[time-nuts] thunderbolt fault

Bob Camp lists at rtty.us
Sat Feb 27 03:16:04 UTC 2010


Hi

It's pretty easy to get a common mode choke that will indeed break up 120 Hz ground loops. Often they are very low impedance. With most supplies the rectified line is what's coming through.

Bob


On Feb 26, 2010, at 10:10 PM, WarrenS wrote:

> 
> 
>>> Common mode choke filter does not get ride of LINE NOISE on the +12 V or LINE VOLTAGE sensitivities...,
>> Please explain how a common mode choke on the +12 and ground does nothing to help keep the supply clean.
> 
> 
> What size is your common mode choke filter?
> To have any effect on 60 Hz PS ripple it would need to bigger than a (small) bread box .
> And to help reduce DC type line voltage variations it would need to be bigger than a planet. (yea, Earth size)
> Common mode filters are for HI freq, not 60 Hz OR DC.
> But then, you already know that so I do not know why your comment???
> 
> ws
> *************
> Hi
> 
> Please explain how a common mode choke on the +12 and ground does nothing to help keep the supply clean.
> 
> Bob
> *****************
> 
> On Feb 26, 2010, at 9:57 PM, WarrenS wrote:
>> 
>>> Lots of questions ....
>> Same Simple answer.
>> Make the +12 volts is as good as you can get it, For the rest any general purpose PS works fine.
>> And a Common mode choke filter does not get ride of line noise on the +12 V or Line voltage sensitivities, both are important on the +12V
>> 
>> ws
>> 
>> ****************
>> Hi
>> 
>> Depending on the supply setup, a common mode choke might also be a good idea.
>> 
>> The +12 runs the OCXO, so it's going to have an impact.
>> 
>> What about the +5 Volts? Obviously it needs to be crud free. Gross changes will impact the temperature of the unit. What about small changes? Is it running the maser reference for the DAC or does that come off the +12? Is +5 just a digital supply?
>> 
>> Lots of questions ....
>> 
>> Bob
>> 
>> On Feb 26, 2010, at 6:59 PM, WarrenS wrote:
>> 
>>> 
>>> 
>>> Yes, I Did that,   The +5 and -12 has NO effect on freq or operation of the unit except for really far out voltages.
>>> I tested mine with the -12 from -2 to -15 and could see no effect in the e-11 range.
>>> The -12 is used for the RS232 and the -Dac out so If you don't need the neg Dac out voltage or neg RS232  Drive, then it can pretty much be anything. But It should be kept in -7 to -13 range, and common sense means there should be little noise on it so it does not couple into other things. BUT the circuit it's self does not care what the supply is at or what is used.
>>> 
>>> The +12 on the other hand, Needs to be stable and quiet with no ripple.
>>> I found using a +15 volt supply feeding a 12V three terminal will heat slinked regulator a good way to go to keep ALL the ripple out of the +12V
>>> 
>>> ws
>>> 
>>> *******************
>>> 
>>> Hi
>>> 
>>> Has anybody actually measured the supply sensitivity on the -12 volt line to see weather a 5 volt change makes any noticeable difference in the output frequency? The power on -12 is very low, so there should be negligible thermal impact from a change.
>>> 
>>> Bob
> 
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