If you get the Rb unit by itself, all you have is an Rb oscillator; it
depends on the XO unit for GPS.  So, if I were to get only one, I'd get
the XO.

John

Richard W. Solomon said the following on 02/01/2007 05:47 PM:

Have we settled the question of whether or not the RB can
be dominated (no, that's not it) disciplined by an external
1 PPS or 10 MHz signal?

If it can, I'd load up on Rb units and discipline them with
a modern GPS receiver - or maybe replace the OXCO in Z3801s.

Bill Hawkins

Z3801s do dissipate about 50 watts, though.

-----Original Message-----
John Ackermann N8UR said,

If you get the Rb unit by itself, all you have is an Rb oscillator;
it depends on the XO unit for GPS.  So, if I were to get only one,
I'd get the XO.

John

Richard W. Solomon said the following, in part, on 02/01/2007 at 05:47
PM:

On Thu, Feb 01, 2007 at 08:57:51PM -0600, Bill Hawkins wrote:

Settled is vastly too strong a word in my case, but I am

currently pretty positive that the Rb is disciplined (naughty Rb) by the
hardware provided which supplies EFC voltage to its C field pin.  I
believe this comes from a 16 bit DAC on the mezzanine board.

AFAIK the jury is still out as to whether there is a way of

making the existing Lucent firmware perform this operation without the
cooperation of firmware running on an XO.  Experiments so far suggest
the RB firmware pays attention to the binary messages from the Oncore
GPS on the XO and  may not be willing to accept that there IS a GPS
supplying 1 PPS to lock to unless that stuff is there and sending out
the right messages.

It does seem at least possible the firmware supports other

reference inputs and it certainly seems rather likely it could be
patched or hacked to accept GPS input from a bare Oncore GPS board -
maybe even one mounted on its unstuffed header.

So probably the best answer is that surely the hardware can

without modification support disciplining of the Rb, and maybe the
existing software can be made to work without an actual XO present and
maybe not.  And maybe  a patched version of the software would do this
even if the existing version won't.

In theory a Z3801 should be able to control a LPRO-101 instead

of its 10811 with very minor hardware tweaks, but one supposes there are
ALL kinds of tweaks in the Z3801 firmware that are 10811 specific (loop
parameters, thermal compensation, oven monitoring  etc) that would be
moderately to highly wrong for a LPRO-101 as 10 MHz source.  And of
course a LPRO-101 generates a lot more heat and would require other
thermal treatment and its related mechanical issues.

I imagine that most of the actual disciplining PLL constants and

other Rb specific stuff in the Lucent RB firmware is relatively isolated
from the higher level part that pays attention to the system
configuration and worries about talking to the companion XO and GPS
about status and configuration. Perhaps someone with time and patience
COULD patch the RB firmware to ignore whatever it tests to validate the
XO state or GPS configuration allowing the 1 PPS tracking PLL to still
work but not need good GPS status or XO messages.  And maybe there is
some configuration process to make this happen anyway as a test mode or
for alternative system architectures with 1 PPS from some other source.

And for those who like such approaches, it might also to be

possible to program a PIC or other cheapo one chip micro with suitable
serial capability to pretend to be the GPS and XO and fool completely
unmodified RB firmware into thinking they were there and fine.  It
stands to reason that the real synchronizing input is the 1 PPS and that
all the rest of the dialog is related to determining whether it is good
or not and whether the RB should turn on its outputs or not based on
higher level system state.  And the PIC code involved might not be
overwhelming - given the option of monitoring a working system and
determining what is looked for and when, it might merely involving
canning the dialog with a good XO and GPS as a script rather than any
intricate decomposition of the actual messages and reformatting them.

--
Dave Emery N1PRE,  die@dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in
celebration of what could have been, but wasn't and is not to be now either."

On Thu, 1 Feb 2007 20:57:51 -0600, "Bill Hawkins" bill@iaxs.net wrote:

"The RB" is a little too vague in this case. I picked up one of the
RFG-RB units and I can't see anyway that there is disciplining in it. I
think it just free runs and was used as a backup if the XO in the XO
unit lost sync from GPS.

From what I have read here, the -m- units may be different and actually
do some kind of disciplining of the RB unit. IOW, the different models
of Lucent stuff seem (from messages here) to be quite a bit different.

The actual LPRO Rb that is in my RFG-RB should be possible to be
disciplined with some other circuity, but as far as I can see, not the
circuitry that is in the box.

I think I got a decent deal for what I paid, but I'll probably remove
the LPRO and not use the board that came in the box.