A lot of devices have a low output impedance so that the signal can be split
using a TEE adapter with little loss or need for a distribution amplifier.
However, the cables must be impedance matched at far end, scope input, to
prevent reflections which are the source of the ringing.
You can match
David thanks what you say seems to be true. I could see the stable 100 Hz
and the 200 Hz was a typical 2 X lissajuo pattern within the 100 Hz pattern.
From your comments then I speculate the following from Tracor.
They used a LO 100 Hz below because the synthesizer was reasonable to
build. Adding t
What a wreck. Just the sort of crazy thing Time-nuts get into.
This should be fun to watch and learn.
Regards
Paul
WB8TSL
On Sun, Sep 14, 2014 at 1:16 PM, wrote:
>
>
> Well, I bet that got your attention!
>
> My Hydrogen Maser "kit" arrived recently.
>
> It's a surplus Sigma Tau VLBA-112 with an
I'll be looking for that blog post. By the way, how did the burnt out
EtherDue go? I remember saying after you had taken your last set of
pictures that you'd popped it...!
On Mon, Sep 15, 2014 at 6:48 AM, Andrew Rodland
wrote:
> Neil,
>
> I'm working on a blog post now, I'm hoping to have it co
Neil,
I'm working on a blog post now, I'm hoping to have it complete by
Monday or Tuesday. I'll send a followup here when it's posted.
On Sun, Sep 14, 2014 at 11:47 AM, Neil Schroeder wrote:
> I have nothing constructive to add at this time but I would truly enjoy
> reviewing your design and bui
I am beginning to understand the complexity of these issues
thanks to everyone's help.
Thanks,
Pete.
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van
Baak
Sent: Sunday, September 14, 2014 2:06 PM
To: Discussion of precise time and frequency me
On Sun, Sep 14, 2014 at 4:29 AM, Andrew Rodland wrote:
> My clock is quantized at 10MHz, so you wouldn't expect better than
> 100ns accuracy. But I added -50ns to the offset in software, making it
> zero in on the edge where the offset is 0 counts 50% of the time and
> -1 count the other 50%. (Dit
On Sun, Sep 14, 2014 at 10:20:48AM -0400, paul swed wrote:
> I still do not see why if I offset the LO to -150 hz I get a useful display
> to judge timing. I am using the lissajous method.
Consider that with the LO offset 150 Hz you will have a 100 Hz
beat note with the mark tone and a 20
On 9/14/14, 8:23 AM, Bob Camp wrote:
Hi
Remember that one model for FSK is a pair of AM signals that “just
happen” to represent an FSK waveform. With normal FSK if you tune to
one side, you will get a nice AM carrier and sidebands. With MSK it’s
a bit more complex since they to do some cute stuf
Hi
Actually your “best case” is where the clock in the Res-T is *not*
12.504000 MHz or a frequency that is +/- (N * 40 ppb) of that
frequency. If it is, you get a “hanging bridge” in the data. At +/- (N * 20
ppb) you don’t get the classic hanging bridge, but you still get a bias. All
Hi
If you are seeing modulo 2 ns jumps, then there is something in your setup
causing them. The Res-T can only put out something about every 40 ns.
That edge is locked to nothing at all, so it does drift. If your particular
12.504 MHz clock is off by 1 ppm, then it’s edge will drift 1 us per s
> They say that the system clock is 12.504 MHz and that they use both the
> rising and falling edges. That is about 40 nS between quantization time
> slots. The PPS can only appear on a 40 nS edge. I should be seeing
> 40 nS jumps in the waveforms. I do see ~40 nS jumps but they are less
I am able to phase track NAA using the following method:
Reception using active whip antenna input into HP 3581C selective vm, tuned
to 24 KHz using its 300 Hz bandpass filter.
Output is taken from "Restored" connection on back panel and input into the
squaring chip AD835, set up on a breadboar
Well, I bet that got your attention!
My Hydrogen Maser "kit" arrived recently.
It's a surplus Sigma Tau VLBA-112 with an unknown physics package problem
that has had its power supply modules, RF receiver modules, synthesizer
and cavity servo tuning modules, and a couple other "bits" removed for
I have nothing constructive to add at this time but I would truly enjoy
reviewing your design and build logs/notes.
On Sunday, September 14, 2014, Andrew Rodland
wrote:
> Hi all,
>
> I've got some figures in from my clock, and I figured I would post
> them here in hopes of getting some eyes on
I don't want to repeat an old discussion. You certainly can
use unterminated coax as long as you are aware of the ringing
issues and the possibility of false triggering.
I am using a terminator on the scope end of the cable. I can
see ringing similar to what is shown on the leapsecond web site
Thank you for that link. I read the section of quantization error.
I am confused with what I am seeing on my scope verses what they are saying
They say that the system clock is 12.504 MHz and that they use both the
rising and falling edges. That is about 40 nS between quantization time
slots.
> Peter,
>
> That depends. To use 1M Ohms input impedance, you need a 50 Ohms series
> impedance at the driver chip. Most sources such as the 58503A and Thunderbolt
> violate that requirement by having only a couple of Ohms output impedance,
> and are thus not suitable and do need the 50 Ohms
Peter,
I should mention that all you need to avoid amplitude-modulating your 10MHz
signal by the 1PPS DC return current and pumping massive current through your
coax and termination resistor is to add a 41 to 47 Ohms series resistor to your
1PPS source as close to the driver as possible... It i
I tried removing the termination and got a little better than 4 nS
risetime.
Isn't the ringing frequency simply a function of the length of
the coax? Isn't it the price you pay for mismatched impedances?
Pete.
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On
Peter,
That depends. To use 1M Ohms input impedance, you need a 50 Ohms series
impedance at the driver chip. Most sources such as the 58503A and Thunderbolt
violate that requirement by having only a couple of Ohms output impedance, and
are thus not suitable and do need the 50 Ohms termination a
Ok, did the math, a 4ns risetime should be ok on a 200MHz scope.
You likely won't see the oscillations and reflections visible in Toms 58503A
plots for example, they are faster than the risetime.
Bye,
Said
Sent From iPhone
> On Sep 14, 2014, at 8:35, Said Jackson via time-nuts
> wrote:
>
>
Hi
If you look at:
ftp://ftp.trimble.com/pub/sct/embedded/bin/Manuals/Old%20Manuals/Resolution%20T%20Final%20Final.pdf
(first hit on Google for Resolution T manual, no other reason for picking it).
In the index, “PPS Quantization Error" is on page 46.
On page 46 they talk about the +/- 20 ns e
Peter,
You don't need nor do you want a 50 ohms end-termination on a series-terminated
50 ohms coax cable.
This has been discussed here extensively before, please check the archives.
Your last sentence is not correct.
Also, you are running into your scope's BW limit if you are measuring a 4ns
Hi
Remember that one model for FSK is a pair of AM signals that “just happen” to
represent an FSK waveform. With normal FSK if you tune to one side, you will
get a nice AM carrier and sidebands. With MSK it’s a bit more complex since
they to do some cute stuff to cut down the bandwidth. It’s st
My rise time is about 4 nS. I am measuring that with my 200 MHz
scope. I am only using 50 Ohm termination, anything else is not
valid when using 50 Ohm coax.
Pete.
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van
Baak
Sent: Saturday, Septe
Hi all,
I've got some figures in from my clock, and I figured I would post
them here in hopes of getting some eyes on them and some help with
interpretation.
Reference is a Spectracom NetClock 9183 with OCXO option. Frequency is
good to better than 10^-9, PPS is specified as +/- 50ns.
Instrument
Pete,
I have not measured the Resolution-T clock frequency. Be aware that the 1PPS
timing spec in the data sheet (e.g., N ns from UTC) is not related to the CPU
clock frequency.
The CPU clock is directly related to the range of the sawtooth corrections, by
the very definition of "quantization"
OK I am use to traditional fsk that typically had a far wide shift then the
baud.
What you say would match what the tracor book says and the system is
designed for.
I still do not see why if I offset the LO to -150 hz I get a useful display
to judge timing. I am using the lissajous method.
Regards
Hi
If it’s the same Res-T that I’ve seen the data sheet on, yes it does have
sawtooth correction data coming out of it. You do have to take out the sawtooth
to get it to run as well as it can.
Bob
On Sep 13, 2014, at 8:52 PM, Peter Reilley wrote:
> I don't see any mention of sawtooth correct
I don't see any mention of sawtooth correction in their documentation.
I take that to imply that sawtooth correction is not necessary to get
the 15 nS that is spec'ed?
Does the 15 nS imply that the internal clock is 33 MHz? That is: +-15 nS
is 30 nS which is 33 MHz. Is that correct? Or do th
b...@evoria.net said:
> "Note: The DAC module is designed specifically for audio applications and is
> not recommended for control type applications."
> I had hoped that it wouldn't be a problem for driving an OCXO, but my
> mistake. The datasheet also notes that the DAC has 16-bit resolution bu
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