[Amps] Time for New Power Meter

[John Simmons]

I worked 27 years at a Motorola Service Shop. We had about 8 Bird 
wattmeters. NONE of them agreed with each other.... and more than 5%!

Measuring RF power accurately is very difficult. Have you ever seen a 
wattmeter that has been certified calibrated to any standard? No, 
because it is impossible.

Why are so many hams obsessed with accurate power measurements? Go figure.

Want to be assured of an accurate power measurement? Buy 10 of your 
'most accurate' wattmeters, take a measurement with all 10, then average 
the reading.

73,
John NI0K
> Jim Thomson <mailto:jim.thom at telus.net>
> Saturday, May 02, 2015 5:44 AM
> Date: Fri, 1 May 2015 11:16:58 -0400
> From: Gerald Williamson via Amps <amps at contesting.com>
> To: drkirkby at kirkbymicrowave.co.uk, k7fm at teleport.com
> Cc: amps at contesting.com
> Subject: Re: [Amps] Time for New Power Meter
>
> Hi All, I also use a Bird 43 as a gold standard. Why? Because I have it
> already. A 5% error amounts to about .2 dB which is close enough for my
> amateur needs.
>
> The capability of easily changing connectors is a plus not available on
> most if not all of the other meters.
>
> Maybe we should call the 43 a "Brown Standard"?
>
> 73,
> Gerald K5GW
>
> ## What freq does bird /cd calibrate their slugs on ?? talking abt the 
> typ 2-30 mhz slug.
> On a side note, IF a CD pep board is installed, or the model 83000 is 
> used, the accuracy is
> +/- 7%.....when switched to pep mode. When a bird pep board is 
> installed on a bird 43, the
> accuracy is now +./- 8%...when switched to pep mode. Both are +/- 5% 
> in average mode.
>
> ## The problem with the bird /cd meters /slugs is... they are +/- 
> 5/7/8 % of full scale...any where on the scale.
> IE: 5% of a 1 kw slug = 50 watts. So if meter reads 800 watts....the 
> true pwr could be 750w...and meter
> is reading 50 watts high. Or true pwr could be 850 watts..and meter is 
> reading 50 watts low.
>
> ## If meter reads 100 watts.... true power could be as little as 50 
> watts......or as high as 150w. In this
> last case, the error could vary from 50-100% outa whack. Bottom line 
> is..u gotta use the smallest slug
> for the job.
>
> ## with a 5 kw slug, my L4B reads 700w. ( low power mode, 1900v). With 
> a 2.5 kw slug, it then reads 650w.
> With a 1 kw slug, it no reads 625 watts..which is very close to dead on.
> Dunno if a bird slug is most accurate on the freq its calibrated 
> for..vs extremes in freq. IE: IF they calibrate it
> at say 16 mhz..... what is accuracy at 2 mhz + also 30 mhz.
>
> ## IMO, the array solutions power master blows both the bird /cd slugs 
> away..hands down. If u don’t like their
> NIST calibration, u are free to re-calibrate it urself.... since the 
> calibration can be changed in 1% increments....
> and with a +/- 15% range. +/- 15%...in 1% increments is as good as is 
> gets. The calibration points are printed on each
> individual coupler..for both frwd and rvs power...for both HF...and 
> again for 6m. 160-6m on one coupler is pretty good.
> Then they have couplers for 144/220/432 etc.
>
> ## with no high swr alarm etc, etc, the bird doesnt cut it anymore. 
> Bird doesn’t sell wattmeters...they sell slugs.
> The only advantage the bird /cd has..is it reads average power if u 
> want to. the array solutions will only read pep.
> U cant see the effects of increased average power when using processor 
> on ssb mode.
> Flip side is..the pep bargraph on the array solutions wattmeter is so 
> sensitive, it will easily show..dithering
> when 3 % ripple is present on a B+ supply..which is typ when 8 series 
> 200 ufs cap are used. Any RF scope
> will also show that effect.
>
> ## the only connectors I use are SO-239 and also 7-16 DIN. I don’t use 
> Type N.... but can easily add an inter series
> adaptor if needed. My 3 kw coupler get the so-239....and my 10 kw 
> coupler gets the 7-16 din.
>
> Jim VE7RF
>
> adaptpr
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