[Amps] Intermittent Bird element

[Paul Higginson]

In message <200504171142280230.080947B3 at mail.ezwv.com>, Will Matney 
<craxd1 at ezwv.com> writes


Hi Will

>Seriously, I thought about making a line of meters similar to the old 
>Drake and actually made a couple of prototypes. To be very honest, 
>those can be just as accurate as any Bird I've seen.

As can any meter if it's adjusted properly and scaled correctly

>Bird is about like buying the name Cadillac when other cars get you 
>there just as good. That's my opinion of course.

We are in danger of starting the Bird thread again.. But of course your 
opinion is correct.. It's just a reasonably robust meter that gives 
reasonably repeatable results. No more.. No less..

>To be honest, I'm leary of adjusting watt meters by having two meters 
>in line and adjusting one from the other. I've seen meters set this 
>way, and after taking one out of line, get a different reading with the 
>same amount of power applied. I would think it was due to the line 
>lengths where a meter and a 3' jumper was taken in and out?

Usually I only tend to adjust such meters if

a: they are demonstrably out of acceptable tolerance ( broken )
b: I want to improve the accuracy at a particular frequency

(  I have a few for 23cm that I adjusted to improve them some time ago 
as out of the factory "in cal" they were way out of spec  )

Then I use a signal source that I can depend upon and can confirm it's 
harmonic content

If I can,  I use attenutors either side of the DUT  ( a challenge at 2Kw 
)

I use an absorption power meter and attenuators at the end of the 
measuring chain.


No, I wouldn't just stick two 43's in line and call them calibrated .. 
despite my suspicion as to how several large calibration facilities used 
to do it.


At the end of the day you can be as careful as you like, you still end 
up with a 43 which despite any protestations to the contrary.. It's 
still not very accurate.

Regards Paul
-- 
73 de Paul GW8IZR
(IO73TI Anglesey)