[UK-CONTEST] Power Limitations

[Rob Harrison]

Hi Ray,

Most antenna gains are specified by the manufacturers, and at VHF/UHF in a 
well designed yagi, the boom length tends to set the gain. So we have 
published figures for manufactured, and ballpark for any other. If you are 
saying the former figures are over inflated, then you need to find out by 
how much or get a better/newer antenna to modern design.

Regards computer modelling, the latest programs are extremely accurate. Not 
sure who you are referring to, but my new 24 ele is at least as good as my 
old 2x21 Tonnas.

Bob G8HGN




----- Original Message ----- 
From: "Ray Hills" <g3hrh at btinternet.com>
To: <uk-contest at contesting.com>
Sent: Saturday, January 28, 2012 4:58 PM
Subject: [UK-CONTEST] Power Limitations


> Bob (HGN),
>
> When in employment, one of my responsibilities was the procurement of
> transmitting antennas for the IBA high power UHF TV sites.  These were
> custom built to a pretty detailed template (impedance, HRP, VRP) and were
> all measured on a calibrated test range before acceptance.  Even in those
> circumstances the measurements were subject to something like +/- 0.5 dB
> accuracy.  I doubt that the manufacturers of antennas for amateur use
> achieve anywhere near that accuracy.  Certainly there is one source which, 
> I
> have been told, relies solely on computer modelling without any practical
> verification.  After all, 1dB is 10% of the power.
>
> For any amateur, accurate measurement of power is readily achieved.
> Measurement of ERP is another story.
>
> Ray G3HRH
>
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