On 10/01/2012 02:11 AM, Frank Hughes wrote:
Hi,
Thanks for all the good advice to get me started in this fun technology!
Last weekend finished putting up the antenna that was obtained from the
suggested China source,
powered up a "new to me" Trimble Thunderbolt, obtained an old used laptop w/
DB-9 serial HW,
and have been experimenting w/ the Trimble and LH software.
I ran the 10Mhz signal into an HP 5087A DA to feed all the other things in the
racks that accept
a 10Mhz external reference, works great!
One thing I am wondering about is disciplining - how much of this is HW and how
much is SW?
How are non-Trimble oscillators disciplined? It it common practice to provide a
GPS antenna input?
You have to realize that the Thunderbolt is an amazingly open design.
Just the fact that there is connectors on the PCB to hook up external
oscillators makes it sane. Using a thunderbolt to control an off-board
oscillator boils down to neither HW or SW details, but rather
configuration details (once the oscillator is hooked up). You need to
adjust the loop gain to match the EFC sensitivity of your oscillator.
The loop bandwidth is another parameter to look for.
Is this a default in HW on some oscillator controllers, and/or is there some
industry standard command set or
protocol to activate disciplining?
Industry standard? I'd love to see one. Just look at the HP family of
SmartClocks (Z3801A etc) and the Thunderbolt series you will realize
they are different in many ways. The different design teams have taken
somewhat different approaches. As long as they do that, their preferred
way of doing things will differ.
Learn your tool and how you can adapt it to your clocks.
I would like to experiment with some other OCXO's, but am not sure about how
they might be disciplined.
If they have an EFC/VC input, check the voltage range and the scale of
that range. It can vary a lot. Prepare to do adapter-boards doing
scaling and level shifting. Toss in an offset trimmer. Using a voltage
reference is highly recommended.
Cheers,
Magnus
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