[time-nuts] Symmetricom X72

Bob Camp lists at rtty.us
Sun Jul 25 17:22:42 EDT 2010


Hi

A couple others to put on the list:

HP 5335
HP 5365
HP 5370(A and B)
HP 5371

All of them come up "from time to time" at prices that are all over the map. The 70 and 71 are a pretty good deal if you can get them for less than $200. The 65 and 35 should be below $150. They all show up with nonsense prices (> $1,000) on a regular basis. I can think of no reason to pay over $300 for any of them. 

Bob


On Jul 25, 2010, at 4:57 PM, Said Jackson wrote:

> Hi Brice,
> 
> One of the best low cost counters is an hp 5334a. Get the one with internal memory (b model?)
> 
> The 1.3ghz third input is also great. You can find them starting at $125.
> 
> If you average for 99 seconds and do offset, it gives you 11 digits of resolution for low $$. 9 digits with 1s gate time.
> 
> Most importantly: it does not have a fan. Some counters like 53132a have fans that run even if the counter is off that can drive you nuts.. 
> 
> Bye, Said
> 
> Sent from my iPad
> 
> On Jul 25, 2010, at 9:55, "Heathkid" <heathkid at heathkid.com> wrote:
> 
>> 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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