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

[Dave M]

Many thanks for the input, Ignacio.  I sent an email to Fluke.l (Bob) asking 
for more details, but haven't received a response yet.  I doubt that he will 
reveal much more info about it than what is in the Ebay description.  Your 
info certainly goes a long way to answer my concerns.
In view of all this, I'll go with a TAPR solution or an Extron video DA.

Cheers,
Dave M


> From: EB4APL <eb4apl at cembreros.jazztel.es>
> Subject: Re: [time-nuts] Efratom 10Mhz frequency standard from Fluke.l

> 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