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From: John W Gould <jwgould@iee.org.uk>
Date: Fri, 25 May 2007 18:28:48 GMT
Message-ID: <Zen-1HreWu-0007OO-MQ@pythagoras.zen.co.uk>
Subject: Re: LF: 500 khz ERP
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Mal, thanks for your input, all noted.  

73 John, G3WKL

Hamilton Mal <g3kev.ham@virgin.net> wrote :

> In response to recent emails about the requirement for more RF out on 500
> khz I am of the opinion that ERP is the way forward.
> 10W erp would be a realistic start and preferably 20W erp, this approach
> would encourage amplifier and antenna design and research on 500 khz.
> At present we have reached stalemate with the 0.1w erp restriction, limiting
> communications to the UK during daytime and during the dark hours to a few
> countries in near EU. There is virtually no hope at present to research
> propagation or work DX on a more international scale.
> To justify my ERP argument and keep the maths simple, look at examples
> below.
> 
> 1. 10W rf output to the antenna and an efficiency of the average antenna 1%
> the ERP would be 0.1W erp, this would be no improvement from the current
> position, increase it to 20W and we get 0.2W again this would be
> insignificent. You would need a lot of Watts to get any real change.
> 
> 2. 10W ERP and the same 1% efficiency would require 1Kw output to the
> antenna and this is the sort of increase that is required for meaningfull
> international communications and propagation studies.
> This power level is modest compared to the commercial users of the past like
> ships and costal stations. Most ships installations were running  1000 watts
> give or take a little and more with good antennas especially on the larger
> ships. Even with this power during daytime the coverage was only in the
> region of a few hundred miles, even sorrounded by the ideal salt water
> earth. Night time was different with longer range but required these powers
> to work back to the appropriate shore stations.
> The transmitter PA tube installations that I encountered were 2 x 4-400, 1 x
> 4cx 1500 b, 4 x 4c250b or 1 x 4-1000a, these seemed to be the norm.
> There were some /MM with less power but this was rare except for emergency
> transmitters.
> The above is an example of my experience and opinion, although from what I
> have read so far on this reflector the ERP approach is the favourite.
> 
> 73 de Mal/G3KEV