|To:||"[email protected]" <[email protected]>|
|Subject:||Re: LF: 33 Hz QRM|
|From:||David Hine <[email protected]>|
|Date:||Tue, 29 Mar 2016 10:19:01 +0000 (UTC)|
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Hi, A very interesting article. The London Underground (Metro) uses a low voltage 4 rail DC system. The 2 'live rails are balanced + and - with regard to the running rails. This system is a 'throw-back' from the days of DC motors and this system reduces corrosion causing currents to flow in the running rails and other track equipment. There is a lot to be said for the self contained diesel units that require no external power supplies with all that infrastructure. Imagine how useless the electric system would be in times of extreme weather or disasters, man made or natural.
The same applies to modern digital radio communications (with all its necessary infrastructure and thousands of tiny transmitters) when compared to the old Long Wave AM broadcasting, where a single large transmitter covers a whole continent. Nowadays 'progress' always results in over-complicated and 'fragile' systems that fail too easily when 'nasty things happen'.
With very kind regards, Dave.
From: Johan Bodin <[email protected]>
To: [email protected]
Sent: Tuesday, 29 March 2016, 8:11
Subject: Re: LF: 33 Hz QRM
That problem can be solved by using a return line and booster transformers that minimises current leakage into surrounding earth:
Den 2016-03-17 kl. 15:18, skrev Andy Talbot:
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