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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