Re: [time-nuts] Secondary phase noise standard & FE405
kb8tq@n1k.org said:
Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS
spurs come straight through. Since the FE-405 compensates for all sorts of
things, the DDS moves around a lot. Even a one bit change on a DDS will move
spurs around. With an ever changing DDS, you have an ever changing forest
of “stuff” on the output.
Is there a web page or such telling me where the spurs will be on a DDS for a
particular constant?
--
These are my opinions. I hate spam.
Hi
It depends both on the DDS “firmware” and the DAC linearity. You can play games to
come up with the firmware side of it. The normal approach is to design the part so the
DAC dominates. More or less, "more firmware bits” is cheaper than improving the DAC.
Bob
On Nov 12, 2016, at 8:13 PM, Hal Murray hmurray@megapathdsl.net wrote:
kb8tq@n1k.org said:
Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS
spurs come straight through. Since the FE-405 compensates for all sorts of
things, the DDS moves around a lot. Even a one bit change on a DDS will move
spurs around. With an ever changing DDS, you have an ever changing forest
of “stuff” on the output.
Is there a web page or such telling me where the spurs will be on a DDS for a
particular constant?
--
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Some AD DDS app notes give examples of spurs and choosing nearby (but not
exactly on freq) numbers that are much less bad for spurs - or at least
that move the spurs outside the cleanup filters/loops. I don't know of a
general example or even code that does this in a general way.
One paper I like on the subject is this:
http://ttcla.org/vsreinhardt/DDS%20spur%20reduction%20techniques.pdf
P.S. I just like saying "Wheatley Jitter Injector". Not for those who are
embarrassed easily... Almost as good as "Wankel Rotary Engine".
One of
On Sat, Nov 12, 2016 at 8:13 PM, Hal Murray hmurray@megapathdsl.net wrote:
kb8tq@n1k.org said:
Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS
spurs come straight through. Since the FE-405 compensates for all sorts
of
things, the DDS moves around a lot. Even a one bit change on a DDS will
move
spurs around. With an ever changing DDS, you have an ever changing
forest
of “stuff” on the output.
Is there a web page or such telling me where the spurs will be on a DDS
for a
particular constant?
--
These are my opinions. I hate spam.
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.
Hi
The “sure fire” way to reduce the spurs is to go to a divisor that “fits” in to
the DAC bit width. If you have a 12 bit dac, those points happen at Fclock / 2^12.
For Time Nut sort of stuff that’s pretty coarse tuning.
Bob
On Nov 13, 2016, at 11:03 AM, Tim Shoppa tshoppa@gmail.com wrote:
Some AD DDS app notes give examples of spurs and choosing nearby (but not
exactly on freq) numbers that are much less bad for spurs - or at least
that move the spurs outside the cleanup filters/loops. I don't know of a
general example or even code that does this in a general way.
One paper I like on the subject is this:
http://ttcla.org/vsreinhardt/DDS%20spur%20reduction%20techniques.pdf
P.S. I just like saying "Wheatley Jitter Injector". Not for those who are
embarrassed easily... Almost as good as "Wankel Rotary Engine".
One of
On Sat, Nov 12, 2016 at 8:13 PM, Hal Murray hmurray@megapathdsl.net wrote:
kb8tq@n1k.org said:
Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS
spurs come straight through. Since the FE-405 compensates for all sorts
of
things, the DDS moves around a lot. Even a one bit change on a DDS will
move
spurs around. With an ever changing DDS, you have an ever changing
forest
of “stuff” on the output.
Is there a web page or such telling me where the spurs will be on a DDS
for a
particular constant?
--
These are my opinions. I hate spam.
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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and follow the instructions there.
Any idea what unit this is?
Has the markings:
Motorola
7ST5H on a bar code
TM-AC on the PCB
BV-AC M447D on PCB
84D43215M03 on PCB
Looks similar to the old ONCORE stuff.
This unit has a BNC added to the Antenna.
Did some searching but no luck yet.
Hope the attachments go thru.
Thanks in advance.
Mitch
J. T. (Mitch) [Amateur radio VE6OH] [CFARS CIW308]
email mitch@andor.net
Mobile Cellular 780 446 8958 SKYPE USER ID "MITCH-VE6OH"
Past RAC Director for Alberta, NWT, NU HTTP://WWW.RAC.CA
On Sun, 13 Nov 2016 11:03:31 -0500
Tim Shoppa tshoppa@gmail.com wrote:
Some AD DDS app notes give examples of spurs and choosing nearby (but not
exactly on freq) numbers that are much less bad for spurs - or at least
that move the spurs outside the cleanup filters/loops. I don't know of a
general example or even code that does this in a general way.
One paper I like on the subject is this:
http://ttcla.org/vsreinhardt/DDS%20spur%20reduction%20techniques.pdf
A treatment of the topic that I found quite good is [1].
The spurs of DDS are very similar to those of delta-sigma modulators
(a DDS is delta-sigma modulator with a non-linear output mapping)
and as far as I have seen, there are more analysis on the spurs of
DS-modulators than on DDS systems (for a good reference on DS-modulators
see [2]). The DDS spur reduction systems all vere very similar to what
has been done to DS-modulators, like using a second or third order
DS-modulator instead of a simple phase accumulator and using more
bits in the sin/cos output and then using a first or second order
DS-modulator there.
Attila Kinali
[1] "Exact Analysis of DDS Spurs and SNR due to Phase Truncation and
Arbitrary Phase-to-Amplitude Errors", by Torosyan and Wilson, 2005
http://tycho.usno.navy.mil/ptti/ptti2005/paper8.pdf
[2] "Understanding Delta-Sigma Converters" by Schreier and Temes, 2005
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
Mitch,
You have either a 6 channel PVT-6 or a 6\8 channel Basic Oncore. Both share size, power and I\O specifications. I'll send the Basic Oncore Engineering Notes to you off list.
We'll also post the Engineering Notes to our website for others who might be interests in this early nineties legacy Motorola product By Tuesday: http://www.synergy-gps.com/index.php?option=com_content&task=view&id=42&Itemid=89.
Art Sepin
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of CIW308 VE6OH
Sent: Sunday, November 13, 2016 1:29 PM
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Subject: [time-nuts] GPS Model ?
Any idea what unit this is?
Has the markings:
Motorola
7ST5H on a bar code
TM-AC on the PCB
BV-AC M447D on PCB
84D43215M03 on PCB
Looks similar to the old ONCORE stuff.
This unit has a BNC added to the Antenna.
Did some searching but no luck yet.
Hope the attachments go thru.
Thanks in advance.
Mitch
J. T. (Mitch) [Amateur radio VE6OH] [CFARS CIW308] email mitch@andor.net
Mobile Cellular 780 446 8958 SKYPE USER ID "MITCH-VE6OH"
Past RAC Director for Alberta, NWT, NU https://na01.safelinks.protection.outlook.com/?url=HTTP%3A%2F%2FWWW.RAC.CA&data=01%7C01%7Cart%40synergy-gps.com%7C85efe09a17e0420e07ac08d40c10cd44%7Cc81f9fdec0e04d8c95779afaa0cad9ed%7C1&sdata=0Xaed5Ff0AHg42sDZd%2BYbKdFEHAC%2FKYOmnIL%2Bc5mecY%3D&reserved=0
I've got some older Oncore stuff too. The specs sound dated but are
orders of magnitude better than needed for NTP servers. It is the kind of
thing you turn on then it just runs for years. Get a good outdoor antenna.
That said, last time, a few months ago when I was looking for an under $10
receiver I ended up with a U-Blox 6 for about $7 shipped. It outperforms
the Oncore in every way
On Sun, Nov 13, 2016 at 3:06 PM, Art Sepin art@synergy-gps.com wrote:
Mitch,
You have either a 6 channel PVT-6 or a 6\8 channel Basic Oncore. Both
share size, power and I\O specifications. I'll send the Basic Oncore
Engineering Notes to you off list.
We'll also post the Engineering Notes to our website for others who
might be interests in this early nineties legacy Motorola product By
Tuesday: http://www.synergy-gps.com/index.php?option=com_content&
task=view&id=42&Itemid=89.
Art Sepin
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of CIW308
VE6OH
Sent: Sunday, November 13, 2016 1:29 PM
To: Discussion of precise time and frequency measurement <
time-nuts@febo.com>
Subject: [time-nuts] GPS Model ?
Any idea what unit this is?
Has the markings:
Motorola
7ST5H on a bar code
TM-AC on the PCB
BV-AC M447D on PCB
84D43215M03 on PCB
Looks similar to the old ONCORE stuff.
This unit has a BNC added to the Antenna.
Did some searching but no luck yet.
Hope the attachments go thru.
Thanks in advance.
Mitch
J. T. (Mitch) [Amateur radio VE6OH] [CFARS CIW308] email
mitch@andor.net
Mobile Cellular 780 446 8958 SKYPE USER ID "MITCH-VE6OH"
Past RAC Director for Alberta, NWT, NU https://na01.safelinks.
protection.outlook.com/?url=HTTP%3A%2F%2FWWW.RAC.CA&data=
01%7C01%7Cart%40synergy-gps.com%7C85efe09a17e0420e07ac08d40c10cd44%
7Cc81f9fdec0e04d8c95779afaa0cad9ed%7C1&sdata=0Xaed5Ff0AHg42sDZd%
2BYbKdFEHAC%2FKYOmnIL%2Bc5mecY%3D&reserved=0
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Chris Albertson
Redondo Beach, California
Moin
On Sun, 13 Nov 2016 23:23:13 +0100
Attila Kinali attila@kinali.ch wrote:
[1] "Exact Analysis of DDS Spurs and SNR due to Phase Truncation and
Arbitrary Phase-to-Amplitude Errors", by Torosyan and Wilson, 2005
http://tycho.usno.navy.mil/ptti/ptti2005/paper8.pdf
Magnus told me that the paper has moved since I last checked.
It's new home is
http://tycho.usno.navy.mil/ptti/2005papers/paper8.pdf
Attila Kinali
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the prosperity and technological sophistication in the world is of no
use without that foundation.
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