[time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Peter Gottlieb]

Ah, thanks, that was enough to get me thinking, to pull me away from my 
job's problems and back to the fun side.


I just replaced my wife's computer, and old obsolete big Dell box, with 
a sleek new (and much faster) laptop.  I was about to throw out the old 
box but now have a use for the large CPU heatsink/fan assembly.  I will 
mount the FE-5680A to an aluminum plate and then to the heatsink.  I 
don't need the plate thermally, but it makes the mechanical mounting 
much easier.  I'll use some thermally conductive pads between things.  I 
will use something like the circuit you provided (thank you), I have a 
bunch of those TO-92 temperature sensors with wires attached, more 
surplus from work, and then will mount the whole thing with power supply 
into a box where I can set up the air flow like I want.


So, here's a question.  One app is a rack of gear which all needs to get 
the 10 MHz.  I could just go find some distribution amp, but I would 
prefer to build something.  Has anyone done this?  I was thinking 
perhaps a good solid reasonably high power op amp buffer feeding 
resistors to each output to each piece of gear?  Anyone done this and 
found any "gotchas" or success stories?


Peter




On 1/6/2012 1:51 PM, ewkeh...@aol.com wrote:

I just grabbed something I had around it is a 24 V 0.1 A.  I run  at 15 V,
dimensions are 80X80X24 mm I just bought some 80X80X10 mm and I am sure
they will work as well.  There are so many choices I recently bought a new  one
with integrated heat sink and tried it on a FRS all for $  6 shipping
included.
Attached are two circuits I use, the top one since I did not have a PC
board. I now have a board and I used in an other application the two stage one
and if you use a heat sink I recommend replacing the feedback resistor on
stage  two with a capacitor.
Bert Kehren


In a message dated 1/6/2012 1:16:01 P.M. Eastern Standard Time,
n...@verizon.net writes:

What  kind of temperature controlled fan did you use?


On 01/06/12,  ewkeh...@aol.com wrote:

I do not understand why this is even discussed.  Running at lower
temperature will extend life and using a fan with  temperature control will
cost no
more than $ 12 and I challenge any of you  how I can get for so little
money
more than one order of magnitude  improvement. As I reported before I
started
out with heat sink only and  quickly realized that I would not be able to
measure aging because the  last 2 digits where all over the place and
unless
you have an environment  where your lab is within 0.1C you are throwing
away the real advantage of  a Rb.
I did enclose the Rb cell and the OCXO on a FEI 5962B, its modularity
lends
it self for such testing, it was not worth the effort and the power  saving
was minimal.
Once my aging tests are completed I will test for  15 V voltage sensitivity.
Bert Kehren


In a message dated  1/6/2012 11:35:02 A.M. Eastern Standard Time,
n...@verizon.net  writes:

A heat sink may not be required, per se, although I would  expect that a
larger thermal mass and/or thermal regulation via a closed  loop fan
controller will help smooth out/stabilize temperature  effects.


On 01/06/12, Chuck Forsberg WA7KGX  N2469R  wrote:

The Tech Manual does not call for  heat sinking (unless I missed
something).
The top has labels over much  of the surface.
The bottom has a plastic sheet between the circuitry and  bottom plate.
It appears the unit was expected to be rather hot when  running.
I have mine mounted on the out side of the box using  standoffs.
On 01/06/2012 07:39 AM, Bob Smither wrote:

-BEGIN  PGP SIGNED MESSAGE-
Hash: SHA1

Chris Albertson  wrote:

On Thu, Jan 5, 2012 at 6:11  PM,<[1]time-n...@custodes.info>  wrote:


  l<[2]http://www.freqelec.com/rb_osc_fe5680a.html>  says 32W peak,

but  then

also 15-18v@700mA, which doesn't make  sense.

It will pull 35W for the first five or so  minutes then the current

drops

rather suddenly to about  700mA.

I have an analog amp meter on my power supply  and I can see a switch

over

after the unit heats up. They must  run an internal oven heater full

tilt

at first then go into  regulated mode.

Some one else said you can cause the  FE5680 to draw more power in

steady

state mode by adding heat  sinking it. Yes that works. Seems the

FE5680

wants to be at  some set temperature and the heat sink means it takes

more

  power to keep at the set point. I just let the fe5680 rest on  a

small

aluminum plate.

Have you measured the case  temperature of your FE5680?

I put mine on a heat sink and the  case temperature stays around 50C.

Without

the heat sink it was  around 60C. Does anyone know what temperature is
recommended? The 50C  seems a little hot, but the unit appears to work

well.

-  --
Bob Smither, PhD Circuit Concepts,  Inc.


===
==

  Government is not healthy for children and other living things.
--  Jeff  Daiell


===

[time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[ed breya]

Most gear probably won't care whether it's sinusoidal or "square" as 
long as the amplitude is right, but if you try to send square waves, 
then the question is how square do they need to be. Sharp edges may 
convey better timing information, but may also cause ringing and 
other effects. I think reasonably clean sine waves or "highly 
rounded" square waves are best, and easiest to send around, and you 
know how much bandwidth is needed.


Ed


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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[paul swed]

Sure have and a gain of 2 typically. Though if its 10 Mhz, not sure how
well that will work.
I was doing 5 Mhz at the time and also using buffer amps I think they were
LH0036 or 18s. Essentially a gain of 2 stage feeding numbers of buffers.
Downside of the approach is that the linear buffer amps suck power.
Since I prefer lower power I evolved over the years.
Regards
Paul.

On Sat, Jan 7, 2012 at 11:39 AM, Peter Gottlieb  wrote:

> Ah, thanks, that was enough to get me thinking, to pull me away from my
> job's problems and back to the fun side.
>
> I just replaced my wife's computer, and old obsolete big Dell box, with a
> sleek new (and much faster) laptop.  I was about to throw out the old box
> but now have a use for the large CPU heatsink/fan assembly.  I will mount
> the FE-5680A to an aluminum plate and then to the heatsink.  I don't need
> the plate thermally, but it makes the mechanical mounting much easier.
>  I'll use some thermally conductive pads between things.  I will use
> something like the circuit you provided (thank you), I have a bunch of
> those TO-92 temperature sensors with wires attached, more surplus from
> work, and then will mount the whole thing with power supply into a box
> where I can set up the air flow like I want.
>
> So, here's a question.  One app is a rack of gear which all needs to get
> the 10 MHz.  I could just go find some distribution amp, but I would prefer
> to build something.  Has anyone done this?  I was thinking perhaps a good
> solid reasonably high power op amp buffer feeding resistors to each output
> to each piece of gear?  Anyone done this and found any "gotchas" or success
> stories?
>
> Peter
>
>
>
>
> On 1/6/2012 1:51 PM, ewkeh...@aol.com wrote:
>
>> I just grabbed something I had around it is a 24 V 0.1 A.  I run  at 15 V,
>> dimensions are 80X80X24 mm I just bought some 80X80X10 mm and I am sure
>> they will work as well.  There are so many choices I recently bought a
>> new  one
>> with integrated heat sink and tried it on a FRS all for $  6 shipping
>> included.
>> Attached are two circuits I use, the top one since I did not have a PC
>> board. I now have a board and I used in an other application the two
>> stage one
>> and if you use a heat sink I recommend replacing the feedback resistor on
>> stage  two with a capacitor.
>> Bert Kehren
>>
>>
>> In a message dated 1/6/2012 1:16:01 P.M. Eastern Standard Time,
>> n...@verizon.net writes:
>>
>> What  kind of temperature controlled fan did you use?
>>
>>
>> On 01/06/12,  ewkeh...@aol.com wrote:
>>
>> I do not understand why this is even discussed.  Running at lower
>> temperature will extend life and using a fan with  temperature control
>> will
>> cost no
>> more than $ 12 and I challenge any of you  how I can get for so little
>> money
>> more than one order of magnitude  improvement. As I reported before I
>> started
>> out with heat sink only and  quickly realized that I would not be able to
>> measure aging because the  last 2 digits where all over the place and
>> unless
>> you have an environment  where your lab is within 0.1C you are throwing
>> away the real advantage of  a Rb.
>> I did enclose the Rb cell and the OCXO on a FEI 5962B, its modularity
>> lends
>> it self for such testing, it was not worth the effort and the power
>>  saving
>> was minimal.
>> Once my aging tests are completed I will test for  15 V voltage
>> sensitivity.
>> Bert Kehren
>>
>>
>> In a message dated  1/6/2012 11:35:02 A.M. Eastern Standard Time,
>> n...@verizon.net  writes:
>>
>> A heat sink may not be required, per se, although I would  expect that a
>> larger thermal mass and/or thermal regulation via a closed  loop fan
>> controller will help smooth out/stabilize temperature  effects.
>>
>>
>> On 01/06/12, Chuck Forsberg WA7KGX  N2469R  wrote:
>>
>> The Tech Manual does not call for  heat sinking (unless I missed
>> something).
>> The top has labels over much  of the surface.
>> The bottom has a plastic sheet between the circuitry and  bottom plate.
>> It appears the unit was expected to be rather hot when  running.
>> I have mine mounted on the out side of the box using  standoffs.
>> On 01/06/2012 07:39 AM, Bob Smither wrote:
>>
>>> -BEGIN  PGP SIGNED MESSAGE-
>>> Hash: SHA1
>>>
>>> Chris Albertson  wrote:
>>>
 On Thu, Jan 5, 2012 at 6:11  PM,<[1]time-n...@custodes.info**>  wrote:

   
 l<[2]http://www.freqelec.com/**rb_osc_fe5680a.html>
>  says 32W peak,
>
 but  then
>>
>>> also 15-18v@700mA, which doesn't make  sense.
>
 It will pull 35W for the first five or so  minutes then the current

>>> drops
>>
>>> rather suddenly to about  700mA.

 I have an analog amp meter on my power supply  and I can see a switch

>>> over
>>
>>> after the unit heats up. They must  run an internal oven heater full

>>> tilt
>>
>>> at first then go into  regulated mode.

 Some one else said you can cause the  FE5

Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Chris Albertson]

On Sat, Jan 7, 2012 at 8:39 AM, Peter Gottlieb  wrote:
> Ah, thanks, that was enough to get me thinking, to pull me away from my
> job's problems and back to the fun side.
>
> I just replaced my wife's computer, and old obsolete big Dell box, with a
> sleek new (and much faster) laptop.  I was about to throw out the old box
> but now have a use for the large CPU heatsink/fan assembly.  I will mount
> the FE-5680A to an aluminum plate and then to the heatsink.  I don't need
> the plate thermally, but it makes the mechanical mounting much easier.  I'll
> use some thermally conductive pads between things.  I will use something
> like the circuit you provided (thank you), I have a bunch of those TO-92
> temperature sensors with wires attached, more surplus from work, and then
> will mount the whole thing with power supply into a box where I can set up
> the air flow like I want.
>
> So, here's a question.  One app is a rack of gear which all needs to get the
> 10 MHz.  I could just go find some distribution amp, but I would prefer to
> build something.  Has anyone done this?  I was thinking perhaps a good solid
> reasonably high power op amp buffer feeding resistors to each output to each
> piece of gear?  Anyone done this and found any "gotchas" or success stories?

I think this is exactly what you want.  An RF distribution amp using
video amplifier chips. The kit is no longer available but the
schematic is.  Look near the end of the user manual and you can get
that here.  This design is well tested and people way it works well.
http://www.tapr.org/kits_tadd-1.html
The transformers in the above are not available but I bet you could
take some using toroid cores.

I guess you could also use an n-way splitter from Mini Circuits, Or
maybe multiple splitters with just one RF power amp.

I think I will build an analog fan controller too.   But in the long
term I want a digital fan controller.  They cost about the same to
build.  Get a "tiny avr", that's uP in an 8-pin DIP package for about
$2.  This will have an A/D converter for the temp sensor and PWM for
the motor but the good part about a digital controller is you can read
the tachometer output from a three wire fan and now you can control
the exact RPM.  The loop can be very stable.  Actually a digital
controller would have two loops, one to server the fan to the set RPM
and one to control the RPM based on temperature.I think you get
the best result from the largest fan you can fit in there running at a
very low RPM.   These digital controllers can hold the temperature
very close.

I happen to like Atmel AVR chips, a PIC could also work.  So I Googled
"AVR fan controller source code" and found dozens of published
projects.  Seems it is the project many beginners do right after the
blinking LED.
>
> Peter
>
>
>
>
> On 1/6/2012 1:51 PM, ewkeh...@aol.com wrote:
>>
>> I just grabbed something I had around it is a 24 V 0.1 A.  I run  at 15 V,
>> dimensions are 80X80X24 mm I just bought some 80X80X10 mm and I am sure
>> they will work as well.  There are so many choices I recently bought a new
>>  one
>> with integrated heat sink and tried it on a FRS all for $  6 shipping
>> included.
>> Attached are two circuits I use, the top one since I did not have a PC
>> board. I now have a board and I used in an other application the two stage
>> one
>> and if you use a heat sink I recommend replacing the feedback resistor on
>> stage  two with a capacitor.
>> Bert Kehren
>>
>>
>> In a message dated 1/6/2012 1:16:01 P.M. Eastern Standard Time,
>> n...@verizon.net writes:
>>
>> What  kind of temperature controlled fan did you use?
>>
>>
>> On 01/06/12,  ewkeh...@aol.com wrote:
>>
>> I do not understand why this is even discussed.  Running at lower
>> temperature will extend life and using a fan with  temperature control
>> will
>> cost no
>> more than $ 12 and I challenge any of you  how I can get for so little
>> money
>> more than one order of magnitude  improvement. As I reported before I
>> started
>> out with heat sink only and  quickly realized that I would not be able to
>> measure aging because the  last 2 digits where all over the place and
>> unless
>> you have an environment  where your lab is within 0.1C you are throwing
>> away the real advantage of  a Rb.
>> I did enclose the Rb cell and the OCXO on a FEI 5962B, its modularity
>> lends
>> it self for such testing, it was not worth the effort and the power
>>  saving
>> was minimal.
>> Once my aging tests are completed I will test for  15 V voltage
>> sensitivity.
>> Bert Kehren
>>
>>
>> In a message dated  1/6/2012 11:35:02 A.M. Eastern Standard Time,
>> n...@verizon.net  writes:
>>
>> A heat sink may not be required, per se, although I would  expect that a
>> larger thermal mass and/or thermal regulation via a closed  loop fan
>> controller will help smooth out/stabilize temperature  effects.
>>
>>
>> On 01/06/12, Chuck Forsberg WA7KGX  N2469R  wrote:
>>
>> The Tech Manual does not call for  heat sinking (u

Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[David]

The FD-5680A specifications say the output is a 0.5 V RMS sine wave
into 50 ohms so there are lots of options if that is the signal you
want to distribute.

There are a number of medium power operational amplifiers specified
for video applications which will operate at a gain of 2 allowing back
termination without signal loss while driving several 50 ohm loads in
parallel.  Most will be current feedback but there are a few voltage
feedback ones as well.  If you use low supply voltages, then you will
need to watch the input common mode voltage range and output voltage
range.  AC coupling will make that easy.

http://www.linear.com/product/LT1206

This amplifier is lower output current but operated at lower supply
voltages as well.  I might try it with an emitter follower buffer.

http://www.linear.com/product/LT1192

Since you are dealing with just a low level sine wave, a single
transistor amplifier for each channel would work fine as well.

I would probably convert the sine wave into a logic level square wave
and maybe use some 50 ohm interface drivers.

On Sat, 07 Jan 2012 11:39:32 -0500, Peter Gottlieb 
wrote:

>So, here's a question.  One app is a rack of gear which all needs to get 
>the 10 MHz.  I could just go find some distribution amp, but I would 
>prefer to build something.  Has anyone done this?  I was thinking 
>perhaps a good solid reasonably high power op amp buffer feeding 
>resistors to each output to each piece of gear?  Anyone done this and 
>found any "gotchas" or success stories?

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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[paul swed]

I ultimately went with the 1 rf amp and splitter method which allowed lower
current consumption and single supply operation. I had seen this approach
in celsite dist amps.
I used a fet IR 510 as I recall cheap and available.

On Sat, Jan 7, 2012 at 12:53 PM, David  wrote:

> The FD-5680A specifications say the output is a 0.5 V RMS sine wave
> into 50 ohms so there are lots of options if that is the signal you
> want to distribute.
>
> There are a number of medium power operational amplifiers specified
> for video applications which will operate at a gain of 2 allowing back
> termination without signal loss while driving several 50 ohm loads in
> parallel.  Most will be current feedback but there are a few voltage
> feedback ones as well.  If you use low supply voltages, then you will
> need to watch the input common mode voltage range and output voltage
> range.  AC coupling will make that easy.
>
> http://www.linear.com/product/LT1206
>
> This amplifier is lower output current but operated at lower supply
> voltages as well.  I might try it with an emitter follower buffer.
>
> http://www.linear.com/product/LT1192
>
> Since you are dealing with just a low level sine wave, a single
> transistor amplifier for each channel would work fine as well.
>
> I would probably convert the sine wave into a logic level square wave
> and maybe use some 50 ohm interface drivers.
>
> On Sat, 07 Jan 2012 11:39:32 -0500, Peter Gottlieb 
> wrote:
>
> >So, here's a question.  One app is a rack of gear which all needs to get
> >the 10 MHz.  I could just go find some distribution amp, but I would
> >prefer to build something.  Has anyone done this?  I was thinking
> >perhaps a good solid reasonably high power op amp buffer feeding
> >resistors to each output to each piece of gear?  Anyone done this and
> >found any "gotchas" or success stories?
>
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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Kevin Rosenberg]

On Jan 7, 2012, at 10:39 AM, Chris Albertson wrote:
> I think this is exactly what you want.  An RF distribution amp using
> video amplifier chips. The kit is no longer available but the
> schematic is.  Look near the end of the user manual and you can get
> that here.  This design is well tested and people way it works well.
> http://www.tapr.org/kits_tadd-1.html
> The transformers in the above are not available but I bet you could
> take some using toroid cores.

TAPR told me last year that the kit discontinuance was due to the Maxim RF 
amplifiers becoming unavailable. I believe the T1-X65 transformers [1]
I just bought from Mini-circuits are similar or identical to the 
transformer mentioned in the schematic.

Kevin

[1] 
http://www.minicircuits.com/MCLStore/ModelPriceDisplay?13259623730480.6126895864089323


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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[John Ackermann N8UR]

Kevin Rosenberg said the following on 01/07/2012 02:02 PM:


TAPR told me last year that the kit discontinuance was due to the Maxim RF
amplifiers becoming unavailable. I believe the T1-X65 transformers [1]
I just bought from Mini-circuits are similar or identical to the
transformer mentioned in the schematic.


Yes, the Max477 chips have become unobtainium.  Minicircuits still sells 
the T1-1 transformers, so no problems there.


I've heard from someone who was going to try to substitute an Analog 
Devices chip that was supposedly drop-in compatible, but haven't had an 
update on whether that worked.


There is a replacement for the TADD-1 in the works, coming along slowly, 
slowly (but with recent activity and progress).


John


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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Hal Murray]

> So, here's a question.  One app is a rack of gear which all needs to get
> the 10 MHz.  I could just go find some distribution amp, but I would  prefer
> to build something.  Has anyone done this?

Sine or square wave?


   I was thinking  
perhaps a good
> solid reasonably high power op amp buffer feeding  resistors to each output
> to each piece of gear?  Anyone done this and  found any "gotchas" or success
> stories? 

The advantage of that scheme is simplicity.  The disadvantage is reduced 
isolation in case you have crap coming back from one of the devices you are 
feeding.

I second the suggestion to scan the documentation for the TAPR distribution 
amplifier.

There are actually two of them, one for RF and another for PPS/digital.
  http://www.tapr.org/kits_tadd-1.html
http://www.tapr.org/~n8ur/TADD-1_Manual.pdf
  http://www.tapr.org/kits_tadd-3.html
http://www.tapr.org/~n8ur/TADD-3_Manual.pdf

Thanks John.



-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[David]

Most of the gear I have expects TTL levels or better.  A 0.6 volt RMS
sine wave (1.2 volts peak to peak) could be a problem.  As far as
ringing, I would design something with back termination and slew rate
limiting and expect the receiver to terminate to ground which is
almost always the situation.  I looked at the TADD-3 design and it
sacrifices back termination impedance for signal swing which results
in ringing but I presume not too much if people were using it
successfully.

If there are time nuts then why not impedance, edge, and
transconductance nuts?

On Sat, 07 Jan 2012 17:11:59 -0800, ed breya  wrote:

>Most gear probably won't care whether it's sinusoidal or "square" as 
>long as the amplitude is right, but if you try to send square waves, 
>then the question is how square do they need to be. Sharp edges may 
>convey better timing information, but may also cause ringing and 
>other effects. I think reasonably clean sine waves or "highly 
>rounded" square waves are best, and easiest to send around, and you 
>know how much bandwidth is needed.
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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Peter Gottlieb]

Oh, there are definitely edge nuts.  I've seen quite a number of posts 
regarding measurement and attainment of ultrafast edges.


I've also seen impedance nuts (and of course those who think it is fine 
to randomly intermix 75 ohm and 50 ohm cables in systems).


But I have yet to run into a transconductance nut!


On 1/7/2012 8:39 PM, David wrote:

Most of the gear I have expects TTL levels or better.  A 0.6 volt RMS
sine wave (1.2 volts peak to peak) could be a problem.  As far as
ringing, I would design something with back termination and slew rate
limiting and expect the receiver to terminate to ground which is
almost always the situation.  I looked at the TADD-3 design and it
sacrifices back termination impedance for signal swing which results
in ringing but I presume not too much if people were using it
successfully.

If there are time nuts then why not impedance, edge, and
transconductance nuts?

On Sat, 07 Jan 2012 17:11:59 -0800, ed breya  wrote:


Most gear probably won't care whether it's sinusoidal or "square" as
long as the amplitude is right, but if you try to send square waves,
then the question is how square do they need to be. Sharp edges may
convey better timing information, but may also cause ringing and
other effects. I think reasonably clean sine waves or "highly
rounded" square waves are best, and easiest to send around, and you
know how much bandwidth is needed.
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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Hal Murray]

davidwh...@gmail.com said:
> I looked at the TADD-3 design and it sacrifices back termination impedance
> for signal swing which results in ringing but I presume not too much if
> people were using it successfully.

If the far end (receiver) is terminated to match the coax, there will be no 
ringing and no reflection so the mismatch in back termination won't be a 
problem.  (I'm being sloppy when I say "coax".  It also works for PCB traces 
or any other transmission line.)


There is an approach that gets full height at the receiver and good back 
termination (and low power).  Digital geeks call it series termination.  The 
idea is to leave the far end (receiver) open and use good back termination to 
catch the reflection.

When switching, the wave will go down the coax at half height.  When it gets to 
the far end (open circuit), it bounces back.  The far end sees a clean switch 
to full height.  That's the sum of the original wave and the reflection.  When 
the reflection gets back to the transmitter, it sees a clean termination and 
doesn't generate any more reflections.

Note that this only works if you have a single receiver at the far end of the 
transmission line.  If you have a receiver half way down the line, it sees a 
half-height signal between the time the outgoing wave goes past and the time 
the reflection gets back.


The TADD-3 uses 3 AC drivers in parallel, each going through a 51 ohm resistor. 
 Changing those resistors to 150 ohms should work.  Maybe a bit lower to 
account for the impedance in the drivers.  I'd probably check it with a scope.


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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Bruce Griffiths]

Hal Murray wrote:

davidwh...@gmail.com said:
   

I looked at the TADD-3 design and it sacrifices back termination impedance
for signal swing which results in ringing but I presume not too much if
people were using it successfully.
 

If the far end (receiver) is terminated to match the coax, there will be no
ringing and no reflection so the mismatch in back termination won't be a
problem.  (I'm being sloppy when I say "coax".  It also works for PCB traces
or any other transmission line.)


There is an approach that gets full height at the receiver and good back 
termination (and low power).  Digital geeks call it series termination.  The 
idea is to leave the far end (receiver) open and use good back termination to 
catch the reflection.

When switching, the wave will go down the coax at half height.  When it gets to 
the far end (open circuit), it bounces back.  The far end sees a clean switch 
to full height.  That's the sum of the original wave and the reflection.  When 
the reflection gets back to the transmitter, it sees a clean termination and 
doesn't generate any more reflections.

Note that this only works if you have a single receiver at the far end of the 
transmission line.  If you have a receiver half way down the line, it sees a 
half-height signal between the time the outgoing wave goes past and the time 
the reflection gets back.


The TADD-3 uses 3 AC drivers in parallel, each going through a 51 ohm resistor. 
 Changing those resistors to 150 ohms should work.  Maybe a bit lower to 
account for the impedance in the drivers.  I'd probably check it with a scope.


   
That approach doesn't do anything for the Vcc and GND bounce exhibited 
by the driver chip.
GND and Vcc bounce is the cause of the high frequency ringing exhibited 
by the TADD-3 outputs.
This ringing can even be observed at the outputs of inverters whose 
inputs are tied low or high in the same package


Damping the crossover current induced transient in the supply leads 
(bondwire and lead frame) inductance is one way to minimise this.
A small resistor in series with the Vcc pin often works well, the 
resistor value being chosen for near critical damping.


Another problem with the TADD-3 is the sharing of a driver chip by 
different input frequencies which leads to intermodulation between the 2 
outputs.


Bruce


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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[David]

On Tue, 10 Jan 2012 21:57:49 +1300, Bruce Griffiths
 wrote:

>Hal Murray wrote:
>>
>> The TADD-3 uses 3 AC drivers in parallel, each going through a 51 ohm 
>> resistor.  Changing those resistors to 150 ohms should work.  Maybe a bit 
>> lower to account for the impedance in the drivers.  I'd probably check it 
>> with a scope.
>>
>That approach doesn't do anything for the Vcc and GND bounce exhibited 
>by the driver chip.
>GND and Vcc bounce is the cause of the high frequency ringing exhibited 
>by the TADD-3 outputs.
>This ringing can even be observed at the outputs of inverters whose 
>inputs are tied low or high in the same package
>
>Damping the crossover current induced transient in the supply leads 
>(bondwire and lead frame) inductance is one way to minimise this.
>A small resistor in series with the Vcc pin often works well, the 
>resistor value being chosen for near critical damping.
>
>Another problem with the TADD-3 is the sharing of a driver chip by 
>different input frequencies which leads to intermodulation between the 2 
>outputs.

I have never seen that much ground bounce before so assumed it was a
termination problem.  Was the driver chip decoupling inadequate?  That
at least would be easy enough to fix.

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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Bob Camp]

Hi

A more ideal solution for the 5680 might be a little board with a 5V
regulator on it, and the 1 pps buffering. Hang it on the existing 9 pin
connector and have another (properly configured) 9 pin on the board for
RS-232 com. 

Pretty small board, pretty cheap parts. If you wanted the full blown
version, drop an LED on the lock output. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of David
Sent: Tuesday, January 10, 2012 10:19 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

On Tue, 10 Jan 2012 21:57:49 +1300, Bruce Griffiths
 wrote:

>Hal Murray wrote:
>>
>> The TADD-3 uses 3 AC drivers in parallel, each going through a 51 ohm
resistor.  Changing those resistors to 150 ohms should work.  Maybe a bit
lower to account for the impedance in the drivers.  I'd probably check it
with a scope.
>>
>That approach doesn't do anything for the Vcc and GND bounce exhibited 
>by the driver chip.
>GND and Vcc bounce is the cause of the high frequency ringing exhibited 
>by the TADD-3 outputs.
>This ringing can even be observed at the outputs of inverters whose 
>inputs are tied low or high in the same package
>
>Damping the crossover current induced transient in the supply leads 
>(bondwire and lead frame) inductance is one way to minimise this.
>A small resistor in series with the Vcc pin often works well, the 
>resistor value being chosen for near critical damping.
>
>Another problem with the TADD-3 is the sharing of a driver chip by 
>different input frequencies which leads to intermodulation between the 2 
>outputs.

I have never seen that much ground bounce before so assumed it was a
termination problem.  Was the driver chip decoupling inadequate?  That
at least would be easy enough to fix.

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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Bruce Griffiths]

David wrote:

On Tue, 10 Jan 2012 21:57:49 +1300, Bruce Griffiths
  wrote:

   

Hal Murray wrote:
 

The TADD-3 uses 3 AC drivers in parallel, each going through a 51 ohm resistor. 
 Changing those resistors to 150 ohms should work.  Maybe a bit lower to 
account for the impedance in the drivers.  I'd probably check it with a scope.

   

That approach doesn't do anything for the Vcc and GND bounce exhibited
by the driver chip.
GND and Vcc bounce is the cause of the high frequency ringing exhibited
by the TADD-3 outputs.
This ringing can even be observed at the outputs of inverters whose
inputs are tied low or high in the same package

Damping the crossover current induced transient in the supply leads
(bondwire and lead frame) inductance is one way to minimise this.
A small resistor in series with the Vcc pin often works well, the
resistor value being chosen for near critical damping.

Another problem with the TADD-3 is the sharing of a driver chip by
different input frequencies which leads to intermodulation between the 2
outputs.
 

I have never seen that much ground bounce before so assumed it was a
termination problem.  Was the driver chip decoupling inadequate?  That
at least would be easy enough to fix.

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No, its due to the high switching speed of the output stage.
Such ground bounce is typical for ACMOS devices without a staged output 
device turn on.
Low inductance decoupling has no effect on internal bondwire and 
leadframe inductance.
Apart from redesigning to chip to have a more gradual output stage turn 
on, damping of the circuit is the only effective cure.
An example of the effectiveness of this can be found in the SRS FS730 
distribution amplifier CMOS output option.


Bruce

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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[shalimr9]

Bruce,

That is at first counterintuitive (conventional wisdom and good design practice 
suggests good decoupling caps across the supply pins), but it makes perfect 
sense.

I have to try this (a small resistor in series with the positive supply rail) 
when I get home.

Thanks for the tip.

Didier KO4BB

Sent from my BlackBerry Wireless thingy while I do other things...

-Original Message-
From: Bruce Griffiths 
Sender: time-nuts-boun...@febo.com
Date: Wed, 11 Jan 2012 07:30:27 
To: Discussion of precise time and frequency measurement
Reply-To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

David wrote:
> On Tue, 10 Jan 2012 21:57:49 +1300, Bruce Griffiths
>   wrote:
>
>
>> Hal Murray wrote:
>>  
>>> The TADD-3 uses 3 AC drivers in parallel, each going through a 51 ohm 
>>> resistor.  Changing those resistors to 150 ohms should work.  Maybe a bit 
>>> lower to account for the impedance in the drivers.  I'd probably check it 
>>> with a scope.
>>>
>>>
>> That approach doesn't do anything for the Vcc and GND bounce exhibited
>> by the driver chip.
>> GND and Vcc bounce is the cause of the high frequency ringing exhibited
>> by the TADD-3 outputs.
>> This ringing can even be observed at the outputs of inverters whose
>> inputs are tied low or high in the same package
>>
>> Damping the crossover current induced transient in the supply leads
>> (bondwire and lead frame) inductance is one way to minimise this.
>> A small resistor in series with the Vcc pin often works well, the
>> resistor value being chosen for near critical damping.
>>
>> Another problem with the TADD-3 is the sharing of a driver chip by
>> different input frequencies which leads to intermodulation between the 2
>> outputs.
>>  
> I have never seen that much ground bounce before so assumed it was a
> termination problem.  Was the driver chip decoupling inadequate?  That
> at least would be easy enough to fix.
>
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> time-nuts mailing list -- time-nuts@febo.com
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>
>
No, its due to the high switching speed of the output stage.
Such ground bounce is typical for ACMOS devices without a staged output 
device turn on.
Low inductance decoupling has no effect on internal bondwire and 
leadframe inductance.
Apart from redesigning to chip to have a more gradual output stage turn 
on, damping of the circuit is the only effective cure.
An example of the effectiveness of this can be found in the SRS FS730 
distribution amplifier CMOS output option.

Bruce

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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[John Ackermann N8UR]

The TADD-3 output circuit with 3 74AC04 output stages paralleled is 
stolen from Tom Clark's design in the original TAC GPS interface board. 
 The 47 ohm resistors aren't intended as back terminations; if you 
assume a low output impedance at the chip, the three resistors are 
effectively in parallel, so more together they are more like 16 ohms 
than 50.


The value was a compromise between output voltage swing (trying to make 
sure that TTL levels are maintained at the far end of the cable) and 
protection against one '04 stage backfeeding another if their switching 
times aren't identical.  There's been discussion that lower values, 
maybe 27 or 33 ohms, might be OK and would deliver more swing at the far 
end.


Bruce is correct about the crosstalk problem -- in a desire to provide 
lots of flexibility, I designed the TADD-3 so that each of the six 
output channels could be jumper-set to a different pulse rate.  Each 
output uses 1/2 of a 74AC04, and between trace radiation and Vcc bounce, 
there is cross-mod if two channels sharing an output chip are set to 
different rates.  The simple answer is to keep each pair (channels 1 and 
2, 3 and 4, 5 and 6) set to the same rate.


John

Bruce Griffiths said the following on 01/10/2012 03:57 AM:


The TADD-3 uses 3 AC drivers in parallel, each going through a 51 ohm
resistor. Changing those resistors to 150 ohms should work. Maybe a
bit lower to account for the impedance in the drivers. I'd probably
check it with a scope.



That approach doesn't do anything for the Vcc and GND bounce exhibited
by the driver chip.
GND and Vcc bounce is the cause of the high frequency ringing exhibited
by the TADD-3 outputs.
This ringing can even be observed at the outputs of inverters whose
inputs are tied low or high in the same package

Damping the crossover current induced transient in the supply leads
(bondwire and lead frame) inductance is one way to minimise this.
A small resistor in series with the Vcc pin often works well, the
resistor value being chosen for near critical damping.

Another problem with the TADD-3 is the sharing of a driver chip by
different input frequencies which leads to intermodulation between the 2
outputs.

Bruce


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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Hal Murray]

>> The TADD-3 uses 3 AC drivers in parallel, each going through a
>> 51 ohm resistor.  Changing those resistors to 150 ohms should
>> work.  Maybe a bit lower to account for the impedance in the
>> drivers.  I'd probably check it with a scope. 


bruce.griffi...@xtra.co.nz said:
> That approach doesn't do anything for the Vcc and GND bounce exhibited  by
> the driver chip. GND and Vcc bounce is the cause of the high frequency
> ringing exhibited  by the TADD-3 outputs. This ringing can even be observed
> at the outputs of inverters whose inputs are tied low or high in the same
> package

I don't see how ground bounce is going to cause ringing.

I'd expect the ringing to come from reflections from a long transmissions 
line.


Anybody know what the driver in a TBolt is like?  Here are 2 pictures looking 
at the PPS from 2 TBolts.

This one has 10 ft of coax from one TBolt and and 25+10 ft from the other, 
with no termination at the scope.
  http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-1.png

This one has 10 ft of coax with a terminator on one side and a 10X scope 
probe right at the BNC on the other.
  http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-2.png


> Damping the crossover current induced transient in the supply leads
> (bondwire and lead frame) inductance is one way to minimise this. A small
> resistor in series with the Vcc pin often works well, the  resistor value
> being chosen for near critical damping.

I'm not sure what you mean by crossover current.

I'd expect a "damping" resistor in the Vcc lead to slow down the rise time.  
If you make it slow enough there won't be any ringing because the rise time 
will be longer than the round trip time.  Then you can treat the transmission 
line as a capacitor.

I'd expect a resistor in the Vcc lead would not slow down the fall times.


If you want a slower rise time, you can also use HC rather than AC.  They 
probably aren't strong enough to drive a 50 ohm terminator.

Using surface mount packages reduces the inductance.  (slightly?)

Another option is the bus driver chips that have multiple Vcc/GND pins.


> Another problem with the TADD-3 is the sharing of a driver chip by
> different input frequencies which leads to intermodulation between the 2
> outputs. 

Yup.  Job security for designers.  :)

If you read the fine print in the data sheets for high speed chips, they 
usually specify a marketing number with only one output changing.  The good 
data sheets tell you how much it slows down when multiple outputs change.


-- 
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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Bruce Griffiths]

Hal Murray wrote:
   

The TADD-3 uses 3 AC drivers in parallel, each going through a
51 ohm resistor.  Changing those resistors to 150 ohms should
work.  Maybe a bit lower to account for the impedance in the
drivers.  I'd probably check it with a scope.
   


bruce.griffi...@xtra.co.nz said:
   

That approach doesn't do anything for the Vcc and GND bounce exhibited  by
the driver chip. GND and Vcc bounce is the cause of the high frequency
ringing exhibited  by the TADD-3 outputs. This ringing can even be observed
at the outputs of inverters whose inputs are tied low or high in the same
package
 

I don't see how ground bounce is going to cause ringing.
   
Some load capacitance is required (even the capacitance of a short track 
on the board plus the output pin and output device capacitances will 
suffice)
One of the ground bounce papers from TI will show the ringing due to 
ground bounce (eg http://www.ti.com/lit/an/szza038b/szza038b.pdf).

I'd expect the ringing to come from reflections from a long transmissions
line.
   
Transmission line current di/dt  will interact with the supply (GND or 
Vcc) and output lead inductance.


Anybody know what the driver in a TBolt is like?  Here are 2 pictures looking
at the PPS from 2 TBolts.

This one has 10 ft of coax from one TBolt and and 25+10 ft from the other,
with no termination at the scope.
   http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-1.png

This one has 10 ft of coax with a terminator on one side and a 10X scope
probe right at the BNC on the other.
   http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-2.png


   
The output driver is a low impedance source possibly a 74AC04M (most 
likely candidate from the list of ICs used: 
http://www.prc68.com/I/ThunderBolt.shtml ).

Damping the crossover current induced transient in the supply leads
(bondwire and lead frame) inductance is one way to minimise this. A small
resistor in series with the Vcc pin often works well, the  resistor value
being chosen for near critical damping.
 

I'm not sure what you mean by crossover current.
   
During the output transition there is a short time interval (in a CMOS 
inverter stage) where both the n channel and p channel devices are both 
on causing a current to flow between Vcc and ground even with no 
external load.

I'd expect a "damping" resistor in the Vcc lead to slow down the rise time.
If you make it slow enough there won't be any ringing because the rise time
will be longer than the round trip time.  Then you can treat the transmission
line as a capacitor.
   
Thats certainly not the case in the FS730C, the risetime isnt 
appreciably affected by the small (4R7) damping resistor in series with Vcc.
Adding a series damping resistor in series with the output is 
insufficient to suppress ringing.

I'd expect a resistor in the Vcc lead would not slow down the fall times.


If you want a slower rise time, you can also use HC rather than AC.  They
probably aren't strong enough to drive a 50 ohm terminator.

Using surface mount packages reduces the inductance.  (slightly?)

Another option is the bus driver chips that have multiple Vcc/GND pins.

   
GND bounce is still readily seen, the amplitude decreases somewhat but 
the associated ringing frequency for a given load increases.
   

Another problem with the TADD-3 is the sharing of a driver chip by
different input frequencies which leads to intermodulation between the 2
outputs.
 

Yup.  Job security for designers.  :)

If you read the fine print in the data sheets for high speed chips, they
usually specify a marketing number with only one output changing.  The good
data sheets tell you how much it slows down when multiple outputs change.


   
Its not quite that simple transients are observed on quiet outputs due 
to output transitions on the switching outputs.
If transitions occur simultaneously on 2 different frequency inputs 
connected to the same chip then simultaneous switching effects modulate 
the effective propagation delay of the output transitions.
e.g. a 1MHz output may exhibit phase modulation at 100KHz if the 1MHz 
and 100KHz signals share the same output driver chip.


Bruce

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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[shalimr9]

I made some tests a while ago using the PPS output from a Thunderbolt.

http://www.ko4bb.com/Test_Equipment/CoaxCableMatching.php

Didier KO4BB

Sent from my BlackBerry Wireless thingy while I do other things...

-Original Message-
From: Hal Murray 
Sender: time-nuts-boun...@febo.com
Date: Wed, 11 Jan 2012 01:59:24 
To: Discussion of precise time and frequency measurement
Reply-To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?


>> The TADD-3 uses 3 AC drivers in parallel, each going through a
>> 51 ohm resistor.  Changing those resistors to 150 ohms should
>> work.  Maybe a bit lower to account for the impedance in the
>> drivers.  I'd probably check it with a scope. 


bruce.griffi...@xtra.co.nz said:
> That approach doesn't do anything for the Vcc and GND bounce exhibited  by
> the driver chip. GND and Vcc bounce is the cause of the high frequency
> ringing exhibited  by the TADD-3 outputs. This ringing can even be observed
> at the outputs of inverters whose inputs are tied low or high in the same
> package

I don't see how ground bounce is going to cause ringing.

I'd expect the ringing to come from reflections from a long transmissions 
line.


Anybody know what the driver in a TBolt is like?  Here are 2 pictures looking 
at the PPS from 2 TBolts.

This one has 10 ft of coax from one TBolt and and 25+10 ft from the other, 
with no termination at the scope.
  http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-1.png

This one has 10 ft of coax with a terminator on one side and a 10X scope 
probe right at the BNC on the other.
  http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-2.png


> Damping the crossover current induced transient in the supply leads
> (bondwire and lead frame) inductance is one way to minimise this. A small
> resistor in series with the Vcc pin often works well, the  resistor value
> being chosen for near critical damping.

I'm not sure what you mean by crossover current.

I'd expect a "damping" resistor in the Vcc lead to slow down the rise time.  
If you make it slow enough there won't be any ringing because the rise time 
will be longer than the round trip time.  Then you can treat the transmission 
line as a capacitor.

I'd expect a resistor in the Vcc lead would not slow down the fall times.


If you want a slower rise time, you can also use HC rather than AC.  They 
probably aren't strong enough to drive a 50 ohm terminator.

Using surface mount packages reduces the inductance.  (slightly?)

Another option is the bus driver chips that have multiple Vcc/GND pins.


> Another problem with the TADD-3 is the sharing of a driver chip by
> different input frequencies which leads to intermodulation between the 2
> outputs. 

Yup.  Job security for designers.  :)

If you read the fine print in the data sheets for high speed chips, they 
usually specify a marketing number with only one output changing.  The good 
data sheets tell you how much it slows down when multiple outputs change.


-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Attila Kinali]

On Thu, 12 Jan 2012 00:50:35 +1300
Bruce Griffiths  wrote:

> Thats certainly not the case in the FS730C, the risetime isnt 
> appreciably affected by the small (4R7) damping resistor in series with Vcc.
> Adding a series damping resistor in series with the output is 
> insufficient to suppress ringing.

How about using a ferit bead into the power supply instead of a resistor?
I'm thinking about something like a BLM18. The DC resistance is much lower
while HF resistance is much higher.

Attila Kinali

-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin

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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?

[Bruce Griffiths]

Attila Kinali wrote:

On Thu, 12 Jan 2012 00:50:35 +1300
Bruce Griffiths  wrote:

   

Thats certainly not the case in the FS730C, the risetime isnt
appreciably affected by the small (4R7) damping resistor in series with Vcc.
Adding a series damping resistor in series with the output is
insufficient to suppress ringing.
 

How about using a ferit bead into the power supply instead of a resistor?
I'm thinking about something like a BLM18. The DC resistance is much lower
while HF resistance is much higher.

Attila Kinali

   

It may be useful if the ferrite bead parameters are just right.
However the bead HF resistance will increase the high frequency output 
impedance in the high state which will adversely affect the high 
frequency source impedance of the line driver.
Whereas a resistor increases the high state output impedance in a more 
predictable way that can be easily compensated for particulalrly if a 
similar resistor were used in series with the ground lead.


Bruce

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Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A? (TADD-1 components)

[Dan Rae]

On 1/7/2012 12:23 PM, John Ackermann N8UR wrote:



I've heard from someone who was going to try to substitute an Analog 
Devices chip that was supposedly drop-in compatible, but haven't had 
an update on whether that worked.


Yes it does John.  I thought I'd already said the AD8055A is a drop in 
replacement, assuming I'm the someone.  I have two boards running with 
them.  It is still available in a DIP version as well.


Dan ac6ao




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