Bird 43 Wattmeter calibration

[Julius Fazekas n2wn]

Hello All,

Does anyone have any suggestions for calibrating a
Bird 43 and the respective slugs? I picked up a used
one and would like to check it out.

Thanks,
Julius
n2wn
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[Stuart Rohre]

There are no user adjustments on the slug or pickup of the Bird that I am
aware of.

You could check it against some other known standard and construct a graph
paper of differences, but the Bird is good plus or minus 5 per cent about as
good as it gets for RF unless you go to high dollar calorimetric measuring
devices.

Check the Bird web site and see what they say about user calibration or not.
The whole idea of a Bird, is a mechanically robust pick up and fixed slug
that plugs in and out.

Now the meter might get off, but that too is mostly rezeroing the mechanical
zero stop.
73,
Stuart
K5KVH


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[marion-22]

> Hello All,
>
> Does anyone have any suggestions for calibrating a
> Bird 43 and the respective slugs? I picked up a used
> one and would like to check it out.
>
> Thanks,
> Julius
> n2wn
>

 Lab cal is done by puting power through it measured with a
known standard. Adjustment is done with pot acessable
after prying off metal label. Check at highest and lowest
and in the middle somewere. Bird rates them at +/- 5%, but
I have yet to see one better than +/- 10%. They are great
for rugged outdoor use, and peaking signal, but no one
I know relies on them for precise measurements of power.
                                                Roy AB7CE
                                                NIST RF Lab Tech



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[W0rw]

Put a good dummy load on your transmitter, set the frequency within the range
of the plug, turn on CW,  and use a calibrated scope to measure the peak to
peak voltage.

Power = (Vp-p)^2/400 for 50 ohms.

Paul w0rw
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[Geoffrey Mackenzie-Kennedy-2]

Julius,

Sorry it has been 30+ years since I had the beast, and gave it away when I
left VEland. Have you tried asking somebody in the test equipment department
of your local friendly communications / broadcast company? You might even
extract a copy of the 43's manual.

73,

Geoff     GM4ESD

----- Original Message -----
From: "J F" <[hidden email]>
To: <[hidden email]>
Sent: Wednesday, September 29, 2004 7:10 PM
Subject: [Elecraft] Bird 43 Wattmeter calibration

> Hello All,
>
> Does anyone have any suggestions for calibrating a
> Bird 43 and the respective slugs? I picked up a used
> one and would like to check it out.
>
> Thanks,
> Julius
> n2wn
>

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[Ron D'Eau Claire-2]

Where the Birds got a great reputation as the "Standard" was that every time
an FCC engineer would show up on site with the FCC test equipment to check
the output power of a transmitter, he would be carrying a Bird.

And he was a lot 'easier going' if there was a discrepancy and the
maintenance tech drug out the station's Bird and showed that the discrepancy
was in the meters. I even had one FCC field engineer doing the annual
inspection on a ship tell me "Don't bother to change the output power. I'll
have this meter checked at the lab and give you a call if there's an issue."


That, and the incredible ruggedness of the Bird design has given them a
mystique all their own...

I have no idea how accurate they really are. As far as I'm concerned even a
20% error is meaningless in terms of range and signal strength in
communications equipment. I think the one I was hauling around on ships in
the early 1990s had a calibration sticker on it dated in the 1960's.

Ron AC7AC
--------------------------------------------------

 Lab cal is done by puting power through it measured with a known standard.
Adjustment is done with pot acessable after prying off metal label. Check at
highest and lowest and in the middle somewere. Bird rates them at +/- 5%,
but I have yet to see one better than +/- 10%. They are great for rugged
outdoor use, and peaking signal, but no one I know relies on them for
precise measurements of power.
                                                Roy AB7CE
                                                NIST RF Lab Tech


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[Jim Wiley-2]

Actually, the Bird type 43 wattmeter elements ("slugs") do have a
calibration adjustment, but it is done at the factory.  The trimmer is
located underneath the "frequency range & power" label, which is glued
to the top of the element.  This adjustment is done once at the factory,
and unless one of the components inside the element has been damaged,
does not need adjustment.  A damaged slug usually makes itself known by
being totally inoperative.  If you are unsure about the condition of a
particular element, a quick comparison check between a known good unit
will tell you all you  need to know.  Remember that because of
calibration tolerances, you might see as much as 10% difference between
two good elements.

- Jim,  KL7CC


J F wrote:

>Hello All,
>
>Does anyone have any suggestions for calibrating a
>Bird 43 and the respective slugs? I picked up a used
>one and would like to check it out.
>
>Thanks,
>Julius
>n2wn
>_______________________________________________
>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft   
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com
>
>  
>

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[G3VVT]

 
As well as the individual calibration on the slugs there is another  
calibration pot inside the Bird 43 feeding the meter movement if my memory is  correct.
 
You need to compare the meter and slugs against a known standard or a  
recently calibrated power meter into an accurate dummy load. Installing a  known
good slug would allow you to check out the meter body. If it is within 10%  leave
it as is.
 
"If it ain't broke don't fix it"
 
Bob, G3VVT

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