subject:"\[time\-nuts\] ocxo"

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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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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 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.
 
 ___
 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.
 
 
 
 
 --
 The power of accurate observation is commonly called cynicism by those

Re: [time-nuts] ocxo

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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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

Re: [time-nuts] ocxo

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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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'

Re: [time-nuts] ocxo

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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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

Re: [time-nuts] ocxo

2014-11-23 Thread Neil Schroeder

Did we answer the q? about schematics?

All of SRS's products have their block diagram and parts list with a
detailed circuit description in their user manual.  Sneak preview: its all
resistors.

NS

On Sun, Nov 23, 2014 at 4:22 PM, Don Latham d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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

Re: [time-nuts] ocxo

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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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

Re: [time-nuts] ocxo

Schematics in KO4BB magnificent storehouse.

Neil Schroeder
 Did we answer the q? about schematics?

 All of SRS's products have their block diagram and parts list with a
 detailed circuit description in their user manual.  Sneak preview: its all
 resistors.

 NS

 On Sun, Nov 23, 2014 at 4:22 PM, Don Latham d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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

Re: [time-nuts] ocxo

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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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

Re: [time-nuts] ocxo

2014-11-23 Thread Neil Schroeder

No but a little math based on your ocxo's range can help... but measuring
it in person does give you the best numbers.

More precision and more bits WON'T hurt here and the application notes from
the leading crystal makers suggest a DAC front ended by a precision op amp
with and that the xo be followed by a buffer.  So I took the nuclear option:

http://www.analog.com/static/imported-files/circuit_notes/CN0257.pdf

My Wenzels don't have a reference out and neither do any of my VCXOs, but
my $30 Vectron from Ebay does - so my circuit for it is modified to accept
its reference voltage (its also plugged into an ADF4001 now)

NS


On Sun, Nov 23, 2014 at 4:56 PM, Bob Camp kb...@n1k.org wrote:

 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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

Re: [time-nuts] ocxo

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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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

Re: [time-nuts] ocxo

Hi

The main question is - is there a PLL between the external ref and the OCXO? If 
so does it go through the DAC? 

If there’s a PLL through the DAC, then bits do matter. If the DAC is simply a 
replacement for a trim pot, then it may not matter much at all. The OCXO will 
likely age more in a few days than the reported LSB resolution of the DAC. I’d 
bet DAC is not part of a PLL.

Bob


 On Nov 23, 2014, at 8:04 PM, Neil Schroeder gign...@gmail.com wrote:
 
 No but a little math based on your ocxo's range can help... but measuring
 it in person does give you the best numbers.
 
 More precision and more bits WON'T hurt here and the application notes from
 the leading crystal makers suggest a DAC front ended by a precision op amp
 with and that the xo be followed by a buffer.  So I took the nuclear option:
 
 http://www.analog.com/static/imported-files/circuit_notes/CN0257.pdf
 
 My Wenzels don't have a reference out and neither do any of my VCXOs, but
 my $30 Vectron from Ebay does - so my circuit for it is modified to accept
 its reference voltage (its also plugged into an ADF4001 now)
 
 NS
 
 
 On Sun, Nov 23, 2014 at 4:56 PM, Bob Camp kb...@n1k.org wrote:
 
 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com wrote:
 
 Hi Bob: no. cobble, not double :-)  A little

Re: [time-nuts] ocxo

The 90 MHz is multiplied up from the 10 MHz, no pll.  Done with a 10 mhz rate
5 ns pulse and a filter chain, followed by a comparator and buffer.

from the manual:
The SR620 has a rear panel input that will accept either a 5 or 10Mhz external
timebase. The SR620 phaselocks its internal timebase to this reference. The
phase-locked loop has a bandwidth of about 20Hz and thus the characteristics
the the SR620's clock, for measurement times longer than 50ms, become that of
the external source. For shorter measurement times the clock characteristics
are unimportant compared to the internal jitter (25ps rms) of the SR620. Thus,
if the signal from a Cesium clock is input into a SR620 with a standard TCXO
oscillator the short-term and long-term stability of the SR620 will become
that of the Cesium clock.

Yes, all jitter is relative...

Don

Bob Camp
 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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 d...@montana.com 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

Re: [time-nuts] ocxo

2014-11-22 Thread Don Latham

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 d...@montana.com 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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 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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 To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
 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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Re: [time-nuts] ocxo

2014-11-22 Thread 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 d...@montana.com 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 d...@montana.com 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
 
 
 ___
 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.
 
 ___
 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.
 
 
 
 
 -- 
 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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 To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] ocxo

2014-11-22 Thread Don Latham

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 d...@montana.com 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 d...@montana.com 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


 ___
 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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 To unsubscribe, go to
 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
 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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 To unsubscribe, go to
 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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 To

[time-nuts] ocxo

2014-11-21 Thread Don Latham


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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and follow the instructions there.

Re: [time-nuts] ocxo

2014-11-21 Thread 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 d...@montana.com 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
 
 
 ___
 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.

Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

2014-09-11 Thread Bernd Neubig

Hi Bob,

your example is correct. However I was not talking about OCXO specifically, but 
about crystal oscillators in general. And the effect I have mentioned is not 
limited to wide-pull VCXO, but may occur at normal VCXO also. I named the 
modulation audio for sake of simplicity of expression - it was certainly not 
accurate enough. If you are modulating data (FSK) then such interferences have 
a risk to occur even at moderate data rates.
I do not talk about theorectical can be's but about practical experience.

Best regards

Bernd
 

-Ursprüngliche Nachricht-
Von: time-nuts [mailto:time-nuts-boun...@febo.com] Im Auftrag von Bob Camp
Gesendet: Donnerstag, 11. September 2014 00:18
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

Hi

If you are modulating a normal OCXO EFC with audio, and the output frequency is 
not being multiplied up, the modulation index will be very low. Low modulation 
index means that the higher order FM sidebands will be quite far down. 

If you take “audio” to be  10 KHz, and a VHF OCXO to be 100 MHz: With a 10 ppm 
EFC range, you get 1.0 KHz of deviation. The modulation index is  1 a decade 
below your upper modulation frequency. That’s already a pretty wide swing OCXO 
and a fairly high modulation frequency for an EFC line. 

If you have a spur that is in the 50 to 150 KHz range, you are talking about 
the 5th to 15th sideband off of 10 KHz or the 50th to 150th sideband off of 1 
KHz. At 50 sidebands out and an index of 1, you are in the “forget about it” 
region. Even at 10 KHz, the sideband is not likely to create much of an issue. 
The distortion from the non-linear EFC slope will be more of a problem in a 
practical sense. 

——

Since the modulation is single sideband, yes it converts PM - AM. It also 
will be impacted by any limiters in the system and will not multiply the same 
way as a pure PM modulation. The phase of the sideband will change as you go 
through the resonance, further messing up the multiplication / limiter math. 

Bob

On Sep 10, 2014, at 12:50 PM, Magnus Danielson mag...@rubidium.dyndns.org 
wrote:

 Bernd,
 
 Brilliant point. Easy to miss if one has a to simple model of the oscillator 
 at hand.
 
 Since it is a single-side-band mode, it will show up both as AM and PM with 
 the same amplitude.
 
 Cheers,
 Magnus
 
 On 09/10/2014 03:27 PM, Bernd Neubig wrote:
 Hi Bob,
 
 your description oft he spurious coming from higher overtone of 
 low-frequency modes is correct. I want to add, that all thickness-shear mode 
 crystals (such as AT, BT and SC-cut) have so-called an-harmonic spurious 
 modes, which is a whole ensemble of spurs located  slightly above above the 
 main mode (fundamental or overtone mode). slightly means starting at about 
 50 kHz to 200 kHz above for fundamental mode and about 30 ... 50 kHz above 
 for overtone modes. These an-harmonic modes are relaled to the length and 
 width of the active area (electrode).
 These spurious modes do not come only into play for wide-pull VCXO, but also 
 in the case that the EFC input is used for modulation with signals in the 
 audio frequency range.
 Remember that a frequency modulated signal has side-lines which are N* the 
 audio frequency apart from the carrier. The amplitude of these side lines 
 follows the so-called Bessel functions and varies with the modulation index.
 If it happens that such a Bessel-line for a particular modulation 
 frequency coincides with such a spur, it comes to an interference, This 
 means the modulation frequency response becomes a discontinuity (dip) at a 
 sharp frequency. Such band breaks do even occur if the spurious is so weak 
 that it can barely be seen on a network analyzer.
 
 Regards
 
 Bernd   DK1AG
 AXTAL GmbH  Co. KG
 www.axtal.com
 
 -Ursprüngliche Nachricht-
 Von: time-nuts [mailto:time-nuts-boun...@febo.com] Im Auftrag von Bob 
 Camp
 Gesendet: Sonntag, 7. September 2014 04:21
 An: Discussion of precise time and frequency measurement
 Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
 
 Hi
 
 Simple answer = crystals are never perfect.
 
 Longer winded, but very incomplete answer =
 
 A spurious response in a crystal normally refers to a mode that is not one 
 of the “identified” modes of the crystal. An AT has a set of identified 
 modes, an SC has a more complex set of modes. In the case of the AT it would 
 be the fundamental and the odd overtones. In the case of the SC you have the 
 A, B, C modes and their odd overtones. None of those are considered spurious.
 
 A spur can come from a lot of different places.  One common one is higher 
 order vibrations in a longer dimension face of the resonator. The 183rd 
 overtone of the width of the blank is still a legitimate resonant mode. 
 Another source are modes other than shear (like flex). Deriving a full 
 catalog of all the modes of an arbitrary blank design is a major project. 
 There are only a handful

Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

2014-09-11 Thread Bob Camp

Hi

I understand that we are talking about a couple of different things. Since we 
started out talking about OCXO’s I figured it was worth it to bring it back to 
where we started.

Bob

On Sep 11, 2014, at 4:32 AM, Bernd Neubig bneu...@t-online.de wrote:

 Hi Bob,
 
 your example is correct. However I was not talking about OCXO specifically, 
 but about crystal oscillators in general. And the effect I have mentioned is 
 not limited to wide-pull VCXO, but may occur at normal VCXO also. I named 
 the modulation audio for sake of simplicity of expression - it was 
 certainly not accurate enough. If you are modulating data (FSK) then such 
 interferences have a risk to occur even at moderate data rates.
 I do not talk about theorectical can be's but about practical experience.
 
 Best regards
 
 Bernd
 
 
 -Ursprüngliche Nachricht-
 Von: time-nuts [mailto:time-nuts-boun...@febo.com] Im Auftrag von Bob Camp
 Gesendet: Donnerstag, 11. September 2014 00:18
 An: Discussion of precise time and frequency measurement
 Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
 
 Hi
 
 If you are modulating a normal OCXO EFC with audio, and the output frequency 
 is not being multiplied up, the modulation index will be very low. Low 
 modulation index means that the higher order FM sidebands will be quite far 
 down. 
 
 If you take “audio” to be  10 KHz, and a VHF OCXO to be 100 MHz: With a 10 
 ppm EFC range, you get 1.0 KHz of deviation. The modulation index is  1 a 
 decade below your upper modulation frequency. That’s already a pretty wide 
 swing OCXO and a fairly high modulation frequency for an EFC line. 
 
 If you have a spur that is in the 50 to 150 KHz range, you are talking about 
 the 5th to 15th sideband off of 10 KHz or the 50th to 150th sideband off of 1 
 KHz. At 50 sidebands out and an index of 1, you are in the “forget about it” 
 region. Even at 10 KHz, the sideband is not likely to create much of an 
 issue. The distortion from the non-linear EFC slope will be more of a problem 
 in a practical sense. 
 
 ——
 
 Since the modulation is single sideband, yes it converts PM - AM. It also 
 will be impacted by any limiters in the system and will not multiply the same 
 way as a pure PM modulation. The phase of the sideband will change as you go 
 through the resonance, further messing up the multiplication / limiter math. 
 
 Bob
 
 On Sep 10, 2014, at 12:50 PM, Magnus Danielson mag...@rubidium.dyndns.org 
 wrote:
 
 Bernd,
 
 Brilliant point. Easy to miss if one has a to simple model of the oscillator 
 at hand.
 
 Since it is a single-side-band mode, it will show up both as AM and PM with 
 the same amplitude.
 
 Cheers,
 Magnus
 
 On 09/10/2014 03:27 PM, Bernd Neubig wrote:
 Hi Bob,
 
 your description oft he spurious coming from higher overtone of 
 low-frequency modes is correct. I want to add, that all thickness-shear 
 mode crystals (such as AT, BT and SC-cut) have so-called an-harmonic 
 spurious modes, which is a whole ensemble of spurs located  slightly above 
 above the main mode (fundamental or overtone mode). slightly means 
 starting at about 50 kHz to 200 kHz above for fundamental mode and about 30 
 ... 50 kHz above for overtone modes. These an-harmonic modes are relaled to 
 the length and width of the active area (electrode).
 These spurious modes do not come only into play for wide-pull VCXO, but 
 also in the case that the EFC input is used for modulation with signals in 
 the audio frequency range.
 Remember that a frequency modulated signal has side-lines which are N* the 
 audio frequency apart from the carrier. The amplitude of these side lines 
 follows the so-called Bessel functions and varies with the modulation index.
 If it happens that such a Bessel-line for a particular modulation 
 frequency coincides with such a spur, it comes to an interference, This 
 means the modulation frequency response becomes a discontinuity (dip) at a 
 sharp frequency. Such band breaks do even occur if the spurious is so weak 
 that it can barely be seen on a network analyzer.
 
 Regards
 
 Bernd   DK1AG
 AXTAL GmbH  Co. KG
 www.axtal.com
 
 -Ursprüngliche Nachricht-
 Von: time-nuts [mailto:time-nuts-boun...@febo.com] Im Auftrag von Bob 
 Camp
 Gesendet: Sonntag, 7. September 2014 04:21
 An: Discussion of precise time and frequency measurement
 Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
 
 Hi
 
 Simple answer = crystals are never perfect.
 
 Longer winded, but very incomplete answer =
 
 A spurious response in a crystal normally refers to a mode that is not one 
 of the “identified” modes of the crystal. An AT has a set of identified 
 modes, an SC has a more complex set of modes. In the case of the AT it 
 would be the fundamental and the odd overtones. In the case of the SC you 
 have the A, B, C modes and their odd overtones. None of those are 
 considered spurious.
 
 A spur can come from a lot of different places.  One common one is higher 
 order vibrations

Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

2014-09-11 Thread Bert Kehren via time-nuts

I have on purpose stayed out of this discussions but I think it is time to  
mention some benchmarks. Last year we did a work over of the Shera 
controller  when we where allowed to release assembly and hex code. In order to 
make 
sure  that the code was solid we ran extensive tests using a 1 pps from a 
tbolt the  original AD1861 which by no means is an ideal DAC and a Morion 
MV89.
The DAC resolution is 1.7 E-13 per bit and after a couple of days  warmup  
the DAC did not change a single bit for 0.2 hrs and 1 bit over 0.4  hrs. 
Over an 80 hr. period the total change was 120 bits mostly aging but you  can 
also see ambient temperature change. 
Data and plots are available but can not be attached because of data  
limitation
Bert Kehren
 
 
In a message dated 9/11/2014 7:37:03 A.M. Eastern Daylight Time,  
kb...@n1k.org writes:

Hi

I  understand that we are talking about a couple of different things. Since 
we  started out talking about OCXO’s I figured it was worth it to bring it 
back to  where we started.

Bob

On Sep 11, 2014, at 4:32 AM, Bernd Neubig  bneu...@t-online.de wrote:

 Hi Bob,
 
 your  example is correct. However I was not talking about OCXO 
specifically, but  about crystal oscillators in general. And the effect I have 
mentioned is not  limited to wide-pull VCXO, but may occur at normal VCXO 
also. I 
named the  modulation audio for sake of simplicity of expression - it was 
certainly not  accurate enough. If you are modulating data (FSK) then such 
interferences have  a risk to occur even at moderate data rates.
 I do not talk about  theorectical can be's but about practical 
experience.
 
 Best  regards
 
 Bernd
 
 
 -Ursprüngliche  Nachricht-
 Von: time-nuts [mailto:time-nuts-boun...@febo.com] Im  Auftrag von Bob 
Camp
 Gesendet: Donnerstag, 11. September 2014  00:18
 An: Discussion of precise time and frequency measurement
  Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
 
  Hi
 
 If you are modulating a normal OCXO EFC with audio, and  the output 
frequency is not being multiplied up, the modulation index will be  very low. 
Low 
modulation index means that the higher order FM sidebands will  be quite 
far down. 
 
 If you take “audio” to be  10 KHz,  and a VHF OCXO to be 100 MHz: With 
a 10 ppm EFC range, you get 1.0 KHz of  deviation. The modulation index is  
1 a decade below your upper modulation  frequency. That’s already a pretty 
wide swing OCXO and a fairly high  modulation frequency for an EFC line. 
 
 If you have a spur  that is in the 50 to 150 KHz range, you are talking 
about the 5th to 15th  sideband off of 10 KHz or the 50th to 150th sideband 
off of 1 KHz. At 50  sidebands out and an index of 1, you are in the “forget 
about it” region. Even  at 10 KHz, the sideband is not likely to create much 
of an issue. The  distortion from the non-linear EFC slope will be more of 
a problem in a  practical sense. 
 
 ——
 
 Since the modulation is  single sideband, yes it converts PM - AM. It 
also will be impacted by  any limiters in the system and will not multiply 
the same way as a pure PM  modulation. The phase of the sideband will change 
as you go through the  resonance, further messing up the multiplication / 
limiter math. 
  
 Bob
 
 On Sep 10, 2014, at 12:50 PM, Magnus Danielson  
mag...@rubidium.dyndns.org wrote:
 
  Bernd,
 
 Brilliant point. Easy to miss if one has a to  simple model of the 
oscillator at hand.
 
 Since it is a  single-side-band mode, it will show up both as AM and PM 
with the same  amplitude.
 
 Cheers,
 Magnus
  
 On 09/10/2014 03:27 PM, Bernd Neubig wrote:
 Hi  Bob,
 
 your description oft he spurious coming  from higher overtone of 
low-frequency modes is correct. I want to add, that  all thickness-shear mode 
crystals (such as AT, BT and SC-cut) have so-called  an-harmonic spurious 
modes, 
which is a whole ensemble of spurs located   slightly above above the main 
mode (fundamental or overtone mode). slightly  means starting at about 50 
kHz to 200 kHz above for fundamental mode and about  30 ... 50 kHz above for 
overtone modes. These an-harmonic modes are relaled to  the length and width 
of the active area (electrode).
 These  spurious modes do not come only into play for wide-pull VCXO, 
but also in the  case that the EFC input is used for modulation with signals 
in the audio  frequency range.
 Remember that a frequency modulated signal  has side-lines which are N* 
the audio frequency apart from the carrier. The  amplitude of these side 
lines follows the so-called Bessel functions and  varies with the modulation 
index.
 If it happens that such a  Bessel-line for a particular modulation 
frequency coincides with such a  spur, it comes to an interference, This means 
the modulation frequency  response becomes a discontinuity (dip) at a sharp 
frequency. Such band breaks  do even occur if the spurious is so weak that 
it can barely be seen on a  network analyzer.
 
 Regards
  
 Bernd   DK1AG
 AXTAL GmbH  Co.  KG

Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

2014-09-10 Thread Bernd Neubig

Hi Bob,

your description oft he spurious coming from higher overtone of low-frequency 
modes is correct. I want to add, that all thickness-shear mode crystals (such 
as AT, BT and SC-cut) have so-called an-harmonic spurious modes, which is a 
whole ensemble of spurs located  slightly above above the main mode 
(fundamental or overtone mode). slightly means starting at about 50 kHz to 200 
kHz above for fundamental mode and about 30 ... 50 kHz above for overtone 
modes. These an-harmonic modes are relaled to the length and width of the 
active area (electrode).
These spurious modes do not come only into play for wide-pull VCXO, but also in 
the case that the EFC input is used for modulation with signals in the audio 
frequency range.
Remember that a frequency modulated signal has side-lines which are N* the 
audio frequency apart from the carrier. The amplitude of these side lines 
follows the so-called Bessel functions and varies with the modulation index.
If it happens that such a Bessel-line for a particular modulation frequency 
coincides with such a spur, it comes to an interference, This means the 
modulation frequency response becomes a discontinuity (dip) at a sharp 
frequency. Such band breaks do even occur if the spurious is so weak that it 
can barely be seen on a network analyzer.

Regards

Bernd   DK1AG
AXTAL GmbH  Co. KG
www.axtal.com

-Ursprüngliche Nachricht-
Von: time-nuts [mailto:time-nuts-boun...@febo.com] Im Auftrag von Bob Camp
Gesendet: Sonntag, 7. September 2014 04:21
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

Hi

Simple answer = crystals are never perfect.

Longer winded, but very incomplete answer =

A spurious response in a crystal normally refers to a mode that is not one of 
the “identified” modes of the crystal. An AT has a set of identified modes, an 
SC has a more complex set of modes. In the case of the AT it would be the 
fundamental and the odd overtones. In the case of the SC you have the A, B, C 
modes and their odd overtones. None of those are considered spurious. 

A spur can come from a lot of different places.  One common one is higher order 
vibrations in a longer dimension face of the resonator. The 183rd overtone of 
the width of the blank is still a legitimate resonant mode. Another source are 
modes other than shear (like flex). Deriving a full catalog of all the modes of 
an arbitrary blank design is a major project. There are only a handful of 
people out there who are into that sort of thing (as opposed to simply cranking 
through some formulas).  

Practical answer = Don’t worry about it. Unless you are building a wide pull 
VCXO or a wide deviation VCXO (often the same thing) you will never notice 
them. 

Bob

On Sep 6, 2014, at 9:13 PM, Hal Murray hmur...@megapathdsl.net wrote:

 
 kb...@n1k.org said:
 The biggest problem comes from crystal spurs rather than crystal Q. 
 
 What's the mechanism for making spurs with a crystal?
 
 --
 These are my opinions.  I hate spam.
 
 
 
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Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

2014-09-10 Thread Magnus Danielson

Bernd,

Brilliant point. Easy to miss if one has a to simple model of the
oscillator at hand.

Since it is a single-side-band mode, it will show up both as AM and PM
with the same amplitude.

Cheers,
Magnus

On 09/10/2014 03:27 PM, Bernd Neubig wrote:

Hi Bob,

your description oft he spurious coming from higher overtone of low-frequency modes
is correct. I want to add, that all thickness-shear mode crystals (such as AT, BT
and SC-cut) have so-called an-harmonic spurious modes, which is a whole ensemble of
spurs located slightly above above the main mode (fundamental or overtone mode).
slightly means starting at about 50 kHz to 200 kHz above for fundamental mode
and about 30 ... 50 kHz above for overtone modes. These an-harmonic modes are
relaled to the length and width of the active area (electrode).
These spurious modes do not come only into play for wide-pull VCXO, but also in
the case that the EFC input is used for modulation with signals in the audio
frequency range.
Remember that a frequency modulated signal has side-lines which are N* the
audio frequency apart from the carrier. The amplitude of these side lines
follows the so-called Bessel functions and varies with the modulation index.
If it happens that such a Bessel-line for a particular modulation frequency
coincides with such a spur, it comes to an interference, This means the modulation
frequency response becomes a discontinuity (dip) at a sharp frequency. Such band breaks
do even occur if the spurious is so weak that it can barely be seen on a network analyzer.

Regards

Bernd DK1AG
AXTAL GmbH Co. KG
www.axtal.com

-Ursprüngliche Nachricht-
Von: time-nuts [mailto:time-nuts-boun...@febo.com] Im Auftrag von Bob Camp
Gesendet: Sonntag, 7. September 2014 04:21
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

Simple answer = crystals are never perfect.

Longer winded, but very incomplete answer =

A spurious response in a crystal normally refers to a mode that is not one of
the “identified” modes of the crystal. An AT has a set of identified modes, an
SC has a more complex set of modes. In the case of the AT it would be the
fundamental and the odd overtones. In the case of the SC you have the A, B, C
modes and their odd overtones. None of those are considered spurious.

A spur can come from a lot of different places. One common one is higher order
vibrations in a longer dimension face of the resonator. The 183rd overtone of
the width of the blank is still a legitimate resonant mode. Another source are
modes other than shear (like flex). Deriving a full catalog of all the modes of
an arbitrary blank design is a major project. There are only a handful of
people out there who are into that sort of thing (as opposed to simply cranking
through some formulas).

Practical answer = Don’t worry about it. Unless you are building a wide pull
VCXO or a wide deviation VCXO (often the same thing) you will never notice them.

Bob

On Sep 6, 2014, at 9:13 PM, Hal Murray hmur...@megapathdsl.net wrote:

kb...@n1k.org said:

The biggest problem comes from crystal spurs rather than crystal Q.

What's the mechanism for making spurs with a crystal?

--
These are my opinions. I hate spam.

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Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

2014-09-10 Thread Bob Camp

Hi

If you are modulating a normal OCXO EFC with audio, and the output frequency is 
not being multiplied up, the modulation index will be very low. Low modulation 
index means that the higher order FM sidebands will be quite far down. 

If you take “audio” to be  10 KHz, and a VHF OCXO to be 100 MHz: With a 10 ppm 
EFC range, you get 1.0 KHz of deviation. The modulation index is  1 a decade 
below your upper modulation frequency. That’s already a pretty wide swing OCXO 
and a fairly high modulation frequency for an EFC line. 

If you have a spur that is in the 50 to 150 KHz range, you are talking about 
the 5th to 15th sideband off of 10 KHz or the 50th to 150th sideband off of 1 
KHz. At 50 sidebands out and an index of 1, you are in the “forget about it” 
region. Even at 10 KHz, the sideband is not likely to create much of an issue. 
The distortion from the non-linear EFC slope will be more of a problem in a 
practical sense. 

——

Since the modulation is single sideband, yes it converts PM - AM. It also 
will be impacted by any limiters in the system and will not multiply the same 
way as a pure PM modulation. The phase of the sideband will change as you go 
through the resonance, further messing up the multiplication / limiter math. 

Bob

On Sep 10, 2014, at 12:50 PM, Magnus Danielson mag...@rubidium.dyndns.org 
wrote:

 Bernd,
 
 Brilliant point. Easy to miss if one has a to simple model of the oscillator 
 at hand.
 
 Since it is a single-side-band mode, it will show up both as AM and PM with 
 the same amplitude.
 
 Cheers,
 Magnus
 
 On 09/10/2014 03:27 PM, Bernd Neubig wrote:
 Hi Bob,
 
 your description oft he spurious coming from higher overtone of 
 low-frequency modes is correct. I want to add, that all thickness-shear mode 
 crystals (such as AT, BT and SC-cut) have so-called an-harmonic spurious 
 modes, which is a whole ensemble of spurs located  slightly above above the 
 main mode (fundamental or overtone mode). slightly means starting at about 
 50 kHz to 200 kHz above for fundamental mode and about 30 ... 50 kHz above 
 for overtone modes. These an-harmonic modes are relaled to the length and 
 width of the active area (electrode).
 These spurious modes do not come only into play for wide-pull VCXO, but also 
 in the case that the EFC input is used for modulation with signals in the 
 audio frequency range.
 Remember that a frequency modulated signal has side-lines which are N* the 
 audio frequency apart from the carrier. The amplitude of these side lines 
 follows the so-called Bessel functions and varies with the modulation index.
 If it happens that such a Bessel-line for a particular modulation 
 frequency coincides with such a spur, it comes to an interference, This 
 means the modulation frequency response becomes a discontinuity (dip) at a 
 sharp frequency. Such band breaks do even occur if the spurious is so weak 
 that it can barely be seen on a network analyzer.
 
 Regards
 
 Bernd   DK1AG
 AXTAL GmbH  Co. KG
 www.axtal.com
 
 -Ursprüngliche Nachricht-
 Von: time-nuts [mailto:time-nuts-boun...@febo.com] Im Auftrag von Bob Camp
 Gesendet: Sonntag, 7. September 2014 04:21
 An: Discussion of precise time and frequency measurement
 Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
 
 Hi
 
 Simple answer = crystals are never perfect.
 
 Longer winded, but very incomplete answer =
 
 A spurious response in a crystal normally refers to a mode that is not one 
 of the “identified” modes of the crystal. An AT has a set of identified 
 modes, an SC has a more complex set of modes. In the case of the AT it would 
 be the fundamental and the odd overtones. In the case of the SC you have the 
 A, B, C modes and their odd overtones. None of those are considered spurious.
 
 A spur can come from a lot of different places.  One common one is higher 
 order vibrations in a longer dimension face of the resonator. The 183rd 
 overtone of the width of the blank is still a legitimate resonant mode. 
 Another source are modes other than shear (like flex). Deriving a full 
 catalog of all the modes of an arbitrary blank design is a major project. 
 There are only a handful of people out there who are into that sort of thing 
 (as opposed to simply cranking through some formulas).
 
 Practical answer = Don’t worry about it. Unless you are building a wide pull 
 VCXO or a wide deviation VCXO (often the same thing) you will never notice 
 them.
 
 Bob
 
 On Sep 6, 2014, at 9:13 PM, Hal Murray hmur...@megapathdsl.net wrote:
 
 
 kb...@n1k.org said:
 The biggest problem comes from crystal spurs rather than crystal Q.
 
 What's the mechanism for making spurs with a crystal?
 
 --
 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.
 
 ___
 time

Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

2014-09-06 Thread Magnus Danielson


Bob,

On 09/06/2014 03:00 AM, Bob Camp wrote:

Hi

Oddly enough (and yes it is odd) you can modulate an oscillator well outside 
the crystal’s bandwidth. The bigger issue is that the EFC does not pull the 
crystal very far on a normal OCXO. The FM modulation index drops to very small 
numbers pretty fast as you go up in modulation frequency.

You typically only worry about modulation sidebands that are above the phase 
noise floor. Since phase modulation sidebands go down as 1/Fmod on an FM 
modulator (for small modulation index) they get pretty low pretty fast.

If your OCXO has an EFC range of 0.1 ppm at 10 MHz, it will swing 1 Hz p-p (+/- 
0.5 Hz) for the full EFC voltage. At 5 Hz, you have a modulation index of 0.1. 
Of course if you are multiplying to 10 GHz, the index could be quite large. 
This gets back to the “this all depends on what you are doing”.

If your EFC is 5V, a reasonably quiet signal would have noise below 0.5 mV. That’s 
already 80 db down. A very quiet supply should be in the  5 nV / sqrt(Hz) 
range.  That would put the noise down 180 db.

It’s unlikely that your OCXO has a phase noise spec of -180 dbc / Hz at 10 Hz. 
We may already be done …

To bring all the numbers together:

At 1 Hz the modulation will do a sideband X db down at your desired frequency.

You will drop 20 db by the time you get to 10 Hz simply due to the 1/F FM-PM.


Since the oscillator integrate frequency into phase, you have a 
1/(2*pi*f) factor. The typical LaPlace model for an oscillator is Ko/s, 
where Ko is the input sensitivity of the oscillator.
A more complete model needs to include the Q of the crystal, naturally, 
unless you are in-band of that Q where it has less drastic properties.



Bottom line - it’s not all that hard to get a quiet enough EFC voltage.


Agreed.

I've found that thinking about systematic noises of low frequency (i.e. 
comparator frequency and overtones) as well as loop dynamics is what one 
should think about. Lack of DAC resolution hurts.


Cheers,
Magnus
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Re: [time-nuts] OCXO Voltage Input?

Hi

By far the most common way to check low level stuff on an OCXO is to measure 
it’s phase noise. There are a variety of approaches. The lowest cost approach 
is usually a dual oscillator into a mixer / quadrature lock. Feed the output to 
a preamp and then into some sort of audio spectrum analyzer. 

If you truly want to look at FM as FM, then you can multiply the output up to 
microwaves and look at it there. After multiplication to 10 GHz, your 20 Hz on 
10 MHz is going to look like 20 KHz. 

If you want to stay off the shelf, then something like a TimePod will do a fine 
job of plotting low level low modulation rate stuff. It will run fast enough 
that you can follow the modulation over many decades. 

For higher rates, some of the HP modulation analyzers are quiet enough to 
properly display 10 or 20 Hz deviation FM. If you are below that level, a 
simple 5X frequency multiplier will get you running with one. 

Yes there are likely another two or three dozen ways to do it. Those four are 
the most common. 

Bob

On Sep 5, 2014, at 10:54 PM, d...@irtelemetrics.com wrote:

 Hi Bob 
 
 You have some good observations. Spread spectrum clocking is one I hadn't 
 considered when looking at this problem. In that case the crystal is pulled a 
 bunch. (It's also cheating in my opinion!)  Correcting for mechanical 
 vibration in aircraft would also tend to indicate it's possible
 
 In the schematic for the 10544 that Tom posted the link to, it appears that 
 when both of the EFC lines are available, only two 20K resistors are in 
 series with the varactor. One would guess that changes on the EFC line could 
 quite easily modulate that varactor. Assuming a similar scheme in other 
 oscillators, one would think that modulation could quite easily happen there 
 also. 
 I supposed that the manual telling the operator to avoid noise on the EFC 
 line, due to FM modulation happening, supports this theory as well! (Big 
 Exclamation point there!) 
 
 Once the question is asked, you have to ask how does one measure such a 
 modulation? At least with simple equipment easily available. Some searching 
 didn't result in anything promising, at least for what I have access to. 
 Initially my thoughts are because the varactor is acting on the crystal to 
 change frequency the assumption is the modulation is FM (Again, the HP manual 
 backs this up). The specified peak to peak deviation is only +/- 20Hz at 
 most. No matter what the modulating frequency is the FM modulation index is 
 virtually zero, so there are no side bands to look for! If they are there, 
 they are very close together. With a lack of FM side bands, one would 
 postulate the low deviation modulation is going to look like just like phase 
 noise. Obviously very hard to measure without a lot of good equipment. 
 
 Is there a way to tease the data out, to at least get a frequency response 
 plot by disturbing the EFC line with a signal generator? Maybe for low 
 frequencies, a TIC and known reference could do it. It's something I'd like 
 to test, but fear it requires more equipment than is easily available. 
 
 The other thought which you brought up is spread spectrum. If spread spectrum 
 is taken as an example, the amplitude of the 10Mhz may change with modulation 
 on a spectrum analyzer. It's an easy enough test to try. 
 
 The bottom line is, at this point, the examples on line and provided here 
 point towards the fact modulation can happen. Given this background 
 information it only makes sense to keep the EFC line as clean as possible. 
 More reading is necessary to understand what the implications are. Any other 
 input regarding real numbers, or actual testing is very welcome!
 
 Dan
 
  
   
 
 
 Some VCXOs actually specify their bandwidth.  High audio is sometimes 
 useful.  I haven't seen anything beyond that, but I'm just listening to 
 discussions like this one.  There could well be applications that use a 
 higher frequency. 
 
 One application is correcting for mechanical vibrations.  This is 
 interesting in radar used on helicopters.  (They do Doppler filtering to 
 remove clutter.  The lower speed of objects that can get through the filter 
 depends on the clock stability.)
  PCs often FM modulate their clocks.  It's a hack to get past the FCC EMI 
 requirements.  It spreads a spike in the frequency domain into a blob with a 
 lower peak.  I think 30 KHz is typical.  The PCI specs were tweaked to allow 
 this so they probably say something about the legal frequency limit. 
 PCs probably don't use expensive OCXOs, but that technology might get used 
 in other applications. 
 
 How do FM modulators work?
 
 
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Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

Hi

Yes indeed, as you go below 1 Hz (or 1 radian/sec) all the things that “help” 
you roll off wise now hurt you. If you are worried about sidebands inside 1 Hz, 
you need to change a sign here and there. The only thing that saves you is that 
the noise floor is now coming up pretty fast. 

If you modulate a crystal oscillator, the loaded frequency of the crystal is 
changed to accomplish the modulation. When your FM swings 100 Hz high, your 
crystal is tuned 100 Hz high. When your modulation swings 100 Hz low, your 
crystal is tuned 100 Hz low. The Q has no impact in this case. No I did not 
believe it worked that way until I did it …. Since then I’ve built a *lot* of 
VCXO’s with modulation bandwidths  than their crystal Q bandwidths. The 
biggest problem comes from crystal spurs rather than crystal Q.

Bob

On Sep 6, 2014, at 6:09 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote:

 Bob,
 
 On 09/06/2014 03:00 AM, Bob Camp wrote:
 Hi
 
 Oddly enough (and yes it is odd) you can modulate an oscillator well outside 
 the crystal’s bandwidth. The bigger issue is that the EFC does not pull the 
 crystal very far on a normal OCXO. The FM modulation index drops to very 
 small numbers pretty fast as you go up in modulation frequency.
 
 You typically only worry about modulation sidebands that are above the phase 
 noise floor. Since phase modulation sidebands go down as 1/Fmod on an FM 
 modulator (for small modulation index) they get pretty low pretty fast.
 
 If your OCXO has an EFC range of 0.1 ppm at 10 MHz, it will swing 1 Hz p-p 
 (+/- 0.5 Hz) for the full EFC voltage. At 5 Hz, you have a modulation index 
 of 0.1. Of course if you are multiplying to 10 GHz, the index could be quite 
 large. This gets back to the “this all depends on what you are doing”.
 
 If your EFC is 5V, a reasonably quiet signal would have noise below 0.5 mV. 
 That’s already 80 db down. A very quiet supply should be in the  5 nV / 
 sqrt(Hz) range.  That would put the noise down 180 db.
 
 It’s unlikely that your OCXO has a phase noise spec of -180 dbc / Hz at 10 
 Hz. We may already be done …
 
 To bring all the numbers together:
 
 At 1 Hz the modulation will do a sideband X db down at your desired 
 frequency.
 
 You will drop 20 db by the time you get to 10 Hz simply due to the 1/F 
 FM-PM.
 
 Since the oscillator integrate frequency into phase, you have a 1/(2*pi*f) 
 factor. The typical LaPlace model for an oscillator is Ko/s, where Ko is the 
 input sensitivity of the oscillator.
 A more complete model needs to include the Q of the crystal, naturally, 
 unless you are in-band of that Q where it has less drastic properties.
 
 Bottom line - it’s not all that hard to get a quiet enough EFC voltage.
 
 Agreed.
 
 I've found that thinking about systematic noises of low frequency (i.e. 
 comparator frequency and overtones) as well as loop dynamics is what one 
 should think about. Lack of DAC resolution hurts.
 
 Cheers,
 Magnus
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Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

2014-09-06 Thread Magnus Danielson


Hi Bob,

Agreed. I often find that modulations eats your margin out.

PWM is interesting in this regard. PWM has the property that the lowest 
frequency has the highest amplitude and the overtones then decay with 
1/f from that. For a given clock rate, as you add a bit of PWM 
precision, you half the PWM repetition rate and thus move the frequency 
down... where we are more sensitive to the modulation it causes, and the 
1/f slope of the oscillator does not help.


I designed a PWM-like signal that has reversed PWM spectrum so that the 
highest frequency has the strongest amplitude. The 1/f of the oscillator 
integration makes the modulation flat among the different bits and much 
easier to handle phase-noise wide.


Another approach is sigma-delta style modulation, which noises out the 
amplitude. Higher-degree sigma-delta needs to avoid idle-tones for 
optimum result.


Thus, paying attention to these details pays of with simplifying the 
effort to achieve good phase-noise properties.


There is more dangers that can occur in PWM-space, but this should be 
enough of a starting-point.


Cheers,
Magnus

On 09/06/2014 01:39 PM, Bob Camp wrote:

Hi

Yes indeed, as you go below 1 Hz (or 1 radian/sec) all the things that “help” 
you roll off wise now hurt you. If you are worried about sidebands inside 1 Hz, 
you need to change a sign here and there. The only thing that saves you is that 
the noise floor is now coming up pretty fast.

If you modulate a crystal oscillator, the loaded frequency of the crystal is changed 
to accomplish the modulation. When your FM swings 100 Hz high, your crystal is tuned 
100 Hz high. When your modulation swings 100 Hz low, your crystal is tuned 100 Hz 
low. The Q has no impact in this case. No I did not believe it worked that way until 
I did it …. Since then I’ve built a *lot* of VCXO’s with modulation bandwidths 
 than their crystal Q bandwidths. The biggest problem comes from crystal 
spurs rather than crystal Q.

Bob

On Sep 6, 2014, at 6:09 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote:


Bob,

On 09/06/2014 03:00 AM, Bob Camp wrote:

Hi

Oddly enough (and yes it is odd) you can modulate an oscillator well outside 
the crystal’s bandwidth. The bigger issue is that the EFC does not pull the 
crystal very far on a normal OCXO. The FM modulation index drops to very small 
numbers pretty fast as you go up in modulation frequency.

You typically only worry about modulation sidebands that are above the phase 
noise floor. Since phase modulation sidebands go down as 1/Fmod on an FM 
modulator (for small modulation index) they get pretty low pretty fast.

If your OCXO has an EFC range of 0.1 ppm at 10 MHz, it will swing 1 Hz p-p (+/- 
0.5 Hz) for the full EFC voltage. At 5 Hz, you have a modulation index of 0.1. 
Of course if you are multiplying to 10 GHz, the index could be quite large. 
This gets back to the “this all depends on what you are doing”.

If your EFC is 5V, a reasonably quiet signal would have noise below 0.5 mV. That’s 
already 80 db down. A very quiet supply should be in the  5 nV / sqrt(Hz) 
range.  That would put the noise down 180 db.

It’s unlikely that your OCXO has a phase noise spec of -180 dbc / Hz at 10 Hz. 
We may already be done …

To bring all the numbers together:

At 1 Hz the modulation will do a sideband X db down at your desired frequency.

You will drop 20 db by the time you get to 10 Hz simply due to the 1/F FM-PM.


Since the oscillator integrate frequency into phase, you have a 1/(2*pi*f) 
factor. The typical LaPlace model for an oscillator is Ko/s, where Ko is the 
input sensitivity of the oscillator.
A more complete model needs to include the Q of the crystal, naturally, unless you are 
in-band of that Q where it has less drastic properties.


Bottom line - it’s not all that hard to get a quiet enough EFC voltage.


Agreed.

I've found that thinking about systematic noises of low frequency (i.e. 
comparator frequency and overtones) as well as loop dynamics is what one should 
think about. Lack of DAC resolution hurts.

Cheers,
Magnus
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Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

Hi

One of the easy things to do with PWM is to dither the LSB. That gives you one 
more bit of precision. It still keeps the main tone at the same place.

Your worst case tone happens at 50% duty cycle (perfect square wave). If you do 
your 50/50 as a square wave at Fmax(not Fmin), your fundamental “worst tone” is 
at your highest frequency rather than the lowest. Not easy with MCU PWM’s, 
pretty simple with an FPGA.

By far the best thing to do is to clock your PWM at a nice high frequency (like 
a couple hundred MHz). That way you get lots of bits and your fundamental tone 
is still pretty high. Again, nice for 400 MHz clock FPGA’s, not so much for 
$0.50  MCU’s. 

Bob

On Sep 6, 2014, at 12:52 PM, Magnus Danielson mag...@rubidium.dyndns.org 
wrote:

 Hi Bob,
 
 Agreed. I often find that modulations eats your margin out.
 
 PWM is interesting in this regard. PWM has the property that the lowest 
 frequency has the highest amplitude and the overtones then decay with 1/f 
 from that. For a given clock rate, as you add a bit of PWM precision, you 
 half the PWM repetition rate and thus move the frequency down... where we are 
 more sensitive to the modulation it causes, and the 1/f slope of the 
 oscillator does not help.
 
 I designed a PWM-like signal that has reversed PWM spectrum so that the 
 highest frequency has the strongest amplitude. The 1/f of the oscillator 
 integration makes the modulation flat among the different bits and much 
 easier to handle phase-noise wide.
 
 Another approach is sigma-delta style modulation, which noises out the 
 amplitude. Higher-degree sigma-delta needs to avoid idle-tones for optimum 
 result.
 
 Thus, paying attention to these details pays of with simplifying the effort 
 to achieve good phase-noise properties.
 
 There is more dangers that can occur in PWM-space, but this should be enough 
 of a starting-point.
 
 Cheers,
 Magnus
 
 On 09/06/2014 01:39 PM, Bob Camp wrote:
 Hi
 
 Yes indeed, as you go below 1 Hz (or 1 radian/sec) all the things that 
 “help” you roll off wise now hurt you. If you are worried about sidebands 
 inside 1 Hz, you need to change a sign here and there. The only thing that 
 saves you is that the noise floor is now coming up pretty fast.
 
 If you modulate a crystal oscillator, the loaded frequency of the crystal is 
 changed to accomplish the modulation. When your FM swings 100 Hz high, your 
 crystal is tuned 100 Hz high. When your modulation swings 100 Hz low, your 
 crystal is tuned 100 Hz low. The Q has no impact in this case. No I did not 
 believe it worked that way until I did it …. Since then I’ve built a *lot* 
 of VCXO’s with modulation bandwidths  than their crystal Q bandwidths. The 
 biggest problem comes from crystal spurs rather than crystal Q.
 
 Bob
 
 On Sep 6, 2014, at 6:09 AM, Magnus Danielson mag...@rubidium.dyndns.org 
 wrote:
 
 Bob,
 
 On 09/06/2014 03:00 AM, Bob Camp wrote:
 Hi
 
 Oddly enough (and yes it is odd) you can modulate an oscillator well 
 outside the crystal’s bandwidth. The bigger issue is that the EFC does not 
 pull the crystal very far on a normal OCXO. The FM modulation index drops 
 to very small numbers pretty fast as you go up in modulation frequency.
 
 You typically only worry about modulation sidebands that are above the 
 phase noise floor. Since phase modulation sidebands go down as 1/Fmod on 
 an FM modulator (for small modulation index) they get pretty low pretty 
 fast.
 
 If your OCXO has an EFC range of 0.1 ppm at 10 MHz, it will swing 1 Hz p-p 
 (+/- 0.5 Hz) for the full EFC voltage. At 5 Hz, you have a modulation 
 index of 0.1. Of course if you are multiplying to 10 GHz, the index could 
 be quite large. This gets back to the “this all depends on what you are 
 doing”.
 
 If your EFC is 5V, a reasonably quiet signal would have noise below 0.5 
 mV. That’s already 80 db down. A very quiet supply should be in the  5 nV 
 / sqrt(Hz) range.  That would put the noise down 180 db.
 
 It’s unlikely that your OCXO has a phase noise spec of -180 dbc / Hz at 10 
 Hz. We may already be done …
 
 To bring all the numbers together:
 
 At 1 Hz the modulation will do a sideband X db down at your desired 
 frequency.
 
 You will drop 20 db by the time you get to 10 Hz simply due to the 1/F 
 FM-PM.
 
 Since the oscillator integrate frequency into phase, you have a 1/(2*pi*f) 
 factor. The typical LaPlace model for an oscillator is Ko/s, where Ko is 
 the input sensitivity of the oscillator.
 A more complete model needs to include the Q of the crystal, naturally, 
 unless you are in-band of that Q where it has less drastic properties.
 
 Bottom line - it’s not all that hard to get a quiet enough EFC voltage.
 
 Agreed.
 
 I've found that thinking about systematic noises of low frequency (i.e. 
 comparator frequency and overtones) as well as loop dynamics is what one 
 should think about. Lack of DAC resolution hurts.
 
 Cheers,
 Magnus
 ___
 time-nuts

Re: [time-nuts] OCXO Voltage Input?

2014-09-06 Thread Demian Martin

I have used an FM tuner pretty successfully to look at modulation and phase 
noise in oscillators. For a 10 MHz oscillator you will be looking at the 10th 
harmonic so modulation and phase noise is multiplied and much easier to see. 
You do need a square wave output to get a lot of harmonics. Sinewave outputs 
will be pretty low at the 10th harmonic if the oscillator is working well. This 
does work and I have tried it  both on 10 MHz and 5 MHz oscillators with some 
success. It's not a replacement for a real phase noise analyzer but its way 
cheaper and adequate to spot real problems.

The math to transform the output of a tuner into quantifiable phase noise was 
more than I had patience for.

The low frequency limit is in the 5-10 Hz range. The AFC of a good tuner will 
eliminate most everything below that frequency.

More details here 
http://www.diyaudio.com/forums/blogs/1audio/983-fm-tuner-jitter-analysis.html 

Subject: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
Message-ID: ccc8bc9e-c7af-4965-88c5-d3d21b41d...@n1k.org
Content-Type: text/plain; charset=windows-1252

Hi

Yes indeed, as you go below 1 Hz (or 1 radian/sec) all the things that “help” 
you roll off wise now hurt you. If you are worried about sidebands inside 1 
Hz, you need to change a sign here and there. The only thing that saves you 
is that the noise floor is now coming up pretty fast. 

If you modulate a crystal oscillator, the loaded frequency of the crystal is 
changed to accomplish the modulation. When your FM swings 100 Hz high, your 
crystal is tuned 100 Hz high. When your modulation swings 100 Hz low, your 
crystal is tuned 100 Hz low. The Q has no impact in this case. No I did not 
believe it worked that way until I did it …. Since then I’ve built a *lot* of 
VCXO’s with modulation bandwidths  than their crystal Q bandwidths. The 
biggest problem comes from crystal spurs rather than crystal Q.

Bob

On Sep 6, 2014, at 6:09 AM, Magnus Danielson mag...@rubidium.dyndns.org 
wrote:

 Bob,
 
 On 09/06/2014 03:00 AM, Bob Camp wrote:
 Hi
 
 Oddly enough (and yes it is odd) you can modulate an oscillator well outside 
 the crystal’s bandwidth. The bigger issue is that the EFC does not pull the 
 crystal very far on a normal OCXO. The FM modulation index drops to very 
 small numbers pretty fast as you go up in modulation frequency.
 
 You typically only worry about modulation sidebands that are above the phase 
 noise floor. Since phase modulation sidebands go down as 1/Fmod on an FM 
 modulator (for small modulation index) they get pretty low pretty fast.
 
 If your OCXO has an EFC range of 0.1 ppm at 10 MHz, it will swing 1 Hz p-p 
 (+/- 0.5 Hz) for the full EFC voltage. At 5 Hz, you have a modulation index 
 of 0.1. Of course if you are multiplying to 10 GHz, the index could be quite 
 large. This gets back to the “this all depends on what you are doing”.
 
 If your EFC is 5V, a reasonably quiet signal would have noise below 0.5 mV. 
 That’s already 80 db down. A very quiet supply should be in the  5 nV / 
 sqrt(Hz) range.  That would put the noise down 180 db.
 
 It’s unlikely that your OCXO has a phase noise spec of -180 dbc / Hz 
 at 10 Hz. We may already be done …
 
 To bring all the numbers together:
 
 At 1 Hz the modulation will do a sideband X db down at your desired 
 frequency.
 
 You will drop 20 db by the time you get to 10 Hz simply due to the 1/F 
 FM-PM.
 
 Since the oscillator integrate frequency into phase, you have a 1/(2*pi*f) 
 factor. The typical LaPlace model for an oscillator is Ko/s, where Ko is the 
 input sensitivity of the oscillator.
 A more complete model needs to include the Q of the crystal, naturally, 
 unless you are in-band of that Q where it has less drastic properties.
 
 Bottom line - it’s not all that hard to get a quiet enough EFC voltage.
 
 Agreed.
 
 I've found that thinking about systematic noises of low frequency (i.e. 
 comparator frequency and overtones) as well as loop dynamics is what one 
 should think about. Lack of DAC resolution hurts.
 
 Cheers,
 Magnus
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 time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] OCXO Voltage Input?

Hi

You get 20 log N multiplication in phase noise as you go up in frequency. On 
the 10th harmonic you will be 20 db higher than on the fundamental. With an 
OCXO running -160 to -170 dbc / Hz phase noise at the fundamental, you will be 
at -140 to -150 dbc / Hz at 100 MHz. If you are at -155 dbc at 100 Hz at 10 
MHz, you will be at -135 dbc/ Hz at 100 MHz.  You get 10 log (bw) when you 
switch bandwidth. A 10 KHz bandwidth will give you another 40 db. That added to 
-140 will get you up to -100 db. That’s pretty quiet for most tuners. 

If you can go in close enough with low enough noise, then yes indeed you can 
look at modulation response quite nicely with this approach. 

Bob
 
On Sep 6, 2014, at 12:31 PM, Demian Martin demianm@gmail.com wrote:

 I have used an FM tuner pretty successfully to look at modulation and phase 
 noise in oscillators. For a 10 MHz oscillator you will be looking at the 10th 
 harmonic so modulation and phase noise is multiplied and much easier to see. 
 You do need a square wave output to get a lot of harmonics. Sinewave outputs 
 will be pretty low at the 10th harmonic if the oscillator is working well. 
 This does work and I have tried it  both on 10 MHz and 5 MHz oscillators with 
 some success. It's not a replacement for a real phase noise analyzer but its 
 way cheaper and adequate to spot real problems.
 
 The math to transform the output of a tuner into quantifiable phase noise was 
 more than I had patience for.
 
 The low frequency limit is in the 5-10 Hz range. The AFC of a good tuner will 
 eliminate most everything below that frequency.
 
 More details here 
 http://www.diyaudio.com/forums/blogs/1audio/983-fm-tuner-jitter-analysis.html 
 
 Subject: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
 Message-ID: ccc8bc9e-c7af-4965-88c5-d3d21b41d...@n1k.org
 Content-Type: text/plain; charset=windows-1252
 
 Hi
 
 Yes indeed, as you go below 1 Hz (or 1 radian/sec) all the things that 
 “help” you roll off wise now hurt you. If you are worried about sidebands 
 inside 1 Hz, you need to change a sign here and there. The only thing that 
 saves you is that the noise floor is now coming up pretty fast. 
 
 If you modulate a crystal oscillator, the loaded frequency of the crystal is 
 changed to accomplish the modulation. When your FM swings 100 Hz high, your 
 crystal is tuned 100 Hz high. When your modulation swings 100 Hz low, your 
 crystal is tuned 100 Hz low. The Q has no impact in this case. No I did not 
 believe it worked that way until I did it …. Since then I’ve built a *lot* 
 of VCXO’s with modulation bandwidths  than their crystal Q bandwidths. 
 The biggest problem comes from crystal spurs rather than crystal Q.
 
 Bob
 
 On Sep 6, 2014, at 6:09 AM, Magnus Danielson mag...@rubidium.dyndns.org 
 wrote:
 
 Bob,
 
 On 09/06/2014 03:00 AM, Bob Camp wrote:
 Hi
 
 Oddly enough (and yes it is odd) you can modulate an oscillator well 
 outside the crystal’s bandwidth. The bigger issue is that the EFC does not 
 pull the crystal very far on a normal OCXO. The FM modulation index drops 
 to very small numbers pretty fast as you go up in modulation frequency.
 
 You typically only worry about modulation sidebands that are above the 
 phase noise floor. Since phase modulation sidebands go down as 1/Fmod on an 
 FM modulator (for small modulation index) they get pretty low pretty fast.
 
 If your OCXO has an EFC range of 0.1 ppm at 10 MHz, it will swing 1 Hz p-p 
 (+/- 0.5 Hz) for the full EFC voltage. At 5 Hz, you have a modulation index 
 of 0.1. Of course if you are multiplying to 10 GHz, the index could be 
 quite large. This gets back to the “this all depends on what you are doing”.
 
 If your EFC is 5V, a reasonably quiet signal would have noise below 0.5 mV. 
 That’s already 80 db down. A very quiet supply should be in the  5 nV / 
 sqrt(Hz) range.  That would put the noise down 180 db.
 
 It’s unlikely that your OCXO has a phase noise spec of -180 dbc / Hz 
 at 10 Hz. We may already be done …
 
 To bring all the numbers together:
 
 At 1 Hz the modulation will do a sideband X db down at your desired 
 frequency.
 
 You will drop 20 db by the time you get to 10 Hz simply due to the 1/F 
 FM-PM.
 
 Since the oscillator integrate frequency into phase, you have a 1/(2*pi*f) 
 factor. The typical LaPlace model for an oscillator is Ko/s, where Ko is the 
 input sensitivity of the oscillator.
 A more complete model needs to include the Q of the crystal, naturally, 
 unless you are in-band of that Q where it has less drastic properties.
 
 Bottom line - it’s not all that hard to get a quiet enough EFC voltage.
 
 Agreed.
 
 I've found that thinking about systematic noises of low frequency (i.e. 
 comparator frequency and overtones) as well as loop dynamics is what one 
 should think about. Lack of DAC resolution hurts.
 
 Cheers,
 Magnus
 ___
 time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
 https

Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

2014-09-06 Thread Magnus Danielson


Hi Bob,

Indeed. The way to keep the MCU PWM doing reasonable stuff is to use a 
higher rate, and then update the PWM value in sync with the wrap-around, 
and then alter the value (dither or whatever) so that the average has 
higher precision. First degree sigma-delta is actually not a bad 
strategy and fairly simple to do.


With FPGA you can do more funky stuff, which is what I do.

It is even better if you can use a linear DAC of sufficient rate and 
resolution.


If you do hold-over functionality with static steering value, that is 
you stop updating the EFC-steering (this is what most folks do), then 
the resolution of the full steering can dominate the initial frequency 
offset. So, one should think about that too.


As you go into hold-over, all of a sudden you can run into idle-tones in 
a way that normal dynamics would dither out.


Cheers,
Magnus

On 09/06/2014 07:01 PM, Bob Camp wrote:

Hi

One of the easy things to do with PWM is to dither the LSB. That gives you one 
more bit of precision. It still keeps the main tone at the same place.

Your worst case tone happens at 50% duty cycle (perfect square wave). If you do 
your 50/50 as a square wave at Fmax(not Fmin), your fundamental “worst tone” is 
at your highest frequency rather than the lowest. Not easy with MCU PWM’s, 
pretty simple with an FPGA.

By far the best thing to do is to clock your PWM at a nice high frequency (like 
a couple hundred MHz). That way you get lots of bits and your fundamental tone 
is still pretty high. Again, nice for 400 MHz clock FPGA’s, not so much for 
$0.50  MCU’s.

Bob

On Sep 6, 2014, at 12:52 PM, Magnus Danielson mag...@rubidium.dyndns.org 
wrote:


Hi Bob,

Agreed. I often find that modulations eats your margin out.

PWM is interesting in this regard. PWM has the property that the lowest 
frequency has the highest amplitude and the overtones then decay with 1/f from 
that. For a given clock rate, as you add a bit of PWM precision, you half the 
PWM repetition rate and thus move the frequency down... where we are more 
sensitive to the modulation it causes, and the 1/f slope of the oscillator does 
not help.

I designed a PWM-like signal that has reversed PWM spectrum so that the highest 
frequency has the strongest amplitude. The 1/f of the oscillator integration 
makes the modulation flat among the different bits and much easier to handle 
phase-noise wide.

Another approach is sigma-delta style modulation, which noises out the 
amplitude. Higher-degree sigma-delta needs to avoid idle-tones for optimum 
result.

Thus, paying attention to these details pays of with simplifying the effort to 
achieve good phase-noise properties.

There is more dangers that can occur in PWM-space, but this should be enough of 
a starting-point.

Cheers,
Magnus

On 09/06/2014 01:39 PM, Bob Camp wrote:

Hi

Yes indeed, as you go below 1 Hz (or 1 radian/sec) all the things that “help” 
you roll off wise now hurt you. If you are worried about sidebands inside 1 Hz, 
you need to change a sign here and there. The only thing that saves you is that 
the noise floor is now coming up pretty fast.

If you modulate a crystal oscillator, the loaded frequency of the crystal is changed 
to accomplish the modulation. When your FM swings 100 Hz high, your crystal is tuned 
100 Hz high. When your modulation swings 100 Hz low, your crystal is tuned 100 Hz 
low. The Q has no impact in this case. No I did not believe it worked that way until 
I did it …. Since then I’ve built a *lot* of VCXO’s with modulation bandwidths 
 than their crystal Q bandwidths. The biggest problem comes from crystal 
spurs rather than crystal Q.

Bob

On Sep 6, 2014, at 6:09 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote:


Bob,

On 09/06/2014 03:00 AM, Bob Camp wrote:

Hi

Oddly enough (and yes it is odd) you can modulate an oscillator well outside 
the crystal’s bandwidth. The bigger issue is that the EFC does not pull the 
crystal very far on a normal OCXO. The FM modulation index drops to very small 
numbers pretty fast as you go up in modulation frequency.

You typically only worry about modulation sidebands that are above the phase 
noise floor. Since phase modulation sidebands go down as 1/Fmod on an FM 
modulator (for small modulation index) they get pretty low pretty fast.

If your OCXO has an EFC range of 0.1 ppm at 10 MHz, it will swing 1 Hz p-p (+/- 
0.5 Hz) for the full EFC voltage. At 5 Hz, you have a modulation index of 0.1. 
Of course if you are multiplying to 10 GHz, the index could be quite large. 
This gets back to the “this all depends on what you are doing”.

If your EFC is 5V, a reasonably quiet signal would have noise below 0.5 mV. That’s 
already 80 db down. A very quiet supply should be in the  5 nV / sqrt(Hz) 
range.  That would put the noise down 180 db.

It’s unlikely that your OCXO has a phase noise spec of -180 dbc / Hz at 10 Hz. 
We may already be done …

To bring all the numbers together:

At 1 Hz the modulation will do a sideband

Re: [time-nuts] OCXO Voltage Input? (Bob Camp)