Thanks Bob. I'm understanding a lot more now. The FE-5680A's that I have
output both the 1pps as well as 10 MHz (and programmable to other
frequencies). Yes, I also understand now how the Rb physics package and the
DDS work together to come up with the output frequency.
With the TBolt on the way now... and in the process of looking for a
good/used "real" counter... I'll get there. :)
Best regards,
Brice
----- Original Message -----
From: "Bob Camp" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Sunday, July 25, 2010 11:01 AM
Subject: Re: [time-nuts] Symmetricom X72
Hi
No, the LPRO is not obviously better than the FE's, depending on which
version of the 5680 you have. The 5680 comes in two common varieties, one
only has a 1 PPS output, the other will put out 10 MHz as well. Both can
be digitally tuned to come up with oddball frequencies in the vicinity of
their intended output.
Bob
On Jul 24, 2010, at 5:46 PM, Heathkid wrote:
Bob, so you're saying the Efratom LPRO is better than the three
FE-5680A's I already have? Sounds like I do need a TBolt anyway.
----- Original Message ----- From: "Bob Camp" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Saturday, July 24, 2010 5:20 PM
Subject: Re: [time-nuts] Symmetricom X72
Hi
The only way to be sure of what's going on is to have several
(hopefully) accurate references. With at least three you can begin to
guess how good they are.
The TBolt is different from the Rb in a couple of regards:
1) It's short term stability isn't as good when locked tightly to the
GPS.
2) It's long term stability is much better than the Rb when it's locked.
3) It's easier to tell what's happening with it if you hook up a PC and
the Lady Heather (free) program.
The Rb will need a couple of things to make it play right:
1) It's got to have a pretty good heat sink on it. An 8 x 10" piece of
1/4" aluminum is a reasonable start
2) It's got to be run for a while (possibly 24 hours) before it will be
stable
3) You need to watch the lock, and lamp voltages to be sure it's not
doing something crazy.
My recommendation based on cost is the Efratom LPRO for a cheap Rb. They
are in the ~$60 range and seem to work pretty well.
Setup wise, I would get a TBolt in addition to the Rb. You need
something to calibrate the Rb (and your counter TCXO) against. Both are
"secondary" standards. They (unlike a Cesium) are adjusted to match a
known good reference.
Once you have the Rb and the TBolt, next step is up to you. Cesium is
always an alternative, so's a Hydrogen Maser ....
Bob
On Jul 24, 2010, at 3:32 PM, Heathkid wrote:
Hello Bob,
What would you recommend? I already have three FE-5680A Rb standards
(which I'm quickly learning likely aren't worth the powder to blow them
to (*insert your own word here*). Okay, that was probably my first
mistake (thoughts?).
My frequency counter is one I built from a kit from aade.com that has
the TCXO option (although I had to tweak it myself so I have NO idea
how close it is to any accuracy or precision). I have access to some
really nice HP counters at work so that's my next step is to try one of
those. My DFD4 measured the output of one of my 5680A's to 10.000.007
MHz after about a 10 minute warm-up. I don't know which one is off.
Reading the specs on the 5680A's before I bought them looked like they
were pretty decent. I'm learning...
So, what "reasonably priced" Rb standard would you recommend?
Should my next step in this process be a Trimble Thunderbolt? Am I
starting over?
Thanks...
----- Original Message ----- From: "Bob Camp" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Saturday, July 24, 2010 9:31 AM
Subject: Re: [time-nuts] Symmetricom X72
Hi
At least looking at the spec sheet it's not really very impressive.
Bob
On Jul 23, 2010, at 11:06 PM, Heathkid wrote:
Hello. Does anyone have any experience with the Symmetricom X72?
Thanks...
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