Jim, LFers
Jim Moritz M0BMU wrote:
I have some samples of old trans-atlantic telephone coax cable - according to
the labels, they are from the TAT-1, TAT-II and CANTAT-2 cables. Measuring
the dimensions of these, they work out to Zo of 57, 45, and 55 ohms
respectively.
I have an ITT technical journal, "Electrical Communication" from 1974 that
contains
some detailed articles about the Cantat-2 cable, 36 pages in all. Very
interesting
reading. One of the articles says that the cable Z was 54 ohms, so you were
close.
The cable had 473 repeaters and it was fed with +7kV at one end and -5.4 kV
(adjustable -3.8..-7kV for compensation during magnetic storms) at the other
end.
The current was 490 mA.
I imagine they must have been designed with low loss in mind;
Probably :-) According to the ITT publication, the total loss at the highest
frequency
(14MHz) was over 18360 dB (yes, read it again!). In comparison, an EME path will
look like a short piece of copper wire...
73
Johan Bodin SM6LKM
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