[UK-CONTEST] Power Limitations

[G4FNL]

Hi Bob

I would suggest that you're on a losing side here with your ERP arguments.
The ERP argument doesn't allow for the variables at HF that exists at VHF
such as the antenna height above ground and the angle of radiation. On VHF
perhaps you can be reasonably accurate with ERP calculations - but it's
entirely different (thank goodness) on HF. 

73 Graham G4FNL 

PS - I think this thread has surely run its course now........



-----Original Message-----
From: uk-contest-bounces at contesting.com
[mailto:uk-contest-bounces at contesting.com] On Behalf Of Rob Harrison
Sent: 28 January 2012 17:13
To: Ray Hills; uk-contest at contesting.com
Subject: Re: [UK-CONTEST] Power Limitations

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
>
> _______________________________________________
> UK-Contest mailing list
> UK-Contest at contesting.com
> http://lists.contesting.com/mailman/listinfo/uk-contest 

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