I compared the OCXO output to the 10 MHz output of both a Z3801A and a
Tbolt and discovered that the CW-12's 10 MHz output is about 1.5e-11 (i.e.
1.5e-4 Hz) low in frequency. I emailed Navsync and they replied:
The CW12 Motorola Binary and NMEA versions both do not phase align the
These Conner Winfield (Navsync) parts are not GPS Disciplined Oscillators,
many folks are initially fooled by this.
They use digital phase hopping techniques to generate something close to
10MHz. You can see the 10MHz 100ns phase jump around on a scope.
I believe their FTS250 and 125
You are right. We use the CW12 (timing version) and it behaves as you
depicted. Of course there is also no holdover on its 10MHz output. Only the
FTS125 (and similar) have first a fixed OCXO to drive the GPS receiver and
then an OCXO to be aligned with the 10MHz to have a real 10MHz with
holdover
On 1/4/2012 2:14 AM, Hal Murray wrote:
I compared the OCXO output to the 10 MHz output of both a Z3801A and a
Tbolt and discovered that the CW-12's 10 MHz output is about 1.5e-11 (i.e.
1.5e-4 Hz) low in frequency. I emailed Navsync and they replied:
The CW12 Motorola Binary and NMEA
I've never said that the CW12 was a GPSDO. What I expected to get was a
noisy NCO that had an average frequency of 10 MHz. What I got was a
worthless noise generator.
What's the point of saying that it's steered by GPS when it's
off-frequency. What does that even mean? Does it steer the
On 1/4/2012 9:29 AM, Ed Palmer wrote:
What's the point of saying that it's steered by GPS when it's
off-frequency. What does that even mean? Does it steer the frequency to
keep the error constant?
If it's constant, maybe they just need to re-spec it as having a
9.985 MHz output. :-)
The output frequency is programmable: try $PRTHS,FRQD,xx.xxxcrlf where
xx.xxx is the desired(?) frequency in MHz with 3 decimal places (they say
for 10KHz set 0.010).
Maybe the slight offset is due to the NCO based on the chipping rate of
10.23MHz:
10.23MHz/2^32*4198404003 is 9.783MHz
On
On 1/4/2012 8:49 AM, Mike S wrote:
On 1/4/2012 9:29 AM, Ed Palmer wrote:
What's the point of saying that it's steered by GPS when it's
off-frequency. What does that even mean? Does it steer the frequency to
keep the error constant?
If it's constant, maybe they just need to re-spec it as
On 1/4/2012 9:00 AM, Azelio Boriani wrote:
The output frequency is programmable: try $PRTHS,FRQD,xx.xxxcrlf where
xx.xxx is the desired(?) frequency in MHz with 3 decimal places (they say
for 10KHz set 0.010).
Unfortunately, the frequency is programmable only with the NMEA software
load.
Yes, the error is greater... then maybe the clock of the NCO is not the
chipping rate. In the FTS125 the clock for the RX is sourced by a 20MHz
OFC5DJ3 fixed OCXO but this doesn't imply that the CW12 has a 20MHz
clock... at the moment no other clue comes to mind.
On Wed, Jan 4, 2012 at 5:35 PM,
Hi Ed,
Since the oscillator is typically free-running in an NCO, and periodically
corrected by phase drops to stay on frequency the error you are seeing may be
caused be the offset in your crystal, combined with the limited digital
resolution of the NCO trying to correct for this offset.
If
Interesting...now i wonder how they can steer the frequency. Usually in C/A
GPS receivers the oscillator is not corrected and any drift is accounted
for in software: usually you see geographic coordinates out of the
receiver. In the Motorola receiver they say the PPS has the granularity of
the
On 1/4/2012 11:13 AM, Said Jackson wrote:
Hi Ed,
Since the oscillator is typically free-running in an NCO, and periodically corrected by
phase drops to stay on frequency the error you are seeing may be caused be
the offset in your crystal, combined with the limited digital resolution of the
Interesting... this explains why they use a 20MHz OCXO (without EFC) in the
FTS125 to clock the receiver that has an NCO steered that clocks a PLL that
synchronize another OCXO (with EFC). Yes, I have opened up an FTS125.
On Wed, Jan 4, 2012 at 8:32 PM, Ed Palmer ed_pal...@sasktel.net wrote:
On
Hello Azelio,
we looked at one here ordered from Digikey, and it had two VCXO's/TCXOs.
They did not use any OCXO's.
Lot's of folks ask us why the CW parts are lower cost than real GPSDO's, I
guess now we know..
bye,
Said
In a message dated 1/4/2012 12:33:34 Pacific Standard Time,
Hi Ed,
sorry to hear that, contact me off-list and I will try to solve your
problem. I tried sending you an email, but my mails must be getting filtered by
your spam filter..
bye,
Said
In a message dated 1/4/2012 11:33:14 Pacific Standard Time,
ed_pal...@sasktel.net writes:
On
It depends on the option ordered: the FTS125s we have are FTS125-COO
(double OCXO) the -CTV option is the TCXO/VCXO option, there is the -COV
option too.
On Wed, Jan 4, 2012 at 10:08 PM, saidj...@aol.com wrote:
Hi Ed,
sorry to hear that, contact me off-list and I will try to solve your
yes, see that now, looks like the OCXO option about doubles the price of
the unit on Digikey..
In a message dated 1/4/2012 13:56:59 Pacific Standard Time,
azelio.bori...@screen.it writes:
It depends on the option ordered: the FTS125s we have are FTS125-COO
(double OCXO) the -CTV option
The OCXO used are marked OFC3DJ1AA (fixed) and OVC3CE1AA (with EFC) but no
data I have found: only OVC5 and OFC5 series.
On Wed, Jan 4, 2012 at 11:04 PM, saidj...@aol.com wrote:
yes, see that now, looks like the OCXO option about doubles the price of
the unit on Digikey..
In a message dated
In the past I've mentioned the Navsync CW-12 GPS board. Oncore M12
drop-in replacement, 1 PPS ( measured Standard Deviation 5 ns., range
~ 30 ns. from min to max for 1000 measurements), and a 10 MHz output
that's 'steered by the GPS receiver'.
The recent discussions about a cheap, simple
Wait...they said it is good enough for government work?
This is an interesting discovery, but I wonder if this is intentional
for some not so obvious reason.
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