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[time-freq] TADD-2 Help Please

John Ackermann N8UR jra at febo.com
Tue Apr 13 12:41:12 UTC 2010

Hi Mack --

The sync function is optional; the divider will work just fine if you 
don't use it.

Without using synchronization, the timing of the output pulses will be 
arbitrary, because the divider just starts counting as soon as power and 
reference input are applied.  So if you don't care about the phase of 
the output pulse, just power the thing up and ignore the SYNC and ARM 

The SYNC function allows you to synchronize the counter to an external 
source.  So, if you want the TADD-2 PPS to be aligned with the Tbolt 
PPS, you would:

(a) start the TADD-2 and supply the input frequency

(b) attach the TBolt PPS to the SYNC IN connector

(c) momentarily short the ARM pins (don't keep them shorted) -- red ARM 
LED should be on

(d) wait for the next TBolt PPS to turn the green "SYNC" LED on

(e) disconnect the TBolt from the SYNC input

That caused the PIC to reset and start counting again on the rising edge 
of the pulse on the SYNC IN connector.

Now, the TADD-2 PPS will be synchronized (in phase) with the TBolt PPS, 
plus or minus the period of the input signal and any processing delays 
-- which means that with a 10 MHz input you'll normally be lined up to 
within about 200 nanoseconds worst case.

Hope this helps.

Mack wrote:
> This is my first post to the list and I could use some advice please.
> I just complete the TADD-2 kit but the instructions are a bit incomplete 
> for me. All I’m trying to do is feed a Rubidium or GPS 10 MHz source 
> into the RF input and be able to divide it into the various outputs 
> offered by the kit. What’s confusing me is the sync input. I can toggle 
> sync input so that the two LED’s light but they never extinguish. I 
> would prefer not to use sync since my Rubidium source only offers 10 MHz 
> output. However if I do use my Thunderbolt GPS what would the settings be?
> Please advise on the proper jumper setting to simply use it as a 
> frequency divider. Thank you in advance.
> 73,
> Mack de WB4MAK
> http://www.nfarl.org <http://www.nfarl.org/>
> http://www.sedxc.org <http://www.sedxc.org/>
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