[time-nuts] Minor TADD-2 Sync Problems

Brian Kirby kilodelta4foxmike at gmail.com
Wed Sep 16 21:48:33 UTC 2009

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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