[time-nuts] Achieving maximum performance when driving 5370A/B inputs
Bob Camp
lists at rtty.us
Sun Feb 28 03:14:38 UTC 2010
Hi
MIght have to move a few things in the shed to fin in an F16.
If they were used in quantity there aught to be cable and connectors out there. The only reason I have the stuff I do is good old IBM and their approach to networking back in the old days. It would be tough to properly drive an R-390 otherwise.
Bob
On Feb 27, 2010, at 10:10 PM, Bruce Griffiths wrote:
> You could look at a surplus F16 (probably wont fit in your garage though) or similar STP was heavily used in MIL STD 1553 avionics buses.
>
> Bruce
>
> Bob Camp wrote:
>> Hi
>>
>> Sure never seen any of them on any gear in my junk pile.
>>
>> I also never seen a customer ask for them as an output connector on an oscillator. I wonder how common they actually are.
>>
>> Bob
>>
>>
>> On Feb 27, 2010, at 9:59 PM, Bruce Griffiths wrote:
>>
>>
>>> Actually there are miniature twinax style connectors, for example:
>>> http://www.amphenolrf.com/products/twinbnc.asp?N=0&sid=4B8860805409E17F& <http://www.amphenolrf.com/products/twinbnc.asp?N=0&sid=4B8860805409E17F&>
>>>
>>> Bruce
>>>
>>> Bob Camp wrote:
>>>
>>>> Hi
>>>>
>>>> I don't even have the counter and already we're butchering it....
>>>>
>>>> The big issue is suitable twin-ax connectors and cable. I have both, but they are *big*. They never really made it into the world of miniature connectors and miniature cable.
>>>>
>>>> Shielded twisted pair would be another option. That eliminates the cable as an issue. Small connectors (BNC drop in) are still an issue though.
>>>>
>>>> Bob
>>>>
>>>>
>>>> On Feb 27, 2010, at 9:48 PM, Bruce Griffiths wrote:
>>>>
>>>>
>>>>
>>>>> Since the input amplifier and trigger circuit are located on a small daughter board it wouldn't be too difficult to replace this with an LVDS to CML stage.
>>>>> The only remaining isue would be what input connector to use (twinax??, SATA??).
>>>>>
>>>>> Bruce
>>>>>
>>>>> Bob Camp wrote:
>>>>>
>>>>>
>>>>>> Hi
>>>>>>
>>>>>> Gee, LVDS what an unusual approach :)....
>>>>>>
>>>>>> It would be nice if these instruments had a balanced input. Common mode noise is indeed an issue in a lot of cases.
>>>>>>
>>>>>> Of course wrapping the coax headed to the counter 10X around a fairly large core can help things a bit.
>>>>>>
>>>>>> Bob
>>>>>>
>>>>>>
>>>>>> On Feb 27, 2010, at 9:32 PM, Bruce Griffiths wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>> If one is feeling paranoid about ground loop noise (and wishes to avoid transformers, optoisolators , or fibre optics), etc one could always use an LVDS driver with a batter powered(?) LVDS to CMOS receiver/translator right at the 5370A/B input BNC connector.
>>>>>>> This may be useful for a DMTD system that uses a 5370A/B.
>>>>>>>
>>>>>>> Bruce
>>>>>>>
>>>>>>> Bob Camp wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Hi
>>>>>>>>
>>>>>>>> AC cmos will easily drive an L pad to match a 50 ohm cable at these levels. That's true at either 3.3 or at 5.0 volts. There are a lot of cmos families out there that beat AC for speed and match the output drive capability.
>>>>>>>>
>>>>>>>> Bob
>>>>>>>>
>>>>>>>>
>>>>>>>> On Feb 27, 2010, at 9:12 PM, Bruce Griffiths wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>> 1) One method with 5V CMOS is to add a resistive voltage divider at the CMOS driver output with a 50 ohm output impedance at the tap that drives the 5370A/B input.
>>>>>>>>>
>>>>>>>>> 2) If one has a 5V 50 ohm driver (eg Thunderbolt PPS output) use a 50 ohm attenuator at the 5370A/B input.
>>>>>>>>> For a 5370A an attenuation of at least 11dB is required.
>>>>>>>>> For a 5370B an attenuation of at least 3dB is required.
>>>>>>>>>
>>>>>>>>> 3) One can always use the 10x input attenuation setting built in to the 5370A/B however this reduces the signal swing to 0.5V at the trigger amplifier input (5V CMOS input).
>>>>>>>>>
>>>>>>>>> 4) Attenuate the output of the logic signal by a factor of 2 and use an npn emitter follower to drive the 50 ohm load.
>>>>>>>>>
>>>>>>>>> 5) Use 3.3V CMOS signal levels for the 5370B.
>>>>>>>>>
>>>>>>>>> 6) Use a current mode emitter or source coupled switch to drive the 5370A/B input.
>>>>>>>>>
>>>>>>>>> The switching jitter of the above drivers will be much lower than the internal noise of the 5370A/B as long as HCMOS or faster logic is employed.
>>>>>>>>>
>>>>>>>>> Bruce
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Bob Camp wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> Hi
>>>>>>>>>>
>>>>>>>>>> Which *still* carefully avoids the issue of how .....
>>>>>>>>>>
>>>>>>>>>> Bob
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Feb 27, 2010, at 8:52 PM, Bruce Griffiths wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> Oops! a small correction (2nd paragraph):
>>>>>>>>>>>
>>>>>>>>>>> For the 5370A attenuating the 5V CMOS signal to a 1V swing with the threshold set to 0.5V is close to optimum.
>>>>>>>>>>> An input signal with limits of 0V and +1.4V with a trigger threshold of 0.7V is the maximum usable (for high performance).
>>>>>>>>>>> An input signal with limits of 0V and +0.3V with a trigger threshold of 0.15V is the minimum usable (for high performance).
>>>>>>>>>>>
>>>>>>>>>>> For the 5370B attenuating the 5V CMOS signal to a 2V swing with the threshold set to 1V is close to optimum.
>>>>>>>>>>> An input signal with limits of 0V and +3.5V with a trigger threshold of 0.7V is the maximum usable (for high performance).
>>>>>>>>>>> An input signal with limits of 0V and +0.3V with a trigger threshold of 0.15V is the minimum usable (for high performance).
>>>>>>>>>>>
>>>>>>>>>>> Thus using the PPS output (~270 ohm is series with a 5V 74AC04 output) from a Synergy evaluation board that uses an M12M or M12+ GPS timing receiver to drive the inputs (with a 0-750mV signal) of a 5370A or 5370B is well within the recommended input signal range for high performance.
>>>>>>>>>>> This avoids having to adding an external 5V 50 ohm driver that some would use.
>>>>>>>>>>>
>>>>>>>>>>> Bruce
>>>>>>>>>>>
>>>>>>>>>>> Bob Camp wrote:
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>> Hi
>>>>>>>>>>>>
>>>>>>>>>>>> So exactly how did you know that I bought a (cheap) 5370B a few hours ago on the e-place and was just about to ask about how best to use it.
>>>>>>>>>>>>
>>>>>>>>>>>> Hmmmm.......
>>>>>>>>>>>>
>>>>>>>>>>>> Bob
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> On Feb 27, 2010, at 7:01 PM, Bruce Griffiths wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>> The attached excerpts from the 5370A and 5370B manuals indicate that for best performance, that the common practice of driving the 5370A/B 1x inputs directly from a 5V CMOS logic signal is a bad idea.
>>>>>>>>>>>>>
>>>>>>>>>>>>> For the 5370A attenuating the 5V CMOS signal to a 1V swing with the threshold set to 0.5V is close to optimum.
>>>>>>>>>>>>> An input signal with limits of 0V and +1.4V with a trigger threshold of 0.7V is the maximum usable (for high performance).
>>>>>>>>>>>>> An input signal with limits of 0V and +0.3V with a trigger threshold of 0.15V is the minimum usable (for high performance).
>>>>>>>>>>>>>
>>>>>>>>>>>>> For the 5370A attenuating the 5V CMOS signal to a 2V swing with the threshold set to 1V is close to optimum.
>>>>>>>>>>>>> An input signal with limits of 0V and +3.5V with a trigger threshold of 0.7V is the maximum usable (for high performance).
>>>>>>>>>>>>> An input signal with limits of 0V and +0.3V with a trigger threshold of 0.15V is the minimum usable (for high performance).
>>>>>>>>>>>>>
>>>>>>>>>>>>> Bruce
>>>>>>>>>>>>>
>>>>>>>>>>>>> <5370ATriggering.png><5370BTriggering.png>_______________________________________________
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>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
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>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
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>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
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>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
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>>>>>>>>>
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>>>>>>
>>>>>
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