[time-nuts] BC637PCI and OCXO

d0ct0r time at patoka.org
Fri Feb 7 10:25:45 EST 2014

Thanks everybody for the bit of information !

I have a "Revsion C" and "Revision K" manuals. In Revison "K" its only 
one note about OCXO:

"An internal 10 MHz VCXO (Voltage Controlled Crystal Oscillator) is 
disciplined to the
reference source. The VCXO output drives all timing functions on the 
card. The VCXO
output and a 1pps signal are provided as outputs. The TFP is also 
capable of disciplining an
external voltage controlled oscillator. As an option, the TFP board can 
be ordered with an
OCXO (Oven Controlled Crystal Oscillator) installed."

As far as I understood, if I'll implement external OCXO to my BC637, 
I'll need to change FW on the card to make it work. If so, its not an 
option for me, since I just bought that card from auction and there is 
no way to obtain new microcode for it.


Aside of that OCXO implementation, I would like to ask some direction 
from time-nuts community about the relatively simple way to compare two 
1PPS signals using some MCU. Lets say I have T-Bolt and BC637. Each has 
1PPS and I would like to see the phase difference between of that two. 
Of course it is some instruments already available for that, but I have 
not own that one (yet). I am thinking to connect both 1PPS to Timers 
input in "capture" mode on MCU. Then register first raising edge, start 
counting of ticks until second timer will not catch another signal 
raise. Then number of ticks will indicate the difference. But may be it 
is more "elegant" way to do that comparison ? Thanks !



On 2014-02-07 03:38, GandalfG8 at aol.com wrote:
> I played with this around five or six years ago but unfortunately  my 
> notes
> from that time are likely to be buried somewhere still  waiting to be
> scanned or indexed.
> All the necessary information though is in the user and SDK manuals,
> connections for the 10MHz external input and EFC output are on the 15 
> way I/O
> connector and there's even demo software which I'm pretty sure was all 
> I  used
> to make the necessary adjustments.
> One manual, pre Symmetricom, even has what looks to be a full set of
> schematics.
> I've just run the software again to check but it won't do much if  it 
> can't
> find the card so would need to fire up another PC with a spare  slot to
> check further.
> I wasn't really happy at the time with my attempts to  condition an
> external Vectron OCXO, it was certainly better than using the
> internal oscillator
> but there were some odd jumps and drifts using either which  suggested 
> these
> might be artifacts of the board itself rather than the  Vectron OCXO.
> I've since acquired another BC637PCI, and want to try both again with
> other oscillators, but that's quite some way down a very  long to do 
> list, now
> reminded though I might take a quick  look later:-)
> In the meantime, I have got copies of manuals and software  etc and 
> will
> get those zipped up today and make them available  for download.
> Regards
> Nigel
> In a message dated 07/02/2014 03:36:46 GMT Standard Time, 
> time at patoka.org
> writes:
> Hello,
> Does anybody seen any links to the information  how to implement 
> external
> OCXO to Symmetricom PCI TFP BC635/BC637  ?
> --
> WBW,
> V.P.
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