Re: [time-nuts] GPS Filter

[Magnus Danielson]

On 03/08/2011 05:22 AM, Hal Murray wrote:



Since you are after timing off of the sat's, having antennas that move,
either physically or electrically seems like a problem. Any shift in the
effective antenna location as you tracked the satellite would be "exciting"
to compensate for. There was an early paper published based on doing this
(early 80's).


You can correct for the antenna orientation.  (That's what software is for.
:)  Radio astronomers have been doing it forever.

I think it's simple, at least in the nice/common cases.  If the antenna
geometry has a point that everything swivels around, consider that to the the
location of the antenna.  I think that covers the typical alt-az mount:
   http://en.wikipedia.org/wiki/Altazimuth_mount
The point is where those two axes intersect.  Now just fudge the coax delay
to correct for the time/distance from the real antenna location to that
point.  That's the before location coax delay (in there with the ionospheric
delay) rather than the post GPS antenna-to-box delay.

Of course, it gets a bit more complicated than that if you want to track
several satellites in real time.  That probably takes an antenna per
satelite.  But again, VLBI  geeks have been doing that sort of math for ages.


You would need to have a DGPS input stream generated in order to 
compensate sat for sat. If you don't have a DGPS input to the GPS 
receiver you are fairly stuck with the shifts...


Cheers,
Magnus

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Re: [time-nuts] GPS Filter

[Chris Albertson]

On Mon, Mar 7, 2011 at 7:34 PM, Bob Camp  wrote:
> Hi
>
> Since you are after timing off of the sat's, having antennas that move, 
> either physically or electrically seems like a problem. Any shift in the 
> effective antenna location as you tracked the satellite would be "exciting" 
> to compensate for. There was an early paper published based on doing this 
> (early 80's).

I don't think anyone would build a phased array GPS antenna but if
they did the elements of the array would only move within a 1/2
wavelength range.  For GPS I think this less than 2 centimeters.   but
the effective center of the antenna would not have to move.

-- 
=
Chris Albertson
Redondo Beach, California

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Re: [time-nuts] MiniMac 2816AT

[Jim Palfreyman]

Well I think there is a difference between the 2816 and the 2816AT. I think
the 2816 is indeed portable. This is definitely not. So the AT is the
stay-at-home- unit.

The power supply on this one looked like a typical old-style PC switching
power supply sending out 5V, 12V and -12V. On input it had a label saying
100-250V 45-60 Hz (roughly). So even though it had the remains of a "115V"
sticker on the outside, armed with this new information I decided to power
it up at my 240V, 50Hz.

The hard drive whirred for a few seconds and then a pretty purplish flash
occured deep within the bowels of the power supply.

I unplugged it pretty quick smart.

I hope the old PS behaved like a good fuse and protected the rest of the
unit.

At least the power supply shouldn't be too hard to replace.

Oh well. We live and learn.

:-)

Jim




On 8 March 2011 06:12, Magnus Danielson  wrote:

> On 03/07/2011 07:41 PM, Hal Murray wrote:
>
>> I love the "lightweight" comment.
>>> It has to weigh 20kg!
>>>
>>
>> Is there a Moore's law for size/weight of GPS receivers?  Has anybody
>> plotted
>> it?
>>
>
> Should be possible, but one should consider similar properties like L1/L2
> carrier phase tracking and storage.
>
> Cheers,
> Magnus
>
>
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Re: [time-nuts] GPS Filter

[Tom Van Baak]

I think it's simple, at least in the nice/common cases.  If the antenna 
geometry has a point that everything swivels around, consider that to the the 
location of the antenna.  I think that covers the typical alt-az mount:

 http://en.wikipedia.org/wiki/Altazimuth_mount
The point is where those two axes intersect.  Now just fudge the coax delay 
to correct for the time/distance from the real antenna location to that 
point.  That's the before location coax delay (in there with the ionospheric 
delay) rather than the post GPS antenna-to-box delay.


Of course, it gets a bit more complicated than that if you want to track 
several satellites in real time.  That probably takes an antenna per 
satelite.  But again, VLBI  geeks have been doing that sort of math for ages.


I've always wondered if someone would do this. Place a bunch
of mini az-el mounts in a 3x3 or 4x4 grid 10 cm apart and let
each 9 or 16 antennas pick a unique SV to listen to. After all,
the receiver knows exactly where each SV is and so can point
right to them. Seems it might also be a way to reduce multi-path
as well since each antenna can then be much, much narrower.
I don't know about the RF side. But phase delays and the offset
within the grid can be handled in software. Or let each antenna
have it's own receiver, sharing a common clock.

It would be very fun to watch this antenna in time-lapse. For a
wonderful demonstration of the GPS constellation, imagine on
a misty evening emitting a laser beam out of each antenna.

This was partly inspired by photos PHK posted many years
ago of an array of M12 receivers.

It also gave rise to the idea of creating an az-el sundial; not a
conventional one where the shadow moved across the face
clockwise each day, but one where a microcontroller and light
sensor array drove the mount so the sundial always had exactly
no shadow at all (another thread from several years ago).

/tvb


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Re: [time-nuts] GPS Filter

[Hal Murray]

> Since you are after timing off of the sat's, having antennas that move,
> either physically or electrically seems like a problem. Any shift in the
> effective antenna location as you tracked the satellite would be "exciting"
> to compensate for. There was an early paper published based on doing this
> (early 80's).  

You can correct for the antenna orientation.  (That's what software is for. 
:)  Radio astronomers have been doing it forever.

I think it's simple, at least in the nice/common cases.  If the antenna 
geometry has a point that everything swivels around, consider that to the the 
location of the antenna.  I think that covers the typical alt-az mount:
  http://en.wikipedia.org/wiki/Altazimuth_mount
The point is where those two axes intersect.  Now just fudge the coax delay 
to correct for the time/distance from the real antenna location to that 
point.  That's the before location coax delay (in there with the ionospheric 
delay) rather than the post GPS antenna-to-box delay.

Of course, it gets a bit more complicated than that if you want to track 
several satellites in real time.  That probably takes an antenna per 
satelite.  But again, VLBI  geeks have been doing that sort of math for ages.




-- 
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[time-nuts] Update on the FRSc RB reference recovery and other info

[paul swed]

Hello to the group.
Its been 2 weeks plus since I heated the FRS c up and regained lamp
ignition. In fact the lamps brightened by about .5-.75v or just over 8 volts
now. Not bad from below 1.83v as I recall. That may not be a valid number at
all. More accurate statement "dead".

So thats been a success and I will document what I have done to add to the
knowledge base created by Magnus and others ahead of me.

While tinkering with this and GPSDOs for the austron 2201 project. Built a
controller that worked ok and can definitely be improved on. But in parallel
I programed up a VE2ZAZ controller. I want to thank Bert for his guidance.
This could be a replacement for the austron 2201 internals if I can't get
the original system cooking. The austrons a very nice case and good
comparator but its looking kind of slim on the recovery.

Back to the GPSDO
My particular solution uses the 10 MC 24 volt Lucent/Piezo oscillator found
in cel sites and generally come along with the Lucent RB references for
nothing. In fact I don't know if anyone pays much attention to them at all.
They make a nice ovenized oscillator and when combined with Bert's
controller do a nice job. But what I like is the whole solution draws 2.6
Watts compared to the steady state FRSc of 9.6 watts.
On battery backup this would allow a small set of  2 X 14 amp hour batteries
to easily run the reference for 32 hours without killing the batteries. The
other thing is that the M12+ locks up very quickly and the VE2ZAZ does a
good job of getting everything under control reasonably fast. Granted it
will not be the stability of a true Time-nuts solution but it will do for my
typical bench needs.

So there you have it projects move along.
Let the GPSDO bake in a bit more and then time to document the FRSc recovery
effort.
Regards
Paul
WB8TSL
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Re: [time-nuts] GPS Filter

[Bob Camp]

Hi

Since you are after timing off of the sat's, having antennas that move, either 
physically or electrically seems like a problem. Any shift in the effective 
antenna location as you tracked the satellite would be "exciting" to compensate 
for. There was an early paper published based on doing this (early 80's). 

I did tear into a Thunderbolt. It certainly looks like there's a filter on the 
front end. It's roughly similar to the filters in the HP splitters. It might 
have the same sort of attenuation. 

Bob


On Mar 7, 2011, at 12:39 PM, Chris Albertson wrote:

> On Mon, Mar 7, 2011 at 5:01 AM, Bob Camp  wrote:
>> Hi
>> 
>> In the case of a GPS, you really can't increase the aperture (gain = 
>> directivity) since you want to cover the entire sky.
> 
> 
> No, in theory it need not be an omnidirectional antenna. One could use
> a very high gain antenna if it were able to track each satellite.  If
> you had access to the GPS firmware one could build a phased array
> antenna that was electronically steered.  I think it could work but
> it's not practical because of the very high cost and large size.
> 
> Would it be possible to build a much simpler version that used a line
> array phased to null the nearby tower.
> 
> -- 
> =
> Chris Albertson
> Redondo Beach, California
> 
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Re: [time-nuts] NTP IRIG config help

[Hal Murray]

> After playing with levels and such for a while, I got it to give me a
> timecode = "00 ", but no other numbers after that, and it appears its not
> sync'ing to it.  If I turn up the audio at all, I start getting errors
> indicating overdriven IRIG, and if I unplug it, I get other errros reported,
> so its clearly seeing "something" there.  However, it never locks and shows
> something other than "00 " for timecode. 

My guess is your input signal is too strong.  I had to add an external 
divider before I could get my setup to work.

The driver has an AGC.  The gain gets printed out in the clockstats line.

---

> This clock has IRIG (modulated and "unmodulated") outputs, as well as PPS
> and 10kPPS.  I know there is a linux PPS driver, but it is unclear to me
> whether it works without an accompanying NEMA feed, and this GPS does not do
> NEMA out.  I also haven't made the custom DB9 cable to feed the PPS into the
> linux box yet.

Several of the drivers will handle the PPS stuff themselves but there is also 
a separate PPS only driver - 22.  It needs something else to tell it the 
second.  It should work with the IRIG driver once you get that going, but 
I've never done it.  (It uses the prefer keyword.)



-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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Re: [time-nuts] NTP IRIG config help

[Russell Rezaian]

This may sound a bit basic, so apologies if you have already passed 
this particular hurdle, but there are several different types of IRIG 
time code.  A number of the clocks I have which generate IRIG can 
generate different versions of IRIG (e.g. IRIG B, IRIG H)


If memory serves, the NTP code expects IRIG B.

Have you confirmed that's what your clock is currently configured to generate?
--
Russell

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Re: [time-nuts] NTP IRIG config help

[Harlan Stenn]

Have you seen:

 http://support.ntp.org/bin/view/Support/ConfiguringIrigRefclocks

Feel free to nose around on other ConfiguringRefclocks pages, and add
questions or improve the content.

H

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Re: [time-nuts] Where does the VXI E1740A fit in ?

[Bob Camp]

Hi

I have never seen any register level info on them. It may be out there.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Poul-Henning Kamp
Sent: Monday, March 07, 2011 8:11 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Where does the VXI E1740A fit in ?

In message <298e3f36-5846-4814-ba22-3e9c520e3...@rtty.us>, Bob Camp writes:
>Hi
>
>They are very cool devices - when you get them working. Without
the custom Windows software, they make a nice piece of wall art. A
lot of them are mated up with non-HP VXI PC's so getting them running
can take you off in multiple directions. Timing wise, they will do
all of the standard stuff (AVAR, MTIE, TDEV etc) at 5370(?) type resolution.


Is there any register-level programming information for them ?

If so, putting an open source UNIX on the VXI PC should be possible...

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] latest on the lightsquared 'saga'

[Matt Osborn]

iLotus has the new TX Oncore timing receiver with a built in saw
filter and -159db sensitivity.  Has anyone had a chance to put it
through its paces?

-- kc0ukk at msosborn dot com

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Re: [time-nuts] GPS Filter

[Hal Murray]

> Would it be possible to build a much simpler version that used a line array
> phased to null the nearby tower. 

I can't see any reason why it wouldn't be possible.

I don't expect it to be high volume so it probably won't be low cost.

It will also kill any satellites in the circle that goes across the sky 
perpendicular to the line of the antenna.  (which will go through the tower 
if you have it aimed right)  The width of that line will be determined by the 
length of the antenna line.  A longer line will be harder to point at the 
tower but blot out less of the sky.
 

-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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Re: [time-nuts] Temex LPFRS-01 analog frequency adjustement

[Mark Spencer]

Thanks

The doccumentation regardings RS232 controll looks usefull.   (I had not seen 
this before, and in case any one else is following this thread here is a link..)
http://www.spectratime.com/documents/lpfrs_rs_232.pdf


Regards
Mark S

 


- Original Message 
From: Magnus Danielson 
To: time-nuts@febo.com
Sent: Mon, March 7, 2011 11:10:13 AM
Subject: Re: [time-nuts] Temex LPFRS-01 analog frequency adjustement

On 03/07/2011 07:45 PM, Mark Spencer wrote:
> Thanks.  I recall seeing documentation that more or less said that directly
> connecting these units to an RS232 port will typically work but is not
> guaranteed.  If you are able to easily check your unit that would be great 
> but 
>I
> will likely try connecting mine to an RS232 port in the next few weeks.

It's easy enough to access. But much easier is it to go to Spectratime website 
and download the manual:
http://www.spectratime.com/products/isource/
http://www.spectratime.com/documents/lpfrs_manual.pdf

Already on page 1 I can read the label of the photo which says

6 : TXD (TTL)
9 : RXD (TTL)

Which is a good hint. Start reading at page 10 in the manual.

> I wanted to get a sense of how well the unit is working prior to putting to 
>much
> effort into this.  As it arrived with a circuit board that includes a 
frequency
> adjust trimmer it was pretty simple to test.
> 
>  The spec sheet indicates that the smallest frequency step for  RS 232 control
> is 1X10-11, and I was also curious if finer frequency control was possible via
> the analog frequency adjust input.  I suspect that 1 x 10-11 is the limit but
> I'm not 100 percent sure of this.

See page 13 of the manual and you fill find your confirmation.

As for status, the serial interface should give you a bunch of status report. I 
just haven't taken the time to hook it up.

Cheers,
Magnus

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Re: [time-nuts] NTP IRIG config help

[Chris Albertson]

There is an NTP email list.   questi...@lists.ntp.org

But really, all you need is the 1PPS output and some pool servers.
If you have PPS working then all you need is a way to number the
seconds and "anything" can do that.  Yes the PPS driver works with
other non-NMEA ref clocks

It would be good to get IRIG working.  One thing you don't say is how
you are adjusting the levels.   Is it a digital control or an analog?
In general you want to keep any digital control at maximum.  Reducing
it even a little causes loss of dymanic range and reduces the
effective with (number of bits) of the sample.  In the extream case
your nice 24 bit WAV file is turned into 4-bit wide samples.   Such is
the nature of integer math.

Also if you are using the bui8lt-in sound on some PC, quality varies a
lot. I'd start with a quality external audio interface.  But eiother
way.  I think the first step is to look at the audio.  capture some to
a file then look at the waveform using an audio editor.  Check for a
reasonable amplitude with no clipping.  You will need to adjust the
analog gain to get a good signa


-- 
=
Chris Albertson
Redondo Beach, California

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Re: [time-nuts] MiniMac 2816AT

[Magnus Danielson]

On 03/07/2011 07:41 PM, Hal Murray wrote:

I love the "lightweight" comment.
It has to weigh 20kg!


Is there a Moore's law for size/weight of GPS receivers?  Has anybody plotted
it?


Should be possible, but one should consider similar properties like 
L1/L2 carrier phase tracking and storage.


Cheers,
Magnus

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Re: [time-nuts] Temex LPFRS-01 analog frequency adjustement

[Magnus Danielson]

On 03/07/2011 07:45 PM, Mark Spencer wrote:

Thanks.   I recall seeing documentation that more or less said that directly
connecting these units to an RS232 port will typically work but is not
guaranteed.  If you are able to easily check your unit that would be great but I
will likely try connecting mine to an RS232 port in the next few weeks.


It's easy enough to access. But much easier is it to go to Spectratime 
website and download the manual:

http://www.spectratime.com/products/isource/
http://www.spectratime.com/documents/lpfrs_manual.pdf

Already on page 1 I can read the label of the photo which says

6 : TXD (TTL)
9 : RXD (TTL)

Which is a good hint. Start reading at page 10 in the manual.


I wanted to get a sense of how well the unit is working prior to putting to much
effort into this.   As it arrived with a circuit board that includes a frequency
adjust trimmer it was pretty simple to test.

  The spec sheet indicates that the smallest frequency step for  RS 232 control
is 1X10-11, and I was also curious if finer frequency control was possible via
the analog frequency adjust input.   I suspect that 1 x 10-11 is the limit but
I'm not 100 percent sure of this.


See page 13 of the manual and you fill find your confirmation.

As for status, the serial interface should give you a bunch of status 
report. I just haven't taken the time to hook it up.


Cheers,
Magnus

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[time-nuts] NTP IRIG config help

[Jim Kusznir]

Hello:

I'm not sure if this is the right place; I've been having trouble
finding "current" info / discussions on NTP on linux.

I have a SEL 2407 clock (http://www.selinc.com/sel-2407/) that I was
trying to make more useful by providing NTP service to the university
(and others).

This clock has IRIG (modulated and "unmodulated") outputs, as well as
PPS and 10kPPS.  I know there is a linux PPS driver, but it is unclear
to me whether it works without an accompanying NEMA feed, and this GPS
does not do NEMA out.  I also haven't made the custom DB9 cable to
feed the PPS into the linux box yet.  However, I had the right
adapters and cables to feed the IRIG into the sound card, so I thought
I'd try that.

After playing with levels and such for a while, I got it to give me a
timecode = "00 ", but no other numbers after that, and it appears its
not sync'ing to it.  If I turn up the audio at all, I start getting
errors indicating overdriven IRIG, and if I unplug it, I get other
errros reported, so its clearly seeing "something" there.  However, it
never locks and shows something other than "00 " for timecode.

I had to guess on a lot of how to make it work, including cabling and
termination and the like, as it seems to be a big deficit in
documentation at a level below "extremely knowledgeable / technical"
level.

Is this the right place to ask?  If so, anyone have any pointers?  If
not, can someone direct me to a more appropriate place?

Thanks!
--Jim

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Re: [time-nuts] Temex LPFRS-01 analog frequency adjustement

[Mark Spencer]

Thanks.   I recall seeing documentation that more or less said that directly 
connecting these units to an RS232 port will typically work but is not 
guaranteed.  If you are able to easily check your unit that would be great but 
I 
will likely try connecting mine to an RS232 port in the next few weeks.
 
I wanted to get a sense of how well the unit is working prior to putting to 
much 
effort into this.   As it arrived with a circuit board that includes a 
frequency 
adjust trimmer it was pretty simple to test.
 
 The spec sheet indicates that the smallest frequency step for  RS 232 control 
is 1X10-11, and I was also curious if finer frequency control was possible via 
the analog frequency adjust input.   I suspect that 1 x 10-11 is the limit but 
I'm not 100 percent sure of this.    



- Original Message 
From: Magnus Danielson 
To: time-nuts@febo.com
Sent: Mon, March 7, 2011 9:43:47 AM
Subject: Re: [time-nuts] Temex LPFRS-01 analog frequency adjustement

On 03/07/2011 05:52 PM, Mark Spencer wrote:
> Greetings.  I'm wondering if any one has any insight (or wishes to speculate) 
>as
> to how the external analog frequency adjustment on a Temex LPFRS-01 Rubidium
> standard functions.
> 
> 
>  From experimenting with one over the last few days there seems to be a step
> function to the adjustment.  I'm wondering if frequency adjustment voltage is
> read by an  ADC which is monitored by the CPU which adjusts the frequency ?
> (Or perhaps I'm just not adjusting the multi turn trimmer properly.)

There is a CPU in there with ADC and DACs. You also have serial interface to 
it, 
so you could hook it up to RS-232. Don't recall from the top of my head if the 
levels is RS-232 or CMOS, but I can check... as I have one.

Cheers,
Magnus

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Re: [time-nuts] MiniMac 2816AT

[Hal Murray]

> I love the "lightweight" comment.
> It has to weigh 20kg!

Is there a Moore's law for size/weight of GPS receivers?  Has anybody plotted 
it?


-- 
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[time-nuts] Temex LPFRS-01 analog frequency adjustement

[Arthur Dent]

“Greetings.  I'm wondering if any one has any insight (or wishes to speculate)
As to how the external analog frequency adjustment on a Temex LPFRS-01 
Rubidium standard functions.”
++

The spec sheet says 0-5 volts for analog adjustment. The unit supplies a 5V
hi-stability reference voltage to feed the pot you are using. An external
10kΩ variable resistor wired between the 5V reference supply and ground with
the wiper connected to the frequency adjust pin can provide this adjustment.

   -Arthur


  
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Re: [time-nuts] Temex LPFRS-01 analog frequency adjustement

[Magnus Danielson]

On 03/07/2011 05:52 PM, Mark Spencer wrote:

Greetings.  I'm wondering if any one has any insight (or wishes to speculate) as
to how the external analog frequency adjustment on a Temex LPFRS-01 Rubidium
standard functions.


 From experimenting with one over the last few days there seems to be a step
function to the adjustment.   I'm wondering if frequency adjustment voltage is
read by an  ADC which is monitored by the CPU which adjusts the frequency ?
(Or perhaps I'm just not adjusting the multi turn trimmer properly.)


There is a CPU in there with ADC and DACs. You also have serial 
interface to it, so you could hook it up to RS-232. Don't recall from 
the top of my head if the levels is RS-232 or CMOS, but I can check... 
as I have one.


Cheers,
Magnus

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Re: [time-nuts] GPS Filter

[Chris Albertson]

On Mon, Mar 7, 2011 at 5:01 AM, Bob Camp  wrote:
> Hi
>
> In the case of a GPS, you really can't increase the aperture (gain = 
> directivity) since you want to cover the entire sky.


No, in theory it need not be an omnidirectional antenna. One could use
a very high gain antenna if it were able to track each satellite.  If
you had access to the GPS firmware one could build a phased array
antenna that was electronically steered.  I think it could work but
it's not practical because of the very high cost and large size.

Would it be possible to build a much simpler version that used a line
array phased to null the nearby tower.

-- 
=
Chris Albertson
Redondo Beach, California

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[time-nuts] Temex LPFRS-01 analog frequency adjustement

[Mark Spencer]

Greetings.  I'm wondering if any one has any insight (or wishes to speculate) 
as 
to how the external analog frequency adjustment on a Temex LPFRS-01 Rubidium 
standard functions.  

 
>From experimenting with one over the last few days there seems to be a step 
function to the adjustment.   I'm wondering if frequency adjustment voltage is 
read by an  ADC which is monitored by the CPU which adjusts the frequency ?   
(Or perhaps I'm just not adjusting the multi turn trimmer properly.)   

Regards
Mark Spencer
VE7AFZ



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Re: [time-nuts] Where does the VXI E1740A fit in ?

[Pete Lancashire]

I pretty much agree. Toss in so many companies trashed the originals
and you are left with luck that someone took a copy home with them.

I'll toss in another one, you get a surplus dealer and he immediately
breaks up a 'system' up to in his mind make more money and many times
that corrugated box with papers floppies etc gets tossed out or a couple
times I've witnessed when I use to go to industrial auctions tossed in
the dumpster  as his is loading his hoard. I made it a point to be around
after everyone has loaded up. Got many a manual, attenuator, scope probe,
etc that way.

The same goes for what HP/Agilent calls CLIPS, or what should be called
real service manual.

After say 1990 all this stuff was on a disk drive somewhere, and should
have been copied to at least a ftp site. Even drawings and manuals could
be eventually recreated.

It actually surprises me the of all companies HP/Agilent does not have all
documentation say after 1990 available.

-pete

On Mon, Mar 7, 2011 at 6:11 AM, paul swed  wrote:
> Indeed as I am slowly learning there is a gap in equipment vintage thats a
> black hole.
> Late 80s to 2005 approx. This is the point that the various test instruments
> went more to a hybrid mix of hardware and software with external software
> loads. When you pick up an instrument there are rarely any software disks.
> Though on 2 occasions I have been lucky. A pair logic analyzers Tek and HP
> obtained less then a week apart, go figure.
> Then about 2001 to now and in the future very good/reasonable home brew gear
> showed up with essentially open software and using the power of the PC and
> modern chips sets.
> Its unfortunate that the gap exists because I have seen some great gear at
> the MIT flea market and obvious as heck 0 chance to make it operational.
> Regards
>
> On Mon, Mar 7, 2011 at 8:11 AM, Poul-Henning Kamp wrote:
>
>> In message <298e3f36-5846-4814-ba22-3e9c520e3...@rtty.us>, Bob Camp
>> writes:
>> >Hi
>> >
>> >They are very cool devices - when you get them working. Without
>> the custom Windows software, they make a nice piece of wall art. A
>> lot of them are mated up with non-HP VXI PC's so getting them running
>> can take you off in multiple directions. Timing wise, they will do
>> all of the standard stuff (AVAR, MTIE, TDEV etc) at 5370(?) type
>> resolution.
>>
>> Is there any register-level programming information for them ?
>>
>> If so, putting an open source UNIX on the VXI PC should be possible...
>>
>> --
>> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
>> p...@freebsd.org         | TCP/IP since RFC 956
>> FreeBSD committer       | BSD since 4.3-tahoe
>> Never attribute to malice what can adequately be explained by incompetence.
>>
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>> and follow the instructions there.
>>
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Re: [time-nuts] Where does the VXI E1740A fit in ?

[paul swed]

Indeed as I am slowly learning there is a gap in equipment vintage thats a
black hole.
Late 80s to 2005 approx. This is the point that the various test instruments
went more to a hybrid mix of hardware and software with external software
loads. When you pick up an instrument there are rarely any software disks.
Though on 2 occasions I have been lucky. A pair logic analyzers Tek and HP
obtained less then a week apart, go figure.
Then about 2001 to now and in the future very good/reasonable home brew gear
showed up with essentially open software and using the power of the PC and
modern chips sets.
Its unfortunate that the gap exists because I have seen some great gear at
the MIT flea market and obvious as heck 0 chance to make it operational.
Regards

On Mon, Mar 7, 2011 at 8:11 AM, Poul-Henning Kamp wrote:

> In message <298e3f36-5846-4814-ba22-3e9c520e3...@rtty.us>, Bob Camp
> writes:
> >Hi
> >
> >They are very cool devices - when you get them working. Without
> the custom Windows software, they make a nice piece of wall art. A
> lot of them are mated up with non-HP VXI PC's so getting them running
> can take you off in multiple directions. Timing wise, they will do
> all of the standard stuff (AVAR, MTIE, TDEV etc) at 5370(?) type
> resolution.
>
> Is there any register-level programming information for them ?
>
> If so, putting an open source UNIX on the VXI PC should be possible...
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
>
> ___
> 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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Re: [time-nuts] Where does the VXI E1740A fit in ?

[Poul-Henning Kamp]

In message <298e3f36-5846-4814-ba22-3e9c520e3...@rtty.us>, Bob Camp writes:
>Hi
>
>They are very cool devices - when you get them working. Without
the custom Windows software, they make a nice piece of wall art. A
lot of them are mated up with non-HP VXI PC's so getting them running
can take you off in multiple directions. Timing wise, they will do
all of the standard stuff (AVAR, MTIE, TDEV etc) at 5370(?) type resolution.  

Is there any register-level programming information for them ?

If so, putting an open source UNIX on the VXI PC should be possible...

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Where does the VXI E1740A fit in ?

[Bob Camp]

Hi

They are very cool devices - when you get them working. Without the custom 
Windows software, they make a nice piece of wall art. A lot of them are mated 
up with non-HP VXI PC's so getting them running can take you off in multiple 
directions. Timing wise, they will do all of the standard stuff (AVAR, MTIE, 
TDEV etc) at 5370(?) type resolution.  

Bob

On Mar 6, 2011, at 7:32 PM, Pete Lancashire wrote:

> Any comparison to the 537x's ?
> 
> -pete
> 
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Re: [time-nuts] GPS Filter

[Bob Camp]

Hi

In the case of a GPS, you really can't increase the aperture (gain = 
directivity) since you want to cover the entire sky. 

The filter needed here is far from trivial. The spacing on the "good to bad" 
signals is pretty tight in this case. A filter can indeed be built, no doubt 
about that. It's going to be a bit more than I can shoot up in the basement or 
make on a simple pc board. 

Bob


On Mar 4, 2011, at 8:59 PM, Mike Feher wrote:

> Well, as you said John, for FWIW. In this case not much. As said low loss,
> so increase in noise temp would be minimal, and, if it makes a difference
> between an overloaded front end or a 0.5 dB loss in NF, it will be welcome.
> Heck, we use filters in front of most of our Satcom LNBs at 21 GHz with
> minimal effect. Been there and done that, as the saying goes. If necessary
> the small increase in noise temp can easily be overcome by a slightly larger
> aperture, especially since a view of the full sky is not really necessary
> and birds below certain elevation angles are typically ignored by software
> settings of one's own choosing. And again, I was talking about people who
> have done this and can do it again. It would not be an issue for me. Regards
> - Mike 
> 
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
> 908-902-3831 cell
> 
> 
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of J. Forster
> Sent: Friday, March 04, 2011 8:47 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] GPS Filter
> 
> I'm not so sure.
> 
> A filter ahead of a preamp significantly increases the system Noise
> Temperature.
> 
> GPS signals are weak and link margins are small. The receiver preamps are
> already very low noise.
> 
> I'd think that a narrow filter might well drive up the systen NF to the
> point it'd be useless.
> 
> FWIW,
> 
> -John
> 
> =
> 
> 
>> I used to make some interdigital filters and amplifiers in the early 80's
>> for MDS TV reception in the 2.3 GHz range. One can easily fabricate a low
>> loss narrow band filter at 1.5 GHz if need be, and as mentioned before,
>> antennas should be easy as well. If this really becomes an issue, I am
>> sure
>> there will be a lot of solutions offered and anyone with some RF
>> experience
>> will also be able to handle it themselves. Regards - Mike
>> 
>> Mike B. Feher, EOZ Inc.
>> 89 Arnold Blvd.
>> Howell, NJ, 07731
>> 732-886-5960 office
>> 908-902-3831 cell
>> 
>> 
>> -Original Message-
>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
>> Behalf Of Ziggy
>> Sent: Friday, March 04, 2011 7:47 PM
>> To: time-nuts@febo.com
>> Subject: Re: [time-nuts] GPS Filter
>> 
>> The discussion got me to thinking about how we used to filter out nearby
>> interference on amateur TV - namely by using interdigital filters. This
>> led to a search for GPS interdigital filters which i did indeed find.
>> See Alison Microwave website at
>>  for one example of an
>> integrated antenna/filter/preamp. (I'm sure these aren't cheap, but I
>> haven't asked.) As for retrofitting, you could add a filter after the
>> antenna/amplifier assembly but I might be concerned that the amplified
>> GPS antenna is pretty wide and may have trouble with a Lightsquared
>> transmitter nearby. There are passive antennas though, and there are
>> in-line amps - you'd need to add the filter in between. We made these
>> ourselves for 439 and 1296 MHz - GPS L1 isn't much above that so with
>> some care it should be doable. The tuning can be finicky though :\
>> 
>> Ziggy
>> 
>> On 03/04/2011 03:31 PM, John Ackermann N8UR wrote:
>>> Here's a measurement we did a few years ago on the HP 58535A:
>>> 
>> 
> http://www.febo.com/pages/hp_gps_splitter/port_1_hp_58535a_two_port_amp.png
>>> 
>>> 
>>> John
>>> 
>>> On 3/4/2011 1:31 PM, Bob Camp wrote:
 Hi
 
 Ok, now it's pretty obvious the RF world near your GPS will be
 changing a *lot* in the near future. Lightsquared and a bunch of
 similar outfits will be camping out right next door with very high
 power gear. They will be running 1.5KW from somewhere in town. GPS is
 running 30 watts from off planet.
 
 Has anybody tossed the various HP / Symmetricom GPS splitters on a
 network analyzer? If so, what do the filters in them look like?
 
 I probably should corner the market on these things before asking a
 question like that.
 
 The new neighbors will be at 1525 to 1559 MHz.  GPS L1 is at 1575.42
 MHz.  That's what we are using for timing. L2 is down at 1227.5,
 right now it's mainly military use. Obviously these guys are a bigger
 deal for civilians than the military.
 
 So the question is - do the built in splitter filters have any real
 rejection 15 to 50 MHz off of center?
 
 Probably worth checking. It would

Re: [time-nuts] MiniMac 2816AT

[Jim Palfreyman]

I love the "lightweight" comment.

It has to weigh 20kg!

On 7 March 2011 19:19,  wrote:

> It seems to be an L1/L2 dual frequency surveying receiver.
> Searching for "minimac 2816", without the "AT", seemed to produce a  few
> more results with the following from 1988 amongst them
>
> _http://cedb.asce.org/cgi/WWWdisplay.cgi?58399_
> (http://cedb.asce.org/cgi/WWWdisplay.cgi?58399)
> ---
>
>  A new portable dual-frequency Global  Positioning System (GPS) receiver is
> being delivered to customers by Aero  Service. The MINI-MAC Model 2816
> receiver is lightweigt, portable, and designed  for operation by one person
> in
> field environments. The receiver is packaged to  withstand harsh
> environmental conditions and deliver dual-frequency data of the  highest
> quality.
> Decoded broadcast ephemerides allow for field data. Time and  pseudoranges
> obtained via the unit’s coarse/acquisition (C/A) code L1 capability  are
> used to
> obtain precise time synchronization. The receivers record on  canonical
> times,
> so it is not necessary to start different receivers at the same  time in
> order to maintain synchronous phase observations. The MINI-MAC 2816
>  Surveyor
> is capable of tracking up to eight satellites simultaneously using C/A
>  code
> on L1 and Aero’s proven proprietary codeless methods on L2. An L1-only
> version, Model 1816, is also available. Phase lock can be maintained on up
> to
> eight satellites in kinematic operations. The receiver is designed for
> future  implementation of kinematic software without any required hardware
> changes.  Various aspects of the receiver are discussed and details of a
> number of
> field  results are provided.
>
> --
>
> regards
>
> Nigel
> GM8PZR
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Re: [time-nuts] MiniMac 2816AT

[bg]

In some references it is said to replace the TI-4100. Maybe something to
document at

   http://www.ion.org/museum/cat_view.cfm?cid=11&scid=9

where some other early receivers are presented.

--

   Björn

> It seems to be an L1/L2 dual frequency surveying receiver.
> Searching for "minimac 2816", without the "AT", seemed to produce a  few
> more results with the following from 1988 amongst them
>
> _http://cedb.asce.org/cgi/WWWdisplay.cgi?58399_
> (http://cedb.asce.org/cgi/WWWdisplay.cgi?58399)
> ---
>
>  A new portable dual-frequency Global  Positioning System (GPS) receiver
> is
> being delivered to customers by Aero  Service. The MINI-MAC Model 2816
> receiver is lightweigt, portable, and designed  for operation by one
> person in
> field environments. The receiver is packaged to  withstand harsh
> environmental conditions and deliver dual-frequency data of the  highest
> quality.
> Decoded broadcast ephemerides allow for field data. Time and  pseudoranges
> obtained via the unit’s coarse/acquisition (C/A) code L1 capability  are
> used to
> obtain precise time synchronization. The receivers record on  canonical
> times,
> so it is not necessary to start different receivers at the same  time in
> order to maintain synchronous phase observations. The MINI-MAC 2816
> Surveyor
> is capable of tracking up to eight satellites simultaneously using C/A
> code
> on L1 and Aero’s proven proprietary codeless methods on L2. An L1-only
> version, Model 1816, is also available. Phase lock can be maintained on up
> to
> eight satellites in kinematic operations. The receiver is designed for
> future  implementation of kinematic software without any required hardware
> changes.  Various aspects of the receiver are discussed and details of a
> number of
> field  results are provided.
>
> --
>
> regards
>
> Nigel
> GM8PZR
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Re: [time-nuts] MiniMac 2816AT

[GandalfG8]

It seems to be an L1/L2 dual frequency surveying receiver.
Searching for "minimac 2816", without the "AT", seemed to produce a  few 
more results with the following from 1988 amongst them
 
_http://cedb.asce.org/cgi/WWWdisplay.cgi?58399_ 
(http://cedb.asce.org/cgi/WWWdisplay.cgi?58399) 
---
 
 A new portable dual-frequency Global  Positioning System (GPS) receiver is 
being delivered to customers by Aero  Service. The MINI-MAC Model 2816 
receiver is lightweigt, portable, and designed  for operation by one person in 
field environments. The receiver is packaged to  withstand harsh 
environmental conditions and deliver dual-frequency data of the  highest 
quality. 
Decoded broadcast ephemerides allow for field data. Time and  pseudoranges 
obtained via the unit’s coarse/acquisition (C/A) code L1 capability  are used 
to 
obtain precise time synchronization. The receivers record on  canonical times, 
so it is not necessary to start different receivers at the same  time in 
order to maintain synchronous phase observations. The MINI-MAC 2816  Surveyor 
is capable of tracking up to eight satellites simultaneously using C/A  code 
on L1 and Aero’s proven proprietary codeless methods on L2. An L1-only  
version, Model 1816, is also available. Phase lock can be maintained on up to  
eight satellites in kinematic operations. The receiver is designed for 
future  implementation of kinematic software without any required hardware 
changes.  Various aspects of the receiver are discussed and details of a number 
of 
field  results are provided.
 
--
 
regards
 
Nigel
GM8PZR
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