[time-nuts] Symmetricom X72

Stan, W1LE stanw1le at verizon.net
Sun Jul 25 12:56:17 EDT 2010


Hello Brice,

I like my HP-5384A freq counter, spec'd to 225 MHz, LCD display and 
enough digits for my ham radio work.
This counter has a small foot print on the bench at ~8.5" wide, 3.5" 
high and 12" deep. low Ac power consumption.
Other older counters have taken up a lot more bench space and electrical 
power.

I use the Trimble T'Bolt as an external 10 MHz reference.

This counter was an upgrade from a HP-5245L/M nixie display counter.
I continue to use a HP-5340A microwave counter, good to 26.5 GHz, LED 
display.

Ebay can be your friend, but the rule of Caveat Emptor still applies, 
either pay the bigger bucks for a vendor's guarantee
or treat it like a flea market item, you will not how it works until you 
get it on your test bench. Bid accordingly.
A permanent search on Ebay can be helpful for specific models you are 
considering.

I have made some scores on Ebay, especially used HP test equipment, but 
I have extraordinary patience.
I have horror stories too.....

Other counters I have considered:
HP-5345
HP/Agilent 53132
Stanford Research Systems model 620

Others will also have some great counter experiences and why a specific 
model satisfied their needs.

Be cautious on the A/B/C models as well as the vendor options.
Most vendors I deal with are simply junque dealers and have no clue as 
to the options and their function.

Stan, W1LE      Cape Cod     FN41sr



On 7/25/2010 12:19 PM, Heathkid wrote:
> Steve,
>
> Thank you for your reply.
>
> 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.
>
> The counter I mentioned (it's a DFD4 - modified with the tcxo as the 
> "a" option wasn't available at the time) is not going to be my primary 
> counter. It's just something I had laying around that I use when I'm 
> working with QRP and QRPp rigs that don't have *any* frequency 
> readout.  I've built a *lot* of tiny transceivers that are either xtal 
> based or use a PTO (you have to learn to love the sound of the chirp 
> but once people learn what it is I'm transmitting with they don't mind 
> as much), or some other form of VFO.  So, a digital readout is quite 
> helpful and necessary, especially with the PTO where the tuning takes 
> place by screwing a 6-32 brass screw in and out of a coil.  That said, 
> I did build it up as a "bench counter" and not a digital display.  It 
> still does what I need it to do (for the ham radios) but there were 
> some mods that were done if you look at the site 
> (http://www.aade.com/DFD4A/dfd4a.htm).  The one I built is actually 
> pictured there.  I know it's not very accurate, precise, or even all 
> that stable. But... once I get a known frequency reference and 
> accurately calibrate it... it'll be better.  Most likely right now 
> it's off around 7 Hz but I usually operate on 40m so at 7.040 MHz +/- 
> a few Hz isn't going to matter much (try adjusting a screw with a knob 
> on the end of it to change the oscillator 1 Hz 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).
>
> 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.
>
> 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".
>
> 73 Brice KA8MAV
>
>
> ----- Original Message ----- From: "Steve Rooke" <sar10538 at gmail.com>
> To: "Discussion of precise time and frequency measurement" 
> <time-nuts at febo.com>
> 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 <sar10538 at gmail.com> 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 <wb6bnq at cox.net> 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" <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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>>>>
>>>>
>>>> _______________________________________________
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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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