subject:"\[time\-nuts\] Anybody want a Thunderbolt power supply"

Hi

The op amp has a PSRR of roughly 90 db at 1 Hz. As frequency goes up, the PSRR
gets worse. What frequency is your “signal” at? 

A very normal 7912 fed by a normal supply will not produce a noticeable 
degradation 
in phase nose on the TBolt. Putting an un-filtered switcher on any of the lines 
is going
to get you noise on the common ground that *will* come through. 

Bob


> On Oct 22, 2016, at 4:15 PM, Scott Stobbe  wrote:
> 
> I think we are coming up to the noise floor here. We have identified a
> potential signal A from a 7912 (likely similar to a 7812, no guarentee).
> The remaining question is if you apply signal A to the power pin of a
> thunderbolt what is signal B added to the output. We know where we want
> signal B to be, below the noise. Knowing the PSSR for each of the power
> inputs would be one way to answer this question.
> 
> On Saturday, 22 October 2016, Bob Camp  wrote:
> 
>> Hi
>> 
>> There is an *enormous* difference between regulation and it’s impact on
>> stability (which is what this drifted off into) and PSRR and it’s impact on
>> phase noise (which got lost at the tread moved on). PSRR does indeed
>> matter, but a fairly simple linear regulator (or pair of cheap ones or
>> coil plus
>> pair) can take care of that.
>> 
>> The EFC reference in the TBolt comes from the TBolt board and not from the
>> OCXO.
>> It is not in any way connected to the -12 V supply line.
>> 
>> Bob
>> 
>> 
>> 
>>> On Oct 22, 2016, at 12:41 PM, Scott Stobbe > > wrote:
>>> 
>>> Bob, this is good data and insights thanks for taking the time to share.
>>> Ultimately the question Nick is hoping to answer is what is the point of
>>> diminishing returns for voltage regulation. I think there are plenty of
>>> folks on this list that have shared data suggesting a switching regulator
>>> which meets these specifications:
>>> 
>>> Table 3-2 Power Specifications (Board-only)
>>> +12v +/-10% max current 750 mA
>>> +5v +/-5% max current 400 mA
>>> -12v +/-10% max current 10 mA
>>> Ripple
>>> +5v 50 mV peak-to-peak, 15 mVrms
>>> +/-12v 75 mV peak-to-peak, 20 mVrms
>>> 
>>> definitely has a degrading impact on the 10MHz phase noise.
>>> 
>>> I would happily agree that PSRR of an opamp buffering the EFC line is not
>>> going to have a significant impact on performance with a jellybean LDO.
>>> 
>>> Do you know if the +- 5V reference is derived on board or is it from an
>> EFC
>>> reference provided by the ocxo?
>>> 
>>> On Sat, Oct 22, 2016 at 11:31 AM, Bob Camp >
>> wrote:
>>> 
 Hi
 
 The -12 V line is not the reference for the EFC. It *is* one supply into
 the op amp circuit
 that drives the EFC. Since the EFC is +/- 5V, there must be both a
 positive and
 a negative supply into the driver circuit for full output swing. The -12
 can be anything between about
 -13 and -7 without significantly impacting the function of the device.
>> In
 fact, people
 with EFC voltages that are slightly positive have accidentally proven
>> that
 the
 TBolt will work (lock up and function correctly) with zero volts on the
 -12V line.
 
 Bob
 
> On Oct 22, 2016, at 10:24 AM, Scott Stobbe > >
 wrote:
> 
> It all depends what the -12V rail is for, some have said it directly
> references the EFC dac. I would hope an ocxo would have a better tuning
> gain on its efc pin than supply pin but maybe that's not always true.
> 
> On Saturday, 22 October 2016, Bob Camp >
>> wrote:
> 
>> Hi
>> 
>> The +12 goes straight to the OCXO. All OCXO’s have a voltage
 sensitivity.
>> That sensitivity is much higher than voltage sensitivity is much
>> higher
>> than
>> what you see on the other two supply pins.
>> 
>> Bob
>> 
>>> On Oct 21, 2016, at 11:06 PM, Scott Stobbe > 
>> > wrote:
>>> 
>>> Interesting, I would have thought that the +12V input would be
 extremely
>>> well regulated since its shared with the oven heater, I*R drops are
 going
>>> to show up every where, if your looking for uV levels of stability.
>>> Just a connector has milliohms of contact resistance, let alone
>> routing
>> and
>>> cables...
>>> 
>>> On Friday, 21 October 2016, Bob Camp 
>> >
>> wrote:
>>> 
 Hi
 
> On Oct 21, 2016, at 7:44 PM, Scott Stobbe <
>> scott.j.sto...@gmail.com 
>> 
 > wrote:
> 
> A little more data on the 7912.
> 
> The first plot shows the tempCo of the 7912 measured with ambient
> temperature swings "7912_TempCo.png". Which is -150 ppm/degC.
> 
> The

Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-22 Thread Nick Sayer via time-nuts

At this point, I have three prototype boards that are functional as far as I 
can tell. Unfortunately I don’t have a better reference which would allow me to 
make comparisons.

If someone with a better reference could make a proper comparison, I’d be happy 
to send them a prototype.



> On Oct 22, 2016, at 1:15 PM, Scott Stobbe  wrote:
> 
> I think we are coming up to the noise floor here. We have identified a
> potential signal A from a 7912 (likely similar to a 7812, no guarentee).
> The remaining question is if you apply signal A to the power pin of a
> thunderbolt what is signal B added to the output. We know where we want
> signal B to be, below the noise. Knowing the PSSR for each of the power
> inputs would be one way to answer this question.
> 
> On Saturday, 22 October 2016, Bob Camp > 
> wrote:
> 
>> Hi
>> 
>> There is an *enormous* difference between regulation and it’s impact on
>> stability (which is what this drifted off into) and PSRR and it’s impact on
>> phase noise (which got lost at the tread moved on). PSRR does indeed
>> matter, but a fairly simple linear regulator (or pair of cheap ones or
>> coil plus
>> pair) can take care of that.
>> 
>> The EFC reference in the TBolt comes from the TBolt board and not from the
>> OCXO.
>> It is not in any way connected to the -12 V supply line.
>> 
>> Bob
>> 
>> 
>> 
>>> On Oct 22, 2016, at 12:41 PM, Scott Stobbe > > wrote:
>>> 
>>> Bob, this is good data and insights thanks for taking the time to share.
>>> Ultimately the question Nick is hoping to answer is what is the point of
>>> diminishing returns for voltage regulation. I think there are plenty of
>>> folks on this list that have shared data suggesting a switching regulator
>>> which meets these specifications:
>>> 
>>> Table 3-2 Power Specifications (Board-only)
>>> +12v +/-10% max current 750 mA
>>> +5v +/-5% max current 400 mA
>>> -12v +/-10% max current 10 mA
>>> Ripple
>>> +5v 50 mV peak-to-peak, 15 mVrms
>>> +/-12v 75 mV peak-to-peak, 20 mVrms
>>> 
>>> definitely has a degrading impact on the 10MHz phase noise.
>>> 
>>> I would happily agree that PSRR of an opamp buffering the EFC line is not
>>> going to have a significant impact on performance with a jellybean LDO.
>>> 
>>> Do you know if the +- 5V reference is derived on board or is it from an
>> EFC
>>> reference provided by the ocxo?
>>> 
>>> On Sat, Oct 22, 2016 at 11:31 AM, Bob Camp >>  >
>> wrote:
>>> 
 Hi
 
 The -12 V line is not the reference for the EFC. It *is* one supply into
 the op amp circuit
 that drives the EFC. Since the EFC is +/- 5V, there must be both a
 positive and
 a negative supply into the driver circuit for full output swing. The -12
 can be anything between about
 -13 and -7 without significantly impacting the function of the device.
>> In
 fact, people
 with EFC voltages that are slightly positive have accidentally proven
>> that
 the
 TBolt will work (lock up and function correctly) with zero volts on the
 -12V line.
 
 Bob
 
> On Oct 22, 2016, at 10:24 AM, Scott Stobbe  
>> >
 wrote:
> 
> It all depends what the -12V rail is for, some have said it directly
> references the EFC dac. I would hope an ocxo would have a better tuning
> gain on its efc pin than supply pin but maybe that's not always true.
> 
> On Saturday, 22 October 2016, Bob Camp   >
>> wrote:
> 
>> Hi
>> 
>> The +12 goes straight to the OCXO. All OCXO’s have a voltage
 sensitivity.
>> That sensitivity is much higher than voltage sensitivity is much
>> higher
>> than
>> what you see on the other two supply pins.
>> 
>> Bob
>> 
>>> On Oct 21, 2016, at 11:06 PM, Scott Stobbe >> 
>> 
>> > wrote:
>>> 
>>> Interesting, I would have thought that the +12V input would be
 extremely
>>> well regulated since its shared with the oven heater, I*R drops are
 going
>>> to show up every where, if your looking for uV levels of stability.
>>> Just a connector has milliohms of contact resistance, let alone
>> routing
>> and
>>> cables...
>>> 
>>> On Friday, 21 October 2016, Bob Camp >>  
>> >
>> wrote:
>>> 
 Hi
 
> On Oct 21, 2016, at 7:44 PM, Scott Stobbe <
>> scott.j.sto...@gmail.com  
>> 
 > wrote:
> 
> A little more data on the 7912.
> 
> The first plot shows the

Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-22 Thread Scott Stobbe

I think we are coming up to the noise floor here. We have identified a
potential signal A from a 7912 (likely similar to a 7812, no guarentee).
The remaining question is if you apply signal A to the power pin of a
thunderbolt what is signal B added to the output. We know where we want
signal B to be, below the noise. Knowing the PSSR for each of the power
inputs would be one way to answer this question.

On Saturday, 22 October 2016, Bob Camp  wrote:

> Hi
>
> There is an *enormous* difference between regulation and it’s impact on
> stability (which is what this drifted off into) and PSRR and it’s impact on
> phase noise (which got lost at the tread moved on). PSRR does indeed
> matter, but a fairly simple linear regulator (or pair of cheap ones or
> coil plus
> pair) can take care of that.
>
> The EFC reference in the TBolt comes from the TBolt board and not from the
> OCXO.
> It is not in any way connected to the -12 V supply line.
>
> Bob
>
>
>
> > On Oct 22, 2016, at 12:41 PM, Scott Stobbe  > wrote:
> >
> > Bob, this is good data and insights thanks for taking the time to share.
> > Ultimately the question Nick is hoping to answer is what is the point of
> > diminishing returns for voltage regulation. I think there are plenty of
> > folks on this list that have shared data suggesting a switching regulator
> > which meets these specifications:
> >
> > Table 3-2 Power Specifications (Board-only)
> > +12v +/-10% max current 750 mA
> > +5v +/-5% max current 400 mA
> > -12v +/-10% max current 10 mA
> > Ripple
> > +5v 50 mV peak-to-peak, 15 mVrms
> > +/-12v 75 mV peak-to-peak, 20 mVrms
> >
> > definitely has a degrading impact on the 10MHz phase noise.
> >
> > I would happily agree that PSRR of an opamp buffering the EFC line is not
> > going to have a significant impact on performance with a jellybean LDO.
> >
> > Do you know if the +- 5V reference is derived on board or is it from an
> EFC
> > reference provided by the ocxo?
> >
> > On Sat, Oct 22, 2016 at 11:31 AM, Bob Camp >
> wrote:
> >
> >> Hi
> >>
> >> The -12 V line is not the reference for the EFC. It *is* one supply into
> >> the op amp circuit
> >> that drives the EFC. Since the EFC is +/- 5V, there must be both a
> >> positive and
> >> a negative supply into the driver circuit for full output swing. The -12
> >> can be anything between about
> >> -13 and -7 without significantly impacting the function of the device.
> In
> >> fact, people
> >> with EFC voltages that are slightly positive have accidentally proven
> that
> >> the
> >> TBolt will work (lock up and function correctly) with zero volts on the
> >> -12V line.
> >>
> >> Bob
> >>
> >>> On Oct 22, 2016, at 10:24 AM, Scott Stobbe  >
> >> wrote:
> >>>
> >>> It all depends what the -12V rail is for, some have said it directly
> >>> references the EFC dac. I would hope an ocxo would have a better tuning
> >>> gain on its efc pin than supply pin but maybe that's not always true.
> >>>
> >>> On Saturday, 22 October 2016, Bob Camp >
> wrote:
> >>>
>  Hi
> 
>  The +12 goes straight to the OCXO. All OCXO’s have a voltage
> >> sensitivity.
>  That sensitivity is much higher than voltage sensitivity is much
> higher
>  than
>  what you see on the other two supply pins.
> 
>  Bob
> 
> > On Oct 21, 2016, at 11:06 PM, Scott Stobbe  
>  > wrote:
> >
> > Interesting, I would have thought that the +12V input would be
> >> extremely
> > well regulated since its shared with the oven heater, I*R drops are
> >> going
> > to show up every where, if your looking for uV levels of stability.
> > Just a connector has milliohms of contact resistance, let alone
> routing
>  and
> > cables...
> >
> > On Friday, 21 October 2016, Bob Camp 
> >
>  wrote:
> >
> >> Hi
> >>
> >>> On Oct 21, 2016, at 7:44 PM, Scott Stobbe <
> scott.j.sto...@gmail.com 
>  
> >> > wrote:
> >>>
> >>> A little more data on the 7912.
> >>>
> >>> The first plot shows the tempCo of the 7912 measured with ambient
> >>> temperature swings "7912_TempCo.png". Which is -150 ppm/degC.
> >>>
> >>> The second plot is off a 7912 logged for an hour or so,
>  "7912_1PLC.png",
> >>> nothing too interesting here. However the environmental temperature
>  swing
> >>> of about 1 degC/hour is pretty conservative for a DUT sitting in
> free
> >> air.
> >>>
> >>> Finally, an allan devation plot looking at the normalized stability
> >> of
>  a
> >>> 7912 regulator "7912_AllanDeviation.png". Interestingly here, is,
> how
> >> quick
> >>> a 15 mK/min temperature swing shoots above the 1/f floor, it's a

Re: [time-nuts] Anybody want a Thunderbolt power supply?

Hi

There is an *enormous* difference between regulation and it’s impact on 
stability (which is what this drifted off into) and PSRR and it’s impact on
phase noise (which got lost at the tread moved on). PSRR does indeed
matter, but a fairly simple linear regulator (or pair of cheap ones or coil plus
pair) can take care of that. 

The EFC reference in the TBolt comes from the TBolt board and not from the 
OCXO. 
It is not in any way connected to the -12 V supply line.

Bob



> On Oct 22, 2016, at 12:41 PM, Scott Stobbe  wrote:
> 
> Bob, this is good data and insights thanks for taking the time to share.
> Ultimately the question Nick is hoping to answer is what is the point of
> diminishing returns for voltage regulation. I think there are plenty of
> folks on this list that have shared data suggesting a switching regulator
> which meets these specifications:
> 
> Table 3-2 Power Specifications (Board-only)
> +12v +/-10% max current 750 mA
> +5v +/-5% max current 400 mA
> -12v +/-10% max current 10 mA
> Ripple
> +5v 50 mV peak-to-peak, 15 mVrms
> +/-12v 75 mV peak-to-peak, 20 mVrms
> 
> definitely has a degrading impact on the 10MHz phase noise.
> 
> I would happily agree that PSRR of an opamp buffering the EFC line is not
> going to have a significant impact on performance with a jellybean LDO.
> 
> Do you know if the +- 5V reference is derived on board or is it from an EFC
> reference provided by the ocxo?
> 
> On Sat, Oct 22, 2016 at 11:31 AM, Bob Camp  wrote:
> 
>> Hi
>> 
>> The -12 V line is not the reference for the EFC. It *is* one supply into
>> the op amp circuit
>> that drives the EFC. Since the EFC is +/- 5V, there must be both a
>> positive and
>> a negative supply into the driver circuit for full output swing. The -12
>> can be anything between about
>> -13 and -7 without significantly impacting the function of the device. In
>> fact, people
>> with EFC voltages that are slightly positive have accidentally proven that
>> the
>> TBolt will work (lock up and function correctly) with zero volts on the
>> -12V line.
>> 
>> Bob
>> 
>>> On Oct 22, 2016, at 10:24 AM, Scott Stobbe 
>> wrote:
>>> 
>>> It all depends what the -12V rail is for, some have said it directly
>>> references the EFC dac. I would hope an ocxo would have a better tuning
>>> gain on its efc pin than supply pin but maybe that's not always true.
>>> 
>>> On Saturday, 22 October 2016, Bob Camp  wrote:
>>> 
 Hi
 
 The +12 goes straight to the OCXO. All OCXO’s have a voltage
>> sensitivity.
 That sensitivity is much higher than voltage sensitivity is much higher
 than
 what you see on the other two supply pins.
 
 Bob
 
> On Oct 21, 2016, at 11:06 PM, Scott Stobbe > wrote:
> 
> Interesting, I would have thought that the +12V input would be
>> extremely
> well regulated since its shared with the oven heater, I*R drops are
>> going
> to show up every where, if your looking for uV levels of stability.
> Just a connector has milliohms of contact resistance, let alone routing
 and
> cables...
> 
> On Friday, 21 October 2016, Bob Camp >
 wrote:
> 
>> Hi
>> 
>>> On Oct 21, 2016, at 7:44 PM, Scott Stobbe 
>> > wrote:
>>> 
>>> A little more data on the 7912.
>>> 
>>> The first plot shows the tempCo of the 7912 measured with ambient
>>> temperature swings "7912_TempCo.png". Which is -150 ppm/degC.
>>> 
>>> The second plot is off a 7912 logged for an hour or so,
 "7912_1PLC.png",
>>> nothing too interesting here. However the environmental temperature
 swing
>>> of about 1 degC/hour is pretty conservative for a DUT sitting in free
>> air.
>>> 
>>> Finally, an allan devation plot looking at the normalized stability
>> of
 a
>>> 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how
>> quick
>>> a 15 mK/min temperature swing shoots above the 1/f floor, it's a
>> matter
>> of
>>> seconds.
>>> 
>>> Now if your PSRR is 1 ppb/V or better, then all of this is
>> comfortably
>>> below the intrinsic noise of a thunderbolt.
>> 
>> The main point is that the internal tempco of the TBolt it’s self is
 much
>> larger than
>> the issues surrounding the power supply pins. The +12 is the only one
 that
>> is
>> sensitive enough to voltage (change in frequency vs voltage) to
 contribute
>> to any
>> significant way to the overall stability.
>> 
>> Bob
>> 
>>> 
>>> On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe <
 scott.j.sto...@gmail.com 
>> >
>>> wrote:
>>> 
 Nick had mention that the -12V rail on the thunderbolt has the
>> poorest

Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-22 Thread Scott Stobbe

Bob, this is good data and insights thanks for taking the time to share.
Ultimately the question Nick is hoping to answer is what is the point of
diminishing returns for voltage regulation. I think there are plenty of
folks on this list that have shared data suggesting a switching regulator
which meets these specifications:

Table 3-2 Power Specifications (Board-only)
+12v +/-10% max current 750 mA
+5v +/-5% max current 400 mA
-12v +/-10% max current 10 mA
Ripple
+5v 50 mV peak-to-peak, 15 mVrms
+/-12v 75 mV peak-to-peak, 20 mVrms

definitely has a degrading impact on the 10MHz phase noise.

I would happily agree that PSRR of an opamp buffering the EFC line is not
going to have a significant impact on performance with a jellybean LDO.

Do you know if the +- 5V reference is derived on board or is it from an EFC
reference provided by the ocxo?

On Sat, Oct 22, 2016 at 11:31 AM, Bob Camp  wrote:

> Hi
>
> The -12 V line is not the reference for the EFC. It *is* one supply into
> the op amp circuit
> that drives the EFC. Since the EFC is +/- 5V, there must be both a
> positive and
> a negative supply into the driver circuit for full output swing. The -12
> can be anything between about
> -13 and -7 without significantly impacting the function of the device. In
> fact, people
> with EFC voltages that are slightly positive have accidentally proven that
> the
> TBolt will work (lock up and function correctly) with zero volts on the
> -12V line.
>
> Bob
>
> > On Oct 22, 2016, at 10:24 AM, Scott Stobbe 
> wrote:
> >
> > It all depends what the -12V rail is for, some have said it directly
> > references the EFC dac. I would hope an ocxo would have a better tuning
> > gain on its efc pin than supply pin but maybe that's not always true.
> >
> > On Saturday, 22 October 2016, Bob Camp  wrote:
> >
> >> Hi
> >>
> >> The +12 goes straight to the OCXO. All OCXO’s have a voltage
> sensitivity.
> >> That sensitivity is much higher than voltage sensitivity is much higher
> >> than
> >> what you see on the other two supply pins.
> >>
> >> Bob
> >>
> >>> On Oct 21, 2016, at 11:06 PM, Scott Stobbe  >> > wrote:
> >>>
> >>> Interesting, I would have thought that the +12V input would be
> extremely
> >>> well regulated since its shared with the oven heater, I*R drops are
> going
> >>> to show up every where, if your looking for uV levels of stability.
> >>> Just a connector has milliohms of contact resistance, let alone routing
> >> and
> >>> cables...
> >>>
> >>> On Friday, 21 October 2016, Bob Camp >
> >> wrote:
> >>>
>  Hi
> 
> > On Oct 21, 2016, at 7:44 PM, Scott Stobbe  >> 
>  > wrote:
> >
> > A little more data on the 7912.
> >
> > The first plot shows the tempCo of the 7912 measured with ambient
> > temperature swings "7912_TempCo.png". Which is -150 ppm/degC.
> >
> > The second plot is off a 7912 logged for an hour or so,
> >> "7912_1PLC.png",
> > nothing too interesting here. However the environmental temperature
> >> swing
> > of about 1 degC/hour is pretty conservative for a DUT sitting in free
>  air.
> >
> > Finally, an allan devation plot looking at the normalized stability
> of
> >> a
> > 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how
>  quick
> > a 15 mK/min temperature swing shoots above the 1/f floor, it's a
> matter
>  of
> > seconds.
> >
> > Now if your PSRR is 1 ppb/V or better, then all of this is
> comfortably
> > below the intrinsic noise of a thunderbolt.
> 
>  The main point is that the internal tempco of the TBolt it’s self is
> >> much
>  larger than
>  the issues surrounding the power supply pins. The +12 is the only one
> >> that
>  is
>  sensitive enough to voltage (change in frequency vs voltage) to
> >> contribute
>  to any
>  significant way to the overall stability.
> 
>  Bob
> 
> >
> > On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe <
> >> scott.j.sto...@gmail.com 
>  >
> > wrote:
> >
> >> Nick had mention that the -12V rail on the thunderbolt has the
> poorest
> >> PSRR with respect to frequency output, so I first took a look at the
> >> venerable 7912.
> >>
> >> The first data-set was taken with a -13.5 VDC input. Attached is the
> >> 0.1
> >> Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a
> >> 10k
> >> resistor was added as load for preliminary evaluation. With a 60 dB
>  preamp
> >> the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band
> noise
>  is
> >> 15 uVrms, which is about 1.3 ppm rms of the DC mean.
> >>
> >> In allan deviation terms, a quiescently loaded 7912 has a spot noise
> >> of
>  7
> >> uV/rtHz at 1 Hz

Re: [time-nuts] Anybody want a Thunderbolt power supply?

Hi

The -12 V line is not the reference for the EFC. It *is* one supply into the op 
amp circuit
that drives the EFC. Since the EFC is +/- 5V, there must be both a positive and
a negative supply into the driver circuit for full output swing. The -12 can be 
anything between about 
-13 and -7 without significantly impacting the function of the device. In fact, 
people
with EFC voltages that are slightly positive have accidentally proven that the
TBolt will work (lock up and function correctly) with zero volts on the -12V 
line. 

Bob

> On Oct 22, 2016, at 10:24 AM, Scott Stobbe  wrote:
> 
> It all depends what the -12V rail is for, some have said it directly
> references the EFC dac. I would hope an ocxo would have a better tuning
> gain on its efc pin than supply pin but maybe that's not always true.
> 
> On Saturday, 22 October 2016, Bob Camp  wrote:
> 
>> Hi
>> 
>> The +12 goes straight to the OCXO. All OCXO’s have a voltage sensitivity.
>> That sensitivity is much higher than voltage sensitivity is much higher
>> than
>> what you see on the other two supply pins.
>> 
>> Bob
>> 
>>> On Oct 21, 2016, at 11:06 PM, Scott Stobbe > > wrote:
>>> 
>>> Interesting, I would have thought that the +12V input would be extremely
>>> well regulated since its shared with the oven heater, I*R drops are going
>>> to show up every where, if your looking for uV levels of stability.
>>> Just a connector has milliohms of contact resistance, let alone routing
>> and
>>> cables...
>>> 
>>> On Friday, 21 October 2016, Bob Camp >
>> wrote:
>>> 
 Hi
 
> On Oct 21, 2016, at 7:44 PM, Scott Stobbe > 
 > wrote:
> 
> A little more data on the 7912.
> 
> The first plot shows the tempCo of the 7912 measured with ambient
> temperature swings "7912_TempCo.png". Which is -150 ppm/degC.
> 
> The second plot is off a 7912 logged for an hour or so,
>> "7912_1PLC.png",
> nothing too interesting here. However the environmental temperature
>> swing
> of about 1 degC/hour is pretty conservative for a DUT sitting in free
 air.
> 
> Finally, an allan devation plot looking at the normalized stability of
>> a
> 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how
 quick
> a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter
 of
> seconds.
> 
> Now if your PSRR is 1 ppb/V or better, then all of this is comfortably
> below the intrinsic noise of a thunderbolt.
 
 The main point is that the internal tempco of the TBolt it’s self is
>> much
 larger than
 the issues surrounding the power supply pins. The +12 is the only one
>> that
 is
 sensitive enough to voltage (change in frequency vs voltage) to
>> contribute
 to any
 significant way to the overall stability.
 
 Bob
 
> 
> On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe <
>> scott.j.sto...@gmail.com 
 >
> wrote:
> 
>> Nick had mention that the -12V rail on the thunderbolt has the poorest
>> PSRR with respect to frequency output, so I first took a look at the
>> venerable 7912.
>> 
>> The first data-set was taken with a -13.5 VDC input. Attached is the
>> 0.1
>> Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a
>> 10k
>> resistor was added as load for preliminary evaluation. With a 60 dB
 preamp
>> the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise
 is
>> 15 uVrms, which is about 1.3 ppm rms of the DC mean.
>> 
>> In allan deviation terms, a quiescently loaded 7912 has a spot noise
>> of
 7
>> uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz.
>> Equivalently speaking, the flicker noise floor of an allan deviation
 plot
>> would be sqrt(2*ln(2)) that figure to be 6.8E-7.
>> 
>> Assuming a thunderbolt should be achieving 1/f floor of around 1E-12,
>> it
>> would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to
>> the
>> trouble of actually measuring it.
>> 
>> So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible
>> with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms,
>> only
 one
>> order of magnitude off.
>> 
>> The bad side of a 7912 is in long-term stability and tempCo, the
>> sample
 I
>> tested had at least a 150 ppm/degC tempCo, which is going to put a
 serious
>> lump/bump in the 10s tau to gps crossover point on an allan deviation
 plot.
>> 
>> 
>> 
>> On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe <
>> scott.j.sto...@gmail.com 
 >
>> wrote:
>> 
>>> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm
>>>

Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-22 Thread Scott Stobbe

It all depends what the -12V rail is for, some have said it directly
references the EFC dac. I would hope an ocxo would have a better tuning
gain on its efc pin than supply pin but maybe that's not always true.

On Saturday, 22 October 2016, Bob Camp  wrote:

> Hi
>
> The +12 goes straight to the OCXO. All OCXO’s have a voltage sensitivity.
> That sensitivity is much higher than voltage sensitivity is much higher
> than
> what you see on the other two supply pins.
>
> Bob
>
> > On Oct 21, 2016, at 11:06 PM, Scott Stobbe  > wrote:
> >
> > Interesting, I would have thought that the +12V input would be extremely
> > well regulated since its shared with the oven heater, I*R drops are going
> > to show up every where, if your looking for uV levels of stability.
> > Just a connector has milliohms of contact resistance, let alone routing
> and
> > cables...
> >
> > On Friday, 21 October 2016, Bob Camp >
> wrote:
> >
> >> Hi
> >>
> >>> On Oct 21, 2016, at 7:44 PM, Scott Stobbe  
> >> > wrote:
> >>>
> >>> A little more data on the 7912.
> >>>
> >>> The first plot shows the tempCo of the 7912 measured with ambient
> >>> temperature swings "7912_TempCo.png". Which is -150 ppm/degC.
> >>>
> >>> The second plot is off a 7912 logged for an hour or so,
> "7912_1PLC.png",
> >>> nothing too interesting here. However the environmental temperature
> swing
> >>> of about 1 degC/hour is pretty conservative for a DUT sitting in free
> >> air.
> >>>
> >>> Finally, an allan devation plot looking at the normalized stability of
> a
> >>> 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how
> >> quick
> >>> a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter
> >> of
> >>> seconds.
> >>>
> >>> Now if your PSRR is 1 ppb/V or better, then all of this is comfortably
> >>> below the intrinsic noise of a thunderbolt.
> >>
> >> The main point is that the internal tempco of the TBolt it’s self is
> much
> >> larger than
> >> the issues surrounding the power supply pins. The +12 is the only one
> that
> >> is
> >> sensitive enough to voltage (change in frequency vs voltage) to
> contribute
> >> to any
> >> significant way to the overall stability.
> >>
> >> Bob
> >>
> >>>
> >>> On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe <
> scott.j.sto...@gmail.com 
> >> >
> >>> wrote:
> >>>
>  Nick had mention that the -12V rail on the thunderbolt has the poorest
>  PSRR with respect to frequency output, so I first took a look at the
>  venerable 7912.
> 
>  The first data-set was taken with a -13.5 VDC input. Attached is the
> 0.1
>  Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a
> 10k
>  resistor was added as load for preliminary evaluation. With a 60 dB
> >> preamp
>  the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise
> >> is
>  15 uVrms, which is about 1.3 ppm rms of the DC mean.
> 
>  In allan deviation terms, a quiescently loaded 7912 has a spot noise
> of
> >> 7
>  uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz.
>  Equivalently speaking, the flicker noise floor of an allan deviation
> >> plot
>  would be sqrt(2*ln(2)) that figure to be 6.8E-7.
> 
>  Assuming a thunderbolt should be achieving 1/f floor of around 1E-12,
> it
>  would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to
> the
>  trouble of actually measuring it.
> 
>  So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible
>  with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms,
> only
> >> one
>  order of magnitude off.
> 
>  The bad side of a 7912 is in long-term stability and tempCo, the
> sample
> >> I
>  tested had at least a 150 ppm/degC tempCo, which is going to put a
> >> serious
>  lump/bump in the 10s tau to gps crossover point on an allan deviation
> >> plot.
> 
> 
> 
>  On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe <
> scott.j.sto...@gmail.com 
> >> >
>  wrote:
> 
> > I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm
> > interested to see the 1/f noise of a classic regulator, what load
> >> current
> > do you expect? I can bias a 7805 for the same load and measure the
> 0.1
> >> to
> > 10 Hz noise.
> >
> > Also if you have a digital scope without a very good builtin FFT,
> >> octave
> > would be one solution.
> >
> > On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts <
> > time-nuts@febo.com  > wrote:
> >
> >> Just an update. I’ve built the second prototype board (I skipped
> over
> >> the first design), and it’s powering my tbolt right now.
> >>
> >> The design calls for 15v in (though it would also work with

Re: [time-nuts] Anybody want a Thunderbolt power supply?

Hi

The +12 goes straight to the OCXO. All OCXO’s have a voltage sensitivity. 
That sensitivity is much higher than voltage sensitivity is much higher than 
what you see on the other two supply pins.

Bob

> On Oct 21, 2016, at 11:06 PM, Scott Stobbe  wrote:
> 
> Interesting, I would have thought that the +12V input would be extremely
> well regulated since its shared with the oven heater, I*R drops are going
> to show up every where, if your looking for uV levels of stability.
> Just a connector has milliohms of contact resistance, let alone routing and
> cables...
> 
> On Friday, 21 October 2016, Bob Camp  wrote:
> 
>> Hi
>> 
>>> On Oct 21, 2016, at 7:44 PM, Scott Stobbe > > wrote:
>>> 
>>> A little more data on the 7912.
>>> 
>>> The first plot shows the tempCo of the 7912 measured with ambient
>>> temperature swings "7912_TempCo.png". Which is -150 ppm/degC.
>>> 
>>> The second plot is off a 7912 logged for an hour or so, "7912_1PLC.png",
>>> nothing too interesting here. However the environmental temperature swing
>>> of about 1 degC/hour is pretty conservative for a DUT sitting in free
>> air.
>>> 
>>> Finally, an allan devation plot looking at the normalized stability of a
>>> 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how
>> quick
>>> a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter
>> of
>>> seconds.
>>> 
>>> Now if your PSRR is 1 ppb/V or better, then all of this is comfortably
>>> below the intrinsic noise of a thunderbolt.
>> 
>> The main point is that the internal tempco of the TBolt it’s self is much
>> larger than
>> the issues surrounding the power supply pins. The +12 is the only one that
>> is
>> sensitive enough to voltage (change in frequency vs voltage) to contribute
>> to any
>> significant way to the overall stability.
>> 
>> Bob
>> 
>>> 
>>> On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe > >
>>> wrote:
>>> 
 Nick had mention that the -12V rail on the thunderbolt has the poorest
 PSRR with respect to frequency output, so I first took a look at the
 venerable 7912.
 
 The first data-set was taken with a -13.5 VDC input. Attached is the 0.1
 Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a 10k
 resistor was added as load for preliminary evaluation. With a 60 dB
>> preamp
 the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise
>> is
 15 uVrms, which is about 1.3 ppm rms of the DC mean.
 
 In allan deviation terms, a quiescently loaded 7912 has a spot noise of
>> 7
 uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz.
 Equivalently speaking, the flicker noise floor of an allan deviation
>> plot
 would be sqrt(2*ln(2)) that figure to be 6.8E-7.
 
 Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, it
 would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to the
 trouble of actually measuring it.
 
 So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible
 with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, only
>> one
 order of magnitude off.
 
 The bad side of a 7912 is in long-term stability and tempCo, the sample
>> I
 tested had at least a 150 ppm/degC tempCo, which is going to put a
>> serious
 lump/bump in the 10s tau to gps crossover point on an allan deviation
>> plot.
 
 
 
 On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe > >
 wrote:
 
> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm
> interested to see the 1/f noise of a classic regulator, what load
>> current
> do you expect? I can bias a 7805 for the same load and measure the 0.1
>> to
> 10 Hz noise.
> 
> Also if you have a digital scope without a very good builtin FFT,
>> octave
> would be one solution.
> 
> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts <
> time-nuts@febo.com > wrote:
> 
>> Just an update. I’ve built the second prototype board (I skipped over
>> the first design), and it’s powering my tbolt right now.
>> 
>> The design calls for 15v in (though it would also work with 13.8v).
>> The
>> +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck
>> converter to make around 6.5 volts, then a DPAK 7805. For -12, there
>> is an
>> MC34063 configured as an inverter to make around -13.75 volts and
>> then a
>> DPAK 7912.
>> 
>> Steady-state, the system appears to be working just fine. The AP1509’s
>> inductor and the D2PAK 7812 are just warm to the touch.
>> 
>> I checked for noise and ripple on the outputs and it’s somewhere
>> around
>> ±2 mV or so generally. From what I can see on the scope, there’s no
>> ripple
>> - it’s all

Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-21 Thread Scott Stobbe

Interesting, I would have thought that the +12V input would be extremely
well regulated since its shared with the oven heater, I*R drops are going
to show up every where, if your looking for uV levels of stability.
Just a connector has milliohms of contact resistance, let alone routing and
cables...

On Friday, 21 October 2016, Bob Camp  wrote:

> Hi
>
> > On Oct 21, 2016, at 7:44 PM, Scott Stobbe  > wrote:
> >
> > A little more data on the 7912.
> >
> > The first plot shows the tempCo of the 7912 measured with ambient
> > temperature swings "7912_TempCo.png". Which is -150 ppm/degC.
> >
> > The second plot is off a 7912 logged for an hour or so, "7912_1PLC.png",
> > nothing too interesting here. However the environmental temperature swing
> > of about 1 degC/hour is pretty conservative for a DUT sitting in free
> air.
> >
> > Finally, an allan devation plot looking at the normalized stability of a
> > 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how
> quick
> > a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter
> of
> > seconds.
> >
> > Now if your PSRR is 1 ppb/V or better, then all of this is comfortably
> > below the intrinsic noise of a thunderbolt.
>
> The main point is that the internal tempco of the TBolt it’s self is much
> larger than
> the issues surrounding the power supply pins. The +12 is the only one that
> is
> sensitive enough to voltage (change in frequency vs voltage) to contribute
> to any
> significant way to the overall stability.
>
> Bob
>
> >
> > On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe  >
> > wrote:
> >
> >> Nick had mention that the -12V rail on the thunderbolt has the poorest
> >> PSRR with respect to frequency output, so I first took a look at the
> >> venerable 7912.
> >>
> >> The first data-set was taken with a -13.5 VDC input. Attached is the 0.1
> >> Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a 10k
> >> resistor was added as load for preliminary evaluation. With a 60 dB
> preamp
> >> the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise
> is
> >> 15 uVrms, which is about 1.3 ppm rms of the DC mean.
> >>
> >> In allan deviation terms, a quiescently loaded 7912 has a spot noise of
> 7
> >> uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz.
> >> Equivalently speaking, the flicker noise floor of an allan deviation
> plot
> >> would be sqrt(2*ln(2)) that figure to be 6.8E-7.
> >>
> >> Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, it
> >> would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to the
> >> trouble of actually measuring it.
> >>
> >> So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible
> >> with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, only
> one
> >> order of magnitude off.
> >>
> >> The bad side of a 7912 is in long-term stability and tempCo, the sample
> I
> >> tested had at least a 150 ppm/degC tempCo, which is going to put a
> serious
> >> lump/bump in the 10s tau to gps crossover point on an allan deviation
> plot.
> >>
> >>
> >>
> >> On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe  >
> >> wrote:
> >>
> >>> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm
> >>> interested to see the 1/f noise of a classic regulator, what load
> current
> >>> do you expect? I can bias a 7805 for the same load and measure the 0.1
> to
> >>> 10 Hz noise.
> >>>
> >>> Also if you have a digital scope without a very good builtin FFT,
> octave
> >>> would be one solution.
> >>>
> >>> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts <
> >>> time-nuts@febo.com > wrote:
> >>>
>  Just an update. I’ve built the second prototype board (I skipped over
>  the first design), and it’s powering my tbolt right now.
> 
>  The design calls for 15v in (though it would also work with 13.8v).
> The
>  +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck
>  converter to make around 6.5 volts, then a DPAK 7805. For -12, there
> is an
>  MC34063 configured as an inverter to make around -13.75 volts and
> then a
>  DPAK 7912.
> 
>  Steady-state, the system appears to be working just fine. The AP1509’s
>  inductor and the D2PAK 7812 are just warm to the touch.
> 
>  I checked for noise and ripple on the outputs and it’s somewhere
> around
>  ±2 mV or so generally. From what I can see on the scope, there’s no
> ripple
>  - it’s all high frequency noise. I am not absolutely certain that the
> noise
>  measurement represents real noise or the limits of my measuring
> ability.
>  I’m just using the scope probes the scope came with, and 2 mV/div is
> its
>  lowest range.
> 
>  I haven’t compared the noise with the ex laptop supply that I was
> using
>  before, but I’d

Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-21 Thread Bob Camp

Hi

> On Oct 21, 2016, at 7:44 PM, Scott Stobbe  wrote:
> 
> A little more data on the 7912.
> 
> The first plot shows the tempCo of the 7912 measured with ambient
> temperature swings "7912_TempCo.png". Which is -150 ppm/degC.
> 
> The second plot is off a 7912 logged for an hour or so, "7912_1PLC.png",
> nothing too interesting here. However the environmental temperature swing
> of about 1 degC/hour is pretty conservative for a DUT sitting in free air.
> 
> Finally, an allan devation plot looking at the normalized stability of a
> 7912 regulator "7912_AllanDeviation.png". Interestingly here, is, how quick
> a 15 mK/min temperature swing shoots above the 1/f floor, it's a matter of
> seconds.
> 
> Now if your PSRR is 1 ppb/V or better, then all of this is comfortably
> below the intrinsic noise of a thunderbolt.

The main point is that the internal tempco of the TBolt it’s self is much 
larger than
the issues surrounding the power supply pins. The +12 is the only one that is
sensitive enough to voltage (change in frequency vs voltage) to contribute to 
any
significant way to the overall stability. 

Bob

> 
> On Fri, Oct 21, 2016 at 12:20 AM, Scott Stobbe 
> wrote:
> 
>> Nick had mention that the -12V rail on the thunderbolt has the poorest
>> PSRR with respect to frequency output, so I first took a look at the
>> venerable 7912.
>> 
>> The first data-set was taken with a -13.5 VDC input. Attached is the 0.1
>> Hz to 10 Hz noise of an essentially quiescently loaded 7912, only a 10k
>> resistor was added as load for preliminary evaluation. With a 60 dB preamp
>> the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise is
>> 15 uVrms, which is about 1.3 ppm rms of the DC mean.
>> 
>> In allan deviation terms, a quiescently loaded 7912 has a spot noise of 7
>> uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz.
>> Equivalently speaking, the flicker noise floor of an allan deviation plot
>> would be sqrt(2*ln(2)) that figure to be 6.8E-7.
>> 
>> Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, it
>> would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to the
>> trouble of actually measuring it.
>> 
>> So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible
>> with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, only one
>> order of magnitude off.
>> 
>> The bad side of a 7912 is in long-term stability and tempCo, the sample I
>> tested had at least a 150 ppm/degC tempCo, which is going to put a serious
>> lump/bump in the 10s tau to gps crossover point on an allan deviation plot.
>> 
>> 
>> 
>> On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe 
>> wrote:
>> 
>>> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm
>>> interested to see the 1/f noise of a classic regulator, what load current
>>> do you expect? I can bias a 7805 for the same load and measure the 0.1 to
>>> 10 Hz noise.
>>> 
>>> Also if you have a digital scope without a very good builtin FFT, octave
>>> would be one solution.
>>> 
>>> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts <
>>> time-nuts@febo.com> wrote:
>>> 
 Just an update. I’ve built the second prototype board (I skipped over
 the first design), and it’s powering my tbolt right now.
 
 The design calls for 15v in (though it would also work with 13.8v). The
 +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck
 converter to make around 6.5 volts, then a DPAK 7805. For -12, there is an
 MC34063 configured as an inverter to make around -13.75 volts and then a
 DPAK 7912.
 
 Steady-state, the system appears to be working just fine. The AP1509’s
 inductor and the D2PAK 7812 are just warm to the touch.
 
 I checked for noise and ripple on the outputs and it’s somewhere around
 ±2 mV or so generally. From what I can see on the scope, there’s no ripple
 - it’s all high frequency noise. I am not absolutely certain that the noise
 measurement represents real noise or the limits of my measuring ability.
 I’m just using the scope probes the scope came with, and 2 mV/div is its
 lowest range.
 
 I haven’t compared the noise with the ex laptop supply that I was using
 before, but I’d have to believe it’s cleaner. I don’t really have a way to
 check the oscillator’s before and after ADEV. My only other reference is an
 FE5680A, and I think the thunderbolt’s going to be far better at lower tau
 (where this all matters).
 
 I know also that ±2 mV is still one and perhaps two orders of magnitude
 higher than some have called for. But before I attempt to reduce the noise
 further, I’d like to know that there are real gains to be had. Would
 someone with a Thunderbolt and better output noise measuring wherewithal be
 willing to take a prototype and compare it with something that does

Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-21 Thread David

On Fri, 21 Oct 2016 10:59:59 +0200, you wrote:

>On Fri, 21 Oct 2016 00:20:43 -0400
>Scott Stobbe  wrote:
>
>> The bad side of a 7912 is in long-term stability and tempCo, the sample I
>> tested had at least a 150 ppm/degC tempCo, which is going to put a serious
>> lump/bump in the 10s tau to gps crossover point on an allan deviation plot.
>
>If the Thunderbolt ist most sensitive to the -12V input, why not use
>something like the LT3090? Its temperature coefficient is quite low
>in the order of a few ppm/°C around room temperature. Using a metal
>film resistor that should keep the output variations low as well.
>As added bonus, you get a very low output noise.
>
>And while you are at it, use three LT3090 for the positive supplies :-)
>
>   Attila Kinali

Or if space is not an issue, use a discrete reference or zener,
operational amplifier, and pass transistor for better performance yet
at less cost.  If all of the supplies are to be regulated, then use a
common reference to further save cost.

Separating the reference, error amplifier, and feedback network from
the power pass transistor lowers the effects from thermal feedback.
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-21 Thread Attila Kinali

On Fri, 21 Oct 2016 06:14:03 -0700
Nick Sayer via time-nuts  wrote:

> Well, because it's easily an order of magnitude more expensive than a 7912. 
> $5 instead of 50¢ (Q:1).
> 
> If it *matters*, then fine, but I am sensitive to cost efficiency in addition 
> to efficacy.

Sorry, I've been hunting ps level delay uncertainties in the last weeks
and kind of forgot that not everyone does things to that extreme.

If you want to go for cheap LDOs, I would recommend going for the
modern variants available from Ti and Linear. Those have much less
noise and drift than the 79xx and 78xx families and are also zero
load impedance stable (ie can be used with ceramic capacitors).
But these are already all in the 1-3USD range if you want to supply 800mA. 
Ie they are at least a factor 2 more expensive than an 78xx.

> If you put the board in a box in a stable temperature environment
> (which I'd kind of assume you'd do if you cared about temperature stability
> generally), then how far do you really have to go?

Let's put a few numbers here:
The stability of a cheap OCXO (SCOCXOHS by Microcrystal) is specced
as <5*10^-7/V. An 7812 (LM7812 by Fairchild) is specced to 0.8mV/°C @ 5mA.
Assuming that using 500mA output makes the Voltage drifft worse by a factor
of 10 (i hope this conservative enough) we are at 8mV/°C. Ie. we get a
total, temperature to supply voltage induced frequency dependence of 4*10^-9/°C.
This is quite noticable. Compare this to the 75ppb over 0°C to 60° of
the temperatur spec of the SXOCXOHS. I.e. we are suddenly adding as much
temperature dependence to the OCXO trough the power supply as it has itself.
Even if you discard the factor 10 for the 7812, that's still 4*10^-10/°C.

Using a more expensive OCXO (AOCJY4 by Abracon) gets you to 3*10^-11/°C
to 3*10^-12/°C, still quite noticable for a GPSDO and again in the order
of its intrinsic temperature coefficient.

And these calculations are only for the temperature of the LDO,
ie they assume an otherwise stable environment. If you start accounting
for drafts of air and changes in humidity, then things become even worse.

Also keep in mind, that unless you start putting cardboard boxes around
everything, then changes of 2-3°C within 10s is pretty normal when you
have people opening/closing doors/windows.

So.. does all this matter? Maybe, maybe not. :-) It depends on what you
actually do with the LDOs. If you put them in a metal box, maybe
with an cardboard box around it, then you dampen the temperature variations
quite a bit and give the GPSDO and its control loop  a chance to compensate.
If you leave them in the open, possibly with an heatsink attached, then
you definitely want to have a lower temperature coefficient.

Attila Kinali

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-21 Thread Bob Camp

Hi

At least in terms of voltage regulation (as opposed to noise), the -12V input 
on the TBolt is 
the *least* sensitive input on the TBolt. It’s issue is only in terms of PSRR. 
The internals of
the unit take care of any drift or really low frequency stuff on the -12 input.

Bob

> On Oct 21, 2016, at 9:14 AM, Nick Sayer via time-nuts  
> wrote:
> 
> Well, because it's easily an order of magnitude more expensive than a 7912. 
> $5 instead of 50¢ (Q:1).
> 
> If it *matters*, then fine, but I am sensitive to cost efficiency in addition 
> to efficacy.
> 
> If you put the board in a box in a stable temperature environment (which I'd 
> kind of assume you'd do if you cared about temperature stability generally), 
> then how far do you really have to go?
> 
> Sent from my iPhone
> 
>> On Oct 21, 2016, at 1:59 AM, Attila Kinali  wrote:
>> 
>> On Fri, 21 Oct 2016 00:20:43 -0400
>> Scott Stobbe  wrote:
>> 
>>> The bad side of a 7912 is in long-term stability and tempCo, the sample I
>>> tested had at least a 150 ppm/degC tempCo, which is going to put a serious
>>> lump/bump in the 10s tau to gps crossover point on an allan deviation plot.
>> 
>> If the Thunderbolt ist most sensitive to the -12V input, why not use
>> something like the LT3090? Its temperature coefficient is quite low
>> in the order of a few ppm/°C around room temperature. Using a metal
>> film resistor that should keep the output variations low as well.
>> As added bonus, you get a very low output noise.
>> 
>> And while you are at it, use three LT3090 for the positive supplies :-)
>> 
>>   Attila Kinali
>> -- 
>> Malek's Law:
>>   Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-21 Thread Nick Sayer via time-nuts

Well, because it's easily an order of magnitude more expensive than a 7912. $5 
instead of 50¢ (Q:1).

If it *matters*, then fine, but I am sensitive to cost efficiency in addition 
to efficacy.

If you put the board in a box in a stable temperature environment (which I'd 
kind of assume you'd do if you cared about temperature stability generally), 
then how far do you really have to go?

Sent from my iPhone

> On Oct 21, 2016, at 1:59 AM, Attila Kinali  wrote:
> 
> On Fri, 21 Oct 2016 00:20:43 -0400
> Scott Stobbe  wrote:
> 
>> The bad side of a 7912 is in long-term stability and tempCo, the sample I
>> tested had at least a 150 ppm/degC tempCo, which is going to put a serious
>> lump/bump in the 10s tau to gps crossover point on an allan deviation plot.
> 
> If the Thunderbolt ist most sensitive to the -12V input, why not use
> something like the LT3090? Its temperature coefficient is quite low
> in the order of a few ppm/°C around room temperature. Using a metal
> film resistor that should keep the output variations low as well.
> As added bonus, you get a very low output noise.
> 
> And while you are at it, use three LT3090 for the positive supplies :-)
> 
>Attila Kinali
> -- 
> Malek's Law:
>Any simple idea will be worded in the most complicated way.
> ___
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-21 Thread Bob Camp

Hi

> On Oct 21, 2016, at 12:20 AM, Scott Stobbe  wrote:
> 
> Nick had mention that the -12V rail on the thunderbolt has the poorest PSRR
> with respect to frequency output, so I first took a look at the venerable
> 7912.
> 
> The first data-set was taken with a -13.5 VDC input. Attached is the 0.1 Hz
> to 10 Hz noise of an essentially quiescently loaded 7912, only a 10k
> resistor was added as load for preliminary evaluation. With a 60 dB preamp
> the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise is
> 15 uVrms, which is about 1.3 ppm rms of the DC mean.
> 
> In allan deviation terms, a quiescently loaded 7912 has a spot noise of 7
> uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz.
> Equivalently speaking, the flicker noise floor of an allan deviation plot
> would be sqrt(2*ln(2)) that figure to be 6.8E-7.
> 
> Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, it
> would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to the
> trouble of actually measuring it.

The EFC on the OCXO is less sensitive than 1 ppm / V. It is a slam dunk 
to say that the whole OCXO is less sensitive than the EFC by a good margin ….

Bob


> 
> So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible
> with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, only one
> order of magnitude off.
> 
> The bad side of a 7912 is in long-term stability and tempCo, the sample I
> tested had at least a 150 ppm/degC tempCo, which is going to put a serious
> lump/bump in the 10s tau to gps crossover point on an allan deviation plot.
> 
> 
> 
> On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe 
> wrote:
> 
>> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm interested
>> to see the 1/f noise of a classic regulator, what load current do you
>> expect? I can bias a 7805 for the same load and measure the 0.1 to 10 Hz
>> noise.
>> 
>> Also if you have a digital scope without a very good builtin FFT, octave
>> would be one solution.
>> 
>> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts <
>> time-nuts@febo.com> wrote:
>> 
>>> Just an update. I’ve built the second prototype board (I skipped over the
>>> first design), and it’s powering my tbolt right now.
>>> 
>>> The design calls for 15v in (though it would also work with 13.8v). The
>>> +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck
>>> converter to make around 6.5 volts, then a DPAK 7805. For -12, there is an
>>> MC34063 configured as an inverter to make around -13.75 volts and then a
>>> DPAK 7912.
>>> 
>>> Steady-state, the system appears to be working just fine. The AP1509’s
>>> inductor and the D2PAK 7812 are just warm to the touch.
>>> 
>>> I checked for noise and ripple on the outputs and it’s somewhere around
>>> ±2 mV or so generally. From what I can see on the scope, there’s no ripple
>>> - it’s all high frequency noise. I am not absolutely certain that the noise
>>> measurement represents real noise or the limits of my measuring ability.
>>> I’m just using the scope probes the scope came with, and 2 mV/div is its
>>> lowest range.
>>> 
>>> I haven’t compared the noise with the ex laptop supply that I was using
>>> before, but I’d have to believe it’s cleaner. I don’t really have a way to
>>> check the oscillator’s before and after ADEV. My only other reference is an
>>> FE5680A, and I think the thunderbolt’s going to be far better at lower tau
>>> (where this all matters).
>>> 
>>> I know also that ±2 mV is still one and perhaps two orders of magnitude
>>> higher than some have called for. But before I attempt to reduce the noise
>>> further, I’d like to know that there are real gains to be had. Would
>>> someone with a Thunderbolt and better output noise measuring wherewithal be
>>> willing to take a prototype and compare it with something that does have µV
>>> levels of noise and ripple so I can get an idea of what there is to gain?
>>> If you like, you can make such comparisons public - no secrets here.
>>> 
 On Aug 30, 2016, at 10:37 PM, Nick Sayer  wrote:
 
 
> On Aug 30, 2016, at 8:48 PM, Cube Central 
>>> wrote:
> 
> I would be interested, I think.  Planning ahead for if the one I have
>>> for my Thunderbolt fails, I guess.  Are there different models or would a
>>> photo of the input ports on mine be useful?
 
 Actually, what I had in mind is to just put a SIP4 header on the board
>>> for the output and people could wire the “last mile” themselves. The input
>>> is a 2.1mm barrel connector. You use whatever 15W 12VDC wall wart is handy
>>> and plug it right in.
 
 What it really amounts to is that you get +12 volts directly from the
>>> input, then there’s a buck converter to drop the +12 down to +5 and an
>>> inverter to generate -12 from the +12. Those 3 voltages, plus a ground go
>>> to the SIP4.
 
 So

Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-21 Thread Attila Kinali

On Fri, 21 Oct 2016 10:59:59 +0200
Attila Kinali  wrote:

> And while you are at it, use three LT3090 for the positive supplies :-)

Ermm... LT3045

Attila Kinali

-- 
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Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-21 Thread Attila Kinali

On Fri, 21 Oct 2016 00:20:43 -0400
Scott Stobbe  wrote:

> The bad side of a 7912 is in long-term stability and tempCo, the sample I
> tested had at least a 150 ppm/degC tempCo, which is going to put a serious
> lump/bump in the 10s tau to gps crossover point on an allan deviation plot.

If the Thunderbolt ist most sensitive to the -12V input, why not use
something like the LT3090? Its temperature coefficient is quite low
in the order of a few ppm/°C around room temperature. Using a metal
film resistor that should keep the output variations low as well.
As added bonus, you get a very low output noise.

And while you are at it, use three LT3090 for the positive supplies :-)

Attila Kinali
-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-20 Thread Scott Stobbe

Nick had mention that the -12V rail on the thunderbolt has the poorest PSRR
with respect to frequency output, so I first took a look at the venerable
7912.

The first data-set was taken with a -13.5 VDC input. Attached is the 0.1 Hz
to 10 Hz noise of an essentially quiescently loaded 7912, only a 10k
resistor was added as load for preliminary evaluation. With a 60 dB preamp
the scale of the scope plot is 20 uV/div. The 0.1Hz to 10Hz band noise is
15 uVrms, which is about 1.3 ppm rms of the DC mean.

In allan deviation terms, a quiescently loaded 7912 has a spot noise of 7
uV/rtHz at 1 Hz (on the 1/f slope), normalized that's 580 ppb/rtHz.
Equivalently speaking, the flicker noise floor of an allan deviation plot
would be sqrt(2*ln(2)) that figure to be 6.8E-7.

Assuming a thunderbolt should be achieving 1/f floor of around 1E-12, it
would need a PSRR of at least 1 ppm/V. I'm sure someone has gone to the
trouble of actually measuring it.

So from a 0.1 Hz to 10 Hz noise standpoint, the 7912 isn't terrible
with 1.3 ppm rms noise, considering an LM399 is about 0.1 ppm rms, only one
order of magnitude off.

The bad side of a 7912 is in long-term stability and tempCo, the sample I
tested had at least a 150 ppm/degC tempCo, which is going to put a serious
lump/bump in the 10s tau to gps crossover point on an allan deviation plot.



On Tue, Oct 18, 2016 at 3:05 PM, Scott Stobbe 
wrote:

> I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm interested
> to see the 1/f noise of a classic regulator, what load current do you
> expect? I can bias a 7805 for the same load and measure the 0.1 to 10 Hz
> noise.
>
> Also if you have a digital scope without a very good builtin FFT, octave
> would be one solution.
>
> On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts <
> time-nuts@febo.com> wrote:
>
>> Just an update. I’ve built the second prototype board (I skipped over the
>> first design), and it’s powering my tbolt right now.
>>
>> The design calls for 15v in (though it would also work with 13.8v). The
>> +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck
>> converter to make around 6.5 volts, then a DPAK 7805. For -12, there is an
>> MC34063 configured as an inverter to make around -13.75 volts and then a
>> DPAK 7912.
>>
>> Steady-state, the system appears to be working just fine. The AP1509’s
>> inductor and the D2PAK 7812 are just warm to the touch.
>>
>> I checked for noise and ripple on the outputs and it’s somewhere around
>> ±2 mV or so generally. From what I can see on the scope, there’s no ripple
>> - it’s all high frequency noise. I am not absolutely certain that the noise
>> measurement represents real noise or the limits of my measuring ability.
>> I’m just using the scope probes the scope came with, and 2 mV/div is its
>> lowest range.
>>
>> I haven’t compared the noise with the ex laptop supply that I was using
>> before, but I’d have to believe it’s cleaner. I don’t really have a way to
>> check the oscillator’s before and after ADEV. My only other reference is an
>> FE5680A, and I think the thunderbolt’s going to be far better at lower tau
>> (where this all matters).
>>
>> I know also that ±2 mV is still one and perhaps two orders of magnitude
>> higher than some have called for. But before I attempt to reduce the noise
>> further, I’d like to know that there are real gains to be had. Would
>> someone with a Thunderbolt and better output noise measuring wherewithal be
>> willing to take a prototype and compare it with something that does have µV
>> levels of noise and ripple so I can get an idea of what there is to gain?
>> If you like, you can make such comparisons public - no secrets here.
>>
>> > On Aug 30, 2016, at 10:37 PM, Nick Sayer  wrote:
>> >
>> >
>> >> On Aug 30, 2016, at 8:48 PM, Cube Central 
>> wrote:
>> >>
>> >> I would be interested, I think.  Planning ahead for if the one I have
>> for my Thunderbolt fails, I guess.  Are there different models or would a
>> photo of the input ports on mine be useful?
>> >
>> > Actually, what I had in mind is to just put a SIP4 header on the board
>> for the output and people could wire the “last mile” themselves. The input
>> is a 2.1mm barrel connector. You use whatever 15W 12VDC wall wart is handy
>> and plug it right in.
>> >
>> > What it really amounts to is that you get +12 volts directly from the
>> input, then there’s a buck converter to drop the +12 down to +5 and an
>> inverter to generate -12 from the +12. Those 3 voltages, plus a ground go
>> to the SIP4.
>> >
>> > So it’s just two switching power supplies to turn a +12 volt only
>> supply into the three-way that the Thunderbolt wants.
>> >
>> > It’d be good for around 1500 mA @ 5V and around 50 mA @ -12 (the +12
>> spec is whatever is left from the source supply’s power spec) - more than
>> enough for a Thunderbolt. Probably enough for a hard disk or a smallish PC.
>>

Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-18 Thread Scott Stobbe

I'm sure I have some 7805s lying around, maybe a 7812/7912. I'm interested
to see the 1/f noise of a classic regulator, what load current do you
expect? I can bias a 7805 for the same load and measure the 0.1 to 10 Hz
noise.

Also if you have a digital scope without a very good builtin FFT, octave
would be one solution.

On Tue, Oct 18, 2016 at 10:46 AM, Nick Sayer via time-nuts <
time-nuts@febo.com> wrote:

> Just an update. I’ve built the second prototype board (I skipped over the
> first design), and it’s powering my tbolt right now.
>
> The design calls for 15v in (though it would also work with 13.8v). The
> +12 output comes from a D2PAK 7812. For +5, there is an AP1509 buck
> converter to make around 6.5 volts, then a DPAK 7805. For -12, there is an
> MC34063 configured as an inverter to make around -13.75 volts and then a
> DPAK 7912.
>
> Steady-state, the system appears to be working just fine. The AP1509’s
> inductor and the D2PAK 7812 are just warm to the touch.
>
> I checked for noise and ripple on the outputs and it’s somewhere around ±2
> mV or so generally. From what I can see on the scope, there’s no ripple -
> it’s all high frequency noise. I am not absolutely certain that the noise
> measurement represents real noise or the limits of my measuring ability.
> I’m just using the scope probes the scope came with, and 2 mV/div is its
> lowest range.
>
> I haven’t compared the noise with the ex laptop supply that I was using
> before, but I’d have to believe it’s cleaner. I don’t really have a way to
> check the oscillator’s before and after ADEV. My only other reference is an
> FE5680A, and I think the thunderbolt’s going to be far better at lower tau
> (where this all matters).
>
> I know also that ±2 mV is still one and perhaps two orders of magnitude
> higher than some have called for. But before I attempt to reduce the noise
> further, I’d like to know that there are real gains to be had. Would
> someone with a Thunderbolt and better output noise measuring wherewithal be
> willing to take a prototype and compare it with something that does have µV
> levels of noise and ripple so I can get an idea of what there is to gain?
> If you like, you can make such comparisons public - no secrets here.
>
> > On Aug 30, 2016, at 10:37 PM, Nick Sayer  wrote:
> >
> >
> >> On Aug 30, 2016, at 8:48 PM, Cube Central 
> wrote:
> >>
> >> I would be interested, I think.  Planning ahead for if the one I have
> for my Thunderbolt fails, I guess.  Are there different models or would a
> photo of the input ports on mine be useful?
> >
> > Actually, what I had in mind is to just put a SIP4 header on the board
> for the output and people could wire the “last mile” themselves. The input
> is a 2.1mm barrel connector. You use whatever 15W 12VDC wall wart is handy
> and plug it right in.
> >
> > What it really amounts to is that you get +12 volts directly from the
> input, then there’s a buck converter to drop the +12 down to +5 and an
> inverter to generate -12 from the +12. Those 3 voltages, plus a ground go
> to the SIP4.
> >
> > So it’s just two switching power supplies to turn a +12 volt only supply
> into the three-way that the Thunderbolt wants.
> >
> > It’d be good for around 1500 mA @ 5V and around 50 mA @ -12 (the +12
> spec is whatever is left from the source supply’s power spec) - more than
> enough for a Thunderbolt. Probably enough for a hard disk or a smallish PC.
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-10-18 Thread Nick Sayer via time-nuts

Just an update. I’ve built the second prototype board (I skipped over the first 
design), and it’s powering my tbolt right now.

The design calls for 15v in (though it would also work with 13.8v). The +12 
output comes from a D2PAK 7812. For +5, there is an AP1509 buck converter to 
make around 6.5 volts, then a DPAK 7805. For -12, there is an MC34063 
configured as an inverter to make around -13.75 volts and then a DPAK 7912.

Steady-state, the system appears to be working just fine. The AP1509’s inductor 
and the D2PAK 7812 are just warm to the touch.

I checked for noise and ripple on the outputs and it’s somewhere around ±2 mV 
or so generally. From what I can see on the scope, there’s no ripple - it’s all 
high frequency noise. I am not absolutely certain that the noise measurement 
represents real noise or the limits of my measuring ability. I’m just using the 
scope probes the scope came with, and 2 mV/div is its lowest range.

I haven’t compared the noise with the ex laptop supply that I was using before, 
but I’d have to believe it’s cleaner. I don’t really have a way to check the 
oscillator’s before and after ADEV. My only other reference is an FE5680A, and 
I think the thunderbolt’s going to be far better at lower tau (where this all 
matters).

I know also that ±2 mV is still one and perhaps two orders of magnitude higher 
than some have called for. But before I attempt to reduce the noise further, 
I’d like to know that there are real gains to be had. Would someone with a 
Thunderbolt and better output noise measuring wherewithal be willing to take a 
prototype and compare it with something that does have µV levels of noise and 
ripple so I can get an idea of what there is to gain? If you like, you can make 
such comparisons public - no secrets here.

> On Aug 30, 2016, at 10:37 PM, Nick Sayer  wrote:
> 
> 
>> On Aug 30, 2016, at 8:48 PM, Cube Central  wrote:
>> 
>> I would be interested, I think.  Planning ahead for if the one I have for my 
>> Thunderbolt fails, I guess.  Are there different models or would a photo of 
>> the input ports on mine be useful?
> 
> Actually, what I had in mind is to just put a SIP4 header on the board for 
> the output and people could wire the “last mile” themselves. The input is a 
> 2.1mm barrel connector. You use whatever 15W 12VDC wall wart is handy and 
> plug it right in.
> 
> What it really amounts to is that you get +12 volts directly from the input, 
> then there’s a buck converter to drop the +12 down to +5 and an inverter to 
> generate -12 from the +12. Those 3 voltages, plus a ground go to the SIP4.
> 
> So it’s just two switching power supplies to turn a +12 volt only supply into 
> the three-way that the Thunderbolt wants.
> 
> It’d be good for around 1500 mA @ 5V and around 50 mA @ -12 (the +12 spec is 
> whatever is left from the source supply’s power spec) - more than enough for 
> a Thunderbolt. Probably enough for a hard disk or a smallish PC.
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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-09-05 Thread Gerhard Hoffmann


Am 01.09.2016 um 06:56 schrieb Gerhard Hoffmann:

Am 01.09.2016 um 05:35 schrieb Charles Steinmetz:


The suggestion to use LT3042s is a good one, but note that it has an 
output current rating of 200mA.  The Tbolt needs ~250mA at +5v, and 
~700mA at +12v [at startup -- but only ~150mA steady-state, depending 
on ambient temperature].  LT3042s can be used in parallel, so two of 
them for the +5v supply and four of them for the +12v supply would be 
required.  That isn't so bad for the +5v supply, but seems excessive 
for the +12v supply (particularly when three of the four are needed 
only during warmup from cold).


I have made a stamp-sized layout for LT3042 + external npn power 
transistor

as shown in the data sheet.
Not fabricated, let alone tested.


update:
fabricated on a rainy Sunday and initially tested.
Output voltage is 5 Volts.

< 
https://www.flickr.com/photos/137684711@N07/29197476530/in/dateposted-public/ 
>


The preliminary noise spectrum is

< 
https://www.flickr.com/photos/137684711@N07/29452163806/in/dateposted-public/>


without appropriate shielding, powered from R NGT20 @ 8V.
The faster than 1/f noise rise is caused by the pre-amplifier.

Still quite OK.

regards, Gerhard




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Re: [time-nuts] Anybody want a Thunderbolt power supply?


James wrote:


Is there a problem running more than one Thunderbolt off of the same linear 
supply (assuming the supply can support the current demands) or does each 
Thunderbolt require its’ own separate linear supply?


I do not anticipate that multiple Tbolts would interact in a negative 
manner if they were connected to a good linear supply capable of driving 
them all.  Of course, there is always a possibility that I'm wrong and 
they would interact.  Only trying it will answer that question.


Note that, as Bob pointed out, the +12v supply will need to source 
700-800mA *per Tbolt* for a few minutes if they are all powered up at 
once from cold.  Even if you wouldn't do this in a manual startup, it 
would happen when the power came back on if you had a power failure 
(unless you devised some automatic means to prevent it).


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-09-01 Thread Stan, W1LE


Jim,

I use a HP 6236B triple power supply to drive 2 each T'Bolts. Works fine 
after the T'Bolts warm up, with limitations on a cold start up.


But once they warm up all is OK.

Using a common outside puck antenna and a HP RF distribution block I can 
run 3 T'Bolts and get essentially the same results.


#1 T'Bolt is on a HP 6235A DC PS and #2 and #3 are on the 6236B. #1 has 
been on for years.


I am planning to box up and use a  Mean Well SMPS common power supply 
that will handle the load current of 3 T'Bolts starting cold.


Adding a few digital panel meters to measure individual load currents 
and voltages.


Stan, W1LE   Cape Cod


On 9/1/2016 9:44 AM, James Robbins wrote:

Is there a problem running more than one Thunderbolt off of the same linear 
supply (assuming the supply can support the current demands) or does each 
Thunderbolt require its’ own separate linear supply?  Jim Robbins
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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-09-01 Thread Gerhard Hoffmann

Am 01.09.2016 um 16:36 schrieb jimlux:

On 8/31/16 10:24 PM, Gerhard Hoffmann wrote:

Am 01.09.2016 um 06:07 schrieb Bruce Griffiths:

I have a quad LT3042 PCB that I must get around to assembling.One
potential issue with the LT3042 is the relatively high noise at low
frequencies when the capacititve bypassing of the resistor that sets
the output voltage is ineffective.

I wonder where that relatively high noise on the LT3042 might hide.

<
https://www.flickr.com/photos/137684711@N07/24070698809/in/datetaken/lightbox/

what's the input source for these measurements? Batteries?

Either NiMH batteries or a R NGT20 with the post filter box as in page
9 of

<
http://www.hoffmann-hochfrequenz.de/downloads/Noise_Measurements_On_Some_Laboratory_Power_Supplies.pdf
>

That would not make much of a difference.

Prefilter/test box and preamp were isolated and in an another large ALU
cargo box with beryllium copper
finger stock on the door and BNC bulkhead feedthroughs. The preamp runs
on NiMH batteries. It's input
connection is just one semirigid SMA cable. If the testbox & preamp box
touch, the resulting loop

creates an explosion of interference.

I used "The Art Of Electronics V3" and Aldert van der Ziel's "Noise in
Solid State Devices And Circuits"

as insulators. A good foundation to build upon, in every respect. :-)

regards, Gerhard

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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-09-01 Thread Bob kb8tq

Hi

The easy answer for a couple dozen Tbolts is a +15 V high current linear supply 
and a low power -15 V linear. Wire them to regulators mounted on chunks of perf 
board.

Bob

> On Sep 1, 2016, at 12:24 AM, DaveH <i...@blackmountainforge.com> wrote:
> 
> Someone could come out with a circuit board for a single configurable
> voltage and decent noise specs. Use three of them for a Tbolt.
> 
> It is really easy to use the transformer from an old microwave oven to make
> your own power transformer - the HV and the 110 volt windings are on
> separate parts of the core so it is a matter of a few minutes to hacksaw off
> the HV winding and you can use standard household THHN wire for your new
> secondary - wind ten turns, measure the voltage and use that to figure how
> many turns you actually needed.
> 
> If someone came out with such a bare board, I would buy 20 of them just to
> keep around for projects.
> 
> Dave
> 
>> -Original Message-
>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf 
>> Of Bob Stewart
>> Sent: Wednesday, August 31, 2016 14:29
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?
>> 
>> OTOH, how many time-nuts have any interest in paying for a 
>> power supply that's up to time-nuts standards?  It's really 
>> not easy to bring a small product to market at a small price. 
>> Even if you completely discount the personal effort of 
>> design, construction, and marketing, there's the issue of 
>> packaging.  Without a package, it's just an amateur effort 
>> not worth considering.  With a package, such as a Hammond 
>> box, the price moves into new territory and nobody's interested.
>> 
>> Bob 
>> 
>> 
>>      From: Charles Steinmetz <csteinm...@yandex.com>
>> To: time-nuts@febo.com 
>> Sent: Wednesday, August 31, 2016 4:24 PM
>> Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?
>> 
>> Mark wrote:
>> 
>>> Some times a full linear supply is not a viable option due
>> to power dissipation/size issues or the utter convenience of 
>> using a switching wall wart.
>> 
>> In the context of the present discussion -- powering a Tbolt for 
>> time-nuts use -- the first consideration would just be 
>> laughable and the 
>> second would be nothing but terminal laziness.
>> 
>> Best regards,
>> 
>> Charles
>> 
>> 
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-09-01 Thread Bob Camp

Hi

The gotcha is that an OCXO acts as a negative resistance load (current goes up 
as voltage goes down). 
That makes wiring up multiple units problematic. It is not impossible to do, 
but you can get in trouble. Putting
regulation at each device eliminates the problem. It may be overkill, but the 
interaction can be tough to spot so 
it is generally a good idea.

Bob

> On Sep 1, 2016, at 10:44 AM, Charles Steinmetz  wrote:
> 
> James wrote:
> 
>> Is there a problem running more than one Thunderbolt off of the same linear 
>> supply (assuming the supply can support the current demands) or does each 
>> Thunderbolt require its’ own separate linear supply?
> 
> I do not anticipate that multiple Tbolts would interact in a negative manner 
> if they were connected to a good linear supply capable of driving them all.  
> Of course, there is always a possibility that I'm wrong and they would 
> interact.  Only trying it will answer that question.
> 
> Note that, as Bob pointed out, the +12v supply will need to source 700-800mA 
> *per Tbolt* for a few minutes if they are all powered up at once from cold.  
> Even if you wouldn't do this in a manual startup, it would happen when the 
> power came back on if you had a power failure (unless you devised some 
> automatic means to prevent it).
> 
> Best regards,
> 
> Charles
> 
> 
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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-09-01 Thread jimlux


On 8/31/16 10:24 PM, Gerhard Hoffmann wrote:

Am 01.09.2016 um 06:07 schrieb Bruce Griffiths:

I have a quad LT3042 PCB that I must get around to assembling.One
potential issue with the LT3042 is the relatively high noise at low
frequencies when the capacititve bypassing of the resistor that sets
the output voltage is ineffective.


I wonder where that relatively high noise on the LT3042 might hide.

<
https://www.flickr.com/photos/137684711@N07/24070698809/in/datetaken/lightbox/






what's the input source for these measurements? Batteries?


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Re: [time-nuts] Anybody want a Thunderbolt power supply


Dave wrote:


The problem on eBay is "tested" means something quite different to what I know as 
"tested'


Well, yes, but that's well-known.  Ebay is what it is and ebay sellers 
are what they are.  No use grousing about it, just deal with it.  The 
important thing is to make sure you have a right of return. 
Interestingly, after the last policy changes (at least here in the US), 
it may actually be better to buy from a seller who does not offer 
returns, because the "ebay money back guarantee" makes the seller refund 
the bid price plus the original shipping, while an individual seller's 
return policy may leave the buyer responsible for the original shipping. 
 Also, in some cases ebay doesn't require the buyer to return the 
defective item, so you may save the return shipping and get the 
defective item to play with to boot.



There are a number of HP power supplies that have over voltage trips. *  *  *  
So even if you accidentally turn the knob and increase the voltage, no damage 
will occur


True, and the Power Designs supplies I mentioned all have OVP that works 
very well.  If any of the supplies goes OV, it shuts all three supplies 
down.  However, many electronic gizmos can be damaged if one of the 
supplies falls too far *below* its nominal voltage while the other 
supplies stay nominal, which of course would not trip the OVP.  So I 
still recommend a dab of RTV on the voltage adjustment knobs when you 
want the voltages to stay where they were set.


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-09-01 Thread Bob Camp

Hi

For multiple TBolts, the simple answer is local regulation. LT1764’s work fine 
for the +12 and +5 side. A well bypassed 79L12 can
do the trick for the -12. Feed them all of of a  bulk +15 (high current) 
llinear supply and a -15 with the lowest output you can find. 

The gotcha is that if you have a power outage … all of them fire up at once. 
The OCXO’s go to max and that condition likely will 
do nasty things to a supply not rated to handle the current. A current limit 
supply will likely *eventually* recover. A holdback supply 
may not ever come back. A supply with defective overload protection may burst 
into flames ….

Lots of fun.

Bob

> On Sep 1, 2016, at 9:44 AM, James Robbins  wrote:
> 
> Is there a problem running more than one Thunderbolt off of the same linear 
> supply (assuming the supply can support the current demands) or does each 
> Thunderbolt require its’ own separate linear supply?  Jim Robbins
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-09-01 Thread James Robbins

Is there a problem running more than one Thunderbolt off of the same linear 
supply (assuming the supply can support the current demands) or does each 
Thunderbolt require its’ own separate linear supply?  Jim Robbins
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Re: [time-nuts] Anybody want a Thunderbolt power supply


Mike wrote:


I use the TAPR HPSDR LPU


I was unfamiliar with the LPU, so I took a look at the docs.  It 
develops several voltages, all from a +13.8v source.  This means that 
the -12v supply necessarily is a switching supply (to get the polarity 
reversal).  It is unfortunate that the power supply that needs to be 
quietest for a Tbolt to perform at its best is the one that will be the 
noisiest from this design.  (That will be true for any supply that uses 
nothing but a positive DC input.)


Speaking of noise, none of the datasheets for the four regulators used 
in the LPU gives any noise data.  It has always been my experience that 
if a manufacturer fails to provide a particular specification, it is 
because the part performs poorly in that respect -- so I presume the 
noise performance of all of the regulators in the LPU are mediocre at 
best for their type.


I have never measured an LPU, but all of the data available makes me 
think it is not a promising candidate if one wants the best performance 
from a Tbolt.


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-09-01 Thread Joakim Langlet


On 2016-09-01 05:35, Charles Steinmetz wrote:

Bruce wrote:


Low noise regulators for the +12V and +5V outputs would also be useful.


Very true.  By focusing on the -12v supply, I did not intend to 
suggest that low noise is unimportant on the +12v and +5v supplies.


The suggestion to use LT3042s is a good one, but note that it has an 
output current rating of 200mA.  The Tbolt needs ~250mA at +5v, and 
~700mA at +12v [at startup -- but only ~150mA steady-state, depending 
on ambient temperature].  LT3042s can be used in parallel, so two of 
them for the +5v supply and four of them for the +12v supply would be 
required.  That isn't so bad for the +5v supply, but seems excessive 
for the +12v supply (particularly when three of the four are needed 
only during warmup from cold).


The LT3088 and LT3080 will deliver 800mA and 1.1A, respectively, with 
low noise (but not as low as the LT3042).  One of those might be a 
better choice for the +12v supply.  Similarly, the LT3085 can deliver 
500mA, so one of those could be used for the +5v supply.


Finally: Linear Technology -- Where is our negative-voltage complement 
to the LT3042?


Best regards,

Charles


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I guess that you could say that I like soldering and the following 
suggestions might not appeal to everyone but it would give you a very 
clean supply for your Thunderbolts.


Since I tend to ignore the the bottom line cost and do things more 
complicated than necessary, you might not agree with my suggestions. On 
the other hand, my designs generally work well.


In the power supply of the GPSDO that I am building right now, I have 
used DC/DC converters for all voltages, but I set the output voltage 
slightly over the wanted voltage. I start off with +15V input from a 
AC/DC supply (purchased).


For +5V, I have used a TPS62160 (TI) with the output voltage set to +5.6V.
Then low dropout (LDO) regulators are used to get to +5V. The LDO 
filters out most the switching noise. The TPS62160 delivers up to 1A and 
can be fitted with all surrounding components in about 16x10mm.


In my case, I use lower currents at several points of load and use a 
TPS7A4901 at each of these. The active GPS antenna LNA is one of the 
consumers. It works well.


For a Thunderbolt, I guess that the TPS7A4501 could be used as the post 
switch regulator.


To generate +12V, I have used TPS54332 which can deliver up to 3A. In my 
case, the +12V doesn't need to be filtered, but if needed a +12V LDO 
(the TPS7A4501 can used here too) is used as a follower, starting with a 
switch output voltage at maybe +12.6V.


For a negative supply, I have used a LT3462A to invert the voltage. This 
could be used to get -12.6V output regulated by a TPS7A3001 down to -12V.


The good thing with this approach is that it generates very little 
excess heat and the output voltages could have noise levels in the order 
of maybe 50uV or less.


I will try to get my act together and create a web site where I can 
publish a bit about my over-complicated GPSDO design.
My problem is that I prefer soldering and programing and I am not the 
best web designer.


Once it is up, I will publish a link on the list.

BR/
Joakim



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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-09-01 Thread Gerhard Hoffmann


Am 01.09.2016 um 07:44 schrieb Charles Steinmetz:


The datasheet shows both NPN and PNP current multipliers.  Just 
curious -- did you choose the NPN circuit for theoretical 
considerations, and if so what was your reasoning -- the lower 
open-loop output impedance?


More belly feeling. The PNP circuit looks like the very low drop regulators
that are always good for a suprise. I did not think deeply about it.
And NPNs are more common.

regards, Gerhard

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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-09-01 Thread Dr. David Kirkby

 Original message 
From: Charles Steinmetz 
Date:09/01/2016 06:07 (GMT+00:00) 
To: time-nuts@febo.com 
Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply? 

Randall wrote:

> Tested and guaranteed samples of all of these can be bought for $25-100 
if you are patient (pay no attention to the loonies who list them for 
$250-350).

The problem on eBay is "tested" means something quite different to what I know 
as "tested'. 

> There are two potential disadvantages.  The first is size (particularly 
WRT the Power Designs units -- the HPs are much smaller).  The second is 
their adjustability.  You would not want to brush against one of the 
voltage-setting knobs accidentally and send your Tbolt to GPS heaven. 
The cure for this is a small dab of RTV on each knob.  

There are a number of HP power supplies that have over voltage trips.  You. can 
program them to switch on with an output voltage of V1 and a trip of V2, where 
V2 > V1. So even if you accidentally turn the knob and increase the voltage, no 
damage will occur as the PSU voltage drops to zrro. 

The above said, I set up an HP 6674A  option J02 (70 V, 30 A, 2100 W) supply to 
switch on at 13.8 V. Setting the trip at anything less than 14.1 V (from 
memory), meant it would trip at startup. If one wanted it to trip at 13.85 V, 
one would need to set the voltage lower,  then slowly increase to 13.8 V.

I have a number of HP/Agilent PSUs, and they all have over voltage trips. None 
of the PSUs I have are their "precision" ones.

The units I have do I believe have a local lockout facility which can be 
programmed by GPIB. 

Dave
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Re: [time-nuts] Anybody want a Thunderbolt power supply


Bruce wrote:


It will show up if the value of the voltage setting bypass capacitor is 
reduced. Both the Johnson and excess noise in this resistor coupled with the 
current source flicker noise should become evident. The datasheet graphs 
indicate that the Johnson noise of the voltage setting resistor(33k2 
~22nV/rtHz) isn't significant in comparison with other sources.


I have found that the voltage setting bypass capacitor can be profitably 
increased to ~22uF, beyond which there is only a very small gain below 
1Hz.  I would use 22uF unless that delayed reaching full voltage for too 
long at start-up.  (With 22uF, it takes ~15 seconds to reach the 3042's 
maximum output voltage of 15v, correspondingly less for lower output 
voltages.)


With 22uF, the output noise density is ~20nV/sqrtHz at 10Hz and 
~80nV/sqrtHz at 1Hz.  I believe most of the remaining noise (at least 
above 0.1Hz) is being generated in the unity-gain amplifier -- the 
reactance of the 22uF capacitor is only ~700 ohms at 10Hz.


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-09-01 Thread Bruce Griffiths

Post should have been:
Acts like noise current flowing in the voltage setting network (R || C).Flicker 
noise appears to kick in below 1Hz or so.
Bruce 

On Thursday, 1 September 2016 8:23 PM, Bruce Griffiths 
 wrote:

 Acts like current  noise flowing in the voltage sett

On Thursday, 1 September 2016 5:08 PM, Charles Steinmetz 
 wrote:

 Randall wrote:

> Wow, given all the responses about the cleanliness of the power into a 
> Thunderbolt, I would be even more interested in a power supply that did *not* 
> leave the "last mile" up to me.  I would be more interested in a "pretty 
> clean" power supply that I could just plug in and go.  Any thoughts of me 
> actually wiring the last bit of it make me break out in a cold sweat and come 
> face to face with my (established, and sadly slow-to-expand) limitations.
>
> Maybe I'm the only one that would be interested in such a solution?  I hope 
> not, but I can see that there is a lot to consider about such a thing.

For those who need an absolutely-no-soldering solution, there are any 
number of good, triple-output linear lab/bench supplies.  My first 
choice among these would be the Power Designs "TP" series -- TP325, 
TP340, TP343 (and their "A" and "B" successors).  The HP 6236A (and B) 
are also good candidates, although the +/-0-20v supplies are only good 
for 500mA -- so the +12v supply to the Tbolt sits in 500mA current limit 
for a short time while the Tbolt oven warms up from a cold start (not a 
problem, just an irregularity).

Tested and guaranteed samples of all of these can be bought for $25-100 
if you are patient (pay no attention to the loonies who list them for 
$250-350).

Examples:

There are two potential disadvantages.  The first is size (particularly 
WRT the Power Designs units -- the HPs are much smaller).  The second is 
their adjustability.  You would not want to brush against one of the 
voltage-setting knobs accidentally and send your Tbolt to GPS heaven. 
The cure for this is a small dab of RTV on each knob.  Set the supplies 
to the desired voltages, then apply a dab of RTV from the skirt of each 
knob to the front panel of the supply.  Check the voltages while the RTV 
is still workable, and adjust if necessary.  Let the RTV set, and it 
would take some effort to change the voltages.

If your Tbolt came with a switching PS that you are replacing, you 
probably already have a power cable that terminates in the proper Molex 
connector to feed the Tbolt.  But what if you don't?  You will need to 
build a power cable using the correct Molex connector shell (Molex p/n 
50-57-9406) and contacts (Molex p/n 16-02-0103).  The contacts are made 
to be crimped to the wires from the power supply.  The Molex crimp tool 
(Molex p/n 63811-8700) is breathtakingly expensive (about $350).  Others 
are less, including (I am told) a pretty cheap one from Radio Shack.

Best regards,

Charles

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Re: [time-nuts] Anybody want a Thunderbolt power supply


I wrote:


I have converted a number of them by replacing the DC-DC converters
and feeding the circuitry from a mains-operated linear DC supply


This should read, "I have converted a number of them by *removing* the 
DC-DC converters and feeding the circuitry from a mains-operated linear 
DC supply"


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply


Gerhard wrote:


I have made a stamp-sized layout for LT3042 + external npn power transistor
as shown in the data sheet.  Not fabricated, let alone tested.


Nice!

The datasheet shows both NPN and PNP current multipliers.  Just curious 
-- did you choose the NPN circuit for theoretical considerations, and if 
so what was your reasoning -- the lower open-loop output impedance?


Thanks,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply?

Randall wrote:

Wow, given all the responses about the cleanliness of the power into a Thunderbolt, I would be even
more interested in a power supply that did *not* leave the "last mile" up to me. I would
be more interested in a "pretty clean" power supply that I could just plug in and go.
Any thoughts of me actually wiring the last bit of it make me break out in a cold sweat and come
face to face with my (established, and sadly slow-to-expand) limitations.

Maybe I'm the only one that would be interested in such a solution? I hope
not, but I can see that there is a lot to consider about such a thing.

For those who need an absolutely-no-soldering solution, there are any
number of good, triple-output linear lab/bench supplies. My first
choice among these would be the Power Designs "TP" series -- TP325,
TP340, TP343 (and their "A" and "B" successors). The HP 6236A (and B)
are also good candidates, although the +/-0-20v supplies are only good
for 500mA -- so the +12v supply to the Tbolt sits in 500mA current limit
for a short time while the Tbolt oven warms up from a cold start (not a
problem, just an irregularity).

Tested and guaranteed samples of all of these can be bought for $25-100
if you are patient (pay no attention to the loonies who list them for
$250-350).

Examples:

There are two potential disadvantages. The first is size (particularly
WRT the Power Designs units -- the HPs are much smaller). The second is
their adjustability. You would not want to brush against one of the
voltage-setting knobs accidentally and send your Tbolt to GPS heaven.
The cure for this is a small dab of RTV on each knob. Set the supplies
to the desired voltages, then apply a dab of RTV from the skirt of each
knob to the front panel of the supply. Check the voltages while the RTV
is still workable, and adjust if necessary. Let the RTV set, and it
would take some effort to change the voltages.

If your Tbolt came with a switching PS that you are replacing, you
probably already have a power cable that terminates in the proper Molex
connector to feed the Tbolt. But what if you don't? You will need to
build a power cable using the correct Molex connector shell (Molex p/n
50-57-9406) and contacts (Molex p/n 16-02-0103). The contacts are made
to be crimped to the wires from the power supply. The Molex crimp tool
(Molex p/n 63811-8700) is breathtakingly expensive (about $350). Others
are less, including (I am told) a pretty cheap one from Radio Shack.

Best regards,

Charles

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Re: [time-nuts] Anybody want a Thunderbolt power supply


Dave wrote:


Getting the required Thunderbolt supply rails from a nominal 12v dc
supply of doubtful cleanliness is an issue that also needs to be
addressed.  I'm still mulling over that one. (and using a triple output
switcher from an inverter backed mains supply meantime!)
The ex-telco GPSDOs all run on a nominal 24-50 volt DC supply but I
don't know how they generate their internal supplies. I suspect switchers?


Yes, they typically have two or three flat-pack DC-DC converters inside. 
 I have converted a number of them by replacing the DC-DC converters 
and feeding the circuitry from a mains-operated linear DC supply 
(usually because one or more of the DC-DC converters was fried and I saw 
it as a golden opportunity rather than a problem of locating spare 
converters of invariably questionable provenance).


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-09-01 Thread Bruce Griffiths

It will show up if the value of the voltage setting bypass capacitor is 
reduced. Both the Johnson and excess noise in this resistor coupled with the 
current source flicker noise should become evident. The datasheet graphs 
indicate that the Johnson noise of the voltage setting resistor(33k2 
~22nV/rtHz) isn't significant in comparison with other sources.

Bruce

On Thursday, 1 September 2016 5:56 PM, Gerhard Hoffmann  
wrote:

 Am 01.09.2016 um 06:07 schrieb Bruce Griffiths:
> I have a quad LT3042 PCB that I must get around to assembling.One potential 
> issue with the LT3042 is the relatively high noise at low frequencies when 
> the capacititve bypassing of the resistor that sets the output voltage is 
> ineffective.

I wonder where that relatively high noise on the LT3042 might hide.

< 
https://www.flickr.com/photos/137684711@N07/24070698809/in/datetaken/lightbox/ 
 >

That is maybe 3 nV/RT Hz at 10 Hz, and the limit is probably not the 
LT3042 but
the GR-like noise of my old preamp below 30 Hz. (rises faster than 1/f)
Remember that 0 dB in the plot is 1 nV rt Hz, which is the equivalent 
INPUT noise voltage
of an AD797 or LT1028.

The LT4042 measurement was taken from an ugly dead bug ad-hoc construction.
Deviating from the 4.7u output cap produces some noise peaks @ > 100 KHz.
(but still 30 dB better than the others)
More is less here.

regards, Gerhard

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Re: [time-nuts] Anybody want a Thunderbolt power supply


Bruce wrote:


Low noise regulators for the +12V and +5V outputs would also be useful.


Very true.  By focusing on the -12v supply, I did not intend to suggest 
that low noise is unimportant on the +12v and +5v supplies.


The suggestion to use LT3042s is a good one, but note that it has an 
output current rating of 200mA.  The Tbolt needs ~250mA at +5v, and 
~700mA at +12v [at startup -- but only ~150mA steady-state, depending on 
ambient temperature].  LT3042s can be used in parallel, so two of them 
for the +5v supply and four of them for the +12v supply would be 
required.  That isn't so bad for the +5v supply, but seems excessive for 
the +12v supply (particularly when three of the four are needed only 
during warmup from cold).


The LT3088 and LT3080 will deliver 800mA and 1.1A, respectively, with 
low noise (but not as low as the LT3042).  One of those might be a 
better choice for the +12v supply.  Similarly, the LT3085 can deliver 
500mA, so one of those could be used for the +5v supply.


Finally: Linear Technology -- Where is our negative-voltage complement 
to the LT3042?


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-08-31 Thread Gerhard Hoffmann


Am 01.09.2016 um 05:35 schrieb Charles Steinmetz:


The suggestion to use LT3042s is a good one, but note that it has an 
output current rating of 200mA.  The Tbolt needs ~250mA at +5v, and 
~700mA at +12v [at startup -- but only ~150mA steady-state, depending 
on ambient temperature].  LT3042s can be used in parallel, so two of 
them for the +5v supply and four of them for the +12v supply would be 
required.  That isn't so bad for the +5v supply, but seems excessive 
for the +12v supply (particularly when three of the four are needed 
only during warmup from cold).



I have made a stamp-sized layout for LT3042 + external npn power transistor
as shown in the data sheet.
Not fabricated, let alone tested.

The LT3088 and LT3080 will deliver 800mA and 1.1A, respectively, with 
low noise (but not as low as the LT3042).  One of those might be a 
better choice for the +12v supply.  Similarly, the LT3085 can deliver 
500mA, so one of those could be used for the +5v supply.


Finally: Linear Technology -- Where is our negative-voltage complement 
to the LT3042?


Yes, that is badly missing.

regards, Gerhard
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread DaveH

Someone could come out with a circuit board for a single configurable
voltage and decent noise specs. Use three of them for a Tbolt.

It is really easy to use the transformer from an old microwave oven to make
your own power transformer - the HV and the 110 volt windings are on
separate parts of the core so it is a matter of a few minutes to hacksaw off
the HV winding and you can use standard household THHN wire for your new
secondary - wind ten turns, measure the voltage and use that to figure how
many turns you actually needed.

If someone came out with such a bare board, I would buy 20 of them just to
keep around for projects.

Dave

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf 
> Of Bob Stewart
> Sent: Wednesday, August 31, 2016 14:29
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?
> 
> OTOH, how many time-nuts have any interest in paying for a 
> power supply that's up to time-nuts standards?  It's really 
> not easy to bring a small product to market at a small price. 
>  Even if you completely discount the personal effort of 
> design, construction, and marketing, there's the issue of 
> packaging.  Without a package, it's just an amateur effort 
> not worth considering.  With a package, such as a Hammond 
> box, the price moves into new territory and nobody's interested.
> 
> Bob 
> 
> 
>   From: Charles Steinmetz <csteinm...@yandex.com>
>  To: time-nuts@febo.com 
>  Sent: Wednesday, August 31, 2016 4:24 PM
>  Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?
>
> Mark wrote:
> 
> > Some times a full linear supply is not a viable option due 
> to power dissipation/size issues or the utter convenience of 
> using a switching wall wart.
> 
> In the context of the present discussion -- powering a Tbolt for 
> time-nuts use -- the first consideration would just be 
> laughable and the 
> second would be nothing but terminal laziness.
> 
> Best regards,
> 
> Charles
> 
> 
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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-08-31 Thread Bruce Griffiths

Just split  the 1uF coupling cap into 2x 2u2 in series in the Cuk dc-dc 
converter add a 1:1 transformer (should be small at 2MHz) between the pair of 
2u2 caps to produce a floating output and use an LT3042 as a post 
regulator.With a mains transformer input supply a separate isolated winding for 
the -12V allows an LT3042 to be used for the negative regulator.
I have a quad LT3042 PCB that I must get around to assembling.One potential 
issue with the LT3042 is the relatively high noise at low frequencies when the 
capacititve bypassing of the resistor that sets the output voltage is 
ineffective.

Bruce
  

On Thursday, 1 September 2016 3:37 PM, Charles Steinmetz 
 wrote:
 

 Bruce wrote:

> Low noise regulators for the +12V and +5V outputs would also be useful.

Very true.  By focusing on the -12v supply, I did not intend to suggest 
that low noise is unimportant on the +12v and +5v supplies.

The suggestion to use LT3042s is a good one, but note that it has an 
output current rating of 200mA.  The Tbolt needs ~250mA at +5v, and 
~700mA at +12v [at startup -- but only ~150mA steady-state, depending on 
ambient temperature].  LT3042s can be used in parallel, so two of them 
for the +5v supply and four of them for the +12v supply would be 
required.  That isn't so bad for the +5v supply, but seems excessive for 
the +12v supply (particularly when three of the four are needed only 
during warmup from cold).

The LT3088 and LT3080 will deliver 800mA and 1.1A, respectively, with 
low noise (but not as low as the LT3042).  One of those might be a 
better choice for the +12v supply.  Similarly, the LT3085 can deliver 
500mA, so one of those could be used for the +5v supply.

Finally: Linear Technology -- Where is our negative-voltage complement 
to the LT3042?

Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-08-31 Thread Dave Brown

Getting the required Thunderbolt supply rails from a nominal 12v dc supply 
of doubtful cleanliness is an issue that also needs to be addressed.  I'm 
still mulling over that one. (and using a triple output switcher from an 
inverter backed mains supply meantime!)
The ex-telco GPSDOs all run on a nominal 24-50 volt DC supply but I don't 
know how they generate their internal supplies. I suspect switchers?

DaveB, NZ

- Original Message - 
From: "Charles Steinmetz" <csteinm...@yandex.com>

To: <time-nuts@febo.com>
Sent: Thursday, September 01, 2016 3:35 PM
Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply



Bruce wrote:


Low noise regulators for the +12V and +5V outputs would also be useful.


Very true.  By focusing on the -12v supply, I did not intend to suggest 
that low noise is unimportant on the +12v and +5v supplies.


The suggestion to use LT3042s is a good one, but note that it has an 
output current rating of 200mA.  The Tbolt needs ~250mA at +5v, and ~700mA 
at +12v [at startup -- but only ~150mA steady-state, depending on ambient 
temperature].  LT3042s can be used in parallel, so two of them for the +5v 
supply and four of them for the +12v supply would be required.  That isn't 
so bad for the +5v supply, but seems excessive for the +12v supply 
(particularly when three of the four are needed only during warmup from 
cold).


The LT3088 and LT3080 will deliver 800mA and 1.1A, respectively, with low 
noise (but not as low as the LT3042).  One of those might be a better 
choice for the +12v supply.  Similarly, the LT3085 can deliver 500mA, so 
one of those could be used for the +5v supply.


Finally: Linear Technology -- Where is our negative-voltage complement to 
the LT3042?


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-08-31 Thread Bob Camp

HI

Just get a linear supply from somebody you have heard of before and it will do 
fine. 
The key point is to avoid a switcher. There are still lots of linears out 
there. The designs
have not changed much for the last 40 years. They pretty much all do it the 
same way.

Bob

> On Aug 31, 2016, at 9:13 PM, Cube Central  wrote:
> 
> With the talk of Thunderbolt power supplies and their qualities, and after
> seeing the post about the TAPR HPSDR LPU... I am beginning to wonder about
> the power source I have for mine, as the "Temp" field shown on the following
> link has always been funny.  It seems to track and keep the outputs up well
> enough, but I wonder if a better power supply is warranted.  I don't have
> the background to feel confident in creating one that plugs into Mains
> power, even with a kit from TAPR.   I've searched for similar issues (some
> time back) but didn't come up with an answer.  Maybe someone here might know
> what is going on?  Thanks in advance (link follows)
> 
> http://i.imgur.com/ByXhFLS.png
> 
> 
>   -Randal
>   (at CubeCentral)
> 
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Jeff AC0C

I bought a module off ebay for a project recently.  It has a LM317/LM337 
pair, small heat sinks, regulator, bypass caps, rectifiers and filtering 
caps all on one board for about $10 delivered.  To this you add a small 
transformer and piggy-back a 7805T/heat sink and that would give the 3 
voltages required by this unit.


Of course it's linear so it's got the linear heat dissipation issue but by 
the right pick of transformer that could be as low as about 3W (around 2KWH 
per month).  Then again, it's also got the linear noise "problems" which are 
pretty much zero.


73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-Original Message- 
From: Bob kb8tq

Sent: Wednesday, August 31, 2016 7:49 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?

Hi

It is not that hard to do. Use a linear rather than a switching approach. 
Run the +12 and +5 supplies off of LT1764 regulators. The -12 is very low 
current, run it off of a low noise op amp. There are lots of toroidal line 
transformers that will drive something like this.


Bob


On Aug 31, 2016, at 6:20 PM, Cube Central <cubecent...@gmail.com> wrote:

Wow, given all the responses about the cleanliness of the power into a 
Thunderbolt, I would be even more interested in a power supply that did 
*not* leave the "last mile" up to me.  I would be more interested in a 
"pretty clean" power supply that I could just plug in and go.  Any 
thoughts of me actually wiring the last bit of it make me break out in a 
cold sweat and come face to face with my (established, and sadly 
slow-to-expand) limitations.


Maybe I'm the only one that would be interested in such a solution?  I 
hope not, but I can see that there is a lot to consider about such a 
thing.


Cheers!

   -Randal
   (at CubeCentral)

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob 
Stewart

Sent: Wednesday, 31 August, 2016 15:29
To: Discussion of precise time and frequency measurement 
<time-nuts@febo.com>

Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?

OTOH, how many time-nuts have any interest in paying for a power supply 
that's up to time-nuts standards?  It's really not easy to bring a small 
product to market at a small price.  Even if you completely discount the 
personal effort of design, construction, and marketing, there's the issue 
of packaging.  Without a package, it's just an amateur effort not worth 
considering.  With a package, such as a Hammond box, the price moves into 
new territory and nobody's interested.


Bob


 From: Charles Steinmetz <csteinm...@yandex.com>
To: time-nuts@febo.com
Sent: Wednesday, August 31, 2016 4:24 PM
Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?

Mark wrote:

Some times a full linear supply is not a viable option due to power 
dissipation/size issues or the utter convenience of using a switching 
wall wart.


In the context of the present discussion -- powering a Tbolt for time-nuts 
use -- the first consideration would just be laughable and the second 
would be nothing but terminal laziness.


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-08-31 Thread Cube Central

With the talk of Thunderbolt power supplies and their qualities, and after
seeing the post about the TAPR HPSDR LPU... I am beginning to wonder about
the power source I have for mine, as the "Temp" field shown on the following
link has always been funny.  It seems to track and keep the outputs up well
enough, but I wonder if a better power supply is warranted.  I don't have
the background to feel confident in creating one that plugs into Mains
power, even with a kit from TAPR.   I've searched for similar issues (some
time back) but didn't come up with an answer.  Maybe someone here might know
what is going on?  Thanks in advance (link follows)

http://i.imgur.com/ByXhFLS.png


-Randal
(at CubeCentral)

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Re: [time-nuts] Anybody want a Thunderbolt power supply?


Bob wrote:


I don't mean to cause offense, but is everything you don't like crap?  The 
reality is that whatever the market will bear is what determines what comes to 
market.  If you can find high quality goods on ebay that can be modified to fit 
your needs, then you win.  There is a substantial market that either cannot do 
those mods or would rather spend their time elsewhere.  So, what they're 
willing to pay is going to determine what's available for sale.


No, but I often view things that don't do the job they need to do as 
crap, especially if they are offered in such a way as to suggest that 
they are, in fact, useful for the intended purpose.  So, let's take the 
proposed power supply -- a switching regulator to develop +5v and -12v 
supplies from an existing +12v supply, with noise of 35mVp-p, offered 
specifically as a power supply solution for Tbolt GPSDOs.  If the 
offering said explicitly that a Tbolt can't provide its best performance 
with the product because of its high noise level, then I might be on the 
fence about whether it was "crap."  But if it were offered as a power 
supply for Tbolts with no mention of what I consider to be a large 
departure from acceptable performance for the intended use, then yes, 
I'd probably consider it "crap."


The issue is that many users do not know what the relevant needs are. 
Rightly or wrongly, they are relying on suppliers to do that job for 
them.  So, offering something for a particular use carries the 
implication that it is really useful for that purpose.  If a seller 
tells a time-nut that a power supply is designed to run a Tbolt, an 
implicit representation has been made that it will work in that role as 
a time-nut would expect it to.  But IMO, the proposed product would not 
do so because of the high noise level.


So, what distinguishes this from packages that have been sold to 
time-nuts in the past that included power supplies that also did not 
work in that role as a time-nut would expect?  In those cases, due 
largely to this list, there was widespread discussion of the issue and 
equally widespread knowledge that for time-nuts-quality results, the PS 
that came with the package needed to be replaced with something better. 
 So at this point, if someone offers a PS to time nuts for use with 
Tbolts, it would be natural to assume that the seller was familiar with 
that history and was offering the "something better."  So today, if that 
is *not* the case, it should be stated explicitly.


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Bob kb8tq

Hi

It is not that hard to do. Use a linear rather than a switching approach. Run 
the +12 and +5 supplies off of LT1764 regulators. The -12 is very low current, 
run it off of a low noise op amp. There are lots of toroidal line transformers 
that will drive something like this. 

Bob

> On Aug 31, 2016, at 6:20 PM, Cube Central <cubecent...@gmail.com> wrote:
> 
> Wow, given all the responses about the cleanliness of the power into a 
> Thunderbolt, I would be even more interested in a power supply that did *not* 
> leave the "last mile" up to me.  I would be more interested in a "pretty 
> clean" power supply that I could just plug in and go.  Any thoughts of me 
> actually wiring the last bit of it make me break out in a cold sweat and come 
> face to face with my (established, and sadly slow-to-expand) limitations.
> 
> Maybe I'm the only one that would be interested in such a solution?  I hope 
> not, but I can see that there is a lot to consider about such a thing.
> 
> Cheers!
> 
>-Randal 
>(at CubeCentral)
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Stewart
> Sent: Wednesday, 31 August, 2016 15:29
> To: Discussion of precise time and frequency measurement <time-nuts@febo.com>
> Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?
> 
> OTOH, how many time-nuts have any interest in paying for a power supply 
> that's up to time-nuts standards?  It's really not easy to bring a small 
> product to market at a small price.  Even if you completely discount the 
> personal effort of design, construction, and marketing, there's the issue of 
> packaging.  Without a package, it's just an amateur effort not worth 
> considering.  With a package, such as a Hammond box, the price moves into new 
> territory and nobody's interested.
> 
> Bob 
> 
> 
>  From: Charles Steinmetz <csteinm...@yandex.com>
> To: time-nuts@febo.com
> Sent: Wednesday, August 31, 2016 4:24 PM
> Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?
> 
> Mark wrote:
> 
>> Some times a full linear supply is not a viable option due to power 
>> dissipation/size issues or the utter convenience of using a switching wall 
>> wart.
> 
> In the context of the present discussion -- powering a Tbolt for time-nuts 
> use -- the first consideration would just be laughable and the second would 
> be nothing but terminal laziness.
> 
> Best regards,
> 
> Charles
> 
> 
> ___
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> 
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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-08-31 Thread Bruce Griffiths

If onen is going to use a dc-dc converter the Cuk converter used here is a nice 
topology in that it can have low input and output ripple currents. However 
input and output filters like the Murata BNX002/BNX005 series would have been 
useful as would an LM3042 linear post regulator for the -12V output.. Low noise 
regulators for the +12V and +5V outputs would also be useful.
Bruce

On Thursday, 1 September 2016 11:48 AM, Mike Naruta AA8K  
wrote:

I use the TAPR HPSDR LPU:

< https://www.tapr.org/kits_lpu.html >

I run two Trimble Thunderbolts on a LPU that uses the house 13.6 
Volt supply that is backed up with two 6 Volt golf cart 
batteries in series.  I didn't bother installing the Anderson 
Power Pole and ATX connectors, but wired directly to the circuit 
board.

Mike - AA8K

On 08/30/2016 10:23 PM, Nick Sayer via time-nuts wrote:
> A little board to generate -12 and +5 from a 15 watt 12 VDC input wouldn’t be 
> too hard to design. If I put one out for $25, would anyone like one?
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Re: [time-nuts] Anybody want a Thunderbolt power supply?


Bob wrote:


OTOH, how many time-nuts have any interest in paying for a power supply that's 
up to time-nuts standards?  It's really not easy to bring a small product to 
market at a small price.  Even if you completely discount the personal effort 
of design, construction, and marketing, there's the issue of packaging.  
Without a package, it's just an amateur effort not worth considering.  With a 
package, such as a Hammond box, the price moves into new territory and nobody's 
interested.


So the answer is to bring crap to market because nobody will pay for 
something that actually does the job?


IMO, the answer is to accept that the small, "little gizmo" providers 
simply cannot fulfill this need efficiently.  I provided one solution, 
using a surplus device from a large supplier and fifteen minutes of 
soldering-iron time.  Even if you buy a box for it, it won't cost much 
more than the $25 the OP proposed (and maybe not as much -- the ones 
I've made have cost less than $25 each).  (And note that the OP did not 
propose a complete, mains-to-Tbolt solution.  The proposed solution 
assumed an existing mains-to-12v supply.)


That is part (the essential part, IMO) of the "little gizmo" provider's 
business model -- find niche markets where things made at that scale 
provide *better* performance than the alternatives.  There are lots of 
areas where this can be done, but also very many more where it cannot. 
The "little gizmo" provider is well-advised to learn how to tell the one 
from the other.


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply

2016-08-31 Thread Mike Naruta AA8K



I use the TAPR HPSDR LPU:

< https://www.tapr.org/kits_lpu.html >


I run two Trimble Thunderbolts on a LPU that uses the house 13.6 
Volt supply that is backed up with two 6 Volt golf cart 
batteries in series.  I didn't bother installing the Anderson 
Power Pole and ATX connectors, but wired directly to the circuit 
board.



Mike - AA8K

On 08/30/2016 10:23 PM, Nick Sayer via time-nuts wrote:

A little board to generate -12 and +5 from a 15 watt 12 VDC input wouldn’t be 
too hard to design. If I put one out for $25, would anyone like one?
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Re: [time-nuts] Anybody want a Thunderbolt power supply?


Chris wrote:


Did you try any passive filters between the switchers and linear regulators?


Yes, I *always* use passive filters on the outputs of switching 
regulators.  As others have posted, it's not just a matter of the 
conducted noise on the supply rail -- switching noise propogates on the 
ground bus, and it is also radiated and coupled into downstream stages, 
including downstream power supply buses.  That is, it can very easily 
bypass whatever filtering you put in the direct conduction path.


Best regards.

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Nick Sayer via time-nuts

When I began the design process, I assumed - as would be reasonable - that ~30 
mV P-P of noise and ripple were acceptable for input power supplies, and that 
before they were used for a precision purpose within the device that there 
would be further filtering if for no other reason that you’d think they’d want 
to limit coupled interference on the power lines. My assumption, given the 
extremely low draw on the -12 line was that they were using the -12 line just 
for the RS-232 level shifter (and that they were too lazy to use a MAX232 like 
everybody else).

Now that I’ve posted and had my assumptions disabused, I’ll need to go back to 
the drawing board for another attempt. The price point won’t likely be $25 
anymore, but the question was whether anyone wanted a Tbolt power supply, and 
if I offer anything at all, I intend for it to be reasonably useful for its 
intended purpose. Like all the things I make for sale, it will be open 
hardware, which will afford everyone here more than enough opportunity for 
Monday morning quarterbacking. :)

> On Aug 31, 2016, at 4:02 PM, Charles Steinmetz  wrote:
> 
> Bob wrote:
> 
>> I don't mean to cause offense, but is everything you don't like crap?  The 
>> reality is that whatever the market will bear is what determines what comes 
>> to market.  If you can find high quality goods on ebay that can be modified 
>> to fit your needs, then you win.  There is a substantial market that either 
>> cannot do those mods or would rather spend their time elsewhere.  So, what 
>> they're willing to pay is going to determine what's available for sale.
> 
> No, but I often view things that don't do the job they need to do as crap, 
> especially if they are offered in such a way as to suggest that they are, in 
> fact, useful for the intended purpose.  So, let's take the proposed power 
> supply -- a switching regulator to develop +5v and -12v supplies from an 
> existing +12v supply, with noise of 35mVp-p, offered specifically as a power 
> supply solution for Tbolt GPSDOs.  If the offering said explicitly that a 
> Tbolt can't provide its best performance with the product because of its high 
> noise level, then I might be on the fence about whether it was "crap."  But 
> if it were offered as a power supply for Tbolts with no mention of what I 
> consider to be a large departure from acceptable performance for the intended 
> use, then yes, I'd probably consider it "crap."
> 
> The issue is that many users do not know what the relevant needs are. Rightly 
> or wrongly, they are relying on suppliers to do that job for them.  So, 
> offering something for a particular use carries the implication that it is 
> really useful for that purpose.  If a seller tells a time-nut that a power 
> supply is designed to run a Tbolt, an implicit representation has been made 
> that it will work in that role as a time-nut would expect it to.  But IMO, 
> the proposed product would not do so because of the high noise level.
> 
> So, what distinguishes this from packages that have been sold to time-nuts in 
> the past that included power supplies that also did not work in that role as 
> a time-nut would expect?  In those cases, due largely to this list, there was 
> widespread discussion of the issue and equally widespread knowledge that for 
> time-nuts-quality results, the PS that came with the package needed to be 
> replaced with something better.  So at this point, if someone offers a PS to 
> time nuts for use with Tbolts, it would be natural to assume that the seller 
> was familiar with that history and was offering the "something better."  So 
> today, if that is *not* the case, it should be stated explicitly.
> 
> Best regards,
> 
> Charles
> 
> 
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Re: [time-nuts] Anybody want a Thunderbolt power supply?


Mark wrote:


Some times a full linear supply is not a viable option due to power 
dissipation/size issues or the utter convenience of using a switching wall wart.


In the context of the present discussion -- powering a Tbolt for 
time-nuts use -- the first consideration would just be laughable and the 
second would be nothing but terminal laziness.


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply?


jim wrote:


with the venerable 2n3055 (1960s!) as the series pass device, and an
exotic TIP29 (my 1985 databook has it, but the original datasheet says
1968) to drive it..

They probably used the 1970s versions of the transistor, of course,
since the 723 didn't come out til early 70s..


Fairchild introduced the orginal 723 (the µA723) in 1968.  I think 
National brought out the LM723 within the year, but can't swear to it.


While the schematic I posted shows a TIP29 driver transistor, that was 
for a different, 3A supply.  The lower-current +/-12v supplies in the 
HTAA-16W-A do without the driver, and connect the 3055 directly to the 
723 output (which can source up to 150mA).  The schematic I posted also 
shows foldback current limiting, which the +/-12v supplies in the 
HTAA-16W-A do not have.


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Bob kb8tq

Hi

The fact is that commercial linear supplies are still out there for pretty 
cheap prices. The price of a usable switcher is a very small fraction of the 
price of a Tbolt. Noise on the switcher is a big deal. Not everybody seems to 
care about low phase noise on the 10 MHz. Switcher frequency supply noise has 
very little impact on the PPS output. 

Bob

> On Aug 31, 2016, at 5:29 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> OTOH, how many time-nuts have any interest in paying for a power supply 
> that's up to time-nuts standards?  It's really not easy to bring a small 
> product to market at a small price.  Even if you completely discount the 
> personal effort of design, construction, and marketing, there's the issue of 
> packaging.  Without a package, it's just an amateur effort not worth 
> considering.  With a package, such as a Hammond box, the price moves into new 
> territory and nobody's interested.
> 
> Bob 
> 
> 
>  From: Charles Steinmetz <csteinm...@yandex.com>
> To: time-nuts@febo.com 
> Sent: Wednesday, August 31, 2016 4:24 PM
> Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?
> 
> Mark wrote:
> 
>> Some times a full linear supply is not a viable option due to power 
>> dissipation/size issues or the utter convenience of using a switching wall 
>> wart.
> 
> In the context of the present discussion -- powering a Tbolt for 
> time-nuts use -- the first consideration would just be laughable and the 
> second would be nothing but terminal laziness.
> 
> Best regards,
> 
> Charles
> 
> 
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> 
> 
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Alexander Pummer

there are peoples and societies for whom the most important parameter is 
the price of the goods, and there are also some societies for them the 
most important is the proffit


73

Alex


On 8/31/2016 3:13 PM, Bob Stewart wrote:

Charles,
said: "So the answer is to bring crap to market because nobody will pay for 
something that actually does the job?"
I don't mean to cause offense, but is everything you don't like crap?  The 
reality is that whatever the market will bear is what determines what comes to 
market.  If you can find high quality goods on ebay that can be modified to fit 
your needs, then you win.  There is a substantial market that either cannot do 
those mods or would rather spend their time elsewhere.  So, what they're 
willing to pay is going to determine what's available for sale.

As an example, my cost for the Hammond box I use with my GPSDO, with finished 
end panels, is just under $60.  From that viewpoint, I shouldn't bother to make 
it, because a surplus unit can always be found for a cheaper price, as long as 
I'm willing to accept whatever unknown baggage (no schematics, unobtainium 
parts, no software, etc) comes with that surplus unit.
Bob
  -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

   From: Charles Steinmetz <csteinm...@yandex.com>
  To: time-nuts@febo.com
  Sent: Wednesday, August 31, 2016 5:02 PM
  Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?

Bob wrote:



OTOH, how many time-nuts have any interest in paying for a power supply that's 
up to time-nuts standards?  It's really not easy to bring a small product to 
market at a small price.  Even if you completely discount the personal effort 
of design, construction, and marketing, there's the issue of packaging.  
Without a package, it's just an amateur effort not worth considering.  With a 
package, such as a Hammond box, the price moves into new territory and nobody's 
interested.

So the answer is to bring crap to market because nobody will pay for
something that actually does the job?

IMO, the answer is to accept that the small, "little gizmo" providers
simply cannot fulfill this need efficiently.  I provided one solution,
using a surplus device from a large supplier and fifteen minutes of
soldering-iron time.  Even if you buy a box for it, it won't cost much
more than the $25 the OP proposed (and maybe not as much -- the ones
I've made have cost less than $25 each).  (And note that the OP did not
propose a complete, mains-to-Tbolt solution.  The proposed solution
assumed an existing mains-to-12v supply.)

That is part (the essential part, IMO) of the "little gizmo" provider's
business model -- find niche markets where things made at that scale
provide *better* performance than the alternatives.  There are lots of
areas where this can be done, but also very many more where it cannot.
The "little gizmo" provider is well-advised to learn how to tell the one
from the other.

Best regards,

Charles


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-
No virus found in this message.
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Version: 2016.0.7752 / Virus Database: 4649/12916 - Release Date: 08/31/16


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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Bob Stewart

Charles,
said: "So the answer is to bring crap to market because nobody will pay for 
something that actually does the job?"
I don't mean to cause offense, but is everything you don't like crap?  The 
reality is that whatever the market will bear is what determines what comes to 
market.  If you can find high quality goods on ebay that can be modified to fit 
your needs, then you win.  There is a substantial market that either cannot do 
those mods or would rather spend their time elsewhere.  So, what they're 
willing to pay is going to determine what's available for sale.

As an example, my cost for the Hammond box I use with my GPSDO, with finished 
end panels, is just under $60.  From that viewpoint, I shouldn't bother to make 
it, because a surplus unit can always be found for a cheaper price, as long as 
I'm willing to accept whatever unknown baggage (no schematics, unobtainium 
parts, no software, etc) comes with that surplus unit.
Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Charles Steinmetz <csteinm...@yandex.com>
 To: time-nuts@febo.com 
 Sent: Wednesday, August 31, 2016 5:02 PM
 Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?

Bob wrote:

> OTOH, how many time-nuts have any interest in paying for a power supply 
> that's up to time-nuts standards?  It's really not easy to bring a small 
> product to market at a small price.  Even if you completely discount the 
> personal effort of design, construction, and marketing, there's the issue of 
> packaging.  Without a package, it's just an amateur effort not worth 
> considering.  With a package, such as a Hammond box, the price moves into new 
> territory and nobody's interested.

So the answer is to bring crap to market because nobody will pay for 
something that actually does the job?

IMO, the answer is to accept that the small, "little gizmo" providers 
simply cannot fulfill this need efficiently.  I provided one solution, 
using a surplus device from a large supplier and fifteen minutes of 
soldering-iron time.  Even if you buy a box for it, it won't cost much 
more than the $25 the OP proposed (and maybe not as much -- the ones 
I've made have cost less than $25 each).  (And note that the OP did not 
propose a complete, mains-to-Tbolt solution.  The proposed solution 
assumed an existing mains-to-12v supply.)

That is part (the essential part, IMO) of the "little gizmo" provider's 
business model -- find niche markets where things made at that scale 
provide *better* performance than the alternatives.  There are lots of 
areas where this can be done, but also very many more where it cannot. 
The "little gizmo" provider is well-advised to learn how to tell the one 
from the other.

Best regards,

Charles

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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Bob Stewart

OTOH, how many time-nuts have any interest in paying for a power supply that's 
up to time-nuts standards?  It's really not easy to bring a small product to 
market at a small price.  Even if you completely discount the personal effort 
of design, construction, and marketing, there's the issue of packaging.  
Without a package, it's just an amateur effort not worth considering.  With a 
package, such as a Hammond box, the price moves into new territory and nobody's 
interested.

Bob 

  From: Charles Steinmetz <csteinm...@yandex.com>
 To: time-nuts@febo.com 
 Sent: Wednesday, August 31, 2016 4:24 PM
 Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply?

Mark wrote:

> Some times a full linear supply is not a viable option due to power 
> dissipation/size issues or the utter convenience of using a switching wall 
> wart.

In the context of the present discussion -- powering a Tbolt for 
time-nuts use -- the first consideration would just be laughable and the 
second would be nothing but terminal laziness.

Best regards,

Charles

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Re: [time-nuts] Anybody want a Thunderbolt power supply?


Mark wrote:


You have to be careful choosing a linear regulator to clean up a switching 
supply.   Many just wind up passing the noise through.  Pay attention to the 
noise, PSRR and CMRR vs frequency specs, etc


Precisely the reason to avoid switchers entirely and use linear-only 
voltage regulators to power noise-sensitive circuits.  As I mentioned 
before, I had to use two stages of well-designed linear regulation to 
make any switching supply acceptable (at a time-nuts level) for use with 
a Tbolt.


Best regards,

Charles


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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Chris Caudle

On Wed, August 31, 2016 2:16 pm, Charles Steinmetz wrote:
> I had to use two stages of well-designed linear regulation to
> make any switching supply acceptable (at a time-nuts level) for use with
> a Tbolt.

Did you try any passive filters between the switchers and linear regulators?

-- 
Chris Caudle

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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread jimlux


On 8/31/16 1:52 PM, Adrian Godwin wrote:

I'm being Devil's Advocate here because I certainly realise switchers do
generate high frequency noise. But wasn't the intention of them to make
filtering easier, with smaller filter components, exactly because they
operate at higher frequencies ?

So why do they fail ? Is it cost-cutting to make them only just good enough
for typical uses ? Shouldn't it be possible to make the best possible
supply from a switcher, if only cost and weight weren't the first
considerations ?



Sure.. you can do a bunch of LC low pass sections and knock it down, but 
building a *wideband* low pass filter with good ultimate rejection is 
also challenging.


In a system I'm actually sitting next to, we have a switcher followed by 
a 60dB rejection lumped LC followed by the power distribution, followed 
by a 60 dB rejection lumped LC followed by a linear regulator.


When you're at this kind of level, layout and mechanical arrangement is 
important, because the switching noise (which is also on the input) can 
couple "around" your other circuits.


The other challenge is that those filters have resistive loss - if you 
want good regulation, how do you get your "sense" voltage back to the 
regulator without that path being the path for the noise - so you'd need 
to put LP filters on the sense line.


And of course, the L's need to be shielded.
And you put it in nesting boxes made of steel

A linear regulator is a LOT easier.

If you aren't power dissipation constrained, then it's often the easiest 
way to get to where you want to be.

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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Adrian Godwin

I'm being Devil's Advocate here because I certainly realise switchers do
generate high frequency noise. But wasn't the intention of them to make
filtering easier, with smaller filter components, exactly because they
operate at higher frequencies ?

So why do they fail ? Is it cost-cutting to make them only just good enough
for typical uses ? Shouldn't it be possible to make the best possible
supply from a switcher, if only cost and weight weren't the first
considerations ?

On Wed, Aug 31, 2016 at 9:45 PM, Mark Sims  wrote:

> Yes,  at times I used a two stage linear regulator.  The first stage had
> excellent low freq rejection and the final stage too care of the high freq
> stuff.
>
> Some times a full linear supply is not a viable option due to power
> dissipation/size issues or the utter convenience of using a switching wall
> wart.
>
> 
>
> > Precisely the reason to avoid switchers entirely and use linear-only
> voltage regulators to power noise-sensitive circuits.  As I mentioned
> before, I had to use two stages of well-designed linear regulation to
> make any switching supply acceptable (at a time-nuts level) for use with
> a Tbolt.
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[time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Mark Sims

Yes,  at times I used a two stage linear regulator.  The first stage had 
excellent low freq rejection and the final stage too care of the high freq 
stuff.

Some times a full linear supply is not a viable option due to power 
dissipation/size issues or the utter convenience of using a switching wall wart.



> Precisely the reason to avoid switchers entirely and use linear-only 
voltage regulators to power noise-sensitive circuits.  As I mentioned 
before, I had to use two stages of well-designed linear regulation to 
make any switching supply acceptable (at a time-nuts level) for use with 
a Tbolt.
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

2016-08-31 Thread Edesio Costa e Silva

Have a look at Linear Application Note 101 by Jim Williams: Minimizing
Switching Regulator Residue in Linear Regulator Outputs


Edésio

On Wed, Aug 31, 2016 at 07:01:44PM +, Mark Sims wrote:
> You have to be careful choosing a linear regulator to clean up a switching 
> supply.   Many just wind up passing the noise through.  Pay attention to the 
> noise, PSRR and CMRR vs frequency specs, etc
> 
> Take a look at the "voltage regulation" section of that home built VNA page 
> for an example:
> http://hforsten.com/cheap-homemade-30-mhz-6-ghz-vector-network-analyzer.html
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Re: [time-nuts] Anybody want a Thunderbolt power supply?