Re: [time-nuts] My Favorite Watch

[al wolfe]

My Timex Indiglo looses about a second a month. I think that's pretty good
for a <$30 watch I got at Walmart.

Al


Virus-free.
www.avast.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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Re: [time-nuts] TrueTime XL-AK Questions

[al wolfe]

Dick,
I have had a couple of the XL-AK receivers here for several years.
They both do not have the down converter option and do put out 5 volts
to the antenna jack. It is simple to measure with a volt meter into
the antenna jack.

While they kind of worked with a hockey-puck antenna, they are
much happier with a bullet type of amplified antenna. They would loose
satellite lock from time to time with the hockey-puck but are rock
steady with the bullet.

If the antenna is open or shorted you will get an alarm. Manual is on line.

IIRC, using the down-converter option for long feedlines was
paired with an up- converter in the  receiver. If you have the
up-converter in your receiver you may be able to just bypass it.

Al


> Hi
>
> The older GPS units had a downconverter in the antenna and passed an IF
> frequency
> back to the receiver. There also was an era when the standard antenna was
> fed 12V
> (rather than 5V) and had 50 db of gain (rather than 20 to 30 db). Most
> modern hockey
> pucks will be unhappy with 12V.
>
> Bob
>
>> On Aug 25, 2017, at 6:13 PM, Richard Solomon  wrote:
>>
>> I was given two of these about 20 some years ago. At that time they both
>> worked
>>
>> fine, except the "keep-alive" batteries were quite low. But they did lock
>> up to the
>>
>> GPS Satellites.
>>
>>
>> I pulled one out today to try out (slow day !!) but I had this nagging
>> feeling that
>>
>> they required a different antenna than the run of the mill GPSDO. I have
>> one of
>>
>> the e-Bay "hockey puck" antennas hooked up to it and the status window
>> says
>>
>> ..."looking for satellites"... .
>>
>>
>> Do the TrueTimes require something special in an antenna ?
>>
>>
>> Thanks, Dick, W1KSZ
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[time-nuts] Mystery Oscillator

[al wolfe]

Found an old oscillator when cleaning out a barn. It is a model
YH890-1 made by Greenray Industries. Since it is 10 mhz. output, I
though it might be useful for something. It has a BNC connector which
I assume is the output and three terminals on the side. One is chassis
ground. The label says both the input and oven are 28 VDC, so I
suppose putting 28 volts on both terminals is the normal hookup but am
not sure. Does anyone have any incite about this?

Thanks,
Al, retired, mostly
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Re: [time-nuts] Frequency counter questions

[al wolfe]

I am surprised that no one has mentioned the idea of heterodyning a
known frequency with the unknown to measure the unknown. I use a
Minicircuits doubly balanced mixer fed on one port from a PTS160
synthesizer that is locked to 10 mhz. from a TrueTime xl-ak GPS locked
receiver. The second port is fed by the unknown though an attenuator.
The third port of the mixer gives me the sum and difference. If the
difference is an audio note then a cheep but frequency locked counter
will read out the difference or measure the period of the beat note
which can be added to the frequency of the synthesizer. A program such
as Lady Heather can also be used to determine the audio frequency to
much less then sub-cycle accuracy. The only fly in the ointment is
figuring out which side of the unknown the synthesizer is set to.

Alternatively, the PTS160 with 0.1 cycle control can be set to nearly
zero beat with the unknown. Then watching either lissajous or dual
trace scope patterns and timing the beat notes one can get the unknown
frequency very close.

Al, retired, mostly
AKA k9si
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Re: [time-nuts] Line Frequency Stability

[al wolfe]

Back in the 1970's I was chief engineer at a couple of local radio
stations. They were automated and needed to carry network programs at
the top of the hour in real time. The switching gear used electrical
motors with cams and roller switches. These motors were locked to the
line frequency and required almost daily adjustment to not get very
sloppy. Often they were off by a few seconds and sounded
unprofessional (at least to the program director who was god).

So we put together our own source of precision 60 cycles. A 10 mhz
oscillator was divided down to 50 hz. A VCO operated at 600 htz and
was divided by 12 and phase locked to the precision 50 htz. The 600
htz was then divided by 10 by a DAC (actually a 7490 and some
resistors). This new 60 htz was low passed and amplified by an old PA
amplifier that drove a filament transformer backwards. This supplied
the AC power to the switching motors and the wall clocks. The 10 mhz
oscillator was checked against WWV from time to time. This solved our
timing motor slop and kept the wall clocks right for months at a time.
We used that system for years. Used all TTL chips.

This was a practical application for me as a time-nut.

Al, retired mostly
k9si
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Re: [time-nuts] WTB: GPSDO

[al wolfe]

Jeff,
I have been using a TrueTime XL-AK purchased on eBay a few years
ago. It has worked flawlessly for the last five years. It seems to
work well with most amplified antennas that I have tried. Supposedly
accurate to better than 10 -12 but I have nothing to compare it to. It
will supposedly control an external oscillator. Mine has five 10 mhz.
sine wave outputs as well as IRIG-B out.

I paid around $150 for mine, but it seems they are asking around
$500 these days. With patients they can be had for less.

Al, k9si


> On 3/9/2017 3:45 AM, Jeff AC0C wrote:
>> We had a small tornado come through north of our house about 1/2 mile on
>> Monday.  Really did a number on the antennas.  Only electronics impacted
>> was my old Nortel GPSDO.  It’s pretty much deaf now, as far as I can tell.
>>  The Nortel always had a hard enough time obtaining the initial lock in
>> the past on startup, but since “the event” it’s been no joy.
>>
>> So I’m in the market for a GPSDO.  Key application here is as a bench
>> precision frequency reference.  Something with good composite noise
>> performance close in.
>>
>> If you have a suitable GPSDO in solid operational condition, kindly
>> contact me off list.  Thanks!
>>
>> 73/jeff/ac0c
>> www.ac0c.com
>> alpha-charlie-zero-charlie
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Re: [time-nuts] Earthmate

[al wolfe]

It seems to me that the Earthmate wants to receive the string "ASTRAL"
before it will send out anything. Haven't used one in fifteen years or
more.

Al, k9si
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[time-nuts] Maser 0.7 nsec jumps solved

[al wolfe]

Maybe the simplest solution would be to try a rudimentary form of
step-start relay to crank the A/C compressor. This used to be quite
common before the days of VFD's and such.

The regular start relay applies power to the motor via a resistor that
limits inrush current to some safe level to start the motor turning.
When the motor reaches a certain speed the voltage across the resistor
drops enough that a relay down stream of the resistor picks up and
shorts out the resistor applying full voltage to the compressor.

This method was used in many motor circuits, several broadcast
transmitters, and some ham radio amplifiers. Some applications use a
timer to energize the second relay. And, of course, there needs to be
some precaution paid to deal with a locked rotor.

Al, aka k9si
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Re: [time-nuts] Trimble Thunderbolt E frequency pulling

[Al Wolfe]

Nigel,
   Set your counter to high impedance. Then install a T connector on the 
input. Then you can install or remove a 50 ohm terminator on the T while 
plotting the results. Then you can see how fast the frequency shift is 
depending on the load.


AL, k9si


Switching the impedance at the counter itself resets any plot  that's in
progress, which does introduce some delay, so I put together a  small 
switch
box that could be inserted into the coax and confirmed it's a  rapid 
effect

that's unlikely to be thermal.


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Re: [time-nuts] modern electronics education/jobs

[Al Wolfe]

   And don't wipe your soldering iron on your wash-and-wear fatigues as we 
used to do with the cotton ones.


Al, k9si


And I agree, don't solder in the nude or while wearing shorts, and don't 
walk barefoot in your workshop.


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Re: [time-nuts] looiking for rakable GPSDO

[Al Wolfe]

Stephane,
   I got a TrueTime Model XL-AK unit from ebay a couple of years ago and 
been quite happy with it It is rackable, has several 10 MHz. outputs, and 
just plays. Using a bullet antenna, also from ebay.


Al, k9si



Hello,

I'm looking for a 10 MHz output GPSDO with external antenna which would
be rackable. Symmetricon doesn't seem to propose some neither Keysight.
Found some stuff  in Oscilloquartz. Any other brand to suggest ?

Thanks & cheers
Stephane


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Re: [time-nuts] Symmetricom / Truetime XL-AK

[Al Wolfe]

Jim,
   I have a Truetime XL-AK and have tried several 5 volt antennas with it 
including the little square magnetic ones. They all worked OK as long as 
they were outside. I did find a $30 imported bullet on ebay that I am using 
now.  Since I installed the bullet last winter I have had no dropouts. But 
then it is mounted higher and in the clear. I think almost 5 volt antenna 
would work for you as long as it has a reasonable look at the sky.


   The XL-AK does measure current to the antenna but other than a short or 
an open I don't know what its limits are to be happy.


Al, k9si



I picked up one of these from the usual site, and it is supposed to be
in working condition.  I wonder if someone may have a suitable antenna
for it I might acquire, or a pointer to one that will work.

It is the type with a 5v amplifier in it from what I was told, and is
working.

I have the manual, but it doesn't mention anything but bullet antenna
as far as the one to be used with the unit or the optional
downconverter.  Multiple discussions are in the list archive about that
requiring switch settings, but I have only found a user manual for the
RS232 interface online for this unit.

thanks
Jim



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Re: [time-nuts] TrueTime AL-AK GPS receiver help

[Al Wolfe]

   Does this AL-AK have a real GPS receiver in it? Does the unit have a 
board with a crystal of 16.368MHz. that is multiplied by 96 up to 1571.328, 
the mixing frequency to get to the GPS freq of 1575.42?


   Since the down convert-up convert is offered as an option perhaps 
TrueTime used an actual GPS receiver in all their units. It stands to reason 
(at least to me) using a stock off-the-shelf GPS receiver in all their boxes 
would be simpler than having to do a custom kluge to work at 4 mhz.


   If this user can find out if his box has an actual GPS receiver then the 
converter section could probably be bypassed.


   FWIW, the TrueTime XL-AK used an external up converter and down 
converter, model 142-6150. Says it's good for up to 1500 feet of RG58. Its 
manual is on line. It uses the above mixing scheme.


Al, retired, mostly
AKA k9si


Someone on ebay advised me to contact your website in hopes that someone 
in your organization can help me with my TrueTime model AL-AK GPS 
Receiver. I need to send it to someone so that they can check it to see if 
it works and can track Satellites.  This receiver has the onboard up/down 
convertor board that changes the receiver input frequency which is set at 
4.092 MHz. I don't have the needed down converter at the antenna. I bought 
this receiver on ebay from someone who told me that he doesn't have the 
down converter as well and can't figure out how to get it to work at 
1575.42 MHz. He also didn't know if this receiver can be setup for a 
1575.42 MHz by removing the onboard converter and changing some DIP 
switches. If one of your members can at least check out the receiver at 
4.092 MHz for satellite tracking That would be a big help ...
snip 


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Re: [time-nuts] KS-24361 Power Module Repair

[Al Wolfe]

Chuck,
   Very sorry, assumed you meant for operation. This makes perfect sense 
for deconstruction purposes. My bad.


Al. k9si



Date: Mon, 13 Apr 2015 15:18:14 -0400
From: Chuck Harris cfhar...@erols.com

No, I meant exactly what I said.

When you are removing epoxy potting compound, put it in an oven
set to 140C, and let it cook until up to temperature.  The potting
epoxy will become about as soft as pencil eraser rubber.  You can
then pick at it, and get pretty big chunks to come off.  When the
epoxy starts to feel hard again, pop it back in the oven.

-Chuck Harris

OBTW, we are not talking about crystal ovens here, but rather unpotting
power supply modules.

Al Wolfe wrote:
This seems a bit toasty and is equivalent to 284F. Maybe meant 140F 
not C?



An oven set to 140C is your friend when doing jobs like
this.
snip 


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Re: [time-nuts] KS-24361 Power Module Repair

[Al Wolfe]

   This seems a bit toasty and is equivalent to 284F. Maybe meant 140F not 
C?



An oven set to 140C is your friend when doing jobs like
this.


   FWIW, the GE Progress Line two-way radios oscillator crystal holders had 
an octal base, held two crystals, and the heating element could be used on 6 
volts or 12 volts depending on which way the holder was plugged in.  I have 
no idea of how well they held the temperature. Always planned to use one 
with an external proportional controller but never got around to it.


Al, k9si 


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Re: [time-nuts] time-nuts Digest, Vol 127, Issue 33

[Al Wolfe]

   I have an XL-DC and it has an internal GPS receiver in it. It supplies 
and monitors 5 volts to a BNC antenna  jack for an external amplified GPS 
antenna. I don't know what the internal GPS engine is but doubt if it is 
anything special.


   The manual describes the down converter system as an option.

Al, k9si



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



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Re: [time-nuts] fast switching quiet synthesizer

[Al Wolfe]

Jim,
   This reminds me of a project I did back in the early1990's. (Hopefully 
we have advanced a bit since then.) It used a bunch of quad latches, some 
74138's, a UART, and an RS232 converter. It drove a PTS 40. The UART used 
the first 4 bits for BCD frequency and the last four bits to address which 
decade on the PTS. It was for a frequency hopping amateur radio project that 
I never finished but that part worked as hoped.


   As far as radar frequecy hopping, I spent several years in the US Air 
Force where our X band radar magnatrons were tuned hydraulically. 3000 PSI 
on a slug in the maggie tuned it very fast!


Al, retired, mostly



At work, I'm putting together a multichannel stepped frequency CW radar
breadboard, and I'm looking for something to serve as a source that I
can step quickly.
I'm looking at stepping every millisecond or so.  Right now, I use a
Ardunino type microcontroller driving a serial DAC driving a VCO, but
that's a bit wonky and noisy, although it's easy to get the step timing
right on.  The spectral purity is, shall we say, downright ugly.

Since I'm going to be doing precision ranging with this, the spectral
purity has to be reasonably good (not 1E-15 at 1000 seconds good,
fortunately)..

I was thinking about a PTS synthesizers  (beloved of time-nuts for all
kinds of reason), and they're nice because they are quiet, and switch
really fast (microseconds).  However, they all seem to have BCD or GPIB
interfaces (only).  Sure, I can code up something on an Arduino or other
microcontroller to drive the BCD on the PTS, but maybe there's something
else out there that might work as well?  And is already off the shelf.



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Re: [time-nuts] GPS-III

[Al Wolfe]

   On eBay the RNY25A1 receiver module sells for $15 and $1 for shipping 
from Taiwan. Supposedly, it does GPS and Glonass. There is a link to a data 
sheet there as well. Might be interesting to play with one and compare the 
results. Stick it in a Tupperware box and nail it to a fence post.


Al, k9si 


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[time-nuts] Diodes as temperature sensors

[Al Wolfe]

Back in the 1970's I was tasked with coming up with a thermometer that could 
be read in the studio of an AM radio station. I bought a Heathkit 
indoor-outdoor unit. It worked great at night but was all over the place in 
the daytime when the AM transmitter was on the air. Turned out the sensor 
was just a silicon diode forward biased. A small ceramic capacitor across 
the diode sensor fixed the RF sensitivity.


Apparently, the forward biased silicon diode was temperature sensitive 
enough that a small D.C. amplifier could drive a meter to read-out with 
reasonable accuracy. Well, maybe not accurate by Time-nut standards but 
close enough for its intended purpose.


A lot of better audio amplifiers use a silicon diode as a temperature sensor 
in the output stages to sense the case temperature to control the biasing 
and prevent thermal run-away.


Seems like there are IC's that contain two diodes, one as a sensor and one 
as a heater. Part numbers escape me now.


Al, retired, mostly 


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Re: [time-nuts] Interesting frequency standard project

[Al Wolfe]

   As stated AM stations in US must maintain 20 Hz accuracy. Most are well 
within that tolerance. I have measured many AM station's frequency as a 
function of my employment before retirement.


   Now comes HD radio. While the merits of HD AM radio are very much open 
to debate, one benefit is that the equipment for HD is GPS locked. If you 
can find an HD AM station you can probably bet they are very close to being 
on frequency. The ones I have measured have been right on and push the 
limits of my test equipment.


Al, retired, mostly
AKA k9si



Date: Sat, 05 Jul 2014 06:20:36 -0400
From: Dale H. Cook starc...@plymouthcolony.net
To: time-nuts@febo.com
Subject: Re: [time-nuts] Interesting frequency standard project

At 06:27 PM 7/4/2014, Hal Murray wrote:

... we have no requirement for that level of stability on the MW 
broadcasts.


How stable are they?


That varies greatly from station to station depending upon what 
transmitter they are running. Note also that compliance with the 20 Hz 
accuracy requirement varies so you would only want to use stations owned 
by companies with a good record of compliance with Part 73.


Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA
http://plymouthcolony.net/starcityeng/index.html


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Re: [time-nuts] FASTTRAX GPS

[Al Wolfe]

   Back in the 1980's I was tasked with installing about 100 terminals 
(VT100 type) to a mainframe computer. These all ran at 9600 baud, RS232. 
Some of the terminals were almost 1000 feet wire distance from the switch. 
We used some Beldon multiple twisted pair to interconnect these devices with 
telco 66 punch blocks in line as well. It worked flawlessly for years before 
individual PC's took over.


   It was only later that I ran across the specs for RS232 that specified 
RS232 as only rated for fifty feet. Oops! Well, it worked for us.


   Anyhow, it appears that the issue here is not the RS232 signals but the 
one second timing pulse width being very short. If I was dealing with this I 
would try a 555 timer as a pulse stretcher. The 555 can operate safely up 
with to 12 volts or more Vcc. It can put out a very robust pulse at that 
voltage. There are cookbook 555 applications on the web for setting up a 
555. Of course the 555 is 30+ years old now and there are probably better 
devices available but the 555 is known to me. The pulse width can be a few 
microsecond to many minutes with this chip depending on the timing 
components, a resistor and a capacitor. The output almost instantly goes to 
nearly the Vcc level when triggered by a negative going trigger. If the GPS 
unit outputs a positive one second timing pulse then a simple one NPN 
transistor inverter should work just fine.


   Set up this way you could shove a robust positive pulse down a piece of 
rusty barbed wire few hundred feet. (Or CAT5 even)


Al, retired, mostly 


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Re: [time-nuts] Measuring the accurcy of a wrist watch

[Al Wolfe]

Tom,
   Thank you for your response. I don't think I could improve on the 
accuracy of this old watch much by trying to regulate it. I was more 
curious to see if there was any way to determine what was going on in side 
it with out actually opening it.


   The buttons on the side have long ceased to function their being clogged 
with sweat and other detritus. Now even with it opened up the little switch 
contacts inside seem to do nothing. It is set to DST so is useful most of 
the year here. I tried to set it to standard time last Fall but gave up. It 
was thirteen seconds fast then and now down to eleven seconds fast. I think 
I will not mess with it any more till the battery dies. I have several other 
toys to play with if I really need to know what time it is.


Al


   I have a Timex watch that's probably seven or eight years old. It has 
an
LCD readout. The buttons haven't worked in years. It looses about one 
second
every three or four months. I have to take out the four microscopic 
screws
in the back to get into it to set it. The only reason I hang onto it is 
that

is the most accurate watch I've ever owned.

   Is there some way to detect its internal frequency inductively? In the
past I have used old relay coils as inductive pickups with success, but
never with a watch.

Al


Hang on to that one; that's an unusually accurate watch.

I have been unsuccessful at picking up timing signals from a LCD watch. I 
did try a webcam once but the timing resolution of an LCD display is 
rather poor, in the 10 to 100 ms millisecond range. If you look a LCD 
closely you'll notice how slowly the contrast transitions occur. The 
acoustic, mechanical, electrical, and magnetic methods offer greater 
resolution, but none of those work on LCD watches.


I wonder if a fine (sub-mm) optical sensor that tracks contrast changes in 
a single segment would work. On a 7-segment display, the 'd' segment is 
the best one to aim for since it changes 8 times every 10 seconds.


If you open it you may see a number of traces from the IC to the LCD with 
pulse rates tied to the main oscillator. The problem here is that by 
opening the case and measuring these extremely low current signals you 
likely introduce a frequency offset.


When you say set it do you mean adjust the time or adjust the rate? One 
idea to reset the time by a few seconds without opening it: raise or lower 
the temperature by many tens of degrees for some number of hours or days.


/tvb


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Re: [time-nuts] Measuring the accurcy of a wrist watch

[Al Wolfe]

   I have a Timex watch that's probably seven or eight years old. It has an 
LCD readout. The buttons haven't worked in years. It looses about one second 
every three or four months. I have to take out the four microscopic screws 
in the back to get into it to set it. The only reason I hang onto it is that 
is the most accurate watch I've ever owned.


   Is there some way to detect its internal frequency inductively? In the 
past I have used old relay coils as inductive pickups with success, but 
never with a watch.


Al


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Re: [time-nuts] fast edge, rise time.

[Al Wolfe]

Years ago I had a cousin who ran a civilian calibration lab. For calibrating 
scopes, etc, for rise time he used a mercury wetted relay which he claimed 
had nearly instant rise time and no bounce. Seems that he used a resistive 
divider and the mercury relay shunted a portion of the divider. With very 
small inductances and capacitance to slow things down it would seem to be 
very fast.


Al, k9si, retired




The target is 4ns, while ideas seemed to be clear at some point, now I'm
having doubts if better to use a MOSFET or a bipolar transistor
as the switch element. Experiments with MOSFETs presented me some
difficulties charging the gate capacitance having some trouble to
achieve something in the 4ns region. Well 4ns seems hard whatever device
anyway.

I would be happy to receive some comments/ideas that may pop out of your
heads.
Thanks.



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Re: [time-nuts] HP 4193A 4815A probe compatibility

[Al Wolfe]

There are many detector chip out there. The venerable AD8307 with greater 
than 80 db dynamic range goes from almost DC to 700 mhz. Linear Technology 
has several currently listed. Their LTC5508 covers 300 to greater than 7 
GHz.


Al


On Oct 17, 2013, at 3:38 PM, Richard Karlquist rich...@karlquist.com 
wrote:



If you are below 80 MHz, Linear Technologies makes a thermal power meter
on a chip.


Alas, the LT1088 is no longer made.

http://www.linear.com/product/LT1088

Best regards,
-Steve

--
Steve Byan steveb...@me.com
Littleton, MA 01460



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Re: [time-nuts] GPSDO choices

[Al Wolfe]

Paul,
   I picked up a TrueTime XL-AK for under $200 on eBay a couple of years 
ago. Advertised at better than 1 x 10 -12. RS232 interface and 1 PPS out as 
well as 10 mhz out and many options. Seems to work well with any of the 5 
volt antennas I've used.


   One rack unit high.

   Have been quite happy with it but then, maybe I don't know any better.

Al Wolfe




I'm looking for a new, ready to go, inexpensive desktop GPSDO.  So
far I've only found the Fury and Thunderbolt E.

Are there other reasonable choices e.g. the J R Miller (although I'm
not sure there's a source of new TU-30 parts).

Thanks.

--
Paul

*Say  $2k


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Re: [time-nuts] FE-5680A Loop Lock Indicator

[Al Wolfe]

   I'm surprised no one suggested using two 2N's in Darlington. Then a 
22K or more from the base to the indicator pin would not load things down 
much. Collector load then 1.2K to 2k in series with the LED.


Al, K9SI


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Re: [time-nuts] 9390-55108 IRIG

[Al Wolfe]

   The TrueTime GPS receiver and frequency standard I have puts out IRIG-B 
as well as 4 each 10 Mhz. signals. What in practical terms is the IRIG-B 
(AM, not DC) good for?


Al, K9SI


The DC code was usually TTL compatible PWM and the IRIG-B would be 3V 
pk-pk AM. Marker 8 cycles, 1 5 cycles and 0 2 cycles wide. Spaces 1V 
pk-pk.



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Re: [time-nuts] NTP Clock suggestions?

[Al Wolfe]

I actually built a contraption like this back in the 1970's. As chief 
engineer at a couple of automated radio stations, I was tasked with keeping 
the network-joiner clocks accurate. It sounded really sloppy to have dead 
air or to up-cut the network. These clocks were 60 htz synchronous motors 
that ran cam switches. Real PITA to adjust. Unfortunately, the utility power 
drifted up and down frequency wise, a few seconds a week. Long term was 
pretty good, though.


   I built a 10 mhz crystal oscillator and divided it down to 50 htz. with 
a string of 7490 decade dividers. Then built a 600 htz VCO out of a pair of 
7400 NAND gates biased linearly. Divided the 600 by 12 with a 7492 and PLLed 
the 50 htz results with the precision 50 htz to control the 600 htz. Then 
divided the 600 by 10 in another 7490 to get 60 htz. Low passed this 60 htz 
square wave so it kind of looked like a sine wave and drove a small PA 
amplifier (pair of 6L6's I think.) This drove a 6.3 V filament transformer 
backwards to supply the 120 VAC to power the synchronous clock motors as 
well as some wall clocks.


   A kluge but it worked great. Every one was happy, the owner, the GM, the 
PD, and me because they got off my back about sloppy timing with the net 
joiner. About once a month or so I would fire up the old SP600 in the rack 
and check zero beat  of the 10 mhz timebase against WWV with Lissijous 
figures on an oscilloscope. (Used the VFO of the SP600 do drive a cathode 
follower into a mixer so the the scope was looking at the low IF frequency. 
Zero beat was very obvious and the stability of the receive was not an 
issue.)


   This thing ran fine for at least ten years. The stations changed formats 
so they didn't need it any more. Probably wound up in a dumpster.


Al,  retired  (A.K.A. K9SI)




albertson.ch...@gmail.com said:
OK, the LOWEST cost option I can think of for driving an analog clock 
with

millisecond accuracy.   Buy a normal AC powered clock that uses a
synchronous AC motor that runs off the 60Hz AC power, not a battery 
powered
clock.  Then have your NTP disciplined computer generate a 60Hz audio 
sine

wave.  Amplify the sine wave to 12 volts then use a small 12:120 volt
transformer to step up to 120VAC.  ...


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Re: [time-nuts] NTP Clock suggestions?

[Al Wolfe]

I actually built a contraption like this back in the 1970's. As chief 
engineer at a couple of automated radio stations, I was tasked with keeping 
the network-joiner clocks accurate. It sounded really sloppy to have dead 
air or to up-cut the network. These clocks were 60 htz synchronous motors 
that ran cam switches. Real PITA to adjust. Unfortunately, the utility power 
drifted up and down frequency wise, a few seconds a week. Long term was 
pretty good, though.


   I built a 10 mhz crystal oscillator and divided it down to 50 htz. with 
a string of 7490 decade dividers. Then built a 600 htz VCO out of a pair of 
7400 NAND gates biased linearly. Divided the 600 by 12 with a 7492 and PLLed 
the 50 htz results with the precision 50 htz to control the 600 htz. Then 
divided the 600 by 10 in another 7490 to get 60 htz. Low passed this 60 htz 
square wave so it kind of looked like a sine wave and drove a small PA 
amplifier (pair of 6L6's I think.) This drove a 6.3 V filament transformer 
backwards to supply the 120 VAC to power the synchronous clock motors as 
well as some wall clocks.


   A kluge but it worked great. Every one was happy, the owner, the GM, the 
PD, and me because they got off my back about sloppy timing with the net 
joiner. About once a month or so I would fire up the old SP600 in the rack 
and check zero beat  of the 10 mhz timebase against WWV with Lissijous 
figures on an oscilloscope. (Used the VFO of the SP600 do drive a cathode 
follower into a mixer so the the scope was looking at the low IF frequency. 
Zero beat was very obvious and the stability of the receive was not an 
issue.)


   This thing ran fine for at least ten years. The stations changed formats 
so they didn't need it any more. Probably wound up in a dumpster.


Al,  retired  (A.K.A. K9SI)




albertson.ch...@gmail.com said:
OK, the LOWEST cost option I can think of for driving an analog clock 
with

millisecond accuracy.   Buy a normal AC powered clock that uses a
synchronous AC motor that runs off the 60Hz AC power, not a battery 
powered
clock.  Then have your NTP disciplined computer generate a 60Hz audio 
sine

wave.  Amplify the sine wave to 12 volts then use a small 12:120 volt
transformer to step up to 120VAC.  ...


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Re: [time-nuts] Measuring Phase diference between different GPSDO

[Al Wolfe]

How about just running the two different 10 mhz outputs into a doubly 
balanced mixer and monitoring the DC output with a volt meter from the IF 
port of the mixer? Sure beats $20,000 for a fancy HP. Of course this is a 
very simple method and is boring as heck to sit and watch a voltmeter but it 
could easily be automated.


Suitable doubly balanced mixers can be often found on eBay for under $50. I 
found a nice Mini-Circuit unit with BNC connectors for around $20 that I 
have often used.


I often just use a scope and Lissajous figures for looking at phase 
differences.


Al, K9SI



Now the trick is:
How to use the 5370B to measure the phase difference.
Anyone care to point me towards an APP note or two?!

mark


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Re: [time-nuts] GPSDO Alternatives

[Al Wolfe]

   Most of the choices I've seen here mention the Tbolts, 3801, 3805, etc, 
but I have never seen anyone mention the TrueTime XL-AK. It advertises 40 
nsec 1 pps. Frequency as 1 x 10-12 per day. I have one and it seems to work 
well but have no way to test it against anything else yet. It has four each 
10 MHz sine output that I have been using for house sync for HP3586, 
HP8924c, PTS160, etc.


   So how does the TrueTime compare to other GPSDO's?

Al, K9SI 



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Re: [time-nuts] Surge Arresters

[Al Wolfe]

Unfortunately, many of the surge arresters available on ebay do not pass DC 
or have a DC shunt to ground internally. This means they won't work with an 
amplified antenna. Make sure any suppressor you get will pass the DC current 
to the antenna.


Al, K9SI, retired 



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Re: [time-nuts] Hi Power LED Light power supply...

[Al Wolfe]

   The LED traffic signals around here are super noisy electrically. They 
rip up my mobile gear from the AM broadcast band through 2 meters any time 
we are close to a traffic light. Some are worse than others. If you can find 
out who makes them then avoid that manufacture like the plague.


Al,  k9si




Date: Tue, 18 Sep 2012 13:23:41 -0400 (EDT)
From: k3...@aol.com
To: time-nuts@febo.com
Subject: Re: [time-nuts] Hi Power LED Light power supply...

If you all check, they are using LEDs in traffic signals now by the
thousands.  These are variations of multiple LEDs used in these signals 
and  they

are all powered by 115vac thru the traffic controllers.

Joe  k3wry




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Re: [time-nuts] High Power LED Light power supply...

[Al Wolfe]

   I spent many years as an electrician/electronics technician in a 
performing art center. Many artists would simply not practice or perform 
under fluorescent light because of the supposed flicker issue. Many of those 
who had no choice complained about it. Dancers were the worst.


Al, k9si




Date: Tue, 18 Sep 2012 11:47:50 -0600
From: Tom Knox act...@hotmail.com
To: Time-Nuts time-nuts@febo.com
Subject: Re: [time-nuts] Hi Power LED Light power supply...


I think that even flicker you cannot consciously see, subconsciously can 
have effects of mental fatigue and eye strain. This is why most florescent 
fixtures are in pairs firing at 180 degrees.
An optical sensor on a scope should allow the power supply to be tweaked 
for a steady light.


Thomas Knox



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Re: [time-nuts] Zero-Crossing Detector Design?

[Al Wolfe]

Chris,
   The simplest zero crossing detector would be to feed your 1 volt, 10 mHz 
from the XL-DC into the input of an IC with schmidt trigger inputs. You 
would need to provide a series coupling cap and probably some DC bias from a 
pot to adjust symmetry of the output. I would also think that if you ran the 
four or six inverters of a schmidt trigger inverter chip in series that you 
would get a pretty good square wave out the end.


   I have an XL-DC with four 10 mHz sine outputs but have not had the need 
yet for a square wave. For that matter, it may be posible to find a 10 mHz 
square wave somewhere inside the box before it is converted to a sine wave 
that could be used for your application.


Al




Subject: [time-nuts] Zero-Crossing Detector Design?

Can anyone suggest a good reference design for a zero-crossing detector? I 
am trying to home an ADC sampler trigger to the 1VRMS (50ohm) 10MHz sin 
from my XL-DC... And now I'm thinking that I should just home the uC clock 
to it, as well.


Essentially, I believe that I'm looking for an efficient, stable, and 
accurate sine-to-square converter... and I'll welcome any advice in this 
area.


This may also be used in a 1KHz 5Vpp IRIG-B decoder... I don't feel like 
rectifying the signal, to be honest. I want to try to keep a smaller BOM, 
sense the waveform primarily, and crunch numbers inside the uC.



-CH

Chris Hoffman
cq.k...@gmail.com
http://ar.ctur.us



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Re: [time-nuts] Zero-Crossing Detector Design?

[Al Wolfe]

   The reason I suggested using a schmidt trigger gate is that a schmidt 
trigger gate switches states at different points at its input. That is, the 
input positive going switch point is higher than the negative going switch 
point, maybe half a volt or so. So, driving this gate with a volt RMS or so 
(3 volts P to P) from the XL-DC should give pretty noiseless, chatter free 
results. Used to use them all the time to generate 60 Hz square waves from 
the power mains. Probably work OK at 10 mHz.


Al



Chris,
   The simplest zero crossing detector would be to feed your 1 volt, 10 
mHz

from the XL-DC into the input of an IC with schmidt trigger inputs. You
snip 



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Re: [time-nuts] Phase modulation detection/NIST plan

[Al Wolfe]

Confucius say: Man with two clocks never know what time it is.

Al


Every piece of equipment in our house shows a different time. I 
wouldn't complain if they all automatically adjusted. My current 
solution is to just stop looking at the clocks, and it's amazing how 
much easier life gets if you just stop worrying about things! :)




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