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Re: [Amps] Bird Element Calibration?

To: G3rzp@aol.com
Subject: Re: [Amps] Bird Element Calibration?
From: David Kirkby <david.kirkby@onetel.net>
Date: Sun, 20 Mar 2005 17:21:31 +0000
List-post: <mailto:amps@contesting.com>
G3rzp@aol.com wrote:

> In a message dated 19/03/2005 22:27:10 GMT Standard Time, 
> philc@texascellnet.com writes:
>
>     but are useless if you
>     > actually want to know the power output.
>
> +/-5% works out, according to my calculator as +/- 0.22dB. Prodigious!!!

It is simply not achievable on Bird 43's - at least not on a regular 
basis. My new element was out of spec the day I got it.

>  If we go look at professional standards for 'Type Approving' 
> equipment, we see that an approved accreditation lab is supposed to 
> measure to +/- 0.75dB at 99.9% certainty. That's nearly 19%.....

I don't know what 'Type Approving' equipment is, but RF power can be 
measured to a lot better than 19%. Using a water Calorimeter an amateur 
should be able to do better than that using a DC/RF substitution method. 
The advantage of that, compared to other techniques, is that it does not 
rely on getting lots of bits of kit calibrated at great cost.
 

>  So personally, I trust the '5%' claim as much as I do a politician.....

Same here.  I *know* is is rubbish. I'm surprised  they have manged to 
get away claiming it for so long.

>  There has been a lot of work done at ETSI, the European 
> Telecommunications Standards Institute, on measurement uncertainty. 
> The reports are pretty major things, but you can download them free 
> from www.etsi.org <http://www.etsi.org>

>  The ones on measurement uncertainty are TR100 028-1 V1.4.1 and TR100 
> 028-2 V1.4.1
>  
> They should help you get to sleep.....

I know there were people who spent most of their working life perfecting 
the measurement of RF power in standards labs. That's not my idea of 
fun, so I won't read the documents.

>  73
>  
> Peter G3RZP



-- 
Dr. David Kirkby, 
G8WRB

Please check out http://www.g8wrb.org/ 
of if you live in Essex http://www.southminster-branch-line.org.uk/



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