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 <[email protected]>
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
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