Topband
[Top] [All Lists]

TopBand: Re: [AMPS] Bird Wattmeter Error on all bands

To: <topband@contesting.com>
Subject: TopBand: Re: [AMPS] Bird Wattmeter Error on all bands
From: w8ji.tom@MCIONE.com (Tom Rauch)
Date: Mon, 01 Jun 1998 09:26:23 +0000
To: <topband@contesting.com>
> Date:          Mon, 01 Jun 1998 00:07:40 -0500
>
> The standard Bird HF slugs like we all use are marked 2-30 mhz. I
> always figured that 1.830 mhz was close enough to the edge to not
> make any difference. Not so...there is a 10% error on the low side
> in the reading!

The standard Bird 43 meter meter and slug has a published error of 
plus or minus 5% of full scale anywhere on the scale.

(That's why a Bird often shows incorrect SWR readings when a high 
power slug is turned around.)

If you have a 2500 watt slug, and are reading 1500 watts forward 
power into a pure 50 ohm load, the actual forward power is anywhere 
from 1625 watts to 1375 watts if the meter is within tolerance. + or 
- 5% of 2500 is + or - 125 watts, and that is the tolerance ANYWHERE 
on the scale ANYWHERE over the slugs range.

If the a Bird 43 indicates 150 watts reflected power with a 2500 watt 
slug, the actual reflected power can range from 25 to 275 watts. 

73, Tom W8JI
w8ji.tom@MCIONE.com

--
FAQ on WWW:               http://www.contesting.com/topband.html
Submissions:              topband@contesting.com
Administrative requests:  topband-REQUEST@contesting.com
Problems:                 owner-topband@contesting.com

<Prev in Thread] Current Thread [Next in Thread>