[time-nuts] No GPS satellites

[Tim Shoppa]

Yes, the XL-DC and other Truetime models had as an option for long cable
runs, a downconverter in the antenna. I don't know how to tell the
difference from part number, but I know the truetimes my employer uses all
have the downconverter option and the option is very common.

Tim N3QE

On Wednesday, February 25, 2015, Doug Ronald > wrote:

> I'm hoping someone can shed some light on my problem receiving any GPS
> satellites.
>
> I have two TrueTime GPS Time & Frequency Receivers, Model XL-DC. One has a
> regular crystal oscillator, and the other one has a rubidium oscillator. I
> have two outdoor GPS antennas with internal LNAs, one a 28 dB gain unit,
> and the other a 40 dB unit. When either antenna is connected to my Lucent
> KS-24361, it locks right up and tracks up to 8 satellites. When either of
> the antennas is connected to the XL-DCs, they just sit there and status :
> "Looking for GPS satellites".
>
> In the Alarm menu of either XL-DC there is an alarm for Antenna. Both
> units say "OK" and if I disconnect the antenna they both logically say
> "Open". So, what is the problem? I can't believe I don't have enough
> signal, after the Lucent locks-up right away. Is it possible the TrueTime
> sanctioned antenna has a down converter in it, perhaps placing the GPS
> signal from L-band to some lower frequency? I would appreciate any info the
> group might have...
>
> -Doug Ronald
> W6DSR
>
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Re: [time-nuts] No GPS satellites

[Michael Perrett]

Since your antennas have a lot of gain I assume they are active and require
a DC voltage to the LNA. Does the XL-DC provide that voltage (sometime you
have to select active or passive antenna)?
Michael / K7HIL

On Wed, Feb 25, 2015 at 12:35 PM, Doug Ronald  wrote:

> I'm hoping someone can shed some light on my problem receiving any GPS
> satellites.
>
> I have two TrueTime GPS Time & Frequency Receivers, Model XL-DC. One has a
> regular crystal oscillator, and the other one has a rubidium oscillator. I
> have two outdoor GPS antennas with internal LNAs, one a 28 dB gain unit,
> and the other a 40 dB unit. When either antenna is connected to my Lucent
> KS-24361, it locks right up and tracks up to 8 satellites. When either of
> the antennas is connected to the XL-DCs, they just sit there and status :
> "Looking for GPS satellites".
>
> In the Alarm menu of either XL-DC there is an alarm for Antenna. Both
> units say "OK" and if I disconnect the antenna they both logically say
> "Open". So, what is the problem? I can't believe I don't have enough
> signal, after the Lucent locks-up right away. Is it possible the TrueTime
> sanctioned antenna has a down converter in it, perhaps placing the GPS
> signal from L-band to some lower frequency? I would appreciate any info the
> group might have...
>
> -Doug Ronald
> W6DSR
>
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Re: [time-nuts] No GPS satellites

[Azelio Boriani]

Yes, the TrueTime unit needs its antenna/downconverter to work. Other
GPSDOs, like the Meinberg units GPS-SA used in the Rohde Schwarz
ED167MP have this arrangement.

On Wed, Feb 25, 2015 at 8:35 PM, Doug Ronald  wrote:
> I'm hoping someone can shed some light on my problem receiving any GPS 
> satellites.
>
> I have two TrueTime GPS Time & Frequency Receivers, Model XL-DC. One has a 
> regular crystal oscillator, and the other one has a rubidium oscillator. I 
> have two outdoor GPS antennas with internal LNAs, one a 28 dB gain unit, and 
> the other a 40 dB unit. When either antenna is connected to my Lucent 
> KS-24361, it locks right up and tracks up to 8 satellites. When either of the 
> antennas is connected to the XL-DCs, they just sit there and status : 
> "Looking for GPS satellites".
>
> In the Alarm menu of either XL-DC there is an alarm for Antenna. Both units 
> say "OK" and if I disconnect the antenna they both logically say "Open". So, 
> what is the problem? I can't believe I don't have enough signal, after the 
> Lucent locks-up right away. Is it possible the TrueTime sanctioned antenna 
> has a down converter in it, perhaps placing the GPS signal from L-band to 
> some lower frequency? I would appreciate any info the group might have...
>
> -Doug Ronald
> W6DSR
>
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Re: [time-nuts] No GPS satellites

[Mike Cook]

The XL-DC Can use either a normal L1 or Down converter Antenna according to the 
manual. 

If your antenna works with the Lucent then it will be a normal one. Does your 
XL-DC have any option codes? 


"Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une 
petite et provisoire sécurité, ne méritent ni liberté ni sécurité."
Benjimin Franklin

> Le 25 févr. 2015 à 20:35, Doug Ronald  a écrit :
> 
> I'm hoping someone can shed some light on my problem receiving any GPS 
> satellites.
> 
> I have two TrueTime GPS Time & Frequency Receivers, Model XL-DC. One has a 
> regular crystal oscillator, and the other one has a rubidium oscillator. I 
> have two outdoor GPS antennas with internal LNAs, one a 28 dB gain unit, and 
> the other a 40 dB unit. When either antenna is connected to my Lucent 
> KS-24361, it locks right up and tracks up to 8 satellites. When either of the 
> antennas is connected to the XL-DCs, they just sit there and status : 
> "Looking for GPS satellites".
> 
> In the Alarm menu of either XL-DC there is an alarm for Antenna. Both units 
> say "OK" and if I disconnect the antenna they both logically say "Open". So, 
> what is the problem? I can't believe I don't have enough signal, after the 
> Lucent locks-up right away. Is it possible the TrueTime sanctioned antenna 
> has a down converter in it, perhaps placing the GPS signal from L-band to 
> some lower frequency? I would appreciate any info the group might have...
> 
> -Doug Ronald
> W6DSR
> 
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Re: [time-nuts] homebrew counter new board test result

[Attila Kinali]

On Wed, 25 Feb 2015 01:44:40 -0800
Hal Murray  wrote:

> The Schmitt trigger mostly avoids glitches on the output.  Does it do 
> anything to reduce timing noise if the input signal is clean enough that it 
> doesn't make any glitches?

A Schmitt Trigger avoids glitches at the input, not the output.
It does prevent the input circuitry in the gate to switch back and forth
between 0 and 1, or, even worse, from going metastable.

This by itself might improve timing, if you have problems due to low
slew rate. But as Magnus wrote, in general does not improve things.


Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] OXCO insulation

[Bob Camp]

Hi

If you try using the powder stuff, good luck cleaning anything up. You 
certainly 
do not want to have it anywhere near a soldering or welding (OCXO seal) 
process. 
The stuff gets everywhere and it will wind up in everything. 

Bob

> On Feb 25, 2015, at 8:24 PM, wb6bnq  wrote:
> 
> Hi Dave,
> 
> It looks like some great stuff !  However, it is a material that has a big 
> dust problem according to the manufacturer.  Here is the web site listing of 
> products :
> 
> http://www.aerogel.com/products-and-solutions/all-insulation-products/
> 
> Read the SPACELOFT safety data sheet on the product at this URL :
> 
> http://www.aerogel.com/_resources/common/userfiles/file/Data%20Sheets/Spaceloft_MSDS.pdf
> 
> It is not dangerous, but can cause medical problems if mishandled.
> 
> BillWB6BNQ
> 
> 
> Dave M wrote:
> 
>> Great find, Arthur.  I had already convinced myself to use fiberglass 
>> insulation to reinsulate my OXCOs, but I'm going to order 2 or 3 sheets of 
>> this to play with.
>> 
>> Thanks a bunch!!
>> Dave M
>> 
>> 
>> Arthur Dent wrote:
>> 
>>> If you check the popular auction site you can find several listing
>>> for Aspen Aerogel SPACELOFT Insulation. One listing has a 10"x14"x.2"
>>> piece for $7 including shipping and another listing has 481 rolls for
>>> $1.8 million, in case you have several ovens you need to re-insulate.
>>> ;-)
>>> 
>>> http://www.ebay.com/itm/171328843398?
>>> 
>>> -Arthur
>>> ___
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>>> the instructions there.
>> 
>> 
>> 
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>> 
> 
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Re: [time-nuts] homebrew counter new board test result

[Magnus Danielson]

Hi Charles,

On 02/26/2015 02:46 AM, Charles Steinmetz wrote:



The Schmitt trigger mostly avoids glitches on the output.  Does it do
anything to reduce timing noise if the input signal is clean enough
that it
doesn't make any glitches?


No, it just avoids flipping state at the transition point(s).


Note also that the hysteresis of logic gates with Schmitt inputs is WAY
too much to be optimal for squaring sine waves (300mV minimum, typically
400 to 450mV, for the 74LVC14).  Fast comparators with internal
hysteresis are optimized for that sort of thing (the LT1719 and LT1720
have a few mV of hysteresis).


Indeed.

If you think about what large hysteresis does on a sine, it moves the 
trigger points further up and down on the sine from the mid-point, which 
moves them into lower slew-rate areas.


If you are picky, amplitude variations will then also move the phase 
more than mid-point triggers.


A bit of hysteresis can help to avoid flipping back, but considering the 
type of signal, it passes the mid-point (0 V) at highest slew-rate, so 
there is very little risk of flipping back and fourth in the first 
place, so hysteresis may not even be needed.


Cheers,
Magnus
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Re: [time-nuts] OXCO insulation

[Neville Michie]

Consider the problems of small detached crumbs of this material
upsetting the interelectrode capacitances of the oscillator.
Fibre material may be more stable.
Just a thought,
Neville Michie



On 26/02/2015, at 6:05 AM, Dave M wrote:

> Great find, Arthur.  I had already convinced myself to use fiberglass 
> insulation to reinsulate my OXCOs, but I'm going to order 2 or 3 sheets of 
> this to play with.
> 
> Thanks a bunch!!
> Dave M
> 
> 
> Arthur Dent wrote:
>> If you check the popular auction site you can find several listing
>> for Aspen Aerogel SPACELOFT Insulation. One listing has a 10"x14"x.2"
>> piece for $7 including shipping and another listing has 481 rolls for
>> $1.8 million, in case you have several ovens you need to re-insulate.
>> ;-)
>> 
>> http://www.ebay.com/itm/171328843398?
>> 
>> -Arthur
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
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>> the instructions there.
> 
> 
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[time-nuts] Trimble Thunderbolt NMEA ?

[Tim]

Hi all,

Is there a way to get NMEA instead of TSIP out of a Thunderbolt ?

Failing that, is there some translating device that I can insert between 
the Thunderbolt and another device that is expecting NMEA ?


thanks

Tim

--
VK2XAX :: QF56if23 :: BMARC :: WIA :: AMSATVK

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[time-nuts] Measuring frequency rather than tuning crystal

[Paul Alfille]

I have a couple of HP 5370s with the beaglebone brain transplant. They come
with a nice 10811 that has a little adjustment screw.

Testing against a Thunderbolt or KS-24361 the 5370 is off by less than 1Hz.

I know the traditional method would be to adjust the crystal slowly and
make careful measurements, but since I have a fancy computer in there, I
wonder if I could just adjust the frequency in software. 64-bit floating
point numbers should have sufficient accuracy. All reported measurments
would be corrected for the actual reference frequency.

Basically, I'd have a 1000.226 Hz internal reference.

In fact, could I connect the beaglebone to a a GPS 1 pps source and make
this a GPS-disciplined-software-corrected oscillator.

So my question is is this a known technique? The discipline feedback
circuit seems a little different, I'd adjusting for drift and offset, but
not the gain of control-oscillator linkage.
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Re: [time-nuts] OXCO insulation

[Brian Inglis]

Articles about handling and cutting these make it clear that it is worse
than fibreglass insulation and protectionmust alwaysbe used.
Cabot Thermal Wrap blanket aerogels are low dust at higher prices:
http://www.buyaerogel.com/product-category/cabot

On 2015-02-25 18:24, wb6bnq wrote:

It looks like some great stuff !  However, it is a material that has a big dust 
problem according to the manufacturer.  Here is the web site listing of 
products :
http://www.aerogel.com/products-and-solutions/all-insulation-products/
Read the SPACELOFT safety data sheet on the product at this URL :
http://www.aerogel.com/_resources/common/userfiles/file/Data%20Sheets/Spaceloft_MSDS.pdf
It is not dangerous, but can cause medical problems if mishandled.

BillWB6BNQ



Dave M wrote:

Great find, Arthur.  I had already convinced myself to use fiberglass 
insulation to reinsulate my OXCOs, but I'm going to order 2 or 3 sheets of this 
to play with.



Arthur Dent wrote:

If you check the popular auction site you can find several listing
for Aspen Aerogel SPACELOFT Insulation. One listing has a 10"x14"x.2"
piece for $7 including shipping and another listing has 481 rolls for
$1.8 million, in case you have several ovens you need to re-insulate.
;-)
http://www.ebay.com/itm/171328843398?

--
Take care. Thanks, Brian Inglis
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[time-nuts] Frequency Divider

[Bruce Hunter via time-nuts]

David,

I am surprised at the lack of interest in your divider boards.  These are great 
units and a very useful addition to shop frequency standards.  I fit my board 
into a former NTSC TV distribution amplifier housing and used the DA's already 
present to distribute 1, 10, and 100 MHz.  A front panel rotary switch and BNC 
allows selection of 1 Hz to 100 kHz square-waves. Along with your board, there 
was  room internally for a 1 MHz sine-wave filter and a 10 to 100 MHz 
multiplier.  By adding a switching convertor, the former NTSC DA's power supply 
was adequate to power all internals.   I have found this to be a very useful 
device.  You obviously spent a great deal of time on the design of the 
circuitry and upon getting the board manufactured and distributed.  Please 
accept my sincere thanks.  I recommend it highly to others.

Best regards,

Bruce, KG6OJI   
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Re: [time-nuts] OXCO insulation

[Richard (Rick) Karlquist]

On 2/25/2015 4:32 AM, Attila Kinali wrote:

On Wed, 25 Feb 2015 10:16:58 +0100
Attila Kinali  wrote:


Actually, you should put the temp sensor close to the heater, not the crystal.
The delay between the actuator (heater) and the feedback (temperature sensor)
defines the dead time. The presence of a crystal somewhere in the system is
of no importance to the oven controller, it's just additional thermal weight.


Bob Camp just reminded me of Rick Karlquist's papers on this topic:

"A low Profile High-Performance Crystal Oscillator for Timekeeping
Applications", by Karlquist, Cutler, Ingman, Johnson, Parisek, 1997
http://www.karlquist.com/osc.pdf

"The Theory of Zero-Gradient Crystal Ovens",
by Karlquist, Cutler, Ingman, Johnson, Parisek, 1997
http://www.karlquist.com/oven.pdf

More can be found on his homepage: http://www.karlquist.com/



A quick summary of the insulation issue in OCXO's:

Virtually any kind of foam, or just still air has similar
insulating properties in an OCXO.  Exotic kinds of insulation
like aerogel, or vacuum, are impractical because you have to
get rid of the heat generated by the electronics.  The E1938A
oscillator described in the above references achieved a thermal
gain in excess of 1,000,000 (in a single stage oven) in prototype 
testing, and routinely achieved many 100's or thousands on a production 
basis and had only 1/4 inch of foam that was nothing special thermally.

We also were able to get high thermal gain with a still air
experiment.

At HP, the main issues with foam were outgassing and mechanical
fatigue, like a mattress getting flat and the foam had to withstand
the oven temperature continuously.  Another issue was what
happens if the oven runs away and the foam burns and produces
toxic gases.  Generally, we are talking manufacturability issues.
The one thing the choice of foam had little to do with was performance.

Rick Karlquist N6RK
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[time-nuts] UK 60 kHz MSF outage

[David J Taylor]

I have received the following:

UK 60 kHz MSF outage: Mon 2 - Thurs 19 March, 08:00-18:00 UTC - service 
off-air each day (will be back on air overnight & at weekends).


Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk 


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Re: [time-nuts] Measuring frequency rather than tuning crystal

[Tom Van Baak]

Paul,

Right, there's no need to physically calibrate the LO when you can simply 
adjust all measurements in software, either inside the instrument or on the PC 
that's logging the measurements from the instrument.

This technique is used for many high-end measurements and also extends to GPS 
post-processing for even greater accuracy.

Look in the archives for GPS disciplined frequency counter. 

If you keep the raw data (DUT-REF, REF-GPS) you essentially avoid the entire 
rats nest of Vref, DAC, EFC, disciplining algorithms, and hard coded tuning 
constants. It just becomes a correlation in software.

/tvb

> On Feb 26, 2015, at 5:30 AM, Paul Alfille  wrote:
> 
> I have a couple of HP 5370s with the beaglebone brain transplant. They come
> with a nice 10811 that has a little adjustment screw.
> 
> Testing against a Thunderbolt or KS-24361 the 5370 is off by less than 1Hz.
> 
> I know the traditional method would be to adjust the crystal slowly and
> make careful measurements, but since I have a fancy computer in there, I
> wonder if I could just adjust the frequency in software. 64-bit floating
> point numbers should have sufficient accuracy. All reported measurments
> would be corrected for the actual reference frequency.
> 
> Basically, I'd have a 1000.226 Hz internal reference.
> 
> In fact, could I connect the beaglebone to a a GPS 1 pps source and make
> this a GPS-disciplined-software-corrected oscillator.
> 
> So my question is is this a known technique? The discipline feedback
> circuit seems a little different, I'd adjusting for drift and offset, but
> not the gain of control-oscillator linkage.
> ___
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Re: [time-nuts] No GPS satellites

[Mike Cook]

Just a heads up as I stumbled on an interesting XL-DC plugin module for sale on 
ebay  while looking for info for Doug.
TrueTime Symmetricom XL-DC FTM-III AC Line Frequency Measurement & Time Monitor

Unfortunately I don’t have an XL-DC, but it looks just just the tick for a time 
nut who has. 


"Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une 
petite et provisoire sécurité, ne méritent ni liberté ni sécurité."
Benjimin Franklin

> Le 25 févr. 2015 à 20:35, Doug Ronald  a écrit :
> 
> I'm hoping someone can shed some light on my problem receiving any GPS 
> satellites.
> 
> I have two TrueTime GPS Time & Frequency Receivers, Model XL-DC. One has a 
> regular crystal oscillator, and the other one has a rubidium oscillator. I 
> have two outdoor GPS antennas with internal LNAs, one a 28 dB gain unit, and 
> the other a 40 dB unit. When either antenna is connected to my Lucent 
> KS-24361, it locks right up and tracks up to 8 satellites. When either of the 
> antennas is connected to the XL-DCs, they just sit there and status : 
> "Looking for GPS satellites".
> 
> In the Alarm menu of either XL-DC there is an alarm for Antenna. Both units 
> say "OK" and if I disconnect the antenna they both logically say "Open". So, 
> what is the problem? I can't believe I don't have enough signal, after the 
> Lucent locks-up right away. Is it possible the TrueTime sanctioned antenna 
> has a down converter in it, perhaps placing the GPS signal from L-band to 
> some lower frequency? I would appreciate any info the group might have...
> 
> -Doug Ronald
> W6DSR
> 
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Re: [time-nuts] No GPS satellites

[Tom Van Baak]

Mike,

That's the same card I used for the 40-day run: 
http://leapsecond.com/pages/mains/

It's robust and professional (used in the electric grid industry) and nice if 
you already have a working XL-DC but most of us now use a $1 microcontroller or 
DCD pin and NTP to track mains phase & frequency. 

/tvb

> On Feb 26, 2015, at 2:27 AM, Mike Cook  wrote:
> 
> Just a heads up as I stumbled on an interesting XL-DC plugin module for sale 
> on ebay  while looking for info for Doug.
> TrueTime Symmetricom XL-DC FTM-III AC Line Frequency Measurement & Time 
> Monitor
> 
> Unfortunately I don’t have an XL-DC, but it looks just just the tick for a 
> time nut who has. 
> 
> 
> "Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une 
> petite et provisoire sécurité, ne méritent ni liberté ni sécurité."
> Benjimin Franklin
> 
>> Le 25 févr. 2015 à 20:35, Doug Ronald  a écrit :
>> 
>> I'm hoping someone can shed some light on my problem receiving any GPS 
>> satellites.
>> 
>> I have two TrueTime GPS Time & Frequency Receivers, Model XL-DC. One has a 
>> regular crystal oscillator, and the other one has a rubidium oscillator. I 
>> have two outdoor GPS antennas with internal LNAs, one a 28 dB gain unit, and 
>> the other a 40 dB unit. When either antenna is connected to my Lucent 
>> KS-24361, it locks right up and tracks up to 8 satellites. When either of 
>> the antennas is connected to the XL-DCs, they just sit there and status : 
>> "Looking for GPS satellites".
>> 
>> In the Alarm menu of either XL-DC there is an alarm for Antenna. Both units 
>> say "OK" and if I disconnect the antenna they both logically say "Open". So, 
>> what is the problem? I can't believe I don't have enough signal, after the 
>> Lucent locks-up right away. Is it possible the TrueTime sanctioned antenna 
>> has a down converter in it, perhaps placing the GPS signal from L-band to 
>> some lower frequency? I would appreciate any info the group might have...
>> 
>> -Doug Ronald
>> W6DSR
>> 
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Re: [time-nuts] homebrew counter new board test result

[Charles Steinmetz]

Magnus wrote:


A bit of hysteresis can help to avoid flipping back, but considering the
type of signal, it passes the mid-point (0 V) at highest slew-rate, so
there is very little risk of flipping back and fourth in the first
place, so hysteresis may not even be needed.


A 1 Vrms, 10MHz sine wave has a zero-cross slew rate of 88v/uS 
(88mV/nS).  One would think that would be enough to avoid indecision 
in a comparator with 5-10nS of propagation delay.  However, the 
LT1016 (10nS) is prone to jitter problems when operating as a ZCD 
with such a signal, and external hysteresis does not help much 
because it is delayed by 10nS.  (The problem appears to be that the 
front end has some indecision at this input slew rate that happens 
faster than the propagation delay to the output -- but this is just 
an inference because the internal nodes are not accessible for 
measurement.)  For this application, the small amount of internal 
hysteresis of the LT1719 and LT1720 is very beneficial.


Best regards,

Charles




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Re: [time-nuts] No GPS satellites

[Bill Hawkins]

Doesn't the DC in the model number mean "down conversion" or something
like that?

Seems to me it did in the obsolete 468-DC GOES time receivers, which had
to down convert to about 1.8 MHz.
Also, the down conversion was more than a simple local oscillator and
mixer. You had to have their antenna to make it work, as the mixer was
in the base of the antenna.

Bill Hawkins
 

-Original Message-
From: Tim Shoppa
Sent: Wednesday, February 25, 2015 7:56 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] No GPS satellites

Yes, the XL-DC and other Truetime models had as an option for long cable
runs, a downconverter in the antenna. I don't know how to tell the
difference from part number, but I know the truetimes my employer uses
all have the downconverter option and the option is very common.

Tim N3QE


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Re: [time-nuts] No GPS satellites

[Doug Ronald]

I want to thank everyone who jumped in to contribute on my issue, especially 
Mike who supplied a much needed manual for this instrument.

Well, one unit with the xtal oscillator, had the upconverter end of the 
downconverter/upconverter chain in the chassis which was easily bypassed. Once 
that was accomplished, it locked up fairly quickly, however the LCD display had 
many bad segments. The rubidium unit has a defective Trimble receiver as it 
never gets out of the "looking for satellites" mode even after hours of on 
time, but it has a pristine LCD display, so I swapped around parts, and now 
have a good working standard. The xtal unit draws about half the power that the 
rubidium unit draws, so that one shall be my standard since it's on 24/7.

It was rewarding to use the TrueTime 10 MHz output for the reference input to 
my HP-5370B, and the frequency input of the counter connected to the Lucent 15 
MHz standard. Both standards are completely independent right up to the 
antennas, and the counter shows only a few milliHertz variation.

Thanks again,
-Doug, W6DSR

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike Cook
Sent: Thursday, February 26, 2015 4:13 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] No GPS satellites
Importance: Low

The XL-DC Can use either a normal L1 or Down converter Antenna according to the 
manual. 

If your antenna works with the Lucent then it will be a normal one. Does your 
XL-DC have any option codes? 


"Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une 
petite et provisoire sécurité, ne méritent ni liberté ni sécurité."
Benjimin Franklin

> Le 25 févr. 2015 à 20:35, Doug Ronald  a écrit :
> 
> I'm hoping someone can shed some light on my problem receiving any GPS 
> satellites.
> 
> I have two TrueTime GPS Time & Frequency Receivers, Model XL-DC. One has a 
> regular crystal oscillator, and the other one has a rubidium oscillator. I 
> have two outdoor GPS antennas with internal LNAs, one a 28 dB gain unit, and 
> the other a 40 dB unit. When either antenna is connected to my Lucent 
> KS-24361, it locks right up and tracks up to 8 satellites. When either of the 
> antennas is connected to the XL-DCs, they just sit there and status : 
> "Looking for GPS satellites".
> 
> In the Alarm menu of either XL-DC there is an alarm for Antenna. Both units 
> say "OK" and if I disconnect the antenna they both logically say "Open". So, 
> what is the problem? I can't believe I don't have enough signal, after the 
> Lucent locks-up right away. Is it possible the TrueTime sanctioned antenna 
> has a down converter in it, perhaps placing the GPS signal from L-band to 
> some lower frequency? I would appreciate any info the group might have...
> 
> -Doug Ronald
> W6DSR
> 
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Re: [time-nuts] No GPS satellites

[Ben Hall]

Hi Tom and list,

I joined the list a few days ago after getting my HP Z3801 back running 
after a couple of years of it being off-line.  I'm using it as a 10 MHz 
frequency standard for my various ham-radio activities.


On 2/26/2015 3:33 PM, Tom Van Baak wrote:
> ...but most of us now use a $1
> microcontroller or DCD pin and NTP to track mains phase & frequency.

I'm going to have to build one of these.  Assume you have some sort of 
circuit that converts low-voltage AC from a transformer secondary to a 
pulse train, start a timer, and count x amount of pulses?


Very interesting.

thanks much,
ben
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Re: [time-nuts] No GPS satellites

[paul swed]

A fellow time-nut shared the manual for the xl-dc and I downloaded it.
It clearly states that it has a down converter. That was very typical of
these generation receivers. As examples the Odetics and Austrons. It
allowed for very short antenna runs or virtually 0 length antenna runs and
losses. The DC468 goes used the same trick.
Almost always the receivers show up without the dowconverter because those
stay on the roof. Without the down converter the units useless.
I have been lucky in some exploits to use odetics down converters with the
austron and the another approach using older styles semi-integrated
receivers to fake it.
So if you want to experiment there is hope. Though it seems each receivers
a bit different.The older Truetime manuals were pretty good with schematics
and explanations. Unfortunately it looks like the new manual has little to
go on.
Regards
Paul
WB8TSL

On Thu, Feb 26, 2015 at 4:46 PM, Bill Hawkins  wrote:

> Doesn't the DC in the model number mean "down conversion" or something
> like that?
>
> Seems to me it did in the obsolete 468-DC GOES time receivers, which had
> to down convert to about 1.8 MHz.
> Also, the down conversion was more than a simple local oscillator and
> mixer. You had to have their antenna to make it work, as the mixer was
> in the base of the antenna.
>
> Bill Hawkins
>
>
> -Original Message-
> From: Tim Shoppa
> Sent: Wednesday, February 25, 2015 7:56 PM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] No GPS satellites
>
> Yes, the XL-DC and other Truetime models had as an option for long cable
> runs, a downconverter in the antenna. I don't know how to tell the
> difference from part number, but I know the truetimes my employer uses
> all have the downconverter option and the option is very common.
>
> Tim N3QE
>
>
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> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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>
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Re: [time-nuts] No GPS satellites

[paul swed]

Boy I ran out to mr google and did a search and now I am wondering if some
versions of the xl-dc just used a plain old GPS antenna. It sure looks like
that could be the case. The manual does say down converter. Maybe it
changed over time.
Regards
Paul
WB8TSL

On Thu, Feb 26, 2015 at 8:15 PM, paul swed  wrote:

> A fellow time-nut shared the manual for the xl-dc and I downloaded it.
> It clearly states that it has a down converter. That was very typical of
> these generation receivers. As examples the Odetics and Austrons. It
> allowed for very short antenna runs or virtually 0 length antenna runs and
> losses. The DC468 goes used the same trick.
> Almost always the receivers show up without the dowconverter because those
> stay on the roof. Without the down converter the units useless.
> I have been lucky in some exploits to use odetics down converters with the
> austron and the another approach using older styles semi-integrated
> receivers to fake it.
> So if you want to experiment there is hope. Though it seems each receivers
> a bit different.The older Truetime manuals were pretty good with schematics
> and explanations. Unfortunately it looks like the new manual has little to
> go on.
> Regards
> Paul
> WB8TSL
>
> On Thu, Feb 26, 2015 at 4:46 PM, Bill Hawkins  wrote:
>
>> Doesn't the DC in the model number mean "down conversion" or something
>> like that?
>>
>> Seems to me it did in the obsolete 468-DC GOES time receivers, which had
>> to down convert to about 1.8 MHz.
>> Also, the down conversion was more than a simple local oscillator and
>> mixer. You had to have their antenna to make it work, as the mixer was
>> in the base of the antenna.
>>
>> Bill Hawkins
>>
>>
>> -Original Message-
>> From: Tim Shoppa
>> Sent: Wednesday, February 25, 2015 7:56 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: [time-nuts] No GPS satellites
>>
>> Yes, the XL-DC and other Truetime models had as an option for long cable
>> runs, a downconverter in the antenna. I don't know how to tell the
>> difference from part number, but I know the truetimes my employer uses
>> all have the downconverter option and the option is very common.
>>
>> Tim N3QE
>>
>>
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>> 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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[time-nuts] Recording mains frequency/phase [WAS: No GPS satellites]

[Charles Steinmetz]

ben wrote:

I'm going to have to build one of these.  Assume you have some sort 
of circuit that converts low-voltage AC from a transformer secondary 
to a pulse train, start a timer, and count x amount of pulses?


Here is a zero-cross detector designed for this purpose:



Most mains-nuts feed the ZCD pulse to the DCD line of a PC's RS232 
port and use the computer to time-stamp the crossings and append them 
to a file of such time stamps.


Alternatively, Tom designed the picPET Precision Event Timer to do 
this sort of timestamping:




An Ardu/berry/bone with a flash card can also be used, so you don't 
need to leave a PC running.


Best regards,

Charles



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