Steve,
I changed the subject line because everything that follows has nothing to do
with the X72. I hope this doesn't confuse anyone but this subject is
probably much better related...
Yes, the FEI 5680A's I got are programmable from 1Hz to 20MHz (SMA output /
currently set to 10MHz) plus has the RS232 for programming and one of those
pins (besides the Rb lock pin that goes low and I've got a LED on it) has
the 1pps. Besides the "C" field potentiometer it also has a 0 to 5V fine
tune voltage. The slowest of the three takes only about 4 seconds to
achieve Rb lock. Here are the exact units I got (and "flyingbest" is a
great and honest seller):
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180435915714
The Thunderbolt I bought from fluke.l as he seems to be the "TBolt seller of
choice" around here. I also got the LCD display option (looks like fun to
see what it's doing when not connected to a PC).
Okay, so today... I bought a "real" frequency counter. After a LOT of
looking and reading... I chose a HP 5335A. It has option 10 (Oven
Oscillator) and 030 (C Channel 1.3 GHz ) plus the HPIB plus math and
statistics functions standard and includes operating and service manuals on
CD. It'll also be calibrated just prior to shipping to me (current Date Due
03/19/11) but it will be re-calibrated just for me so at least I know it'll
work and if there is a problem, I can return it. :)
So, now I have the following (when the rest shows up):
(3) FEI 5680A Programmable Rubidium Frequency Standards w/ 1pps
(1) Thunderbolt "Complete Kit" w/ LCD display - from fluke.l
(1) HP 5335A Universal Counter w/ Options 10 (Oven Oscillator) & 030 (C
Channel 1.3 GHz)
Hopefully, Stanley got my payment for the PICTIC II boards and I got an
email back from Bob about getting me on the list for the programmed PICs.
That's where I'm at right now.
73 Brice KA8MAV
----- Original Message -----
From: "Steve Rooke" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Monday, July 26, 2010 7:54 AM
Subject: Re: [time-nuts] Symmetricom X72
Yes, it's because of the various types that you need to verify exactly
what you have. A number of them are made to customer specifications
with undocumented option numbers but if you have anything like an
option 8 then you have the 1Hz to 20MHz version. Beware that to
program the thing you need to provide +5V as well as the +15V to run
it. Along with the output options, there are a slew of options on such
things as ageing and temperature stability. If you have one from a
telecom's cellular tower, it's likely to be of higher spec.
Steve
On 26/07/2010, Bob Camp <[email protected]> wrote:
Hi
One issue with the FE's is they often show up as conversions. Various
sellers take the 1 pps version and hack in a 10 MHz output. There is a
lot
of room for error in the conversion process.
Bob
On Jul 26, 2010, at 7:06 AM, Steve Rooke <[email protected]> wrote:
Brice,
On 26/07/2010, Heathkid <[email protected]> wrote:
Last night, as suggested by several people on this list... I ordered a
Trimble Thunderbolt from Bob Mokia, fluke.l so I should be in pretty
good
shape there to get started once it arrives.
Sounds like your starting on the long path to time-nuttiness :) Bob
has supplied a lot of stuff to people on this list and he will look
after you if anything is amiss.
The counter I mentioned (it's a DFD4 - modified with the tcxo as the
"a"
...
anyway). :) By the way, when I built it, I calibrated it by zero
beating
against WWV at 10 and 20 MHz. That was the best way I had at the time
and
if the DFD4 is now 7 Hz off after all these years... it's not doing so
bad
(based on it's limitations).
Not bad considering it's a TCXO.
So... that's what that counter is for and not for what I'm doing now.
I'm
currently looking for a nice/used HP counter. Please don't think I'm
going
to use the DFD4 for measuring my Rb standards. It's a wonderful
counter
for
what it was designed for and that's it.
Dependant upon what your looking for in a counter, you could broaden
your choices as there are other useful counters out there that may be
more affordable but still as good. Try looking for a Racal-Dana 1992,
preferably with the high stability option timebase (although these
turn up seperately anyway and are a doddle to fit). It makes a nice
footprint 1ns counter and can be referenced to your T'Bolt.
I'm not giving up on the FEI's anytime soon. I understand now that
along
with the Trimble Thunderbolt (and a decent counter) I'll be on my way
to
"getting started".
You'll have to see if those FEI's are the programmable types which can
be set to produce frequencies up to 20MHz. Do they have jut the D'Sub
connector or have an RF connector as well. There are different
variants of these produced by FEI under the same product code.
73 de Steve ZL3TUV & G8KVD
73 Brice KA8MAV
----- Original Message -----
From: "Steve Rooke" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Sunday, July 25, 2010 8:40 AM
Subject: Re: [time-nuts] Symmetricom X72
Excuse my replying to my own posting please.
This post is really about the DFD1 frequency counter.
Heathkid: You are comparing a Rb against a frequency counter with a
TCXO that you tweaked yourself to calibrate it against no known
frequency standard. Try running the three FEI-5660s for 24 hours and
then measure the output of each with your frequency counter. Pick the
mean of them and adjust your DFD1 to match that. At least you should
be in a better position than you are now.
As you built the DFD1 yourself, you should have the schematic and may
be able to engineer in a connection for an external reference. There
is plenty of people here who would be happy to advise you on a
suitable interface if you can attach the part of the circuit where the
TCXO is located. If you do get a T'Both, you would be able to use it
as a reference or, perhaps, build in one of the FEI-5660s as an
internal reference. The limiting factor though is how good is the
circuit used in the DFD1 which will limit it's stability and accuracy.
There are many factors, including input circuit, voltage regulation,
counter stage design, level detection, etc. which have a major impact
here. What I'm getting at is that to write-off a bunch of FEI-5660s
after checking them with such a device as this, is a very poor
decision.
Maybe you could look at a better counter on fleeBay before you make
further assumptions.
73,
Steve
On 26/07/2010, Steve Rooke <[email protected]> wrote:
Sage advice Bill!
Heathkid, you don't need another Rb unit when you have 3 perfectly
decent ones! You really need a standard to calibrate your Rb units
to,
a Trimble Thunderbolt is likely to be the cheapest choice for you.
Bob
Mokia, fluke.l, on fleeBay sells them separately or as a starter kit
with everything there to get you going. Once you have this up and
running for quite some time and see that things are looking stable in
the Lady Heather application, then you can start to think about
calibrating the FEI-5680's but only after you have run them in well.
I
don't know your counter but does it have an input for an external
reference source? If so you will be able to use the T'Bolt as an
external reference for it, providing the required reference is 10MHz.
If it's not, you can divide down the T'Bolt's output to match. If
your
frequency counter has no reference input (apart from throwing it in
the bin) you should be able to engineer it into the instrument,
depending on your skill set.
So, first get yourself a frequency standard to work with, IE. a
T'Bolt
or the like.
My 2c worth,
Steve
On 25/07/2010, WB6BNQ <[email protected]> wrote:
To Bob and Stan (W1LE),
[p.s. But not just to you two alone]
Why complicate the answers to Heathkid (now Brice KA8MAV) with a
bunch
of
different directions that should only be decided after one gains
enough
knowledge and understanding (they are not the same) to properly
grasp
the
subject matter ? ? ? ?
Clearly Heathkid needs some guidance. The form should be to start
out
with
the very basics and get his feet on the ground. He already has
three
(3)
Rb
sources that should keep him busy for quite some time. However, his
counter
is really junk from a lab point of view. Nonetheless, even it can
be
useful
if it is understood how to apply it after understanding its
limitations.
What Heathkid needs to understand is it is not about equipment. It
is
all
about how to measure and account for errors and unknowns. Actually,
quite
a
daunting task depending upon the level of achievement.
I agree he needs some kind of external reference and I agree the
Trimble
Thunderbolt (Tbolt) would be the right item for his true reference.
Even
the Tbolt has its issues that need to be understood.
He will also need a method of comparison. The oscilloscope is a
good
start
but very tedious. Here Burt's project would help him a lot when
Burt
gets
it done. I guess he is close. I guess, also, the PICTIC II would
fit
the
bill after he understands what it is.
Still he needs to understand how to apply and use this stuff.
Confusing
him
with suggesting all of the different Rb sources available is only
making
him
think a better one { relative statement } would be the answer which
is
not
true. His FEI-5680's are so much better for his particular level,
it
is
not
even funny.
What has not been asked of him is what are his goals and intentions.
If
it
is to just say you have an atomic frequency reference, then sit the
FEI-5680
on the coffee table; job done. One cannot be properly guided if the
goals
are unknown.
Bill....WB6BNQ
Bob Camp wrote:
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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--
Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at
once.
- Einstein
--
Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
- Einstein
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--
Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
- Einstein
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--
Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
- Einstein
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