, do you mean by "corroded Rb tube interfaces ?"
>
> bILL....wb6bnq
>
>
> "Steve ." wrote:
>
> > snip
> >
> > Also It appears that quite a few of
> > these have corroded Rb tube interfaces.
> >
> > Thanks,
> > Steve
(Continue reading)

Hal Murray | 1 Dec 08:42 2011
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Re: Line Voltage frequency Interface morphed to batteries


[Context is HP 5334B inputs.]

> The unit is specified to be able to handle 200 volts DC + peak AC on the
> input  in high impedance mode either X1 or X10. 

Thanks for the heads up.  Somehow, I thought they were much more delicate 
than that.

--

-- 
These are my opinions, not necessarily my employer's.  I hate spam.

WB6BNQ | 1 Dec 09:25 2011
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Re: Heated crystal? & Rb tube corrosion (FE-5680A)

Steve,

I viewed not just the picture you referenced but all of the pictures at that site
and was unable to detect ANY corrosion of any kind.  What you are seeing are
scratch marks in the anodized plating due to having the Rb removed from heavily
plated circuit board that is used as a heat sink for the Rb.  At one end of the
physic package is a circular shaped housing which has some rosin left on it, a
thermistor or two attached and some kind of bonding material used for mounting
the heating transistors that has changed color because that part is heated when
it is running; that is not corrosion.  The screws attaching that item to the rest
of the physic package have fiberous material for a mounting washer to buffer
vibration or are used as insulators; that is not corrosion.  The screws that are
holding down the circuit board press down on a gold plated circular area used for
grounding besides being used for a mounting point; that is not corrosion.

I think you need to reboot "your" internal operating system and then do a serious
update on your help files.

Bill....WB6BNQ

"Steve ." wrote:

> Bill,
>
> I was starting to think i may have to crack open an instrument to get a
> picture. But i found a reference online.
> http://n1.taur.dk/fe5680a-2/IMG_1375.JPG
>
> Note the corrosion around the cheaper metal parts (screws, spacers, shell).
> I can't speak for the FE-5680A, but when i see something like this in the
(Continue reading)


Gmane