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 <doug@dougronald.com
javascript:_e(%7B%7D,'cvml','doug@dougronald.com');> wrote:

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 doug@dougronald.com wrote:

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 doug@dougronald.com wrote:

The XL-DC Can use either a normal L1 or Down converter Antenna according to the manual. http://www.prostudioconnection.net/1112/xl-dc-manual.pdf

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

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

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

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:

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

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-bounces@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. http://www.prostudioconnection.net/1112/xl-dc-manual.pdf

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

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.

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 bill@iaxs.net wrote:

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 paulswedb@gmail.com wrote:

ben wrote:

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

http://www.ko4bb.com/manuals/download.php?file=02_GPS_Timing/Simple_AC_Mains_Zero_Crossing_Detector.pdf

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:

http://www.leapsecond.com/pic/picpet.htm

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

On 2/26/15 20:39, Charles Steinmetz wrote:

If we all did this, then I realize that we could identify the different
power grids. However, I wonder if there is any interesting variation
within a grid. As the electricity flows vary throughout the day, it
seems possible that the phase difference between two people on the same
grid would actually change (a bit).

Has anybody done this experiment?

Philip

Hi

All of these older rack mount “GPSDO” products had a fairly long lifespan compared
to the advances in GPS receivers. When some / most of them first came out, the only practical /proven
way to do timing off GPS was with a downconverter. Without things like serial numbers / date codes it’s
tough to figure out if this sample of box A has anything at all to do with another sample of the same box.
On top of that, these are very low volume products compared to normal HP or Fluke
test gear. It’s unlikely that anybody has a database that tells what is what simply from
the serial numbers or date codes. I’d bet that many of them were built to order and rarely in
groups larger than a few dozen.

Bob

HI

It’s done by utilities to monitor power flow and balance electric grids. The first data on this (grid vs GPS) date to the 1980’s. I think the
paper I recall was done by Quebec Hydro. Since then it’s become a pretty standard monitoring tool.

Bob

Yes, it's really quite interesting and very easy to do. Check the time nuts archives -- over the years there are by now hundreds of postings about measuring mains phase and frequency. See also:

http://leapsecond.com/pages/mains/
http://leapsecond.com/pages/mains/mains-picpet-23.gif
http://leapsecond.com/pages/ac-detect/

There are many wonderful web sites that deal with power line frequency; some with live plots. Just google for words like: mains frequency detect accuracy stability measurement

Also, make sure to read the growing literature about ENF:
http://en.wikipedia.org/wiki/Electrical_network_frequency_analysis

/tvb

Like this?

http://fnetpublic.utk.edu/gradientmap.html

I am the dot just below the Canadian border in WA State.

Dave

Hi Bob,

On 02/27/2015 08:24 PM, Bob Camp wrote:

Yes. They implemented the first Phasor-Measurement Unit (PMU), it went
into the IEEE 1344 standard, but had many issues with it and created a
new standard in IEEE C37.118, which has since been split into IEEE
C37.118.1 and C37.118.2 with the advent of the IEC 61850 context, where
the data-transport is being replaced, but the measurement methods is
maintained in C37.118.1.

For an intro, you can read this paper:
http://rubidium.dyndns.org/~magnus/papers/KTH_paper1.pdf

Cheers,
Magnus

Dave,

That's cool. I am the dot just above the US / Canada border and just
below the Ontario/Quebec border in Eastern Ontario.

There are many (many) documents that can found using Google on the
subject of power grids and frequency and monitoring. I have only been
able to read through only a small handful. An interesting application of
time and frequency measurement.

cheers, Graham ve3gtc

On 2015-02-28 19:50, DaveH wrote: