[time-nuts] Symmetricom X72

Sun Jul 25 17:22:28 UTC 2010

I bought two HP 5345A's for short money on e-Pay. The second 
one is the organ donor !!
I bought these primarily because it has a 1,000 second gate 
time. When using a GPSDO as the reference, I can resolve down 
to mHz (If I believe that !!). But, the resolution is a lot 
better than the HP's that have a 10 second Gate Time.

73, Dick, W1KSZ

-----Original Message-----
>From: Heathkid <heathkid at heathkid.com>
>Sent: Jul 25, 2010 12:55 PM
>To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
>Subject: Re: [time-nuts] Symmetricom X72
>
>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" <lists at rtty.us>
>To: "Discussion of precise time and frequency measurement" 
><time-nuts at febo.com>
>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" <lists at rtty.us>
>>> To: "Discussion of precise time and frequency measurement" 
>>> <time-nuts at febo.com>
>>> 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" <lists at rtty.us>
>>>>> To: "Discussion of precise time and frequency measurement" 
>>>>> <time-nuts at febo.com>
>>>>> 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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>>>>>>
>>>>>>
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>>>>>
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>>>>
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