Hi,
Sorry for this late response but I was away from home.
I did the 1 PPS mod a year ago. I just cut the trace between TP14 and
U405 pin 6 and soldered a wire between TP14 and TP33.
Now you have 1PPS on the former 9.8304 MHz output. Not being a cellular
tower operator I did not have any use for this frequency.
Comparing the 1PPS with the .5 PPS pulses, there are an offset, which is
not constant. In my case it can be 540, 440, 340, 240 or 140 ns, it
changes before locking but after the lock condition it remains constant.
Studying the circuit and the Nortel specs, the 1/2 PPS must be
synchronous with the 9.8304 MHz signal, so this is probably the cause.
I still have to check with an independent 1PPS reference (a Rb one) to
see if this PPS is reliable.
Regards,
Ignacio EB4APL
El 10/08/2016 a las 21:25, Clay Autery escribió:
1) Need a 24 VDC power supply. Am considering just buying an Astron
VLS-35M Adjustable Voltage/Current supply (5-32V/1.5A to limit) since I
don't own a variable power supply yet, this is a linear, and the same
size package as my RS-70M. I can worry about a dedicated supply later
if I decide to keep this GPSTM after I finish modding/testing it.
Anyone have any recommendations to the contrary? Why?
2) Need to bring the PPS out from the TP in this article:
https://www.i3detroit.org/wiki/Nortel_GPSTM The article shows a buffer
circuit being used to accomplish this... Need help locating a datasheet
on the Motorola chip used... It's obsolete and I need to find a pin
compatible replacement...
Or, I need to find another buffer schematic/plan,
Or, alternatively.... has anyone ever tried pulling the 1pps out and
hooking it to the 9.8 MHz driver (severing the drive line to it and
jumpering in the 1pps)? The 9.8MHz and the 10MHz signal out ports SEEM
to use identical driver/buffer circuits on this board... Seems like a
possibility...
Preferably, I find the Motorola chip, copy the buffer circuit and move
on...
I'm pretty new at this, so any help is appreciated, and not slapping me
about for "not knowing" stuff is greatly appreciated! :)
Sincerely,
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