[ntp:questions] Thunderbolt at NTP ref clock.
spam at goes.nowhere.com
Tue Aug 6 08:18:04 UTC 2013
Subject: Re: Thunderbolt at NTP ref clock.
From: DaveB <spam at goes.nowhere.com>
In article <6C1FE0E5A70C9640B597F869A899C017033BD406 at tmpExch.non-
stop.com.au>, marks at non-stop.com.au says...
> Sorry typo - 74AC121 should say 74AC123
> -----Original Message-----
> From: questions-bounces+marks=non-stop.com.au at lists.ntp.org [mailto:questions-bounces+marks=non-stop.com.au at lists.ntp.org] On Behalf Of Mark C. Stephens
> Sent: Friday, 2 August 2013 11:01 AM
> To: DaveB; questions at lists.ntp.org
> Subject: Re: Thunderbolt at NTP ref clock.
> You can control the thunderbolt PPS width with Lady Heather software:
> Or build the TAPR fat PPS Pulse stretcher section on breadboard, not so complicated, just use the 1/2 of 74HC121 and a 74AC04 (or MAX232) to drive the serial port (or LPT port - less jitter) make sure any unused inputs are on the other 1/2 are tied to ground or pulled up to VCC.
> The circuit for the 74AC04 can be lifted from the output section of the TAPR PPS distribution amp (TADD-3).
> Or, you can use Just use the FATPPS circuit in its entirety - I built 3-in-1 custom PPS stretchers on one breadboard and it took me 1-2 hours.
> Please drop me an email if you need me to express this in a circuit.
I'm an long time hardware fiddler too, so monostables (IC and descrete)
are understood by me. (As well as multi kW broadband RF amps and
transmission lines.) Thanks anyway.
LH can indeed control the PPS signal, but only turn it on or off, or
change it's polarity, & position (delay) wrt selected reference time
(cable delay and all that.)
The default is 0 to +5V, the "other" polarity, is 0 to -5V. I checked
with my trusty Tek 465 (and through term!) No ability to adjust the
pulse width/duration, so a stretcher will be built.
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