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To: <rsgb_lf_group@blacksheep.org>
From: John W Gould <jwgould@iee.org.uk>
Date: Fri, 25 May 2007 07:29:58 GMT
Message-ID: <Zen-1HrUFK-0002wE-G7@rutherford.zen.co.uk>
Subject: Re: LF: RE: 500kHz Distance
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Jim, thanks for clarifying - I thought that you were opting more for the existing ERP approach.  

I feel that we are more likely to get a better response asking for an increase in ERP as this is easier for Ofcom to assess in terms of coordination, is consistent with some other bands and also our original request back in 2004.  

Aerial efficiency experiments apart an increase in ERP would allow more experimentation to be done over longer paths, which in terms of providing technical understanding to support a case for Amateur service access in some future WRC agenda item would be very beneficial.

73 John, G3WKL

James Moritz <james.moritz@btopenworld.com> wrote :

> Dear John, LF Group,
> 
> As a simple answer, I would favour sticking with an ERP limit - based on the
> present experience the existing 0.1W ERP limit is adequate for a UK-only
> band, but if we are looking towards an international 500kHz band, it seems a
> bit low if international amateur communications using "conventional" HF-like
> techniques are going to be possible on a routine basis over the longer
> distances. There doesn't seem to be any problems due to the existing 0.1W
> level on 500kHz, and 1W ERP is still very low compared  to other spectrum
> users in this frequency range. So if the possibility of an increased ERP
> limit exists, I would go for at least 1W ERP, or more if you feel it could
> be justified to Ofcom.
> 
> A TX output power limit by itself would be OK, provided that power limit was
> quite high. But if Ofcom are concerned to limit the maximum field strength
> due to amateur transmissions, then they would have to specify low maximum
> power to cover the case of an amateur using a relatively efficient antenna
> with the "legal limit" TX power. A low TX power would then severely restrict
> the possibilities of the band for stations with small antennas and very
> limited possibilities for improving them.
> 
> Rik's suggestion is quite nice from an amateur's point of view, in that it
> gives an "incentive" to produce more efficient antennas, but at the same
> time would allow stations who are unable to put up efficient antennas due to
> restricted space, etc., still to produce a usable signal by throwing more
> power at the antenna. But I think it could be difficult to sell such a
> proposal to Ofcom. For the sake of argument, take Rik's figures - in
> principle, there is no limit to the ERP that could be obtained with 20W TX
> power limit, given gain antennas. Practical large amateur antennas could
> give at least several watts ERP with 20W TX power. If Ofcom accept this,
> what is the motivation from a regulatory viewpoint for restricting amateurs
> with inefficient antennas to 100mW ERP? Why would they care how much power
> the transmitter generates, provided the actual amount of power radiated
> remains reasonably low?
> 
> Cheers, Jim Moritz
> 73 de M0BMU