[time-nuts] FE5680A Calibration

Bob Camp lists at rtty.us
Thu Mar 15 16:25:33 UTC 2012


Hi

Drive the GPS pps into the set input on a flip flop, drive the pps from the
FE into the reset input. Use the UC10 to measure the period of the waveform
on the Q output. Not super high resolution, but if you are patient, you can
get the job done.

Bob 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of David
Sent: Wednesday, March 14, 2012 7:34 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FE5680A Calibration

I picked up a gimpy Beckman UC10 universal counter not long ago for
about $10 from Ebay.  Even better, I just repaired a Tektronix 7D15
(it has a whole board full of those junk TI integrated circuit sockets
which need to be replaced) although you need to leave an entire
oscilloscope mainframe on to use it.  The advantage of the later is
adjustable slope, sensitivity, and triggering.

On Wed, 14 Mar 2012 17:50:28 -0400, Bob Camp <lists at rtty.us> wrote:

>At least the "don't mess to much with it" part has sunk in. That puts you
ahead of most people at this point.
>
>A usable counter should be a sub $100 sort of thing either at auction or
surplus. With some careful shopping it can be a sub $40 item.
>
>On Mar 14, 2012, at 4:25 PM, "Chris Stake" <stake at btinternet.com> wrote:
>
>> Hi Bob,
>> Thanks for pointing-out the noisy output of the FE5680A. I'll probably
try
>> to lock a crystal oscillator to it.
>> Unfortunately I don't have a suitable counter.
>> I was hoping I could use some sort of higher frequency standard but I
>> confess I had not really grasped the fact that the unit may well be
within
>> millihertz of the nominal frequency: too delicate to twiddle with
anything
>> other than precision equipment and long timebases.
>> Kind regards
>> Chris
>> 
>>> -----Original Message-----
>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>>> Behalf Of Bob Camp
>>> Sent: 14 March 2012 16:57
>>> To: 'Discussion of precise time and frequency measurement'
>>> Subject: Re: [time-nuts] FE5680A Calibration
>>> 
>>> Hi
>>> 
>>> Do you have a dual channel counter that you can put the GPS into on the
>>> "start" and the FE into as the "stop"? The HP 5334, 5335, and 5345 are
all
>>> examples of this sort of counter.
>>> 
>>> Bob
>>> 
>>> -----Original Message-----
>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>>> Behalf Of Chris Stake
>>> Sent: Wednesday, March 14, 2012 12:49 PM
>>> To: 'Discussion of precise time and frequency measurement'
>>> Subject: Re: [time-nuts] FE5680A Calibration
>>> 
>>> Nice idea,
>>> But I haven't got a DSO and the persistence of my scope isn't good
enough
>>> to
>>> view 10Mhz sampled at 1pps.
>>> Chris
>>> 
>>>> -----Original Message-----
>>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>>>> Behalf Of EB4APL
>>>> Sent: 14 March 2012 15:46
>>>> To: time-nuts at febo.com
>>>> Subject: Re: [time-nuts] FE5680A Calibration
>>>> 
>>>> My fast approach would be to trigger a scope with the 1 PPS from the
GPS
>>>> receiver and observe the how the 10 MHz output of your Rb drifts.  1
>>>> full cycle per second is 1 e-7 so you'll need to use an stopwatch to
>>>> time long periods when you are fine adjusting .
>>>> Building (or buying) a GPSDO allows yo to make the comparison between
>>>> both 10 MHz outputs without the jitter in the GPS receiver 1 PPS.
>>>> Probably others in this list can suggest more elaborated and convenient
>>>> approaches to this.
>>>> 
>>>> On 14/03/2012 16:17, Chris Stake wrote:
>>>>> Hello all,
>>>>> 
>>>>> I purchased a FE5680A from a Chinese  Ebay vendor. I have connected it
>>>> to a
>>>>> 16.5V laptop supply, added 7805-based 5V rail and a PMOS Fet switch to
>>>> drive
>>>>> a LED for the "locked" signal. I can communicate with it using the
>>>> excellent
>>>>> Fe5680Calibrator software. As received the frequency offset is set to
>>>> Zero
>>>>> and the unit seems to work well.
>>>>> 
>>>>> I plan to put it into service as a workshop frequency reference and so
>>>> would
>>>>> like to set it close to 10.0Mhz. I have various oscillator modules,
>>>> signal
>>>>> generators, SDR receivers, GPS receivers, a scanner, some uncalibrated
>>>>> test-gear. I live in a river valley in North Devon UK so radio
>>> reception
>>>> is
>>>>> a bit restricted but I receive digital television via a masthead
>>>> amplifier
>>>>> and long downlead.
>>>>> 
>>>>> Could someone please suggest a way of going about this?
>>>>> 
>>>>> 
>>>>> 
>>>>> Regards
>>>>> 
>>>>> Chris Stake
>>>>> 
>>>>> 
>>>>> 
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>>>>> 
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