[time-nuts] Minor TADD-2 Sync Problems

[John Ackermann]

Bruce, not sure just which clock you're talking about, but JP4 on the 
TADD-2 allows you to select rising or falling edge for the sync pulse.

John
----

Bruce Griffiths said the following on 09/16/2009 06:18 PM:
> Brian
> 
> Is the behaviour the same when you insert a delay of around 1/2 or 1/4
> the clock period in the sync line?
> Alternatively can you invert the clock polarity?
> A pity that the slope of the clock cannot be selected in the TADD-2.
> Overdriving the sync input with a 5.8V signal may cause the input clamp
> diodes to conduct and produce some substrate current in the 74AC04 which
> will degrade its performance but not by as much as you observe.
> 
> Bruce
> 
> Brian Kirby wrote:
>> I have built two TADD-2's and have been using them in the timing
>> shop.  I noticed a synchronization problem and I wanted to pass it on
>> and see if anybody else seen the same problems.
>>
>> What I noticed is the units seem to want to sync within three discreet
>> values of time ; of the source.  I have to press the sync button and
>> watch the output to confirm where its set.  I have to press the sync
>> button several times to get the proper value.  Attached is a drawing
>> of the test setup.
>>
>> The data is for two TADD-2 units, I will call them units A & B.
>>
>> Using 10 Mhz input , unit A will either sync to 171 nS, 571 ns or 971
>> ns.   Unit B will sync to 71 nS, 471 nS or 871 ns.
>>
>> Using 5 Mhz input, unit A will sync 400 ns, 1.200 uS or 2.000 uS. 
>> Unit B will sync to 600 nS, 1.400 uS or 2.200 uS.
>>
>> The Austron 1210 shows 3.5 volts P-P terminated sine waves on the
>> scope for 10 and 5 Mhz, the 1 PPS is +5.8 volts peak, also terminated.
>>
>> Both TADD-2 were acquired and built less than a month ago - so the
>> parts should be identical values.  The only difference is power
>> supply.  Unit A runs off my 12 volt system that powers my GPS
>> receivers.  Unit B has a 9 volt DC wall wart rated at 0.5A.
>>
>> I changed the RF Input to my HP5065A and I still see three different
>> values of time; Unit A -102 nS, 698 nS, and 1498 nS.  Unit B shows 502
>> nS, 1302 nS and 2102 nS.
>>
>> I change to other RF and PPS sources and I see the same problem.
>>
>> My concern is this is repeatable, in my case, and I have to watch the
>> output to get the sync as close to the source, timing wise with the
>> TADD-2.   My other dividers, based on async logic do not show this
>> problem.  One unit syncs solid at 160 nS on 10 Mhz, the other unit at
>> 210 nS (they were built several years apart and probably different
>> brands of gates).
>>
>> Brian - KD4FM
>>
>>
>>
>>
>>
>>
>>
>>
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>>
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> 
> 
> 
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