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@telus.net>
Saturday, May 02, 2015 5:44 AM
Date: Fri, 1 May 2015 11:16:58 -0400
From: Gerald Williamson via Amps <amps@contesting.com>
To: drkirkby@kirkbymicrowave.co.uk, k7fm@teleport.com
Cc: amps@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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