[UK-CONTEST] Re High Power

[Giles Herbert]

Hello,
 
RF exposure at hf frequencies were experienced by BBC Transmitter engineers in increasing levels since the first Empire Service transmissions started in 1932.  Many simultaneous transmissions of hundreds of Kw each were normal for each transmitting site with perhaps only 60 minutes quiet in 24 hours.  Until relatively recently, the selection of aerials was made at the far end of balanced feeders by someone moving flexible tails on the end of the feeder run, to tails to the individual aerials.  Several individual aerials, typically sterba curtain arrays with reflectors, designed for different target areas in the world on different bands but sharing a common bearing are suspended between adjacent masts.  
 
My father joined the BBC in the mid 1930's and quickly settled on HF transmitting sites.  He specialised in aerial theory and maintenance and in the end used this experience to design them.  He married one of the war time Women technical staff that were recruited to fill the vacancies made by conscription, and in due course my brother and I arrived.  Any of you who have seen the HF sites at Rampisham Dorset, Wooferton Shropshire, Skelton A & B in Cumbria or the now defunct Daventry site in Northamptonshire will realise the scale of the operation.  Others on the reflector who have built and or operated such sites can give greater information and the practical operational side of things.  My Father's responsibility was the maintenance and later design of the aerials.  This often meant working in the outdoors among the masts and exposed to the RF fields produced by sum of the transmissions being made at any one time.  His involvement was over the vast majority of the period 1937 to 1969.
 
I am sad to say that my mother died in her 80's and my Father last year at 93.  What is the point of this response?  No amateur, any where in the world, even the Super Super contest stations come anywhere near this sort of RF exposure level and at their maximum, it is only for a fraction of the time.  The avoidance of hysterical press whipping up fear, as in the case of Cell Phone installations and the Sutton Coldfield TV Transmitter site, should be a serious consideration as the proving a negative is near enough impossible, and the failure to do so is taken as proof of a conspiracy to hide the truth.  I do not believe that Amateur radio insurance schemes cover you for the costs of court cases in the same way you can pay £20.00 an get legal assistance coverage with your motor policy.  Nor do I think that the average operator wants picketing members of the general public at our gates. 

 

While sympathetic to these people's worry, I do not agree with their argument and I see little point in offering them unnecessary opportunities.

Giles Herbert
G0NXA
Often QRV 3.716 MHz


 
> Date: Mon, 23 Feb 2009 22:53:05 +0100
> From: f5vnb at orange.fr
> To: uk-contest at contesting.com
> Subject: Re: [UK-CONTEST] Re High Power
> 
> FYI a new regulation has just been introduced for French amateurs, 
> giving them several months to submit details of their eirp on each band. 
> If this becomes a Euro-standard, operation in a crowded UK suburban 
> environment may become a bit more fraught.
> 
> Some of you might find the http://n5xu.ece.utexas.edu/rfsafety/ 
> calculator interesting - although it seems to indicate that I should 
> have been dead thirty years ago after operating QRO with my head ~25ft 
> below a box of 4 x 19el 144MHz yagis. Probably sitting in a null; still 
> got my hair.
> 
> 73 Pete F5VNB/G4PLZ (and G8LEF with those 144 yagis)
> 
> 
> Tim Hague wrote:
> > I think some people calling for higher powers should beware the `Daily 
> > Mail' brigade. I have already seen somewhere a call
> > for a requirement to check the radiated field levels from Amateur 
> > transmitters in neighbors gardens and houses, Its quite possible
> > that a station running 1.5kW to a dipole at 40ft would fall foul of the 
> > ICNIRP levels, especially around 28 MHz where the permitted
> > levels are more stringent.
> > 
> > It may be best not to stir up the vocal unknowing!
> > 
> > Tim M0AFJ
> 
> 
> 
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