There have been many questions posted here about the units, here are a few
answers I have collected:
1. the 8140 can drive up to 25 total downstream 8410T taps on the combined
outputs. The mopdels are frequency specific, and are not easily changed, 10Mhz
is the most common. The front selector provides TTL divided waveforms from the
input rear clock.
2. yes, the taps are needed, as the output of the 8140 itself is a sinewave and
+12VDC. using the tap allows long cable distances, and provides the extracted,
buffered sinewave. long cable runs of RG58 up to 500 feet are possible, with
T-taps all along the way, and all 4 outputs can have long runs. the manual says
a capactively coupled 50 ohm load is meant to terminate the line, but I have not
found it to be required so far, as the sine wave drive produces very little ringing.
3. yes, it works WITHOUT the taps, if you add a 0.47uF good quality cap in
series with each BNC output, run distance is then short into 50 ohms.
4. YES, taps are different, if you have a 10Mhz source, you must have 10Mhz taps
(8410T10). beware of the 8410TTL10, it has a TTL 10 Mhz output, not a sinewave.
5. the operating quality of the system is excellent, do not be deterred by it's
modest appearance, it works just as well as the racal, fluke and hp distribution
amps I have and use. Late ones are much better made (they have black, not blue
vinyl tops), if you can score one.
6. Phasing: my measurements show approximately a 190 degree phase difference
between the input sine, and the output waveform at 10Mhz...not an issue for me,
but maybe for others?
7. The system checks for DC output shorts (excessive loading) and loss of input
clock, these drive the red front indicator (output fault). An option can also
drive a sonalert.
8. the taps are not generally repairable, as they are potted with foam. bummer.
9. System details, and downloads are here at Spectracom:
http://www.spectracomcorp.com/ProductsServices/TimingSynchronization/TimeandFrequencyDistribution/8140FrequencyDistributionSystem/tabid/133/Default.aspx
10. Note, there are no schematics for Taps, if anybody has some to send me, I'd
really appreciate it, just to satisfy my curiosity.
so, if you find one in good condition, it is a great addition to your lab, for
distributing your master reference all around the shop area to counters,
spectrum analyzers, generators, etc. it works with literally all common clock
sources, from 0.3Vrms to 2Vrms, should be a sine wave.
regards,
walter
Walter Shawlee 2, President - Sphere Research Corporation
3394 Sunnyside Road, Kelowna, B.C., CANADA V1Z 2V4
URL: http://www.sphere.bc.ca E-Mail: walt...@sphere.bc.ca
Phone: +1 (250) 769-1834 Fax: +1 (250) 769-4106
--Home of the Slide Rule Universe--
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