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LF: RE: 500kHz Distance

To: <[email protected]>
Subject: LF: RE: 500kHz Distance
From: John W Gould <[email protected]>
Date: Wed, 23 May 2007 21:26:01 GMT
Cc: <[email protected]>
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Thought that I had better respond to Laurie's e-mail, now a few days ago.

This is because the matter of the power level is to an extent under review by 
Ofcom.  If you recall we, RSGB, asked back in 2004 for a 1W ERP limit as that 
was consistent with experience at 136kHz.  A ERP limit also gives Ofcom a real 
view as to what the likely coverage would be at any particular bandwidth.  That 
we were offered -10dBW ERP reflects both a bold step by Ofcom and also some 
caution, given that they have to an extent taken an interesting view of ITU 
Radio Regulation 5.58 to our benefit.  RR 5.58 defines 500kHz as an 
international distress and calling frequency for Morse radiotelegraphy.  Ofcom 
may have taken the decision as they may expect to be withdrawn at WRC07, and on 
knowledge that in this part of the world 500kHz is no longer used as an 
international distress calling frequency.  Other authorities have not been so 
minded, as Dick, PA0SE, recently discovered; they prefer to wait until such 
time as RR 5.58 has been deleted.

Whilst we are currently limited to -10dBW RSGB/Ofcom are keeping the matter 
under review and it may be timely, now that we have a good body of experience 
to request that the limit be reconsidered.  As far as I am aware no 
interference complaints, or even local RFI problems have been received, and our 
operating and conformance to licencing conditions have been exemplary.  From 
comments on this group it may be better to request say a 10 or 20W power limit 
at the aerial feed-point, for reasons mentioned by Laurie.  Whatever change to 
the limit is agreed, if indeed any in the near term, it will have to be a 
cautious change until such time as the Radio Regulations are more helpful in 
allowing administrations to consider proper secondary allocation to the Amateur 
service.  This may or may not happen for a while, as we are only really working 
at present to get the matter firmly on the WRC2011 agenda, such is the speed of 
the ITU.  There is good practical reason for making a request of this nature as 
one of the reasons why the ITU process seems so slow is that for normal 
protocol to be followed one needs to have had technical studies completed that 
relate to the new proposals for the part of the spectrum in question.  Our 
activity between 502 and 504kHz, along with that by the US, Germany and Sweden 
may qualify as such a study, so continuing the experiments at a higher power, 
with the added challenge of maximising ERP from a fixed feed-point power limit 
would add some breadth to our work.

Of course, the unexpected could always happen, and we get something sooner in 
the margins of Agenda Item 1.14 at this year's WRC.  However, as Agenda Item 
1.14 is to review the operational procedures and requirements for GMDSS and 
other related provisions our chances are slim, as the Maritime service is 
likely to want to reuse the frequency around 500kHz.  However, it is an agenda 
item concerning this part of the spectrum so the possibility, however distant, 
must be there.

I'd be interested in any further views to Laurie's proposal; I'am open to 
suggestions as to the power level, but it will be important to hit a target 
that is both challenging to the experimenter, helpful for continued propagation 
research and also one that will not provide too much risk for Ofcom in terms of 
coordination with the primary user service.

73 John, G3WKL
RSGB HF Manager
IARU Region 1 LF Coordinator






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