[time-nuts] Lighting Grounding info

[John Allen]

Here are two sources of grounding and other information.

 

The Moto R56 is 518 pages of grounding and equipment protection info.

 

https://www.dropbox.com/s/f3xjx1u15ipys26/Motorola_R56_2005_manual.pdf

 

http://wiki.radioreference.com/index.php/RF_Engineering

 

Regards, John K1AE

 

 

 

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Re: [time-nuts] HP10811 Double oven, oven jump?

[Bob Camp]

Hi

The thing that looks like a second oven on that unit really is not one it is a 
boost heater. It should be off under normal conditions.

Assuming it is off, it is not the problem.

Next thing to check is the input power.

Bob

Sent from my iPhone

> On Nov 26, 2014, at 9:53 PM, d...@irtelemetrics.com wrote:
> 
>Hi Bob,
> 
> Yeah it did. This is running as part of one of Bob Stewart's GPSDO's. It's 
> been up for about two weeks now. The log indicated there was a phase jump 
> compared to the GPS PPS input. EFC made a jump to correct for it. A few hours 
> later, it made a small jump back in the other direction, with a corresponding 
> phase and EFC correction there also. By the phase jump, I would have though 
> it was the crystal doing something. But the fact that it showed up in the 
> oven monitor voltage also has me a bit worried. 
> 
> The outer oven controller didn't show anything similar. 
> 
> I've been wracking my brain about what could be causing this. It's way to 
> sudden to be anything one would expect from a normal analog circuit. The room 
> temp cycles are visible, but are nice and smooth compared to this. It makes 
> me think there is something mechanical going on. 
> 
> Who knows, maybe the crystal changing affects power dissipation from the 
> oven? Still trying to figure out exactly how much of a change in oven power 
> this is, but I suspect it's very small. With the three transistors in 
> darlington and 100K resistor feeding the base, a 1mV change on the inner oven 
> controller differential amp would indeed be a small change. 
> I was thinking, I also need to rule out the power supply. But, I need to 
> setup a voltage divider to get that to within the ADC input range... 
> 
> Dan
> 
>> 
>> Hi
>> 
>> Did the frequency shift at the same time? If not, the first suspect would be 
>> the data collection system. 
>> Bob
>> 
>> > On Nov 26, 2014, at 11:00 AM, Dan Kemppainen  
>> > wrote:
>> > > Hi All,
>> > > I've been playing with some double oven HP10811's. I've been monitoring 
>> > > the internal oven feedback vs. temperature and noticed something 
>> > > interesting last night. There was a sudden step change in internal oven 
>> > > feedback voltage. This is the voltage coming from the amplifier 
>> > > monitoring the bridge that feeds the heater transistors. > > The step 
>> > > change was on the order of two or three times as large as normal swings 
>> > > caused by the furnace cycling in the house. The voltage was being 
>> > > monitored by a 8Ch ADC card. All of the other voltages on that card were 
>> > > stable. > > The jump was very small. I don't recall exactly (Not near 
>> > > that unit right now), but somewhere around a mV or less. But it was very 
>> > > sudden and compared to everything else on that line, or other voltages 
>> > > being monitored. > > I'm wondering if there is something going on in 
>> > > there that may require attention. Bad solder, cracked trace, bad 
>> > > component???
>> > > Any idea what might have caused this?
>> > > Has anyone seen anything similar?
>> > > Thanks,
>> > Dan
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Re: [time-nuts] HP10811 Double oven, oven jump?

[dan]

Hi Bob,

 Yeah it did. This is running as part of one of Bob Stewart's GPSDO's. 
It's been up for about two weeks now. The log indicated there was a 
phase jump compared to the GPS PPS input. EFC made a jump to correct 
for it. A few hours later, it made a small jump back in the other 
direction, with a corresponding phase and EFC correction there also. By 
the phase jump, I would have though it was the crystal doing something. 
But the fact that it showed up in the oven monitor voltage also has me 
a bit worried. 


 The outer oven controller didn't show anything similar. 

 I've been wracking my brain about what could be causing this. It's 
way to sudden to be anything one would expect from a normal analog 
circuit. The room temp cycles are visible, but are nice and smooth 
compared to this. It makes me think there is something mechanical going 
on. 


 Who knows, maybe the crystal changing affects power dissipation from 
the oven? Still trying to figure out exactly how much of a change in 
oven power this is, but I suspect it's very small. With the three 
transistors in darlington and 100K resistor feeding the base, a 1mV 
change on the inner oven controller differential amp would indeed be a 
small change. 

 I was thinking, I also need to rule out the power supply. But, I need 
to setup a voltage divider to get that to within the ADC input range... 


 Dan



Hi

Did the frequency shift at the same time? If not, the first suspect 
would be the data collection system. 


Bob

> On Nov 26, 2014, at 11:00 AM, Dan Kemppainen  wrote:
> > Hi All,
> > I've been playing with some double oven HP10811's. I've been 
monitoring the internal oven feedback vs. temperature and noticed 
something interesting last night. There was a sudden step change in 
internal oven feedback voltage. This is the voltage coming from the 
amplifier monitoring the bridge that feeds the heater transistors. 
> > The step change was on the order of two or three times as large 
as normal swings caused by the furnace cycling in the house. The 
voltage was being monitored by a 8Ch ADC card. All of the other 
voltages on that card were stable. 
> > The jump was very small. I don't recall exactly (Not near that 
unit right now), but somewhere around a mV or less. But it was very 
sudden and compared to everything else on that line, or other 
voltages being monitored. 
> > I'm wondering if there is something going on in there that may 
require attention. Bad solder, cracked trace, bad component???

> > Any idea what might have caused this?
> > Has anyone seen anything similar?
> > Thanks,
> Dan
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Re: [time-nuts] Lucent KS-24361 GPS Time vs. UTC

[Bob Camp]

Hi

Which port are you putting the commands into? 

The box *may* respond to some things on the Diag port that it does not respond 
to on the PPS port. I have not investigated this, but it is a possibility. 

Bob

> On Nov 26, 2014, at 12:52 PM, Mitchell Janoff  wrote:
> 
> I now have my KS-24361 operating and I've successfully communicated via RS232 
> (using the hack described previously) with both SatStat and GPSCon using 
> Win7. The time I'm getting out of the unit is the GPS time (+16 seconds). 
> I've tried to convert the time to UTC by first changing the mode from 
> continuous output to a manual time update(:PTIM:TCOD:CONT 0), and then 
> changing the time to UTC from GPS using the :PTIM:UTC 1 command. Neither of 
> these commands seem to work with this unit. 
> 
> Has anyone experienced this and did you come up with a solution?
> 
> Thanks.
> 
> Mitch.
> 
> 
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Re: [time-nuts] NIST isolation amplifiers

[Bob Camp]

Hi

If you look at some of the wire that they use, the rating may be as much a wire 
rating as a core rating. They use *small* wire !!!

I’ve always assumed that if you go over 30 ma anywhere on any winding you are 
in trouble. I suspect that DC through the entire winding (ignoring the center 
tap) is a “legal” thing to do.

Bob


> On Nov 26, 2014, at 6:39 PM, Charles Steinmetz  wrote:
> 
> Dave wrote:
> 
>> The magnetic field in the core due to the current in the windings is 
>> proportional to current times number of turns.  If there are more than one 
>> winding, add the currents.  Yes, 2 x 20mA certainly exceeds 30mA.   The core 
>> will be driven closer or into saturation and the inductance will be 
>> decreased.
> 
> Right, that's how you calculate ampere-turns.  But the question is, when MCL 
> says "DC: 30mA" with no elaboration, does that mean 30mA through one winding, 
> 30mA in the same direction through two windings, or 30mA in the same 
> direction through all three windings?  (Whereas, 30mA through one winding and 
> 30mA through another equal winding in the *opposite* direction creates no net 
> magnetic field because the flux cancels.  This is the case, for example, if 
> two windings are used as a CT primary for a push-pull amplifier with Vcc 
> applied to the CT.  "No net field" presupposes perfect matching -- in 
> practice, there will be some residual imbalance.)
> 
> Best regards,
> 
> Charles
> 
> 
> 
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Re: [time-nuts] HP10811 Double oven, oven jump?

[Bob Camp]

Hi

Did the frequency shift at the same time? 

If not, the first suspect would be the data collection system.

Bob

> On Nov 26, 2014, at 11:00 AM, Dan Kemppainen  wrote:
> 
> Hi All,
> 
> I've been playing with some double oven HP10811's. I've been monitoring the 
> internal oven feedback vs. temperature and noticed something interesting last 
> night. There was a sudden step change in internal oven feedback voltage. This 
> is the voltage coming from the amplifier monitoring the bridge that feeds the 
> heater transistors.
> 
> The step change was on the order of two or three times as large as normal 
> swings caused by the furnace cycling in the house. The voltage was being 
> monitored by a 8Ch ADC card. All of the other voltages on that card were 
> stable.
> 
> The jump was very small. I don't recall exactly (Not near that unit right 
> now), but somewhere around a mV or less. But it was very sudden and compared 
> to everything else on that line, or other voltages being monitored.
> 
> I'm wondering if there is something going on in there that may require 
> attention. Bad solder, cracked trace, bad component???
> 
> Any idea what might have caused this?
> 
> Has anyone seen anything similar?
> 
> Thanks,
> Dan
> 
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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Bob Camp]

Hi

You need a good antenna setup to get a good disciplined oscillator. The bigger 
question is if you *need* the sort of “better” it gives you. If you are running 
a simple TCXO based GPSDO, you will have a number of issues to deal with 
compared to an OCXO or Rb based system. If “better” is an objective, consider 
the entire system. 

Bob

> On Nov 26, 2014, at 7:30 PM, Dr. David Kirkby (Kirkby Microwave Ltd) 
>  wrote:
> 
> On 27 Nov 2014 01:14, "Chris Albertson"  wrote:
> 
>> After this minimum you have th think about the probability of a strike.
> If
>> you live in Orlando Florida then it might be 100% and nearly zero in other
>> places and then you ask what the radio equipment cost.   I paid $18 for
> my
>> Motorola Encore GPS receiver.
> 
> Chris,
> if a GPS receiver was the only item that would get damaged I would not care.
> 
> If it damaged 3 signal generators,  three VNAs, a frequency counter, and a
> spectrum analyzer, I would care.
> 
> My experience with the lighting going down the telephone line and
> destroying a few computers, printer and modem would make me unhappy about
> an external antenna.
> 
> Nobody has answered my other question - whether one gets a better
> disciplined oscillator with an external antenna.
> 
> Dave.
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Re: [time-nuts] NIST isolation amplifiers

[Bob Camp]

Hi

I very much would not implement that circuit these days. A logic buffer based 
design beats it on pretty much ever (useful) spec in the book.

Bob
> On Nov 26, 2014, at 7:52 AM, Charles Steinmetz  wrote:
> 
> Bruce wrote:
> 
>> A single 2N or equivalent transistor in a suitable circuit dissipating 
>> about 200mW or so can achieve a reverse isolation of 35dB with distortion of 
>> around -40dBc (output +13dBm) with a gain of unity, and an output impedance 
>> of 50 ohms with a PN floor of around -180dBc/Hz or so.
> 
> For those wondering, I suspect Bruce had in mind something like the attached  
> (he posted the basic design a few years ago).  I built 8 channels using 
> toroids on FT37-61 cores.  I think the Mini-Circuits T622 should work, but I 
> have not tried it.  The analyses are from my simulation, and the constructed 
> unit performed similarly.  The Miller effect limits fan-out to about 10 for a 
> 10MHz distribution amp.  [Note: the 50 ohm resistors on the outputs represent 
> the external loads, and are not part of the amplifier.]
> 
> Best regards,
> 
> Charles
> 
> 
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Re: [time-nuts] NIST isolation amplifiers

[Bob Camp]

Hi

Run in common base ( with things done properly) you can get well over 60 db 
isolation on a single stage.

Bob

> On Nov 26, 2014, at 2:59 AM, Bruce Griffiths  
> wrote:
> 
> A single 2N or equivalent transistor in a suitable circuit dissipating 
> about 200mW or so can achieve a reverse isolation of 35dB with distortion of 
> around -40dBc (output +13dBm) with a gain of unity, and an output impedance 
> of 50 ohms with a PN floor of around -180dBc/Hz or so.
> Bruce 
> 
> On Wednesday, 26 November 2014 9:13 PM, Charles Steinmetz 
>  wrote:
> 
> 
> Bruce wrote:
> 
>> Another issue is that if even one output needs high reverse isolation and
>> low crosstalk, then even those outputs that arent so critical will also need
>> high reverse isolation and low crosstalk to avoid degrading the crosstalk
>> to the critical output.
> 
> This brings up the distinction between *isolation* amplifiers and 
> *distribution* amplifiers.  Most of us need a dozen or three feeds 
> for various test equipment, radios, etc.  These feeds should have 50 
> ohm output impedance, moderate isolation (35dB or more), and should 
> not noticeably degrade the noise, PN, distortion, or xDEV of the 
> source.  That is the job of a distribution amp.
> 
> I would generally not use anything like one of the NIST circuits for 
> this, but rather some version of a two- or three-transistor Class A 
> buffer amplifier.  There are lots of circuits to choose from.  Many 
> are transformer (or autoformer) coupled, some are not (the JPL 
> circuits come to mind) and can also be used to distribute lower 
> frequencies.  You can get build-out the NIST way (buffer amp input 
> impedance high so you parallel a bunch of them at the input 
> connector), or by using one stage with low output impedance to drive 
> a number of output amplifiers in parallel, or by using an amplifier 
> with very low output impedance (perhaps a high-current monolithic 
> amplifier) to drive a number of 50 ohm build-out resistors, or by 
> fanning out with CMOS logic and following each CMOS final buffer with 
> a Tee network to generate sine waves.
> 
> Then there are the times when you are making measurements of 
> oscillators and must absolutely ensure that there is no interaction 
> between them.  That is the job of an isolation amp.  Rarely will you 
> need more than two or three feeds per oscillator, so what you need 
> are several, one-to-three iso amps (one for each oscillator).  Here, 
> something like the NIST amplifiers makes sense.
> 
> Note that I'm advocating distributing sine waves exclusively, NOT 
> square waves or pulse trains.  You will find that it is hard enough 
> keeping 1, 5, or 10 MHz from getting into everything in the shop (and 
> radio room), without adding the much-increased difficulty of keeping 
> all of the harmonics under control.  Also, you would like the 
> harmonic content to be rather lower than is often thought because (i) 
> even harmonics cause asymmetry, which can cause phase modulation when 
> the signal is AC coupled or feeds a comparator-type zero-cross 
> detector, and (ii) variations in the phase of harmonics in relation 
> to the fundamental cause phase modulation (this is "harmonic 
> dispersion," which is caused by temperature changes and other circuit 
> variations such as modulation of semiconductor capacitances by low 
> frequecies).  NIST published a paper on this (see Walls and 
> Ascarrunz, "The Effect of Harmonic Distortion on Phase Errors in 
> Frequency Distribution and Synthesis").
> 
> Best regards,
> 
> Charles
> 
> 
> 
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Re: [time-nuts] CentOS 7, Motorola GPS receiver and NTP

[Neil Schroeder]

 Check out the synergy m12 eval board. It's about $100 with the m12m on it
and a little less if you're going to install your own.

The most recent ftdi in-tree driver will automatically support the
adapter.  Previous versions you need to echo the VPI to the sys
tree  interface of the ftdi_sio driver - which is trivial to do in
rc.local.


On Wednesday, November 26, 2014, Paul  wrote:

> On Wed, Nov 26, 2014 at 11:49 AM, xaos >
> wrote:
>
> > Question: How do I setup NTP with a 1 PPS from serial port
> > and the Motorola receiver hooked up?
> >
>
> You'll want to review the documents at ntp.org and the list <
> http://lists.ntp.org/listinfo/questions>.
> The folks there will be happy to assist you.
>
> There are two important points:
>
> 1) Until 4.2.8 is released you'll want to build a recent version of 4.2.7.
> Don't use 4.2.6
>
> 2) Review the many and varied posts on the subtleties of using PPS via ATOM
> or as part of a refclock like ONCORE <
> http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver30.html>.  It can
> have surprising side-effects.
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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Mark Spencer]

In my opinion,

I'd be inclined to find a way to run a suitable wire around the building.I 
don't think you want your interior electrical wiring serving as the only bond 
between two different grounds if energy from a lightning strike flows thru your 
antenna feed line and then thru your time nuts gear that probably has a path to 
the other ground thru the wiring in the building.

Other fault conditions that cause significant currents to flow thru your ground 
system could also cause issues if the only bond between the two ground systems 
is thru your house wiring and time nuts gear.

Disclaimer I'm not an electrical engineer or lightning protection expert so 
please don't rely on this comment.



Mark Spencer

On 2014-11-26, at 2:54 PM, Hal Murray  wrote:

> 
> albertson.ch...@gmail.com said:
>> The ground rod needs to be bonded to the rest of the building ground system.
> 
> How do I do that effectively if the power goes in the front of the building 
> and the antenna is on the back?
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Mark Spencer]

Sweet.   I settled on #3 copper for my antenna grounding system on economic 
grounds and had a "debate" with a residential electrical contractor about 
bonding the antenna ground to the electrical service ground.   The city 
inspector passed the system with the bond installed.

I haven't used poly phasers but do hope to at least stop the house from burning 
down in the event of a lightning strike on the roof mounted antennas.   

I also found that the metallic city water supply pipe is by far the best ground 
I have (at least for 60 cycle AC.) (Using a clamp on meter I can measure an 
appreciable current thru it, unlike the other two grounds.   I presume the 
current is being diverted from the utility neutral and is eventually making 
it's way back to the transformer that powers my house.) I'm glad the water pipe 
is also bonded to the electrical service ground.   I'm happy that I don't have 
any appreciable currents flowing thru my antenna ground.This might be 
something to carefully consider (or possibly have looked at by a pro) if you 
have a really low impedance ground.   I've heard anecdotal accounts of sparks 
occurring when low impedance antenna grounds are connected to an electrical 
service ground.

My usual disclaimer of I'm not an expert in this field, the preceding is only 
my opinion,  and don't rely on this applies.

Mark Spencer

On 2014-11-26, at 2:56 PM, Martin A Flynn  wrote:

> On 11/26/2014 5:14 PM, Jim Lux wrote:
>> On 11/26/14, 2:00 PM, Martin A Flynn wrote:
>>> The N2MO station has an external GPS antenna on the gable end of the
>>> building.  It's connected to the polyphaser arrestor with FSJ4-50
>>> superflex.
>>> 
>>> The antenna mounting pipe has a #2 ground wire  (33.6 mm/2)  the
>>> polyphaser has it's own #2 ground wire.  Both connect to an 8' x 5/8"
>>> (2.4m x 16mm) driven ground rod.  The jacket of the superflex is
>>> grounded with the factoryt Andrew kit as well
>>> 
>>> Even with the GPS antenna lower in elevation then the HF beam and other
>>> antenna (with similar protection)  I have concerns about leaving it
>>> connected all the time.
>> AWG #2 seems a tad overkill, the current in a stroke can be carried by AWG 
>> #10 without melting, but maybe you had a lot of it around for other reasons. 
>>  I suspect the coax shield has smaller cross sectional area than AWG #2 and 
>> you'll protect your grounding wire by blowing up the coax. (in fact, 
>> looking at the data sheet for FSJ4-50, the DC resistance of the outer 
>> conductor is 1 ohm/1000 ft = AWG 10.. it's actually more resistance than the 
>> inner conductor (the inner conductor is 0.820ohms/kft, and 0.140 inch in 
>> diameter, compare to AWG 10 which is very close to 0.100 inch in diameter).
>> 
>> Hopefully your driven ground rod is bonded to the other system grounds?
>> 
>> I'd worry about multipath from the HF beam and tower (although maybe you're 
>> not using that GPS for time-nuts 1E-20 precision...)
> The #2 copper was recycled.   The main RF grounding trapeze is tied to the 
> grounding electrode system with 1/0, which was also recycled from another 
> project.
> 
> Re the time-nuttery:  Only 1E-14.  Can't afford better (yet).
> 
> 
> 
> 
> 
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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Jim Lux]

On 11/26/14, 5:23 PM, Chris Albertson wrote:

On Wed, Nov 26, 2014 at 4:03 PM, Jim Lux  wrote:


On 11/26/14, 2:14 PM, Chris Albertson wrote:


You CAN (almost) lightening proof your system.  The trick is to give
lightening a low impedence path to grind at very opportunity.

Start with the antenna mast and call.  Use iron pipe for the mast and feed
the antenna cable down the center of the pipe.  Place two large ground
clamps on this pipe and connect a large diameter wire that takes a
straight
path to a group rod.This will go a long way to diverting energy to
ground because high voltage likes to flow on the outside of a conductor
which would be the pipe and not so much the antenna cable.



Not so much high voltage, as AC and skin effect.  However, bear in mind
that lightning has a rise time of a microsecond or so: you can think of it
having a fundamental of 300-500 kHz (e.g. the first quarter cycle of a
sinewave), with most of the power below  1MHz.

Skin depth at 1 MHz in copper is 0.065mm.

In iron (using conductivty of 9.6 and relative mu of 1000) skin depth is
0.005 mm

So, steel/iron pipe is a terrible conductor for a lightning impulse,
compared to that nice copper coax next to it, or inside it.



Really?  What you care about is the impedance, not the depth of the skin
effect.   Also not the the coax is NOT exposed to the environment.  Tacitly
the coax comes out from the user side of the antenna, so it never sees
daylight.  The current flows in that first .005mm of steel.   Running the
coax down the side of the pipe would be a really bad idea.



Skin effect greatly affects the resistive impedance.

Compare a copper pipe vs a steel pipe of the same diameter.

The copper is basically conductive ring 0.065 mm thick and resistivity 
of 1.67 and the steel is .005mm thick and resistivity 9.6


So the resistance ratio is 26:1920.. that is 2 orders of magnitude.

However.. the dominant impedance at lightning frequencies (at least for 
copper) is the inductance, which is very weakly dependent on the shape 
and cross-sectional size of the conductor: it's close to 1 uH/meter 
regardless..


A copper pipe that is 2 cm in diameter and 1 meter long has a resistance 
at 1 MHz of 0.004 Ohm


A steel/iron pipe that is 2 cm in diameter and 1 meter long has a 
resistance at 1 MHz of 1.43 Ohm


The inductive impedance is about 6.3 ohms.

So the steel has a somewhat higher impedance than the coax inside it. 
Yeah, there probably is some shielding effect, but I'm going to guess 
that there's some insulating gap between the "bottom of antenna" and 
"top of pipe", although that gap may be bridged by the plasma from your 
lightning strike.


It's just that I'm not sure I'd trust the "shielding effect" of the 
pipe, nor any preferential current distribution from the magnetic 
fields.  For all one knows, that pipe might wind up filled with a plasma 
of vaporized coax.



I'd just consider the antenna and feedline sacrificial, and worry about 
dealing with the transient at the point of entry to the building, 
assuming that the coax is carrying all of it.



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Re: [time-nuts] NIST isolation amplifiers

[Charles Steinmetz]

Dave wrote:

The magnetic field in the core due to the current in the windings is 
proportional to current times number of turns.  If there are more 
than one winding, add the currents.  Yes, 2 x 20mA certainly exceeds 
30mA.   The core will be driven closer or into saturation and the 
inductance will be decreased.


Right, that's how you calculate ampere-turns.  But the question is, 
when MCL says "DC: 30mA" with no elaboration, does that mean 30mA 
through one winding, 30mA in the same direction through two windings, 
or 30mA in the same direction through all three windings?  (Whereas, 
30mA through one winding and 30mA through another equal winding in 
the *opposite* direction creates no net magnetic field because the 
flux cancels.  This is the case, for example, if two windings are 
used as a CT primary for a push-pull amplifier with Vcc applied to 
the CT.  "No net field" presupposes perfect matching -- in practice, 
there will be some residual imbalance.)


Best regards,

Charles



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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 27 Nov 2014 01:14, "Chris Albertson"  wrote:

> After this minimum you have th think about the probability of a strike.
If
> you live in Orlando Florida then it might be 100% and nearly zero in other
> places and then you ask what the radio equipment cost.   I paid $18 for
my
> Motorola Encore GPS receiver.

Chris,
if a GPS receiver was the only item that would get damaged I would not care.

If it damaged 3 signal generators,  three VNAs, a frequency counter, and a
spectrum analyzer, I would care.

My experience with the lighting going down the telephone line and
destroying a few computers, printer and modem would make me unhappy about
an external antenna.

Nobody has answered my other question - whether one gets a better
disciplined oscillator with an external antenna.

Dave.
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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Chris Albertson]

On Wed, Nov 26, 2014 at 4:03 PM, Jim Lux  wrote:

> On 11/26/14, 2:14 PM, Chris Albertson wrote:
>
>> You CAN (almost) lightening proof your system.  The trick is to give
>> lightening a low impedence path to grind at very opportunity.
>>
>> Start with the antenna mast and call.  Use iron pipe for the mast and feed
>> the antenna cable down the center of the pipe.  Place two large ground
>> clamps on this pipe and connect a large diameter wire that takes a
>> straight
>> path to a group rod.This will go a long way to diverting energy to
>> ground because high voltage likes to flow on the outside of a conductor
>> which would be the pipe and not so much the antenna cable.
>>
>
> Not so much high voltage, as AC and skin effect.  However, bear in mind
> that lightning has a rise time of a microsecond or so: you can think of it
> having a fundamental of 300-500 kHz (e.g. the first quarter cycle of a
> sinewave), with most of the power below  1MHz.
>
> Skin depth at 1 MHz in copper is 0.065mm.
>
> In iron (using conductivty of 9.6 and relative mu of 1000) skin depth is
> 0.005 mm
>
> So, steel/iron pipe is a terrible conductor for a lightning impulse,
> compared to that nice copper coax next to it, or inside it.
>

Really?  What you care about is the impedance, not the depth of the skin
effect.   Also not the the coax is NOT exposed to the environment.  Tacitly
the coax comes out from the user side of the antenna, so it never sees
daylight.  The current flows in that first .005mm of steel.   Running the
coax down the side of the pipe would be a really bad idea.



>
>
>
>> The ground rod needs to be bonded to the rest of the building ground
>> system.
>>
>> Then the antenna cable passes through a metal bulkhead with a bulkhead
>> connector and all this is also grounded.  After this is might be a high
>> voltage e on the center conductor.  Use an "lightening arrester that is
>> bolted to the bulkhead.
>>
>
> From a electrical code standpoint, a grounded bulkhead connector isn't
> compliant: you need one of those clamps that attaches to the shield in a
> quasi permanent way. I'm not sure of the entire rationale, but I think it's
> because connectors can become disconnected, but bolted connections less so.
>
>
>
>> At this point you are reasonably safe.  Remember that Ethernet is always
>> gavalically isolated by transformers
>>
>
> Which won't necessarily stand off a 10 kV lightning impulse. and, of
> course, a common mode impulse carried on both wires of a pair might couple
> via either capacitance, or more likely, through magnetic fields.
>
> the ethernet galvanic isolation does a nice job dealing with the 10s or
> maybe 100V common mode issues, and protects the network if there is an
> internal short in a piece of equipment connected to the network.
>
> Of course, with the increased prevalence of Power Over Ethernet, some
> implementations of which are, shall we say, sketchy, that PoE system might
> be a dandy conductor of transient energy.  For instance, a point to point
> microwave network terminal up on a mast running power for the circuit up
> the network cable.
>
>
>
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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Chris Albertson]

On Wed, Nov 26, 2014 at 3:10 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkir...@kirkbymicrowave.co.uk> wrote:

> On 26 November 2014 at 22:14, Chris Albertson 
> wrote:
> > You CAN (almost) lightening proof your system.
>
> BUT if the almost is not quite enough, one could damage a lot of
> expensive test kit.
>

You can never be 100% but you can be nearly 100%.

The minimum is to follow the electrical code.  That might cost $40 in
materials for a single story house.  They allow bare aluminum grounding
wire which really reduces the cost.

After this minimum you have th think about the probability of a strike.  If
you live in Orlando Florida then it might be 100% and nearly zero in other
places and then you ask what the radio equipment cost.   I paid $18 for  my
Motorola Encore GPS receiver.

The iron pipe mast if it also provides a good path to ground will take
almost all the current.
-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Chris Albertson]

You really do have to bond the two of them.  The VERY best way is to dig a
trench all the way around the building and install a loop of wire, #8 at
least (although I use much larger wire after the time and money to dug a
trench.)  This wire connects the rods and the water system.  While a full
loop is best yo can simply run a wire to the building's service entrance
but I think code requires these wires to be "protected" by any of several
methods.

You have to connect the grounds because otherwire you have a problem where
indoors there are two different ground potentials.  The Earth is just that
way, there is or may be a voltage potential between two spots.  There WILL
be a difference during a lightening strike.



On Wed, Nov 26, 2014 at 2:54 PM, Hal Murray  wrote:

>
> albertson.ch...@gmail.com said:
> > The ground rod needs to be bonded to the rest of the building ground
> system.
>
> How do I do that effectively if the power goes in the front of the building
> and the antenna is on the back?
>
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California
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[time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Arthur Dent]

Here is a link to a good 12 page description of grounding
practices/requirements.

http://www.reeve.com/Documents/Articles%20Papers/AntennaSystemGroundingRequirements_Reeve.pdf
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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Jim Lux]

On 11/26/14, 2:54 PM, Hal Murray wrote:


albertson.ch...@gmail.com said:

The ground rod needs to be bonded to the rest of the building ground system.


How do I do that effectively if the power goes in the front of the building
and the antenna is on the back?



AWG 6 wire with no breaks or splices between the two.

The goal of bonding all the grounding systems together is not for 
transient suppression.  It's to make sure that there's no DC or line 
frequency potential difference between "electrical safety ground" at 
various places in the building.


The background on the whole grounding/bonding requirement is more about 
safety when a power carrying conductor, either inside equipment or 
overhead, touches something that people might touch. And, to a lesser 
extent to ensure that if there's an internal short, that the breaker or 
fuse will trip.


NEC requirements for grounding and bonding aren't there for transient 
suppression.


A copy of IEEE 1100 (the Emerald Book) is good reading for the whole 
bonding and equipotential planes, etc.  (unfortunately not free from IEEE).


A good book on transient protection is Ronald Standler's book 
"protection of electronic circuits from overvoltages"

Something like $20 from Dover...

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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Jim Lux]

On 11/26/14, 2:14 PM, Chris Albertson wrote:

You CAN (almost) lightening proof your system.  The trick is to give
lightening a low impedence path to grind at very opportunity.

Start with the antenna mast and call.  Use iron pipe for the mast and feed
the antenna cable down the center of the pipe.  Place two large ground
clamps on this pipe and connect a large diameter wire that takes a straight
path to a group rod.This will go a long way to diverting energy to
ground because high voltage likes to flow on the outside of a conductor
which would be the pipe and not so much the antenna cable.


Not so much high voltage, as AC and skin effect.  However, bear in mind 
that lightning has a rise time of a microsecond or so: you can think of 
it having a fundamental of 300-500 kHz (e.g. the first quarter cycle of 
a sinewave), with most of the power below  1MHz.


Skin depth at 1 MHz in copper is 0.065mm.

In iron (using conductivty of 9.6 and relative mu of 1000) skin depth is 
0.005 mm


So, steel/iron pipe is a terrible conductor for a lightning impulse, 
compared to that nice copper coax next to it, or inside it.






The ground rod needs to be bonded to the rest of the building ground system.

Then the antenna cable passes through a metal bulkhead with a bulkhead
connector and all this is also grounded.  After this is might be a high
voltage e on the center conductor.  Use an "lightening arrester that is
bolted to the bulkhead.


From a electrical code standpoint, a grounded bulkhead connector isn't 
compliant: you need one of those clamps that attaches to the shield in a 
quasi permanent way. I'm not sure of the entire rationale, but I think 
it's because connectors can become disconnected, but bolted connections 
less so.





At this point you are reasonably safe.  Remember that Ethernet is always
gavalically isolated by transformers


Which won't necessarily stand off a 10 kV lightning impulse. and, of 
course, a common mode impulse carried on both wires of a pair might 
couple via either capacitance, or more likely, through magnetic fields.


the ethernet galvanic isolation does a nice job dealing with the 10s or 
maybe 100V common mode issues, and protects the network if there is an 
internal short in a piece of equipment connected to the network.


Of course, with the increased prevalence of Power Over Ethernet, some 
implementations of which are, shall we say, sketchy, that PoE system 
might be a dandy conductor of transient energy.  For instance, a point 
to point microwave network terminal up on a mast running power for the 
circuit up the network cable.



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Re: [time-nuts] NIST isolation amplifiers

[David McQuate]

The magnetic field in the core due to the current in the windings is 
proportional to current times number of turns.  If there are more than one 
winding, add the currents.  Yes, 2 x 20mA certainly exceeds 30mA.   The core 
will be driven closer or into saturation and the inductance will be decreased.

Dave

 Original message 
From: Charles Steinmetz  
Date:2014/11/26  12:54 PM  (GMT-08:00) 
To: Discussion of precise time and frequency measurement  
Subject: Re: [time-nuts] NIST isolation amplifiers 

Bruce wrote:

>Almost. 1:1:2 (turns ratio) transformers used in each stage and 1:1
>transformer on input.  This allows a lower power supply voltage to be used.

I spent a little time (emphasis on "little") fiddling with the 
simulation, and I did not immediately find any solution with 1:1:2 
and 1:1 transformers that I liked as well as the design with 1:1:1 
and 1:2 transformers.  For those who are winding their own 
transformers (which I recommend, partly for the reason given below), 
the simplicity of three equal windings may, by itself, outweigh any 
potential advantage of using a lower power supply voltage.  Each 
constructor should evaluate this for him- or herself.

>One thing to watch with minicircuits transformers is core saturation due to
>dc flowing in the windings.

Good point, I too have found that some MCL transformers have skimpy 
cores.  I have no idea whether the MCL T622 (1:1:1) or T613 (1:1:2) 
would work in this circuit.  They are both specified for 30mA, and I 
had the 3904s biased at 20mA -- but I'm not sure what MCL means by 
30mA.  In this circuit, 20mA flows in the same direction in two of 
the windings.  If the 30mA applies only if one winding has DC flowing 
(or more generally, if the allowable net DC is equal to 30mA through 
just one winding), then the core would not be adequate.

Best regards,

Charles



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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Bob Stewart]

Surround your house with a complete loop of #6 wire with 8-10 ft long ground 
rods every 10-12 ft (but no less than 6ft), bonded (clamped) to the ground at 
the service entrance. That's the simple answer.  The somewhat longer answer is 
in a recent copy of the ARRL Handbook.  Some will argue for smaller wire, etc, 
but those are just details.  I am not an expert in this field.

Bob - AE6RV

  From: Hal Murray 
 To: Discussion of precise time and frequency measurement  
Cc: hmur...@megapathdsl.net 
 Sent: Wednesday, November 26, 2014 4:54 PM
 Subject: Re: [time-nuts] lightening protection of a GPSDO system / optical 
isolated distribution amp
   

albertson.ch...@gmail.com said:
> The ground rod needs to be bonded to the rest of the building ground system.

How do I do that effectively if the power goes in the front of the building 
and the antenna is on the back?



-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Martin A Flynn]

On 11/26/2014 5:54 PM, Hal Murray wrote:

albertson.ch...@gmail.com said:

The ground rod needs to be bonded to the rest of the building ground system.

How do I do that effectively if the power goes in the front of the building
and the antenna is on the back?
If cost is no object, a ring ground circling the building. Otherwise a 
bonding jumper between the electrical system ground and the antenna 
grounding connection, preferably staying outside the building.

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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 26 November 2014 at 22:14, Chris Albertson  wrote:
> You CAN (almost) lightening proof your system.

BUT if the almost is not quite enough, one could damage a lot of
expensive test kit.

> Remember that Ethernet is always
> gavalically isolated by transformers

I lost Ethernet ports on

* Sun Blade 2000 workstation
* Sun Ultra 60 workstation
* Sun Netra T1 server
* HP Printer
* ADSL modem

All went at the same time. The next time just the modem went.

But I think I will be using an internal antenna.

Dave
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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Martin A Flynn]

On 11/26/2014 5:14 PM, Jim Lux wrote:

On 11/26/14, 2:00 PM, Martin A Flynn wrote:

The N2MO station has an external GPS antenna on the gable end of the
building.  It's connected to the polyphaser arrestor with FSJ4-50
superflex.

The antenna mounting pipe has a #2 ground wire  (33.6 mm/2)  the
polyphaser has it's own #2 ground wire.  Both connect to an 8' x 5/8"
(2.4m x 16mm) driven ground rod.  The jacket of the superflex is
grounded with the factoryt Andrew kit as well

Even with the GPS antenna lower in elevation then the HF beam and other
antenna (with similar protection)  I have concerns about leaving it
connected all the time.

AWG #2 seems a tad overkill, the current in a stroke can be carried by 
AWG #10 without melting, but maybe you had a lot of it around for 
other reasons.  I suspect the coax shield has smaller cross sectional 
area than AWG #2 and you'll protect your grounding wire by blowing up 
the coax. (in fact, looking at the data sheet for FSJ4-50, the 
DC resistance of the outer conductor is 1 ohm/1000 ft = AWG 10.. it's 
actually more resistance than the inner conductor (the inner conductor 
is 0.820ohms/kft, and 0.140 inch in diameter, compare to AWG 10 which 
is very close to 0.100 inch in diameter).


Hopefully your driven ground rod is bonded to the other system grounds?

I'd worry about multipath from the HF beam and tower (although maybe 
you're not using that GPS for time-nuts 1E-20 precision...)
The #2 copper was recycled.   The main RF grounding trapeze is tied to 
the grounding electrode system with 1/0, which was also recycled from 
another project.


Re the time-nuttery:  Only 1E-14.  Can't afford better (yet).





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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Hal Murray]

albertson.ch...@gmail.com said:
> The ground rod needs to be bonded to the rest of the building ground system.

How do I do that effectively if the power goes in the front of the building 
and the antenna is on the back?



-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Chris Albertson]

You CAN (almost) lightening proof your system.  The trick is to give
lightening a low impedence path to grind at very opportunity.

Start with the antenna mast and call.  Use iron pipe for the mast and feed
the antenna cable down the center of the pipe.  Place two large ground
clamps on this pipe and connect a large diameter wire that takes a straight
path to a group rod.This will go a long way to diverting energy to
ground because high voltage likes to flow on the outside of a conductor
which would be the pipe and not so much the antenna cable.

The ground rod needs to be bonded to the rest of the building ground system.

Then the antenna cable passes through a metal bulkhead with a bulkhead
connector and all this is also grounded.  After this is might be a high
voltage e on the center conductor.  Use an "lightening arrester that is
bolted to the bulkhead.

At this point you are reasonably safe.  Remember that Ethernet is always
gavalically isolated by transformers

On Wed, Nov 26, 2014 at 1:37 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkir...@kirkbymicrowave.co.uk> wrote:

> Said mentioned on an earlier thread that if a GPS antenna is used
> outside, lightening protection should be used. This immediately
> reminded me of something that happened about 10 years ago to me
>
> 1) Lightening damaged my ADSL modem. It because totally dead.
> 2) Every computer and a printer connected to that had the Ethernet
> ports blown up.
>
> After a hell of a fight with my insurance company, they paid up on my
> household insurance. The total cost was about £10,000, as all were Sun
> workstations, so a bit more expensive than a typical home computer.
>
> A few years after that, a similar thing happened, but just the ADSL
> modem got destroyed - no computers.
>
> Clearly if an external antenna is put in a high enough E-field or
> H-field, it can do damage to the antenna, and potentially anything
> connected to it, which would be all your test equipment, in much the
> same way all my computers got their Ethernet ports blown up.
>
> I would be *very* reluctant to use an external antenna, which is in
> some way connected to a distribution unit into the back of every bit
> of test equipment I have. I can see a potential (excuse the pun), of
> doing a serious amount of damage.
>
> The only way I would consider doing it, is if there was some optical
> isolation. In principle one could modulate a laser at 10 MHz, pass it
> down an optical fibre, then have a photodiode to recover the
> modulation. Can would obviously be needed not to compromise the
> signal, and that might be impossible.
>
> I realize the signal strength from an external antenna will be higher
> than an internal antenna, but does that make much (any?) difference to
> the operation of the GPSDO?
>
>
> FUNNY, SAD but TRUE story.
>
> After I got hit by lightening for the second time down my telephone
> line, I decided I needed to do something about it. So I got onto my
> service provider (BT) and asked them what could be done, as my
> telephone is fed via an overhead line. After arguing with them for
> months, they agree to fit some lightening protection to my telephone
> line. The day they came to fit this was a lesson in how incompetent
> some technicians, and their managers can be. Of course BT call them
> engineers, but this guy is not an engineering in my mind.
>
> BT TECHNICIAN: I need to run an earth wire
> ME: That is ok, so I assume you are going to put an earth rod into the
> ground.
> BT TECHNICIAN: No, I wont use an earth rod.
> ME: So how are you going to earth it? What sort of wire is it?
> BT TECHNICIAN: My manager said to move some earth away with my
> fingers, poke the wire into the ground, then move the earth back with
> my hand. The wire is 1 mm^2.
> ME: That is no good. Let me speak to your manager.
>
> The BT technician then rings his manager, and puts him on the phone. I
> explain that is not acceptable.
>
> MANAGER: So how do you suggest we earth it?
> ME: I don't know how to do it. This is not my area of expertise, but I
> know that what you are proposing, with 1 mm wire and poking the wire
> into the ground with your fingers is not acceptable.
>
>
>
>
> Dr. David Kirkby Ph.D CEng MIET
> Kirkby Microwave Ltd
> Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3
> 6DT, UK.
> Registered in England and Wales, company number 08914892.
> http://www.kirkbymicrowave.co.uk/
> Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Lucent KS-24361

[Rob040 .]

Thanks a lot, that's a big help.

> To: time-nuts@febo.com
> From: hmur...@megapathdsl.net
> Date: Wed, 26 Nov 2014 12:46:44 -0800
> CC: hmur...@megapathdsl.net
> Subject: Re: [time-nuts] Lucent KS-24361
> 
> 
> rob...@live.nl said:
> > Onother question... here in Europe was use screws and nuts with 'metric'
> > (mm) threat. What is used for the mounting screws, how do you call that?
> 
> 6-32
> 
> Web price is $3.49 for a box of 100 at my local hardware chain.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Jim Lux]

On 11/26/14, 2:00 PM, Martin A Flynn wrote:

The N2MO station has an external GPS antenna on the gable end of the
building.  It's connected to the polyphaser arrestor with FSJ4-50
superflex.

The antenna mounting pipe has a #2 ground wire  (33.6 mm/2)  the
polyphaser has it's own #2 ground wire.  Both connect to an 8'  x 5/8"
(2.4m x 16mm) driven ground rod.  The jacket of the superflex is
grounded with the factoryt Andrew kit as well

Even with the GPS antenna lower in elevation then the HF beam and other
antenna (with similar protection)  I have concerns about leaving it
connected all the time.




AWG #2 seems a tad overkill, the current in a stroke can be carried by 
AWG #10 without melting, but maybe you had a lot of it around for other 
reasons.  I suspect the coax shield has smaller cross sectional area 
than AWG #2 and you'll protect your grounding wire by blowing up the 
coax. (in fact, looking at the data sheet for FSJ4-50, the DC 
resistance of the outer conductor is 1 ohm/1000 ft = AWG 10.. it's 
actually more resistance than the inner conductor (the inner conductor 
is 0.820ohms/kft, and 0.140 inch in diameter, compare to AWG 10 which is 
very close to 0.100 inch in diameter).


Hopefully your driven ground rod is bonded to the other system grounds?


I'd worry about multipath from the HF beam and tower (although maybe 
you're not using that GPS for time-nuts 1E-20 precision...)




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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Jim Lux]

On 11/26/14, 1:37 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:

Said mentioned on an earlier thread that if a GPS antenna is used
outside, lightening protection should be used. This immediately
reminded me of something that happened about 10 years ago to me

1) Lightening damaged my ADSL modem. It because totally dead.
2) Every computer and a printer connected to that had the Ethernet
ports blown up.




Here's what we do at JPL for spaceflight equipment: reradiators.

Antenna with preamp on the roof... long coax to wherever the signal is 
needed, amp(maybe), DC bias T (minicircuits has them, as do others, or 
build one), and a variable attenuator (in case the system has too much 
gain), feeding a passive antenna.  Another passive antenna (or your GPS 
receiver or your whatever) is a meter or so away.


The inside antennas can be pretty crude.  I suspect stripping back 1/4 
wavelength of coax shield would work.   We use ones that resemble a 
hockey puck and that have the required bandwidth (L1,L2, L5).


You could, if you like, build some sort of shielding box with absorber 
around the two antennas which would cut down on multipath reflections, 
etc.   But that box would require some design so that it doesn't become 
the path for the lightning to your gear.



The entire path from roof antenna to reradiator is sacrificial.



The only way I would consider doing it, is if there was some optical
isolation. In principle one could modulate a laser at 10 MHz, pass it
down an optical fibre, then have a photodiode to recover the
modulation. Can would obviously be needed not to compromise the
signal, and that might be impossible.


Sure, there's all sorts of RF over fiber stuff available. Some is even 
designed for GPS signals specifically.






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Re: [time-nuts] NIST isolation amplifiers

[Charles Steinmetz]

Bruce wrote:


Almost. 1:1:2 (turns ratio) transformers used in each stage and 1:1
transformer on input.  This allows a lower power supply voltage to be used.


I spent a little time (emphasis on "little") fiddling with the 
simulation, and I did not immediately find any solution with 1:1:2 
and 1:1 transformers that I liked as well as the design with 1:1:1 
and 1:2 transformers.  For those who are winding their own 
transformers (which I recommend, partly for the reason given below), 
the simplicity of three equal windings may, by itself, outweigh any 
potential advantage of using a lower power supply voltage.  Each 
constructor should evaluate this for him- or herself.



One thing to watch with minicircuits transformers is core saturation due to
dc flowing in the windings.


Good point, I too have found that some MCL transformers have skimpy 
cores.  I have no idea whether the MCL T622 (1:1:1) or T613 (1:1:2) 
would work in this circuit.  They are both specified for 30mA, and I 
had the 3904s biased at 20mA -- but I'm not sure what MCL means by 
30mA.  In this circuit, 20mA flows in the same direction in two of 
the windings.  If the 30mA applies only if one winding has DC flowing 
(or more generally, if the allowable net DC is equal to 30mA through 
just one winding), then the core would not be adequate.


Best regards,

Charles



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Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Martin A Flynn]

The N2MO station has an external GPS antenna on the gable end of the 
building.  It's connected to the polyphaser arrestor with FSJ4-50 
superflex.


The antenna mounting pipe has a #2 ground wire  (33.6 mm/2)  the 
polyphaser has it's own #2 ground wire.  Both connect to an 8'  x 5/8" 
(2.4m x 16mm) driven ground rod.  The jacket of the superflex is 
grounded with the factoryt Andrew kit as well


Even with the GPS antenna lower in elevation then the HF beam and other 
antenna (with similar protection)  I have concerns about leaving it 
connected all the time.


73 Martin Flynn
W2RWJ

On 11/26/2014 4:37 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:

Said mentioned on an earlier thread that if a GPS antenna is used
outside, lightening protection should be used. This immediately
reminded me of something that happened about 10 years ago to me
(33.6
1) Lightening damaged my ADSL modem. It because totally dead.
2) Every computer and a printer connected to that had the Ethernet
ports blown up.

After a hell of a fight with my insurance company, they paid up on my
household insurance. The total cost was about £10,000, as all were Sun
workstations, so a bit more expensive than a typical home computer.

A few years after that, a similar thing happened, but just the ADSL
modem got destroyed - no computers.

Clearly if an external antenna is put in a high enough E-field or
H-field, it can do damage to the antenna, and potentially anything
connected to it, which would be all your test equipment, in much the
same way all my computers got their Ethernet ports blown up.

I would be *very* reluctant to use an external antenna, which is in
some way connected to a distribution unit into the back of every bit
of test equipment I have. I can see a potential (excuse the pun), of
doing a serious amount of damage.

The only way I would consider doing it, is if there was some optical
isolation. In principle one could modulate a laser at 10 MHz, pass it
down an optical fibre, then have a photodiode to recover the
modulation. Can would obviously be needed not to compromise the
signal, and that might be impossible.

I realize the signal strength from an external antenna will be higher
than an internal antenna, but does that make much (any?) difference to
the operation of the GPSDO?


FUNNY, SAD but TRUE story.

After I got hit by lightening for the second time down my telephone
line, I decided I needed to do something about it. So I got onto my
service provider (BT) and asked them what could be done, as my
telephone is fed via an overhead line. After arguing with them for
months, they agree to fit some lightening protection to my telephone
line. The day they came to fit this was a lesson in how incompetent
some technicians, and their managers can be. Of course BT call them
engineers, but this guy is not an engineering in my mind.

BT TECHNICIAN: I need to run an earth wire
ME: That is ok, so I assume you are going to put an earth rod into the ground.
BT TECHNICIAN: No, I wont use an earth rod.
ME: So how are you going to earth it? What sort of wire is it?
BT TECHNICIAN: My manager said to move some earth away with my
fingers, poke the wire into the ground, then move the earth back with
my hand. The wire is 1 mm^2.
ME: That is no good. Let me speak to your manager.

The BT technician then rings his manager, and puts him on the phone. I
explain that is not acceptable.

MANAGER: So how do you suggest we earth it?
ME: I don't know how to do it. This is not my area of expertise, but I
know that what you are proposing, with 1 mm wire and poking the wire
into the ground with your fingers is not acceptable.




Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2014.0.4794 / Virus Database: 4189/8634 - Release Date: 11/26/14





--
V/R
Martin A. Flynn

Chief Technology Officer
Information Age Learning Center
2201 Marconi Road
Wall Township, NJ 07719
Cell: 732-585-9913
Email: mailto:mar...@infoage.org";>mar...@infoage.org
Visit us online at: http://www.infoage.org";>www.infoage.org
Likes us on https://www.facebook.com/infoagesciencemuseum";>Facebook!


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[time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp

[Dr. David Kirkby (Kirkby Microwave Ltd)]

Said mentioned on an earlier thread that if a GPS antenna is used
outside, lightening protection should be used. This immediately
reminded me of something that happened about 10 years ago to me

1) Lightening damaged my ADSL modem. It because totally dead.
2) Every computer and a printer connected to that had the Ethernet
ports blown up.

After a hell of a fight with my insurance company, they paid up on my
household insurance. The total cost was about £10,000, as all were Sun
workstations, so a bit more expensive than a typical home computer.

A few years after that, a similar thing happened, but just the ADSL
modem got destroyed - no computers.

Clearly if an external antenna is put in a high enough E-field or
H-field, it can do damage to the antenna, and potentially anything
connected to it, which would be all your test equipment, in much the
same way all my computers got their Ethernet ports blown up.

I would be *very* reluctant to use an external antenna, which is in
some way connected to a distribution unit into the back of every bit
of test equipment I have. I can see a potential (excuse the pun), of
doing a serious amount of damage.

The only way I would consider doing it, is if there was some optical
isolation. In principle one could modulate a laser at 10 MHz, pass it
down an optical fibre, then have a photodiode to recover the
modulation. Can would obviously be needed not to compromise the
signal, and that might be impossible.

I realize the signal strength from an external antenna will be higher
than an internal antenna, but does that make much (any?) difference to
the operation of the GPSDO?


FUNNY, SAD but TRUE story.

After I got hit by lightening for the second time down my telephone
line, I decided I needed to do something about it. So I got onto my
service provider (BT) and asked them what could be done, as my
telephone is fed via an overhead line. After arguing with them for
months, they agree to fit some lightening protection to my telephone
line. The day they came to fit this was a lesson in how incompetent
some technicians, and their managers can be. Of course BT call them
engineers, but this guy is not an engineering in my mind.

BT TECHNICIAN: I need to run an earth wire
ME: That is ok, so I assume you are going to put an earth rod into the ground.
BT TECHNICIAN: No, I wont use an earth rod.
ME: So how are you going to earth it? What sort of wire is it?
BT TECHNICIAN: My manager said to move some earth away with my
fingers, poke the wire into the ground, then move the earth back with
my hand. The wire is 1 mm^2.
ME: That is no good. Let me speak to your manager.

The BT technician then rings his manager, and puts him on the phone. I
explain that is not acceptable.

MANAGER: So how do you suggest we earth it?
ME: I don't know how to do it. This is not my area of expertise, but I
know that what you are proposing, with 1 mm wire and poking the wire
into the ground with your fingers is not acceptable.




Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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Re: [time-nuts] CentOS 7, Motorola GPS receiver and NTP

[Paul]

On Wed, Nov 26, 2014 at 11:49 AM, xaos  wrote:

> Question: How do I setup NTP with a 1 PPS from serial port
> and the Motorola receiver hooked up?
>

You'll want to review the documents at ntp.org and the list <
http://lists.ntp.org/listinfo/questions>.
The folks there will be happy to assist you.

There are two important points:

1) Until 4.2.8 is released you'll want to build a recent version of 4.2.7.
Don't use 4.2.6

2) Review the many and varied posts on the subtleties of using PPS via ATOM
or as part of a refclock like ONCORE <
http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver30.html>.  It can
have surprising side-effects.
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Re: [time-nuts] Lucent KS-24361

[Hal Murray]

rob...@live.nl said:
> Onother question... here in Europe was use screws and nuts with 'metric'
> (mm) threat. What is used for the mounting screws, how do you call that?

6-32

Web price is $3.49 for a box of 100 at my local hardware chain.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] LTE-Lite Plans

[Don Latham]

yes please!
Don

> On Nov 26, 2014, at 11:45 AM, Jim Sanford  wrote:
> 
> Didier:
> Please DO share.  Thanks!
> Jim
> 
> On 11/25/2014 7:47 PM, Didier Juges wrote:
>> Jim,
>> 
>> I have somewhere a piece of VB 6.0 code that decodes NMEA sentences and puts 
>> it pretty on the screen (at least that's how I remember it :). I am not at 
>> home at the moment but I'll be glad to send it to you if you are interested. 
>> May not do what you want, but it will get you started.
>> 
>> Didier KO4BB
>> www.ko4bb.com
>> 
>> On November 25, 2014 1:42:42 PM CST, Jim Miller  wrote:
>>> I have one of the LTE-Lite 20Mhz units and plan to use it as a
>>> frequency
>>> reference for my ham radio gear. My planned setup is as follows:
>>> 
>>> I'm putting it in the recommended Hammond enclosure powered by a USB
>>> cable
>> >from my PC. I had originally planned to use the wall wart provided but
>>> I
>>> want to get status from the unit without hacking a window in the top to
>>> see
>>> the LEDs so I plan to use TBD software to provide a status check. I
>>> briefly
>>> thought about doing something with an Arduino and display shields but
>>> that
>>> seemed like too much work for now.
>>> 
>>> I'm using a inverting D FF from TI (SN74aup1g80) as a divide by 2 to
>>> provide 10Mhz. The chip and associated passives will be on a little
>>> circuit
>>> board mounted in the open area normally reserved for the external
>>> oscillator. The output of the chip will be connected via a series
>>> resistor
>>> of about 400 ohms to a SMA connector. This resistor will limit the load
>>> on
>>> the FF and the LTE-Lite power source. Power will be taken from C6.
>>> 
>>> This output will only go a few inches to a DEMI 10Mhz 4 way splitter
>>> The
>>> input of the splitter will be equipped with an additional ERA-2+
>>> amplifier
>>> (50 ohm input) which will restore the signal levels lost due to the
>>> series
>>> resistor in the LTE-Lite addon. The DEMI splitter will also be equipped
>>> with a manual power switch which will allow me to kill the output of
>>> the
>>> box if the GPSDO fails for some reason.
>>> 
>>> The little hockey puck antenna will be mounted directly outside the
>>> shack
>>> wall near a south facing wall which will limit the visibility to only
>>> half
>>> the horizon. I'm assuming this will be enough for my modest needs.
>>> 
>>> The four outputs will be used as follows:
>>> 
>>> One will go to the K3 ExtREF to provide an external reference.
>>> 
>>> Two will go to separate TX/RX converters for low frequency (<600Khz)
>>> use
>>> and be used with the transverter I/O on the K3.
>>> 
>>> The last will be used as a general calibration reference.
>>> 
>>> When the power switch on the DEMI splitter is turned off the K3 will
>>> revert
>>> to using its internal TXCO.
>>> 
>>> I leave the PC running 24/7 and the power to the LTE-Lite would only be
>>> interrupted when the PC is rebooted. I don't need a frequency reference
>>> during the reboot time since I always operate my rig with the PC on and
>>> running. The TBD status software will tell me when the LTE-Lite is
>>> synched
>>> up again. The PC is served by a UPS and the shack circuit is one which
>>> is
>>> served by our whole house generator.
>>> 
>>> I have the DEMI splitter built up and working. Now just waiting on
>>> enclosure from Digikey. I should have everything running by mid
>>> December.
>>> 
>>> I still need to figure out what to use for the status software. Ideally
>>> I'd
>>> like an applet to display appropriate status indications on my monitor
>>> for
>>> now I'll examine the uBlox and Putty and if not satisfactory perhaps
>>> I'll
>>> write something in VB.
>>> 
>>> Feedback and suggestions welcome.
>>> 
>>> 73
>>> 
>>> Jim ab3cv
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> 
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> 


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Re: [time-nuts] CentOS 7, Motorola GPS receiver and NTP

[Chris Albertson]

On Wed, Nov 26, 2014 at 10:36 AM, Edesio Costa e Silva <
time-n...@tardis.net.br> wrote:

> Hello!
>
> Current version of NTP supports Motorola Oncore and PPS. Take a look at
> http://support.ntp.org/bin/view/Support/ConfiguringMotorolaOncoreRefclocks
>
> Edésio
>
>
The above is certainly required reading.   But in addition  What I would do
is first set up the NTP server using about 3 or 5 Internet "pool" servers
and make sure your other computers are able to connect.

Next work on connecting the hardware.   Many times you can directly connect
the 5 volt TTL level encode to an RS232 serial port.  They are spec'd for
different voltages but is works most of the time.To be 100% sure you
need to convert the TL level to the rs232 level.

One place where an error is easy to getting the polarity go the PPS signal
correct.  It you invert it then yo are syncing on the trailing edge, you
want the leading edge.

-- 

Chris Albertson
Redondo Beach, California
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[time-nuts] F.S. CORRECTION to model #... EFRATOM SLCR-101 Rb Freq Std

[Don Murray via time-nuts]

 
Hello All...
 
CORRECTION to the Model #...  Sorry
 
SELLING: EFRATOM SLCR-101 Rb Freq Std
10MHz sine out...  +24VDC required
 
This is a very small unit measuring:
3 11/16"  x  4 15/16" (5 1/2" to end of  connector)  x  1 1/16"
 
Slightly bigger than  a 3 x 5 filing card!!
 
I do not have the matching 8 pin female connector
 
Unit was purchased for a past project that never  happened!
 
SOLD AS-IS...  I have never powered up the  unit.
 
Physical condition is good.  No dents.  No  dings.
 
BEST OFFER received by end of day, Dec 5th, is the  winner.
 
I will pay shipping.  
 
U.S. buyer only.  I don't want to hassle with  customs!  Sorry.
 
Payment:  Money Order, Personal check or PayPal, your  choice.
 
Please contact me OFF LIST.  w4wj at  aol.com
 
Thank you.
 
 
73
Don
W4WJ
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[time-nuts] F.S. EFRATOM SLCK-101 Rb Freq Std

[Don Murray via time-nuts]

 
Hello All...
 
SELLING: EFRATOM SLCK-101 Rb Freq Std
10MHz sine out...  +24VDC required
 
This is a very small unit measuring:
3 11/16"  x  4 15/16" (5 1/2" to end of  connector)  x  1 1/16"
 
Slightly bigger than  a 3 x 5 filing card!!
 
I do not have the matching 8 pin female connector
 
Unit was purchased for a past project that never  happened!
 
SOLD AS-IS...  I have never powered up the  unit.
 
Physical condition is good.  No dents.  No  dings.
 
BEST OFFER received by end of day, Dec 5th, is the  winner.
 
I will pay shipping.  
 
U.S. buyer only.  I don't want to hassle with  customs!  Sorry.
 
Payment:  Money Order, Personal check or PayPal, your  choice.
 
Please contact me OFF LIST.  w4wj at  aol.com
 
Thank you.
 
 
73
Don
W4WJ
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Re: [time-nuts] LTE Lite SkyTraq chip info

[Edesio Costa e Silva]

Sorry, seems this did not show first time.

Edésio

On Tue, Nov 25, 2014 at 09:16:20PM -0200, Edesio Costa e Silva wrote:
> Hi!
> 
> Navspark has one board with Glonass
> (http://navspark.mybigcommerce.com/navspark-gl-arduino-compatible-development-board-with-gps-glonass/)
> and one board with Beidou
> (http://navspark.mybigcommerce.com/navspark-bd-arduino-compatible-development-board-with-gps-beidou/).
>  Both
> use a Venus 8 engine.
> 
> There is also a timming version
> (http://www.navspark.com.tw/blog/more-ns-t-programmable-frequency-testing)
> with a programmable frequency output.
> 
> It has a LEON3 Sparc-V8 core and can be programmed with Arduino IDE.
> 
> Edésio
> 
> On Tue, Nov 25, 2014 at 10:29:19PM +, Poul-Henning Kamp wrote:
> > 
> > In message <7da89.51b7dfcf.41a65...@aol.com>, "S. Jackson via time-nuts" 
> > writes
> > :
> > 
> > >Now that the cat is out of the bag - notice that on these boards we used  
> > >the special -T timing version which is more than twice as expensive than  
> > >the 
> > >normal navigation version used by others.. 
> > 
> > That reminds me:  I have yet to see anthing that uses Galileo or
> > GNONASS in a position-hold mode, are those constellations still
> > not competitive with GPS in that niche ?
> > 
> > -- 
> > Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> > p...@freebsd.org | TCP/IP since RFC 956
> > FreeBSD committer   | BSD since 4.3-tahoe
> > Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] LTE-Lite Plans

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 25 November 2014 at 19:51, S. Jackson via time-nuts
 wrote:
> Jim,
>
> please remember you need proper lightning protection if you put the antenna
>  outside..
>
> bye,
> Said
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[time-nuts] Lucent KS-24361 GPS Time vs. UTC

[Mitchell Janoff]

I now have my KS-24361 operating and I've successfully communicated via RS232 
(using the hack described previously) with both SatStat and GPSCon using Win7. 
The time I'm getting out of the unit is the GPS time (+16 seconds). I've tried 
to convert the time to UTC by first changing the mode from continuous output to 
a manual time update(:PTIM:TCOD:CONT 0), and then changing the time to UTC from 
GPS using the :PTIM:UTC 1 command. Neither of these commands seem to work with 
this unit. 

Has anyone experienced this and did you come up with a solution?

Thanks.

Mitch.


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Re: [time-nuts] LTE-Lite Plans

[Jim Sanford]

Didier:
Please DO share.  Thanks!
Jim

On 11/25/2014 7:47 PM, Didier Juges wrote:

Jim,

I have somewhere a piece of VB 6.0 code that decodes NMEA sentences and puts it 
pretty on the screen (at least that's how I remember it :). I am not at home at 
the moment but I'll be glad to send it to you if you are interested. May not do 
what you want, but it will get you started.

Didier KO4BB
www.ko4bb.com

On November 25, 2014 1:42:42 PM CST, Jim Miller  wrote:

I have one of the LTE-Lite 20Mhz units and plan to use it as a
frequency
reference for my ham radio gear. My planned setup is as follows:

I'm putting it in the recommended Hammond enclosure powered by a USB
cable

>from my PC. I had originally planned to use the wall wart provided but

I
want to get status from the unit without hacking a window in the top to
see
the LEDs so I plan to use TBD software to provide a status check. I
briefly
thought about doing something with an Arduino and display shields but
that
seemed like too much work for now.

I'm using a inverting D FF from TI (SN74aup1g80) as a divide by 2 to
provide 10Mhz. The chip and associated passives will be on a little
circuit
board mounted in the open area normally reserved for the external
oscillator. The output of the chip will be connected via a series
resistor
of about 400 ohms to a SMA connector. This resistor will limit the load
on
the FF and the LTE-Lite power source. Power will be taken from C6.

This output will only go a few inches to a DEMI 10Mhz 4 way splitter
The
input of the splitter will be equipped with an additional ERA-2+
amplifier
(50 ohm input) which will restore the signal levels lost due to the
series
resistor in the LTE-Lite addon. The DEMI splitter will also be equipped
with a manual power switch which will allow me to kill the output of
the
box if the GPSDO fails for some reason.

The little hockey puck antenna will be mounted directly outside the
shack
wall near a south facing wall which will limit the visibility to only
half
the horizon. I'm assuming this will be enough for my modest needs.

The four outputs will be used as follows:

One will go to the K3 ExtREF to provide an external reference.

Two will go to separate TX/RX converters for low frequency (<600Khz)
use
and be used with the transverter I/O on the K3.

The last will be used as a general calibration reference.

When the power switch on the DEMI splitter is turned off the K3 will
revert
to using its internal TXCO.

I leave the PC running 24/7 and the power to the LTE-Lite would only be
interrupted when the PC is rebooted. I don't need a frequency reference
during the reboot time since I always operate my rig with the PC on and
running. The TBD status software will tell me when the LTE-Lite is
synched
up again. The PC is served by a UPS and the shack circuit is one which
is
served by our whole house generator.

I have the DEMI splitter built up and working. Now just waiting on
enclosure from Digikey. I should have everything running by mid
December.

I still need to figure out what to use for the status software. Ideally
I'd
like an applet to display appropriate status indications on my monitor
for
now I'll examine the uBlox and Putty and if not satisfactory perhaps
I'll
write something in VB.

Feedback and suggestions welcome.

73

Jim ab3cv
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Re: [time-nuts] CentOS 7, Motorola GPS receiver and NTP

[Edesio Costa e Silva]

Hello!

Current version of NTP supports Motorola Oncore and PPS. Take a look at
http://support.ntp.org/bin/view/Support/ConfiguringMotorolaOncoreRefclocks

Edésio

On Wed, Nov 26, 2014 at 11:49:59AM -0500, xaos wrote:
> Hello everyone.
> 
> Currently my Stratum 1 NTP server is made up of the following:
> 
> Pentium 4 Motherboard, Single core, 1.4GHz., 1GB memory
> Slackware Linux, 11.0.0
> PPSkit-2.1.7 Kernel
> uname -a:
> Linux timelord 2.4.33.3-NANO #1 Fri Nov 12 21:28:51 EST 2010 i686
> pentium4 i386 GNU/Linux
> 
> Motorola, GPS Receiver Version: 3, Revision: 1, Software Date: 1A30,
> Model: R5222U1114/[UT], Serial: R0AZSU
> 
> As far as I know the PPSKit was never released for the
> later kernels and this machine is showing it's age.
> I want to get a new box and run CentOS 7 on it.
> 
> Question: How do I setup NTP with a 1 PPS from serial port
> and the Motorola receiver hooked up?
> 
> I hope that some here have done this already and
> I wont have to start from scratch.
> 
> I was thinking about the Atom driver?
> How do I tell the driver to use the data from the serial port?
> 
> Any help would be greatly appreciated.
> 
> George, N2FGX
> 
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[time-nuts] F.S. HP 10544A Xtal Osc

[Don Murray via time-nuts]

Hello All...
 
SELLING: HP 10544A Xtal Osc
 
Osc Assembly and converter board that goes from  the
Osc TRW/Cinch connector to 15 pin edge connector.
 
Unit was purchased for a past project that never  happened!
 
SOLD AS-IS...  I have never powered up the  unit.
 
Physical condition is good.
 
BEST OFFER received by end of day, Dec 5th, is the  winner.
 
I will pay shipping.  
 
U.S. buyer only.  I don't want to hassle with  customs!  Sorry.
 
Payment:  Money Order, Personal check or PayPal, your  choice.
 
Please contact me OFF LIST.  w4wj at  aol.com
 
Thank you.
 
 
73
Don
W4WJ
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Re: [time-nuts] Lucent KS-24361

[Rob040 .]

List,

I received my set (REF-0 & REF-1) today and both units have production date 
2000 week 5 and were packed in blue foam and a mylar ESD save bag.
The outer box was opened by eBay, easy to detect due to the eBay tape that was 
used to close the box again. Maybe because it was shipped via UK and eBay is 
taking care of the import duties and taxes. The inner boxes were still original.

Nice small rugged units!

I recognized the GPS unit as Oncore UT+, anyone already checked the software 
version? V2.2 or V3.2 seems to be the best ones, the others may cause some 
problems, as I remember from older posts.

Onother question... here in Europe was use screws and nuts with 'metric' (mm) 
threat. What is used for the mounting screws, how do you call that? Maybe I can 
find some nuts on eBay as well. I want to make a simple rack for the units.

Best regards,

Rob.


> Date: Tue, 25 Nov 2014 19:26:16 -0500
> From: planoph...@aei.ca
> To: time-nuts@febo.com
> Subject: [time-nuts] Lucent KS-24361
> 
> received my Lucent KS-24361 today.
> 
> just as being described, appears new in original box. I bought one of 
> the pairs REF-0 and REF-1 plus one additional REF-0. There is a date of 
> manufacture on each box, the pair was 2000 week 20 and 21 whereas the 
> additional REF-0 was 2000 week 5.
> 
> I mention this only in passing as the packaging inside the box for 
> additional REF-0 was a bit different than for the pair. The pair was 
> packed with the pink colored foam and the units were wrapped in clear 
> plastic bag whereas the individual REF-0 had a blue colored foam and the 
> unit was wrapped in a mylar ESD bag.  Perhaps an indication of different 
> sources or different manufacturing or assembly plants?
> 
> It will be a while til everything is hooked up and working but in the 
> mean time I continue to the discussion on the list.
> 
> cheers, Graham ve3gtc
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Re: [time-nuts] LTE Lite SkyTraq chip info

[Neil Schroeder]

Poul are you teferring  to the lte lite specifically?  My Resolution SMT GG
will go single sat or OD mode with only non GPS sats available.

On Tuesday, November 25, 2014, Poul-Henning Kamp  wrote:

> 
> In message <7da89.51b7dfcf.41a65...@aol.com >, "S. Jackson
> via time-nuts" writes
> :
>
> >Now that the cat is out of the bag - notice that on these boards we used
> >the special -T timing version which is more than twice as expensive than
> the
> >normal navigation version used by others..
>
> That reminds me:  I have yet to see anthing that uses Galileo or
> GNONASS in a position-hold mode, are those constellations still
> not competitive with GPS in that niche ?
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] LTE Lite SkyTraq chip info

[Edesio Costa e Silva]

Hi!

Navspark has one board with Glonass
(http://navspark.mybigcommerce.com/navspark-gl-arduino-compatible-development-board-with-gps-glonass/)
and one board with Beidou
(http://navspark.mybigcommerce.com/navspark-bd-arduino-compatible-development-board-with-gps-beidou/).
 Both
use a Venus 8 engine.

There is also a timming version
(http://www.navspark.com.tw/blog/more-ns-t-programmable-frequency-testing)
with a programmable frequency output.

It has a LEON3 Sparc-V8 core and can be programmed with Arduino IDE.

Edésio

On Tue, Nov 25, 2014 at 10:29:19PM +, Poul-Henning Kamp wrote:
> 
> In message <7da89.51b7dfcf.41a65...@aol.com>, "S. Jackson via time-nuts" 
> writes
> :
> 
> >Now that the cat is out of the bag - notice that on these boards we used  
> >the special -T timing version which is more than twice as expensive than  
> >the 
> >normal navigation version used by others.. 
> 
> That reminds me:  I have yet to see anthing that uses Galileo or
> GNONASS in a position-hold mode, are those constellations still
> not competitive with GPS in that niche ?
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] LTE-Lite Plans

[Said Jackson via time-nuts]

Jim,

A double tragedy. I was working with Jim Williams on one of our designs a week 
before he passed away. Then Bob crashed his car coming from Jim's funeral 
(grief?) and died too.

Two of the greatest analog minds lost within days.

Bye,
Said

Sent From iPhone

> On Nov 26, 2014, at 9:34, Jim Sanford  wrote:
> 
> Interesting comment. . . . I'm reading Bob's book now!
> Never met him, but felt like I knew him from all of his writings.
> 
> His death was very sad
> 
> Jim
> wb4...@amsat.org
> 
>> On 11/26/2014 12:20 PM, Didier Juges wrote:
>> Said,
>> 
>> Your drawing looks better than those byBob Pease,  and he was never
>> embarrassed by his :)
>> Thank you for your extensive contributions to time nuts
>> 
>> Didier KO4BB
>> 
>> 
>> On Tue, Nov 25, 2014 at 7:28 PM, S. Jackson via time-nuts <
>> time-nuts@febo.com> wrote:
>> 
>>> Guys,
>>> 
>>> I never expected such an intense discussion about using and buffering  the
>>> outputs from the LTE-Lite board since the actual circuit to use can  be
>>> quite simple.
>>> 
>>> To address these questions, I drew up a simple schematic that uses a DIP-14
>>>  74AC04 gate, six resistors, and two caps. Everyone who can solder should
>>> be able  to build this simple circuit as a dead-bug type build on a
>>> copper-clad  board.
>>> 
>>> This circuit will buffer all three outputs (1PPS, TCXO RF, and Synthesixed
>>> RF) of the LTE-Lite eval board with CMOS 3.0V levels that can drive 50 Ohms
>>>  terminations. For simplicity I grab the 3.0V power from the DIP-14 TCXO on
>>> pin  14 of that part on the eval board, even though I would strongly
>>> suggest to use a  separate low noise 3.3V or 5V power supply to power the
>>> 74AC04
>>> chip.
>>> 
>>> You can add 100nF caps in series to the two RF signals before they feed
>>> into the coax output connectors for less power consumption and removing DC
>>> for
>>>  instruments that don't like DC inputs.
>>> 
>>> Using a single IC for the three signals will result in crosstalk between
>>> the signals, but it should be clear from the schematics how one could break
>>> up the signals by using three independent ICs to minimize crosstalk.
>>> 
>>> We use this circuit in a small box here using SMT components, and it works
>>> really well.
>>> 
>>> Excuse my horrible writing, using keyboards has made my fingers  numb..
>>> 
>>> Hope that helps,
>>> Said
>>> 
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>> 
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>> 
> 
> 
> 
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Re: [time-nuts] LTE-Lite Plans

[Jim Sanford]

Interesting comment. . . . I'm reading Bob's book now!
Never met him, but felt like I knew him from all of his writings.

His death was very sad

Jim
wb4...@amsat.org

On 11/26/2014 12:20 PM, Didier Juges wrote:

Said,

Your drawing looks better than those byBob Pease,  and he was never
embarrassed by his :)
Thank you for your extensive contributions to time nuts

Didier KO4BB


On Tue, Nov 25, 2014 at 7:28 PM, S. Jackson via time-nuts <
time-nuts@febo.com> wrote:


Guys,

I never expected such an intense discussion about using and buffering  the
outputs from the LTE-Lite board since the actual circuit to use can  be
quite simple.

To address these questions, I drew up a simple schematic that uses a DIP-14
  74AC04 gate, six resistors, and two caps. Everyone who can solder should
be able  to build this simple circuit as a dead-bug type build on a
copper-clad  board.

This circuit will buffer all three outputs (1PPS, TCXO RF, and Synthesixed
RF) of the LTE-Lite eval board with CMOS 3.0V levels that can drive 50 Ohms
  terminations. For simplicity I grab the 3.0V power from the DIP-14 TCXO on
pin  14 of that part on the eval board, even though I would strongly
suggest to use a  separate low noise 3.3V or 5V power supply to power the
74AC04
chip.

You can add 100nF caps in series to the two RF signals before they feed
into the coax output connectors for less power consumption and removing DC
for
  instruments that don't like DC inputs.

Using a single IC for the three signals will result in crosstalk between
the signals, but it should be clear from the schematics how one could break
up the signals by using three independent ICs to minimize crosstalk.

We use this circuit in a small box here using SMT components, and it works
really well.

Excuse my horrible writing, using keyboards has made my fingers  numb..

Hope that helps,
Said

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Re: [time-nuts] LTE-Lite Plans

[Said Jackson via time-nuts]

:)

Sent From iPhone

> On Nov 26, 2014, at 9:20, Didier Juges  wrote:
> 
> Said,
> 
> Your drawing looks better than those by Bob Pease, and he was never 
> embarrassed by his :)
> Thank you for your extensive contributions to time nuts
> 
> Didier KO4BB
> 
> 
>> On Tue, Nov 25, 2014 at 7:28 PM, S. Jackson via time-nuts 
>>  wrote:
>> Guys,
>> 
>> I never expected such an intense discussion about using and buffering  the
>> outputs from the LTE-Lite board since the actual circuit to use can  be
>> quite simple.
>> 
>> To address these questions, I drew up a simple schematic that uses a DIP-14
>>  74AC04 gate, six resistors, and two caps. Everyone who can solder should
>> be able  to build this simple circuit as a dead-bug type build on a
>> copper-clad  board.
>> 
>> This circuit will buffer all three outputs (1PPS, TCXO RF, and Synthesixed
>> RF) of the LTE-Lite eval board with CMOS 3.0V levels that can drive 50 Ohms
>>  terminations. For simplicity I grab the 3.0V power from the DIP-14 TCXO on
>> pin  14 of that part on the eval board, even though I would strongly
>> suggest to use a  separate low noise 3.3V or 5V power supply to power the 
>> 74AC04
>> chip.
>> 
>> You can add 100nF caps in series to the two RF signals before they feed
>> into the coax output connectors for less power consumption and removing DC 
>> for
>>  instruments that don't like DC inputs.
>> 
>> Using a single IC for the three signals will result in crosstalk between
>> the signals, but it should be clear from the schematics how one could break
>> up the signals by using three independent ICs to minimize crosstalk.
>> 
>> We use this circuit in a small box here using SMT components, and it works
>> really well.
>> 
>> Excuse my horrible writing, using keyboards has made my fingers  numb..
>> 
>> Hope that helps,
>> Said
>> 
>> ___
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> 
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Re: [time-nuts] NIST isolation amplifiers

[Bruce Griffiths]

Almost. 1:1:2 (turns ratio) transformers used in each stage and 1:1 
transformer on input.  This allows a lower power supply voltage to be used.
One thing to watch with minicircuits transformers is core saturation due to 
dc flowing in the windings.
Bruce
On Wednesday, November 26, 2014 08:52:14 AM Charles Steinmetz wrote:
> Bruce wrote:
> >A single 2N or equivalent transistor in a suitable circuit
> >dissipating about 200mW or so can achieve a reverse isolation of
> >35dB with distortion of around -40dBc (output +13dBm) with a gain of
> >unity, and an output impedance of 50 ohms with a PN floor of around
> >-180dBc/Hz or so.
> 
> For those wondering, I suspect Bruce had in mind something like the
> attached  (he posted the basic design a few years ago).  I built 8
> channels using toroids on FT37-61 cores.  I think the Mini-Circuits
> T622 should work, but I have not tried it.  The analyses are from my
> simulation, and the constructed unit performed similarly.  The Miller
> effect limits fan-out to about 10 for a 10MHz distribution
> amp.  [Note: the 50 ohm resistors on the outputs represent the
> external loads, and are not part of the amplifier.]
> 
> Best regards,
> 
> Charles

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Re: [time-nuts] LTE-Lite Plans

[Didier Juges]

Said,

Your drawing looks better than those by Bob Pease, and he was never
embarrassed by his :)
Thank you for your extensive contributions to time nuts

Didier KO4BB


On Tue, Nov 25, 2014 at 7:28 PM, S. Jackson via time-nuts <
time-nuts@febo.com> wrote:

> Guys,
>
> I never expected such an intense discussion about using and buffering  the
> outputs from the LTE-Lite board since the actual circuit to use can  be
> quite simple.
>
> To address these questions, I drew up a simple schematic that uses a DIP-14
>  74AC04 gate, six resistors, and two caps. Everyone who can solder should
> be able  to build this simple circuit as a dead-bug type build on a
> copper-clad  board.
>
> This circuit will buffer all three outputs (1PPS, TCXO RF, and Synthesixed
> RF) of the LTE-Lite eval board with CMOS 3.0V levels that can drive 50 Ohms
>  terminations. For simplicity I grab the 3.0V power from the DIP-14 TCXO on
> pin  14 of that part on the eval board, even though I would strongly
> suggest to use a  separate low noise 3.3V or 5V power supply to power the
> 74AC04
> chip.
>
> You can add 100nF caps in series to the two RF signals before they feed
> into the coax output connectors for less power consumption and removing DC
> for
>  instruments that don't like DC inputs.
>
> Using a single IC for the three signals will result in crosstalk between
> the signals, but it should be clear from the schematics how one could break
> up the signals by using three independent ICs to minimize crosstalk.
>
> We use this circuit in a small box here using SMT components, and it works
> really well.
>
> Excuse my horrible writing, using keyboards has made my fingers  numb..
>
> Hope that helps,
> Said
>
> ___
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>
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[time-nuts] HP10811 Double oven, oven jump?

[Dan Kemppainen]

Hi All,

I've been playing with some double oven HP10811's. I've been monitoring 
the internal oven feedback vs. temperature and noticed something 
interesting last night. There was a sudden step change in internal oven 
feedback voltage. This is the voltage coming from the amplifier 
monitoring the bridge that feeds the heater transistors.


The step change was on the order of two or three times as large as 
normal swings caused by the furnace cycling in the house. The voltage 
was being monitored by a 8Ch ADC card. All of the other voltages on that 
card were stable.


The jump was very small. I don't recall exactly (Not near that unit 
right now), but somewhere around a mV or less. But it was very sudden 
and compared to everything else on that line, or other voltages being 
monitored.


I'm wondering if there is something going on in there that may require 
attention. Bad solder, cracked trace, bad component???


Any idea what might have caused this?

Has anyone seen anything similar?

Thanks,
Dan

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[time-nuts] CentOS 7, Motorola GPS receiver and NTP

[xaos]

Hello everyone.

Currently my Stratum 1 NTP server is made up of the following:

Pentium 4 Motherboard, Single core, 1.4GHz., 1GB memory
Slackware Linux, 11.0.0
PPSkit-2.1.7 Kernel
uname -a:
Linux timelord 2.4.33.3-NANO #1 Fri Nov 12 21:28:51 EST 2010 i686
pentium4 i386 GNU/Linux

Motorola, GPS Receiver Version: 3, Revision: 1, Software Date: 1A30,
Model: R5222U1114/[UT], Serial: R0AZSU

As far as I know the PPSKit was never released for the
later kernels and this machine is showing it's age.
I want to get a new box and run CentOS 7 on it.

Question: How do I setup NTP with a 1 PPS from serial port
and the Motorola receiver hooked up?

I hope that some here have done this already and
I wont have to start from scratch.

I was thinking about the Atom driver?
How do I tell the driver to use the data from the serial port?

Any help would be greatly appreciated.

George, N2FGX

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Re: [time-nuts] LTE Lite SkyTraq chip info

[paul swed]

As I say a most useless website.
Regards


On Tue, Nov 25, 2014 at 10:35 PM, Dave Martindale  wrote:

> I spent a bit of time poking around the SkyTraq web site on the weekend.  I
> couldn't find a datasheet for the chip on the LTE-Lite - perhaps it's so
> new that SkyTraq has not put together the datasheet yet.
>
> Under "timing", they only list the Venus638LPx-T, which is a older (2011
> copyright on the datasheet) 65-channel receiver.  The LTE-Lite
> documentation mentions 65 channels somewhere too, suggesting that the
> LTE-Lite started out using this chip.  Under navigation receivers, Skytraq
> lists the newer (2013) Venus838FLPx with 167 channels.  So I would assume
> that the Venus838LPx-T-L used in the LTE-Lite is the same 167-channel
> hardware with timing firmware, and that the LTE-Lite switched from the
> 638LPx-T to the 838LPx-T-L sometime during development.
>
> - Dave
>
> On Tue, Nov 25, 2014 at 5:12 PM, S. Jackson via time-nuts <
> time-nuts@febo.com> wrote:
>
> > Now that the cat is out of the bag - notice that on these boards we used
> > the special -T timing version which is more than twice as expensive than
> > the
> > normal navigation version used by others.. I personally use the uBlox
> > software because the Skytrack software had a habit of crashing itself and
> > my
> > computer from time to time..
> >
> >
> > In a message dated 11/25/2014 14:02:41 Pacific Standard Time,
> > paulsw...@gmail.com writes:
> >
> > Here is  a link to a company that at least shares details of the SkyTraq
> > venus 8  chip on the LTE-Lite. The actual skytraq sites is pretty
> useless.
> >
> >
> >
> https://www.tindie.com/products/smokingresistor/venus838flpx-gps-breakout-bo
> > ard/
> >
> > There  is a program that will read the nema codes and such also.
> > Have used it and  its not better or worse then ublox. A bit of humor it
> > only
> > ever shows Asia  for the ground track.
> >
> > The venus 8 seems to have a lot of capability.  Not sure how to get to
> it,
> > but the fact is for the LTE Lite its not needed.  It has a single job to
> > perform.
> > It would be curious to obtain the board  tindie sells because it supports
> > all of the satellites. But have to say  thats a project for another day
> > wa down the list.
> > But at least you  can have some further technical details for the
> system.
> > Regards
> > Paul
> > WB8TSL
> > ___
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Re: [time-nuts] NIST isolation amplifiers

[Charles Steinmetz]

Bruce wrote:

A single 2N or equivalent transistor in a suitable circuit 
dissipating about 200mW or so can achieve a reverse isolation of 
35dB with distortion of around -40dBc (output +13dBm) with a gain of 
unity, and an output impedance of 50 ohms with a PN floor of around 
-180dBc/Hz or so.


For those wondering, I suspect Bruce had in mind something like the 
attached  (he posted the basic design a few years ago).  I built 8 
channels using toroids on FT37-61 cores.  I think the Mini-Circuits 
T622 should work, but I have not tried it.  The analyses are from my 
simulation, and the constructed unit performed similarly.  The Miller 
effect limits fan-out to about 10 for a 10MHz distribution 
amp.  [Note: the 50 ohm resistors on the outputs represent the 
external loads, and are not part of the amplifier.]


Best regards,

Charles


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Re: [time-nuts] Phase, One edge or two? (was Digital mixing with a D Flip Flop)

[pablo alvarez]

>  ...The problem is that this decoded data clock is locked to the incoming
> data by means of a PFD in the Spartan6/Virtex6 GTP. The PFD normaly only
> looks at rising edges, so any change in the clock duty cycle will translate
> in a phase change in the falling edge and not in the rising edge. I am not
> sure this is really the case, but we certainly had this discussion at the
> time, but I don't remember if there was any real measurement made.
>

Well, I don't like correcting myself but this is not right. The PFD is only
used in the TX path. In the RX path the clock is decoded using CDR using a
VCO which operates at the 1.25Gb/s and then is divided down to 125, so the
duty cycle problem is not really a big issue here. In any case it is the
typical bug one tries to avoid when doing precise timing. Notice that in
this case it would not have been a good idea to sample with the system
clock falling edge to increase the performance.

pablo




>
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Re: [time-nuts] anyone tried the cheap Lea-6T modules seen on eBay?

[Dale J. Robertson]

They use the LEA-6T for DIY drone applications because it provides raw 
carrier phase information. The raw carrier info is compared with the raw 
carrier data from a nearby fixed (and surveyed for an extended period) GPS 
receiver.  The position error of the fixed station is subtracted from the 
reported position of the 'roamer' , the resultant position is supposed to be 
accurate to within 10cm of true position. All this is done via a suite of 
open source applications called RTKLib. ublox was the only relatively 
inexpensive gps module that provided the phase data needed to make all this 
work. More recently a few of the other module vendors including skytraq 
(sp?) have provided this function. Getting a module that provided carrier 
data for less than $100 US was a big deal for the drone community. The only 
other cheap module that I know about is the synergy ssr-6t which works very 
well but (very minor nit) has a small pitch connector that was a nuisance to 
make the interconnects for. These chinese modules look to be much easier to 
interface. I'll probably buy one eventually just to see if the deviations 
from the pcb design rec's have impacted the performance in my application.


Regards,
Dale NV8U

-Original Message- 
From: S. Jackson via time-nuts

Sent: Tuesday, November 25, 2014 2:41 PM
To: ewkeh...@aol.com ; time-nuts@febo.com
Subject: Re: [time-nuts] anyone tried the cheap Lea-6T modules seen on eBay?

Bert,

the LEA-6T actually has software bugs that show up in moving  applications
and that need to be handled by the users' software, and they are  selling it
for drone applications. Without any monitoring for these bugs the  units
may really only be useful for stationary applications.

Why they would choose the 6T unit instead of a non-T unit at half the price
would only be because they got those as surplus really cheap I would
think.

bye,
Said


In a message dated 11/25/2014 09:50:12 Pacific Standard Time,
time-nuts@febo.com writes:

A Lea-6T  is only worth any extra money if you are using the sawtooth
correction data coming out of it. With out correction a $ 14 unit is just
as
good.
Bert Kehren


In a message dated 11/25/2014  11:25:34 A.M. Eastern Standard Time,
michael.c...@sfr.fr  writes:

You may  have seen them as   in

There   are other sellers with the same.
My idea was to see if one was suitable  as  a 1PPS locking source for my
PRS10. The interest for me being  that it powers  directly from a USB
connection
and can be configured  with the Ublox’s u-center  software, so
implementation is a no  brainer.
All I needed to do was to  replace the patch antenna with an  SMA-F
connector and add a wire for the 1PPS.  Despite having less  than ideal
antenna
position, once the survey was complete  I was  getting +/-20ns jitter on
the 1PPS
which is within spec and stable  over  the day.
However I was most disappointed to see that the 1PPS  output  voltage is
only 2.16 +/-0.4V. According to spec it should be  Vcc+/-0.4V and I  have
Vcc
measuring 3.3V.  I can’t see the  board trace but the measured  voltage is
the
same on the PPS pad next  to the JST-SH connector and on the GPS  modules
pin
28 so it is not a  board issue. Unfortunately this is too low to  tickle
the
PRS10 1PPS  input. I guess I could add a buffer or AND gate to fix  it, but
that  sort of defeats the object and introduces extra jitter and  offset.
It  is however enough for a Raspberry-Pi GPIO input, so I have  relegated
it
to NTP PPS.

Has anyone out there got one of these and  seen  the same symptoms? Or
maybe
you have one and it is OK? I’d like to   know.

You will be able to see from the eBay photos that this a  6T-0-000  version
which is an early version and it could be that they  are cheap as  some/all
have this defect. So   beware.


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Re: [time-nuts] Phase, One edge or two? (was Digital mixing with a D Flip Flop)

[pablo alvarez]

Hi Warren,

I arrive a bit late to this discussion, but I hope I can help. I guess the
reason for using only one edge is based on the fact that WR is originally
designed to measure the phase between a decoded data clock and a system
clock. The problem is that this decoded data clock is locked to the
incoming data by means of a PFD in the Spartan6/Virtex6 GTP. The PFD
normaly only looks at rising edges, so any change in the clock duty cycle
will translate in a phase change in the falling edge and not in the rising
edge. I am not sure this is really the case, but we certainly had this
discussion at the time, but I don't remember if there was any real
measurement made.

Cheers,

Pablo
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[time-nuts] Comic

[Hal Murray]

http://www.gocomics.com/pickles/2014/11/26

-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] NIST isolation amplifiers

[Charles Steinmetz]

Bruce wrote:


Another issue is that if even one output needs high reverse isolation and
low crosstalk, then even those outputs that arent so critical will also need
high reverse isolation and low crosstalk to avoid degrading the crosstalk
to the critical output.


This brings up the distinction between *isolation* amplifiers and 
*distribution* amplifiers.  Most of us need a dozen or three feeds 
for various test equipment, radios, etc.  These feeds should have 50 
ohm output impedance, moderate isolation (35dB or more), and should 
not noticeably degrade the noise, PN, distortion, or xDEV of the 
source.  That is the job of a distribution amp.


I would generally not use anything like one of the NIST circuits for 
this, but rather some version of a two- or three-transistor Class A 
buffer amplifier.  There are lots of circuits to choose from.  Many 
are transformer (or autoformer) coupled, some are not (the JPL 
circuits come to mind) and can also be used to distribute lower 
frequencies.  You can get build-out the NIST way (buffer amp input 
impedance high so you parallel a bunch of them at the input 
connector), or by using one stage with low output impedance to drive 
a number of output amplifiers in parallel, or by using an amplifier 
with very low output impedance (perhaps a high-current monolithic 
amplifier) to drive a number of 50 ohm build-out resistors, or by 
fanning out with CMOS logic and following each CMOS final buffer with 
a Tee network to generate sine waves.


Then there are the times when you are making measurements of 
oscillators and must absolutely ensure that there is no interaction 
between them.  That is the job of an isolation amp.  Rarely will you 
need more than two or three feeds per oscillator, so what you need 
are several, one-to-three iso amps (one for each oscillator).  Here, 
something like the NIST amplifiers makes sense.


Note that I'm advocating distributing sine waves exclusively, NOT 
square waves or pulse trains.  You will find that it is hard enough 
keeping 1, 5, or 10 MHz from getting into everything in the shop (and 
radio room), without adding the much-increased difficulty of keeping 
all of the harmonics under control.  Also, you would like the 
harmonic content to be rather lower than is often thought because (i) 
even harmonics cause asymmetry, which can cause phase modulation when 
the signal is AC coupled or feeds a comparator-type zero-cross 
detector, and (ii) variations in the phase of harmonics in relation 
to the fundamental cause phase modulation (this is "harmonic 
dispersion," which is caused by temperature changes and other circuit 
variations such as modulation of semiconductor capacitances by low 
frequecies).  NIST published a paper on this (see Walls and 
Ascarrunz, "The Effect of Harmonic Distortion on Phase Errors in 
Frequency Distribution and Synthesis").


Best regards,

Charles



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Re: [time-nuts] NIST isolation amplifiers

[Bruce Griffiths]

A single 2N or equivalent transistor in a suitable circuit dissipating 
about 200mW or so can achieve a reverse isolation of 35dB with distortion of 
around -40dBc (output +13dBm) with a gain of unity, and an output impedance of 
50 ohms with a PN floor of around -180dBc/Hz or so.
Bruce 

 On Wednesday, 26 November 2014 9:13 PM, Charles Steinmetz 
 wrote:
   

 Bruce wrote:

>Another issue is that if even one output needs high reverse isolation and
>low crosstalk, then even those outputs that arent so critical will also need
>high reverse isolation and low crosstalk to avoid degrading the crosstalk
>to the critical output.

This brings up the distinction between *isolation* amplifiers and 
*distribution* amplifiers.  Most of us need a dozen or three feeds 
for various test equipment, radios, etc.  These feeds should have 50 
ohm output impedance, moderate isolation (35dB or more), and should 
not noticeably degrade the noise, PN, distortion, or xDEV of the 
source.  That is the job of a distribution amp.

I would generally not use anything like one of the NIST circuits for 
this, but rather some version of a two- or three-transistor Class A 
buffer amplifier.  There are lots of circuits to choose from.  Many 
are transformer (or autoformer) coupled, some are not (the JPL 
circuits come to mind) and can also be used to distribute lower 
frequencies.  You can get build-out the NIST way (buffer amp input 
impedance high so you parallel a bunch of them at the input 
connector), or by using one stage with low output impedance to drive 
a number of output amplifiers in parallel, or by using an amplifier 
with very low output impedance (perhaps a high-current monolithic 
amplifier) to drive a number of 50 ohm build-out resistors, or by 
fanning out with CMOS logic and following each CMOS final buffer with 
a Tee network to generate sine waves.

Then there are the times when you are making measurements of 
oscillators and must absolutely ensure that there is no interaction 
between them.  That is the job of an isolation amp.  Rarely will you 
need more than two or three feeds per oscillator, so what you need 
are several, one-to-three iso amps (one for each oscillator).  Here, 
something like the NIST amplifiers makes sense.

Note that I'm advocating distributing sine waves exclusively, NOT 
square waves or pulse trains.  You will find that it is hard enough 
keeping 1, 5, or 10 MHz from getting into everything in the shop (and 
radio room), without adding the much-increased difficulty of keeping 
all of the harmonics under control.  Also, you would like the 
harmonic content to be rather lower than is often thought because (i) 
even harmonics cause asymmetry, which can cause phase modulation when 
the signal is AC coupled or feeds a comparator-type zero-cross 
detector, and (ii) variations in the phase of harmonics in relation 
to the fundamental cause phase modulation (this is "harmonic 
dispersion," which is caused by temperature changes and other circuit 
variations such as modulation of semiconductor capacitances by low 
frequecies).  NIST published a paper on this (see Walls and 
Ascarrunz, "The Effect of Harmonic Distortion on Phase Errors in 
Frequency Distribution and Synthesis").

Best regards,

Charles



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[time-nuts] SR620 - "register as being warmed up" ????

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I am hoping to buy a SR620 from a seller who is not familiar with the
instrument,  but who

1) Has knowledge of electronic test equipment in general.

2) Is willing to test the SR620 before an international shipment.

This puts me in a somewhat better position than typicall eBay sale with
comments such as

a) "Comes from a working environment" or

b) "Plugged it in and it lights up".

I gave the seller a link to the manual and asked him to

1) run the autocal procedure described on page 18 of the manual (page 33 of
the PDF)

2) Do at least the front panel tests on page 61 (page 77 of the PDF), plus
any other he could do - it is unreasonble to expect him to do them.

He wrote back and said

"I tried to run that test, but the unit never registered itself as being
warmed up. I waited about two hours with the calibration switch
in both positions. Do you know anything about these?"

I am a bit confused by his comment. Can anyone understand what he may mean,
or suggest how one might verify  the instrument can be tested? As far as I
can see from the manual,  there's no indication when the oven is warm.  The
instrument has the high stability timebase option.

Dave
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