No PLL there.
10 MHz goes into a ECL gate that creates a 5 ns short pulse, amplified
and the 90 MHz overtone is selected and filtered with tuned crystal filters.
Cheers,
Magnus
On 11/24/2014 03:17 AM, Bob Camp wrote:
Hi
The ADEV of the reference source (OCXO / external reference) will most
certainly impact the performance of the counter. The device is just comparing
the input signal to the reference. Which ever one has the worse stability will
limit the measurement. At some point (inside the 90 MHz VCXO’s PLL) jitter on
the reference is no different than jitter on the signal you are trying to
measure. If they do as many do, there’s a PLL that locks the OCXO up to the
external reference through a narrowband loop. You then have two filter corners
to worry about. One between the 90 MHz and the OCXO, the other between the
external ref and the OCXO.
Bob
On Nov 23, 2014, at 8:48 PM, Don Latham <[email protected]> wrote:
From the manual, I infer the dac is 10 bit. ( 4096 max count) Span is 5 volts.
I've connected the gpsdo and the clock error light does not light; I'm
assuming the morion is locking to the gpsdo OK. I do have the original, was
going to open it up sometime. I suspect something wrong with the heater.
Should just start by measuring current into + and - 15 volts.
I think that Said's device could just be put inside the SR fb, and convert the
external input bnc to the gps antenna. No sweat. Even the low end clock osc
would work quite well, no fancy ocxo needed. SR can also be used with internal
clock if needed. The dac value is saved so the internal osc is automatically
calibrated by this technique.
I'm really impressed by this box! A lot of thought went into it.
Don
Bob Camp
Hi
About the only other question would be the proper resolution for the DAC.
There’s not much of a way to to answer that one without playing with a woking
original OCXO.
Bob
On Nov 23, 2014, at 7:22 PM, Don Latham <[email protected]> wrote:
No question about that. The morion does run a little warmer than the old
unit
apparently did. Fan is temp-controlled, so I think OK. will monitor box temp
with a digital :-) thermometer, very poor resolution, but probably ok.
When I get the last obs done. will do a little blurb to the group.
Don
Bob Camp
Hi
That sounds fine. Without knowing just what they did or didn’t do, it’s
always
worth being a bit careful.
Bob
On Nov 23, 2014, at 6:40 PM, Don Latham <[email protected]> wrote:
Running very nearly continuously for about 4 days now. The self-measured
jitter is mean 0 and sdev of 8 ps. I don't think there is a problem with
the
Morion. I'm using my newly acquired cs source and a couple of z3801's for
checking. 1 bit on the SR's frequency calibration dac seems to be about
4-5
parts in 10^-10 if I'm reading things right. Next test is a z3801 driving
the
external freq port on the sr to see if the frequency change direction of
the
morion is OK.
The scope display output from the SR620 is great!
Lots to learn. Also have one of Said's units coming. Gone nuts for time,
won't
do anything much new, but it's new to me. All this to drive moonbounce...
Don
Bob Camp
Hi
If all the “good stuff” runs on the 90 MHz, the 5 MHz issue may not be
important at all. It’s just something to watch for. If you start seeing
data
in two groups, each one 20 ps wide and separated by maybe 200 ps, you are
seeing a problem from the 5 MHz.
Running the box for a while before doing a full detailed cal is a very
good
idea. It’s a bit warm inside and some of the stuff is temperature
sensitive.
You want it to reach equilibrium.
Bob
On Nov 23, 2014, at 1:06 AM, Don Latham <[email protected]> wrote:
Ah. Got it finally! Doh. Just finished trying out the Morion this
afternoon.
Electrically works very well. Used a 7812 to drop the +15 volts from the
option 1 ocxo, there is enough power headroom to bring the Morion up
from
cold
and run it comfortably. As you said, the control voltage for the
original
is
indeed 5 v, and can be set by the internal d/a. The output of the
oscillator
passes through an emitter follower voltage adjuster and through a low-q
filter
to three stages of ECL buffer and then out to the 10 MHz system bus
clock.
Another path proceeds to a relay-switched divide by 2 to the phase
detector
so
an external 5/10 MHz source can lock the internal oscillator.
The external 5/10 MHz source proceeds to the phase detector thru an
identical
buffer chain without the switched divider. The remainder of the clock
circuits is a multiplier to 90 MHz.
I'll run the autocal tomorrow and then get some jitter stats if
possible.
This
is an early specimen, s/n about 700 or so. I can imagine seldom used,
and
sitting on standby for 20 years or so, pushing the ocxo out of
tolerance.
The saga continues; I may have to look for a 10 MHz replacement on epay,
there
isn't room to put in an Hp, unfortunately.
Don
Bob Camp
Hi
At least the Morion’s I have seen have 5 MHz crystals in them rather
than
10
MHz. They have a 10 MHz output due to an internal doubler. Since the
circuit
is not perfect, there is cycle to cycle variation in the 10 MHz. It’s
way
more
jitter (measured in picoseconds) than the oscillator has due to phase
noise.
My concern is that a counter might be bothered by this is some subtle
way.
Bob
On Nov 22, 2014, at 3:55 PM, Don Latham <[email protected]> wrote:
Hi Bob: no. cobble, not double :-) A little research has me thinking
I
can
easily adapt a morion. I can try it at least by starting with the
morion
on
an
external power supply and patching the output and control voltages in
to
the
sr.
The sr620 has a control circuit which apparently accomplishes your
suggestions; they claim to use the internal oscillator for short term
and
"lock" it to a supplied external source for longer term. Probably has
a
long
time constant on the built-in phase lock to do this.
Anyhow, autocal calibrates everything except, guess what, the 10 mhz
source.
Thats done separately.
So a bootup self check shows OK even if the frequency standard is way
off.
Onward and upward.
Don
Bob Camp
Hi
I believe that the SR620 uses a “true” 10 MHz OCXO. I would be
careful
using a
5 MHz doubled to 10 OCXO. The counter may or may not be happy with
sub-harmonic induced jitter.
Best bet at the specs:
+12V power
0-5V EFC
Sine wave out +7dbm
+/- 5x10^-9 0 to 70C
Pinout - trace what you have.
Bob
On Nov 21, 2014, at 6:59 PM, Don Latham <[email protected]> wrote:
So, I got a reasonable deal on a SR620 ho ho. Know your dealer. The
ocxo
is
out of tolerance. All self tests pass with flying colors, autocal
works
as
well. So the best parts are OK.
Does anyone:
1) have a spare Isotemp OCXO36-53 10.000 MHz p/n 6-00051?
2) know the specs, ie the input voltage/current and the control
voltage
span
and direction? pinout?
I have some Morion mv-89's and could easily cobble one in if it
will
work.
Apparently a correct oscillator must be in place to use an external
source,
if
I read the manual right.
3) do we have a source for the schematics for the SR 620?
The FTS 4060 is up, pumpin' and firmly locked. At least for now.
That
dealer
was not lyin'
Much thanks to all of you.
The adventure continues
--
"The power of accurate observation is commonly called cynicism by
those
who
have not got it."
-George Bernard Shaw
Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
Huson, MT, 59846
mail: POBox 404
Frenchtown MT 59834-0404
VOX 406-626-4304
Skype: buffler2
www.lightningforensics.com
www.sixmilesystems.com
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--
"The power of accurate observation is commonly called cynicism by
those
who
have not got it."
-George Bernard Shaw
Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
Huson, MT, 59846
mail: POBox 404
Frenchtown MT 59834-0404
VOX 406-626-4304
Skype: buffler2
www.lightningforensics.com
www.sixmilesystems.com
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--
"The power of accurate observation is commonly called cynicism by those
who
have not got it."
-George Bernard Shaw
Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
Huson, MT, 59846
mail: POBox 404
Frenchtown MT 59834-0404
VOX 406-626-4304
Skype: buffler2
www.lightningforensics.com
www.sixmilesystems.com
_______________________________________________
time-nuts mailing list -- [email protected]
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time-nuts mailing list -- [email protected]
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and follow the instructions there.
--
"The power of accurate observation is commonly called cynicism by those
who
have not got it."
-George Bernard Shaw
Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
Huson, MT, 59846
mail: POBox 404
Frenchtown MT 59834-0404
VOX 406-626-4304
Skype: buffler2
www.lightningforensics.com
www.sixmilesystems.com
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to
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time-nuts mailing list -- [email protected]
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and follow the instructions there.
--
"The power of accurate observation is commonly called cynicism by those who
have not got it."
-George Bernard Shaw
Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
Huson, MT, 59846
mail: POBox 404
Frenchtown MT 59834-0404
VOX 406-626-4304
Skype: buffler2
www.lightningforensics.com
www.sixmilesystems.com
_______________________________________________
time-nuts mailing list -- [email protected]
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and follow the instructions there.
--
"The power of accurate observation is commonly called cynicism by those who
have not got it."
-George Bernard Shaw
Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
Huson, MT, 59846
mail: POBox 404
Frenchtown MT 59834-0404
VOX 406-626-4304
Skype: buffler2
www.lightningforensics.com
www.sixmilesystems.com
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