[time-nuts] Symmetricom X72

Heathkid heathkid at heathkid.com
Sat Jul 24 21:46:28 UTC 2010


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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