[time-nuts] Buffering the 1pps output from a Z3801A

[Peter Vince]

Bruce, et al,

The 1pps output of an HP Z3801A and Trimble Thunderbolt is 
only available (as far as I know) as a balanced ECL signal on the 
25-pin connector, with dire warnings in the manuals about not 
earthing either side of the ECL signals.  Would you be able to advise 
on a simple buffer circuit that would allow me to drive the usual 
unbalanced 50-ohm coax please?

Thanks,

Peter Vince  (London, England)

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Re: [time-nuts] Buffering the 1pps output from a Z3801A

[John Franke]

See;  http://www.realhamradio.com/sidecar.htm

John WA4WDL

- Original Message - 
From: "Peter Vince" <[EMAIL PROTECTED]>
To: 
Sent: Wednesday, March 26, 2008 9:29 AM
Subject: [time-nuts] Buffering the 1pps output from a Z3801A


> Bruce, et al,
>
> The 1pps output of an HP Z3801A and Trimble Thunderbolt is
> only available (as far as I know) as a balanced ECL signal on the
> 25-pin connector, with dire warnings in the manuals about not
> earthing either side of the ECL signals.  Would you be able to advise
> on a simple buffer circuit that would allow me to drive the usual
> unbalanced 50-ohm coax please?
>
> Thanks,
>
> Peter Vince  (London, England)
>
> ___
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> 


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[time-nuts] anyone built a replacement antenna for a Spectracom 8170?

[Scott Burris]

Hi,

I'm finally getting around to trying to get a Spectracom 8170 WWVB
receiver doing something useful.
Unfortunately, I only have the unit, not the antenna/preamp.

Anyone built a replacement antenna for this?  Could this be made to work with
a commercial ferrite core antenna, maybe something like

http://www.c-max-time.com/products/showProduct.php?id=18

with a little preamp circuit of some sort run off the 12v supplied by the 8170?

If someone has already built something like this and could point me to
a schematic, that would be much appreciated.  Otherwise I guess I'll roll
something of my own.

Thanks.

Scott

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Re: [time-nuts] Buffering the 1pps output from a Z3801A

[Magnus Danielson]

From: Peter Vince <[EMAIL PROTECTED]>
Subject: [time-nuts] Buffering the 1pps output from a Z3801A
Date: Wed, 26 Mar 2008 13:29:36 +
Message-ID: <[EMAIL PROTECTED]>

> Bruce, et al,
> 
>   The 1pps output of an HP Z3801A and Trimble Thunderbolt is 
> only available (as far as I know) as a balanced ECL signal on the 
> 25-pin connector, with dire warnings in the manuals about not 
> earthing either side of the ECL signals.  Would you be able to advise 
> on a simple buffer circuit that would allow me to drive the usual 
> unbalanced 50-ohm coax please?

Look at the side-car project for the PPS output. You can skip the NE555 if you
don't need the pulse-length thing. A single RS-485 receiver should do it.
Notice how both the positive and negativ signal is DC terminated as this is
what you need for a PPS signal.

Come to think of it, I need to cook up something similar for my Z3801A too.
Another project in the heap of projects. Hurray!

There are times when real ECL outputs are nice too. If I had any suitable
ECL buffers lying around I would provide ECL output buffers too.

Cheers,
Magnus

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Re: [time-nuts] Buffering the 1pps output from a Z3801A

[Jeff Mock]

That's a cool box, but I took a more quick and dirty approach that has 
served me well.  There's a TTL level PPS inside the box, if I remember 
correctly the part has quite a lot of drive and is fine for driving a 
50-ohm cable.  I needed a proper UTC PPS signal for a radio astronomy 
project and I made the following mod to my z3801a:

solder a 50-ohm resistor to the TTL PPS signal inside the Z3801A.

Use a nibbler tool to widen a cooling hole enough for a piece of
rg-58.

Zip tie a short piece of rg-58 coax into the hole in the side
of the box.  I have a female connector dangling outside the box.

Wire the coax to ground and the 50-ohm resistor of the TTL drive.

This has served me well for many years and driven a variety
of spectrometers.  The signal looks great on a scope when terminated
to 50-ohms, but it is a bit of a quick and dirty solution that might
not be appealing to some.

I can't tell you which chip/pin is the PPS signal, it was several years
ago. I'll remove the lid and tell you the proper pin if you take this
approach.

jeff


John Franke wrote:
> See;  http://www.realhamradio.com/sidecar.htm
> 
> John WA4WDL
> 
> - Original Message - 
> From: "Peter Vince" <[EMAIL PROTECTED]>
> To: 
> Sent: Wednesday, March 26, 2008 9:29 AM
> Subject: [time-nuts] Buffering the 1pps output from a Z3801A
> 
> 
>> Bruce, et al,
>>
>> The 1pps output of an HP Z3801A and Trimble Thunderbolt is
>> only available (as far as I know) as a balanced ECL signal on the
>> 25-pin connector, with dire warnings in the manuals about not
>> earthing either side of the ECL signals.  Would you be able to advise
>> on a simple buffer circuit that would allow me to drive the usual
>> unbalanced 50-ohm coax please?
>>
>> Thanks,
>>
>> Peter Vince  (London, England)
>>


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Re: [time-nuts] Buffering the 1pps output from a Z3801A

[John Ackermann N8UR]

Here's how I added 1 pps and 10 MHz TTL outputs to my Z3801A:
http://www.febo.com/time-freq/gps/z3801a/mods/index.html

John


Peter Vince said the following on 03/26/2008 09:29 AM:
> Bruce, et al,
> 
>   The 1pps output of an HP Z3801A and Trimble Thunderbolt is 
> only available (as far as I know) as a balanced ECL signal on the 
> 25-pin connector, with dire warnings in the manuals about not 
> earthing either side of the ECL signals.  Would you be able to advise 
> on a simple buffer circuit that would allow me to drive the usual 
> unbalanced 50-ohm coax please?
> 
>   Thanks,
> 
>   Peter Vince  (London, England)
> 
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> 
> 


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Re: [time-nuts] anyone built a replacement antenna for a Spectracom 8170?

[John Ackermann N8UR]

I've used my Spectracom WWVB receivers with an active LF antenna (the
AMRAD design) with very good results.  At least here in Ohio, and after
the WWVB ERP upgrade, it doesn't seem to take much of a wet noodle to
get a good signal.

John


Scott Burris said the following on 03/26/2008 12:45 PM:
> Hi,
> 
> I'm finally getting around to trying to get a Spectracom 8170 WWVB
> receiver doing something useful.
> Unfortunately, I only have the unit, not the antenna/preamp.
> 
> Anyone built a replacement antenna for this?  Could this be made to work with
> a commercial ferrite core antenna, maybe something like
> 
> http://www.c-max-time.com/products/showProduct.php?id=18
> 
> with a little preamp circuit of some sort run off the 12v supplied by the 
> 8170?
> 
> If someone has already built something like this and could point me to
> a schematic, that would be much appreciated.  Otherwise I guess I'll roll
> something of my own.
> 
> Thanks.
> 
> Scott
> 
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> 


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Re: [time-nuts] Close-in phase noise measurements

[Jeff Mock]

This is a half-baked idea I've thinking about for awhile.  I wonder if 
it might be possible to create a single measurement to combine allan 
variance and phase noise in the same plot.  Allan variance usually plots 
tau in seconds on the x-axis.  Instead, you might plot 1/s or frequency 
on the x-axis.  This way, allan variance looks more like very close-in 
phase noise.

For example, a point where tau=1000s becomes the phase noise at 1mHz 
(milli-hertz) from the carrier.  Combining this with more typical phase 
noise measurements, you can create a single log-log graph covering 
micro-hertz to hundreds of kilo-hertz.  The advantage of combining the 
measurements into a single entity is that you get most of the 
characterization parameters for a timebase in a single graph.

Would this work?  Half-baked, I know...
jeff


Shane wrote:
> Do you know much about the R&S FSUP50?
> 
> http://www2.rohde-schwarz.com/en/products/test_and_measurement/product_categ
> ories/spectrum_analysis/FSUP-%7C-Key_Facts-%7C-4-%7C-966.html
> 
> 
> -Original Message-
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
> Behalf Of Bruce Griffiths
> Sent: Tuesday, March 25, 2008 8:22 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Close-in phase noise measurements
> 
> Shane wrote:
>> Wenzel has a setup you can purchase at low cost.  
>>
>> http://www.wenzel.com/pdffiles1/PNTS%201000/BP-1000-SC.pdf
>>
>> Phase noise test sets can be pricey... $200K
>>   
> Shane
> 
> Their calibration method is somewhat problematic at the low frequency 
> end where the effect of the PLL and the audio amplifier low frequency 
> cutoff may be significant.
> The NIST calibration technique: 
> http://tf.nist.gov/timefreq/general/pdf/1000.pdf is far superior.
> 
> Bruce
> 


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Re: [time-nuts] Buffering the 1pps output from a Z3801A

[Dave Brown]

Peter
All comments so far relate only to the Z3801A. The Trimble Thunderbolt 
has a TTL level 1 pps 10 uSec pulse output on a BNC connector intended 
to be loaded with 50 ohms.  AFAIK there is no ECL level pps output 
available from the Thunderbolt via its 9 pin serial port connector. 
It's cetainly not mentioned in the Thunderbolt documentation if it is.

DaveB, NZ

- Original Message - 
From: "Peter Vince" <[EMAIL PROTECTED]>
To: 
Sent: Thursday, March 27, 2008 2:29 AM
Subject: [time-nuts] Buffering the 1pps output from a Z3801A


> Bruce, et al,
>
> The 1pps output of an HP Z3801A and Trimble Thunderbolt is
> only available (as far as I know) as a balanced ECL signal on the
> 25-pin connector, with dire warnings in the manuals about not
> earthing either side of the ECL signals.  Would you be able to 
> advise
> on a simple buffer circuit that would allow me to drive the usual
> unbalanced 50-ohm coax please?
>
> Thanks,
>
> Peter Vince  (London, England)
>
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>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG.
> Version: 7.5.519 / Virus Database: 269.22.0/1342 - Release Date: 
> 25/03/2008 10:26
>
> 


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Re: [time-nuts] Buffering the 1pps output from a Z3801A

[Bruce Griffiths]

Peter Vince wrote:
> Bruce, et al,
>
>   The 1pps output of an HP Z3801A and Trimble Thunderbolt is 
> only available (as far as I know) as a balanced ECL signal on the 
> 25-pin connector, with dire warnings in the manuals about not 
> earthing either side of the ECL signals.  Would you be able to advise 
> on a simple buffer circuit that would allow me to drive the usual 
> unbalanced 50-ohm coax please?
>
>   Thanks,
>
>   Peter Vince  (London, England)
>
>   
Peter

The dire warnings about not connecting the outputs to ground indicate 
that the ECL logic is biased with Vcc ~ +5V(exact supply voltage depends 
on ECL family), Vee = GND.
This is known as PECL (not pseudo  ECL as some would have it, but 
positive (supply) ECL as opposed to NECL - negative (supply) ECL where 
Vee ~ -5V (exact supply voltage depends on ECL family). With NECL 
biasing shorting an ECL output to ground merely reverse biases the base 
emitter junction of the output npn follower, which won't destroy 
anything however no useful output will be produced. When Vcc is +5V then 
shorting the emitter follower output to ground produces a very high 
emitter current which may destroy the output device. Connecting a PECL 
output to ground via a 50 ohm coax termination will cause the output 
device emitter current to exceed its ratings.

If the PECL outputs have suitable pulldown resistors then the 
differential output can be used to drive a twisted pair line terminated 
differentially (ungrounded resistor connected across the line) in its 
characteristic impedance. If the balanced transmission line is short 
(where the maximum length depends on the ECL output transition time) the 
termination may be omitted. The termination can also by omitted if the 
ECL outputs are back terminated with series resistors to match the 
balanced line impedance (provided that the line one way delay is less 
than 1/2 the minimum time between output signal transitions.).

A differential input receiver can be used to translate the differential 
ECL signal to TTL/CMOS levels.
Whilst one can use an RS422 or RS485 receiver, a PECL to ECL level 
translator will add less jitter since it doesnt have a built in 
resistive attenuator.
Since several variants of PECL to TTL translators exist, one first has 
to determine if the outputs are conventional 5V PECL or reduced voltage 
PECL.
This is easy to determine by measuring the PECL output signal levels 
using a high impedance scope probe, failing that even a high impedance 
DVM will work as the ECL output swing is 0.8V or less. Once you've 
determined the PECL supply voltage you can probably obtain PECL/TTL 
translators from Farnell (at least thats where Bilal Amin obtained his 
last year - SY100ELT23ZG for +5V PECL).
The TTL/CMOS output should then be followed by a set of paralleled TTL 
input compatible (eg ACTXX ) CMOS inverters (in the same package with 
small resistors in series with each output to improve current sharing) 
to drive the 50 ohm load (just swap over the PECL (or other differential 
receiver) inputs if the output polarity is wrong. Alternatively if you 
prefer a quieter output stage, one could cascade a couple of long tailed 
pairs, one to drive the 50 ohm load and one to act as input level 
translator, however you will need a +12V 110mA supply for this.

If an RS422 or RS485 differential signal has to be converted to TTL then 
using an RS422 or RS485 receiver is preferable as the RS422 or RS485 
signal levels are not PECL compatible.

It is also possible to use a fast differential comparator to do the 
level translation if nothing else is available. However some care is 
necessary particularly with single supply 5V comparators to ensure that 
the input common mode range isnt exceeded.

Will post circuits shortly.

Bruce

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Re: [time-nuts] Buffering the 1pps output from a Z3801A

[Didier Juges]

The Thunderbolt's output impedance on the PPS output is much less than 50
ohms, more like 5 ohms.

If you terminate the other end of the cable with a good 50 ohms termination,
you will be OK, even though it would be better to put a ~47 ohms series
resistor right at the TB output before driving the cable. This will reduce
the available amplitude, but will reduce ringing even more.

Check this page:

http://www.ko4bb.com/Test_Equipment/CoaxCableMatching.html

I used the PPS output of the Thunderbolt as a fast rise time pulse generator
for cable matching/reflections experiments.

It will show you what to expect when you use that output to drive a long
cable. 

Didier KO4BB

> -Original Message-
> From: [EMAIL PROTECTED] 
> [mailto:[EMAIL PROTECTED] On Behalf Of Dave Brown
> Sent: Wednesday, March 26, 2008 2:57 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Buffering the 1pps output from a Z3801A
> 
> Peter
> All comments so far relate only to the Z3801A. The Trimble 
> Thunderbolt has a TTL level 1 pps 10 uSec pulse output on a 
> BNC connector intended to be loaded with 50 ohms.  AFAIK 
> there is no ECL level pps output available from the 
> Thunderbolt via its 9 pin serial port connector. 
> It's cetainly not mentioned in the Thunderbolt documentation if it is.
> 
> DaveB, NZ
> 
> - Original Message -
> From: "Peter Vince" <[EMAIL PROTECTED]>
> To: 
> Sent: Thursday, March 27, 2008 2:29 AM
> Subject: [time-nuts] Buffering the 1pps output from a Z3801A
> 
> 
> > Bruce, et al,
> >
> > The 1pps output of an HP Z3801A and Trimble Thunderbolt is
> > only available (as far as I know) as a balanced ECL signal on the
> > 25-pin connector, with dire warnings in the manuals about not
> > earthing either side of the ECL signals.  Would you be able to 
> > advise
> > on a simple buffer circuit that would allow me to drive the usual
> > unbalanced 50-ohm coax please?
> >
> > Thanks,
> >
> > Peter Vince  (London, England)
> >
> > ___
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> > To unsubscribe, go to 
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
> >
> > -- 
> > No virus found in this incoming message.
> > Checked by AVG.
> > Version: 7.5.519 / Virus Database: 269.22.0/1342 - Release Date: 
> > 25/03/2008 10:26
> >
> > 
> 
> 
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> Checked by AVG. 
> Version: 7.5.519 / Virus Database: 269.21.8/1339 - Release 
> Date: 3/22/2008 4:43 PM
>  
> 

No virus found in this outgoing message.
Checked by AVG. 
Version: 7.5.519 / Virus Database: 269.21.8/1339 - Release Date: 3/22/2008
4:43 PM
 


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[time-nuts] uBlox developers?

[Dan Veeneman]

Hello,

I'm wondering if anyone on the list has experience developing
"shared" applications with the uBlox TIM-LP GPS module.

For the curious, uBlox (www.u-blox.com) sells GPS chips and
modules.  For a time they sold a TIM-LP module, which was
a GPS engine built around an ARM7 microprocessor core.  Because
the GPS functions did not require all of the available ARM7
resources, uBlox marketed the ability for third-party developers
to create applications which would utilize the remaining
processor and memory.

I would be interested in chatting with anyone who has developed
TIM-LP applications in the past.  Please contact me off-list.


Regards,

Dan

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Re: [time-nuts] Buffering the 1pps output from a Z3801A

[Bruce Griffiths]

Didier Juges wrote:
> The Thunderbolt's output impedance on the PPS output is much less than 50
> ohms, more like 5 ohms.
>
> If you terminate the other end of the cable with a good 50 ohms termination,
> you will be OK, even though it would be better to put a ~47 ohms series
> resistor right at the TB output before driving the cable. This will reduce
> the available amplitude, but will reduce ringing even more.
>
> Check this page:
>
> http://www.ko4bb.com/Test_Equipment/CoaxCableMatching.html
>
> I used the PPS output of the Thunderbolt as a fast rise time pulse generator
> for cable matching/reflections experiments.
>
> It will show you what to expect when you use that output to drive a long
> cable. 
>
> Didier KO4BB
>
>   
A 5V PECL to CMOS level translator capable of driving a 50 ohm load is 
shown:

http://www.eds-fl.com/~bruce/5V_PECLtoCMOS_50_OhmDriver.html 


Input transistors can be 2N3907 although they will be a little slow 
since the transistor capacitances will be larger than usual because of 
the low collector base voltages, however the input stage propagation 
delay will only be a few nanosec. For a faster input stage use high ft 
low capacitance transistors (eg BFT92/93).

The values of the output series resistors can be changed to 240 ohms to 
provide a better match to a 50 ohm load if the load and consequently 
lower reflections termination has significant shunt capacitance.

Bruce

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[time-nuts] 58532a ANTENNA CABLE?

[jshank]

Hi,
I am in the process of setting up a Z3801A and would like to know what type of 
cable I should use for a 50' run to an 58532A antenna.

Also I need to purchase one of the monitoring software programs for this 
Z3801A,  any suggestions.

jshank
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Re: [time-nuts] 58532a ANTENNA CABLE?

[Jeff Mock]

I use 100 feet of LMR-400, which is fantastic, but overkill.  It 
probably loses about 6db for 100-feet at 1.5GHz.  There are a lot of 
online vendors that will sell you any length you want with N-type 
connectors on both ends.

jeff


jshank wrote:
> Hi,
> I am in the process of setting up a Z3801A and would like to know what type 
> of cable I should use for a 50' run to an 58532A antenna.
> 
> Also I need to purchase one of the monitoring software programs for this 
> Z3801A,  any suggestions.
> 
> jshank
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