Message-ID: <000a01c31588$e7869bc0$162965d5@oemcomputer>
From: "Johan Bodin" <sm6lkm.jbeab@swipnet.se>
To: rsgb_lf_group@blacksheep.org
References: <5.1.0.14.0.20030430120518.00ade070@gemini.herts.ac.uk> <001501c31001$6a079780$bee5fc3e@l8p8y6> <5.1.0.14.0.20030502115241.025564e8@gemini.herts.ac.uk> <5.1.0.14.0.20030508141801.00b0dfb8@gemini.herts.ac.uk>
Date: Thu, 8 May 2003 19:39:46 +0200
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Subject: Re: LF: Mains Cable and other transmission lines
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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