[time-nuts] PPS Divider

John Ackermann N8UR jra at febo.com
Tue Mar 31 12:42:37 UTC 2009

I'm a little nervous about this posting, as it is a couple of weeks 
earlier than I'd intended, but with the recent discussion about PPS 
dividers, I thought it was appropriate to mention a new TAPR product 
that will be shipping within the next month or so.

I've finally finished the TADD-2, which is a 5 or 10 MHz input device 
with six low impedance outputs that can be individually jumpered to 1 
PPS or 10 Hz through 10 kHz outputs.  Each output can be jumpered for 
normal (low, going high on the leading edge) or inverted outputs.  The 
divider has an ARM/SYNC function that allows syncing the pulses to an 
external source.

The TADD-2 uses a 16F630 PIC running a version of TVB's code, modified 
by Richard McCorkle to support selectable input frequencies and a more 
modern PIC device.  A programmed PIC is included with each unit, but 
source code will be available for folks who want to experiment.

The TADD-2 is the same form factor as the other TADDs (about 6 x 4 
inches) and will fit in the TADD enclosure that TAPR offers.  It 
operates from a nominal 12 volt power supply.

The TADD-2 will be sold as a kit; it uses through-hole parts and the 
assembly difficulty will be similar to that for the TADD-3 (it takes me 
a little over two hours to build a TADD, but then again I have some 
experience...).  We expect that the price will be $62 for TAPR members 
and $69 for non-members, though that could change by a couple of dollars 
as we review the final BOM cost.  Assembled units may be available by 
special order.

TAPR is *not* ready to accept TADD-2 orders yet, but hopefully we'll be 
doing so by the end of April.  I'll post another message here when we 
have the web order page up.

In the interest of full disclosure, I'm also working on a second board, 
the TADD-2 Mini ("T2-Mini"), which is a "dongle" built on a 0.75 x 2.0 
inch board with a BNC connector on each end.  It is a single channel 
device with PPS output only.  It's not nearly as flexible as the TADD-2, 
but may be useful for temporary experiments, or for integrating into 
existing frequency standards where space is tight.

The T2-Mini uses surface mount parts (though the PIC is a socketed 8 pin 
DIP) and will be offered as an assembled and tested unit only.  Price 
has not yet been determined, and availability is still a few months off 
-- we hope to have it available early in the summer, but no guarantees. 
  Look for an announcement here when we're ready to proceed.

BTW -- the jitter tests I posted last night were made using two T2-Mini 
Rev. A prototypes.


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