[time-nuts] Efratom 10Mhz frequency standard from Fluke.l

EB4APL eb4apl at cembreros.jazztel.es
Sun Feb 13 23:21:25 UTC 2011


Hi,

Since David asked about levels, I connected the unit and got these figures:

Sine output: 2.8 VPP when loaded with 50 Ohm, internal capacitor coupled
Square wave: 0 to +2.5 V  loaded with 50 Ohm.
There are other two internal SMA connectors with TTL levels: one is the 
inverted comparator output and the other is from one of the buffer outputs.

Initial current is .35 A at startup, decreasing to .16 A in about 10 
minutes, when the oven reached its working temperature.

If you want other measurements, pictures, etc., let me know.

Regards,
Ignacio


El 13/02/2011 18:48, EB4APL wrote:
> David,
>
> I I told yesterday it was too late for writing an explanation.  Here 
> it is.
>
> I bought one of these units around last June, my intended use was to 
> distribute the 10 MHz from my Rb oscillator to be used as the 
> reference for various synthesizers and counters in my home lab.  I 
> didn't put it to use yet, but I made some test with the gadget and 
> this is what I found:
>
> - The power supply should be some 15V, not 12 as announced.  There is 
> a 3 pin 12 volt linear regulator7812CT which needs some overhead to 
> work, and a DC-DC converter to generate +5V which is specified at 15V 
> input and in fact it doesn't work well below it.
>
> - The 10 MHz oscillator is a EFRATOM 105243-003 and there is a jumper 
> for selecting this oscillator or an external 10 MHz input.  The 
> circuit has a 8.7 V regulator built with a 431 programmable zener with 
> an opamp and a multiturn pot which is accessible from outside for 
> adjusting the oscillator frequency.  There is also a hole in the 
> oscillator for adjusting the frequency.
>
> - The oscillator output is squared with an unknown comparator and fed 
> to the inputs of what seems to be a 74ACT244DW which 8 outputs drive 
> the output connectors through coupling networks.  The PCB has 
> provisions for 8 SMA output connectors, with only 4 populated.  I 
> bought a bunch of identical connectors from other supplier and I'll 
> install them when I'll put the unit into operation, I'll only have to 
> drill 4 holes for them in the case and solder the output networks, 
> nothing critical.
>
> - Currently the unit has 2 output networks configured for square wave 
> output (just a 50 ohm resistor in series) and the 2 remaining for sine 
> wave output.  In this case the network consist on a 50 Ohm series 
> resistor, a pi LC filter a and a series capacitor. According to the 
> silkscreen labels it was the manufacturer intended configuration.  It 
> is easy to transform any output for square or sine because the parts 
> are smd but of reasonable size.
>
> - I don't have the means to measure the jitter or phase noise 
> introduced by this schema, but any expert here could give his opinion 
> about it.  The ovenized oscillator on my unit doesn't perform very 
> well in terms of aging or time to stabilize, it is worse that my other 
> oscillators ( ) from the same source, I compared them with my Rb and 
> maybe I didn't waited enough days, but anyway the others 2 were very 
> stable after 1 week and this one not.
>
> -. I don't know the exact parts used for the comparator and the buffer 
> because the tops have been filed.  When I reverse engineered the 
> schematic I offered it to fluke.l, in the believe that it could be 
> useful for his customers but his answer suggested that he had filed 
> the IDs in the fear of other Chinese competition could copy his 
> modifications and refused to give me the parts numbers.
>
> If you want more info don't hesitate to ask for it.
>
> Regards,
> Ignacio, EB4APL
>
>
>
> El 12/02/2011 22:03, Dave M wrote:
>> Does anyone have any experience or knowledge of the "Efratom Multiplexed
>> output 10Mhz frequency standard" from Fluke.l on EBay (item 
>> 290329156915)?
>> I wonder if it could be used as a distribution amp, but no details about
>> output impedance, output current capability, etc.  He indicates that the
>> output voltage is 1.8 - 2.3 volts (doesn't say if it's open circuit or
>> terminated).  From the images on the listing, looks like he didn't 
>> terminate
>> any of the lines to the counters or scopes.
>>
>> Thanks
>> David
>> dgminala at mediacombb dot net
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