Now, I too am interested to see if anyone has any knowledge of doing
such thing - the procedure, equipment used, etc. IF it is something I
can do with my own - then by all means, I'll do it. I've got a
decently equipped bench.



IF - you have an accurate standard available to compare your Bird
Wattmeter against, then I see no reason you can not do a calibration on
your Bird Wattmeter Slug yourself.

The information you need is readily available.... in fact QST,
September 2006 issue, page 49, provides enough information for most hams
to figure out how to calibrate their Bird Meter's slug. The article
actually allows some rather neat features, too, if you are "slug" poor.


Ed K7AAT

"Ed" wrote in message
. 192.196...


Now, I too am interested to see if anyone has any knowledge of doing
such thing - the procedure, equipment used, etc. IF it is something I
can do with my own - then by all means, I'll do it. I've got a
decently equipped bench.



IF - you have an accurate standard available to compare your Bird
Wattmeter against, then I see no reason you can not do a calibration on
your Bird Wattmeter Slug yourself.

The information you need is readily available.... in fact QST,
September 2006 issue, page 49, provides enough information for most hams
to figure out how to calibrate their Bird Meter's slug. The article
actually allows some rather neat features, too, if you are "slug" poor.


Ed K7AAT

Damned, I'll have to see if my friend still gets QST. I don't. Thanks!

L.

Bird is still in business in Solon, Ohio.

And Coaxial Dynamics, just up the road from Bird, who also makes slugs that
will fit the old 43, will calibrate Bird slugs.


wrote in message
oups.com...
I have a 2,500 watt, HF slug that I don't have confidence in. Anyone
know who calibrates slugs for a reasonable fee?

Thanks.
Jeff
W8KZW

"EchoBlip" wrote in message
.. .
Bird is still in business in Solon, Ohio.

And Coaxial Dynamics, just up the road from Bird, who also makes slugs
that will fit the old 43, will calibrate Bird slugs.


wrote in message
oups.com...
I have a 2,500 watt, HF slug that I don't have confidence in. Anyone
know who calibrates slugs for a reasonable fee?

Thanks.
Jeff
W8KZW


While we didn't get a "price" from Bird to calibrate - another poster
suggested they weren't "reasonable". I wonder if you might have any
experience - price wise - with Coaxial Dynamics? Or perhaps able to do a
side by side price comparison - from past experiences?

L.

Using the technique practiced in the National HRO, you can simply make a
calibration chart for each particular slug. That makes it useful over a
much wider frequency than it is marked. The directivity remains even though
the slug is used "off frequency". It does not matter what the power reads
on the meter - if you know by a calibration chart what the actual power is.

Colin K7FM

Yes, there is some good information floating around. However, it all
boils down to, in your words, having an accurate standard available. I
do not.

Another poster essentially suggested "close is good enough" - match the
slug against some other meter reading. I understand that reasoning,
and for the most part that's fine. However, I didn't buy a Bird to
calibrate against my MFJ. I want to know power out (+/- Bird
tolerance), not just estimate it.

I bet I have a dozen or more wattmeters, but I only have one Bird 43,
and I want it to be within spec.

It's starting to look like I should just borrow someone else's 2,500
watt slug known to be accurate, and then just adjust the pot in mine to
match! Anyone want to lend me theirs? ;-)


Ed wrote:

Now, I too am interested to see if anyone has any knowledge of doing
such thing - the procedure, equipment used, etc. IF it is something I
can do with my own - then by all means, I'll do it. I've got a
decently equipped bench.



IF - you have an accurate standard available to compare your Bird
Wattmeter against, then I see no reason you can not do a calibration on
your Bird Wattmeter Slug yourself.

The information you need is readily available.... in fact QST,
September 2006 issue, page 49, provides enough information for most hams
to figure out how to calibrate their Bird Meter's slug. The article
actually allows some rather neat features, too, if you are "slug" poor.


Ed K7AAT

"Yes, there is some good information floating around. However, it all
boils down to, in your words, having an accurate standard available. I
do not."


This is what ham radio is all about. We make do without adequate test
equipment - we just need to put a little more effort into figuring how to
use what we have.

Take a dummy load. Use a dvm to measure the dc resistance. That should
also be the rf impedance. You can determine power going into the load by
measuring the rf voltage across it. Some of the surplus voltmeters will
measure rf voltage. Or, borrow one. Knowing the rf voltage across 50 ohms,
you can calculate power. P= e squared / R.

It is likely that the linearity of the Bird is ok, even if the power reading
is incorrect. So, once you check the accuracy at one point, you have it for
all points.

Colin K7FM

"COLIN LAMB" wrote in message
news
"Yes, there is some good information floating around. However, it all
boils down to, in your words, having an accurate standard available. I
do not."


This is what ham radio is all about. We make do without adequate test
equipment - we just need to put a little more effort into figuring how to
use what we have.

Take a dummy load. Use a dvm to measure the dc resistance. That should
also be the rf impedance. You can determine power going into the load by
measuring the rf voltage across it. Some of the surplus voltmeters will
measure rf voltage. Or, borrow one. Knowing the rf voltage across 50
ohms, you can calculate power. P= e squared / R.

It is likely that the linearity of the Bird is ok, even if the power
reading is incorrect. So, once you check the accuracy at one point, you
have it for all points.

Colin K7FM


Exactly...... I have a bird, and am interested in it's upkeep. However -
prior to the bird - I had an occasion sometime before - when I had a 2 way
radio come in - my wattmeter then had decided to flake out on me. So, I used
an RF probe with an Eico 232 across the dummy load which was 52 ohms. I was
able to get by with that til I could get a wattmeter going again. Ya just
have to learn to adapt. AND for the hell of it, I did some comparisons from
the Wattmeter to the Eico with the RF Probe. WE're talking maybe a quarter
watt - or less.
No big deal in most cases unless you're dealing with "low" power. At least
the 2 way radio was back on the air!

L.
L.

Thank you for telling me what ham radio is all about. 41 years of
ignorance now cured. And I also deeply appreciate your pointing out my
lack of effort figuring out how to use what I have. What a slackard I
have been. I'll try to mend my ways. Finally, thank you so much for
restating Ohm's law - I'll attempt to better understand it.

Ok, let's cut to the chase here, OM ... first, if I wanted to "make do"
I wouldn't have bothered to post my question, let alone invest in a
Bird. Not all of us lie down and just "make do". I really don't need
you to tell me how to set / lower my standards.

And secondly, if I'm questioning the accuracy of a Bird slug, why on
earth would I want to now rely on the accuracy of some "DVM" or
"surplus voltmeter" at the kilovolt level? It simply doesn't make
sense.

Perhaps I am over-reacting, but your attitude is clearly condescending:
all I asked was if anyone knew where I might get a slug recalibrated.
I really didn't ask what you thought ham radio is all about, nor for
you to judge my level of effort.



COLIN LAMB wrote:
"Yes, there is some good information floating around. However, it all
boils down to, in your words, having an accurate standard available. I
do not."


This is what ham radio is all about. We make do without adequate test
equipment - we just need to put a little more effort into figuring how to
use what we have.

Take a dummy load. Use a dvm to measure the dc resistance. That should
also be the rf impedance. You can determine power going into the load by
measuring the rf voltage across it. Some of the surplus voltmeters will
measure rf voltage. Or, borrow one. Knowing the rf voltage across 50 ohms,
you can calculate power. P= e squared / R.

It is likely that the linearity of the Bird is ok, even if the power reading
is incorrect. So, once you check the accuracy at one point, you have it for
all points.

Colin K7FM

Well, I was trying to be helpful. Instead, I am condescending.

I have been a ham longer than 41 years, and I learn things all the time.
Sometimes, I forget simple ways to do things.

The Bird is not a model of accuracy. Accuracy is specified as a % of full
scale. I do not have my books handy, but I recall it is 5% of full scale.
If my recollection of 5% is correct, that means that it could be off (oh,
oh, here is simple math) 125 watts at full scale or 125 watts when you are
reading 500 watts. Using another Bird is not a good method of setting the
accuracy.

You have to use the dvm to check out the dummy load, anyway. If the dummy
load is off in resistance, the Bird wattmeter will not read correctly -
since it is assuming that the load is 50 ohms. I have checked dvms and
found even the cheap ones are quite accurate - much higher than the accuracy
specified for the Bird. I have also check dummy loads and found they are
often off. A friend asked me to come over because he was measuring 3200
watts out of his amplifier and thought it was high. It was - the dummy load
was also high.

If you are interested in an accurate reading slug, then calibrating it
against another Bird slug does not make much sense - since that might be
inaccurate. Forget the surplus rf voltmeter and simply measure the heat
rise of the dummy load. That will be an exact measurement of the power
going in and yield much more accurate readings than the Bird. It will
simply take a thermometer and a bit of math. I will not detail how to do
it, because that might be condescending.

I have a number of Bird wattmeters and slugs. I use them for quick and
crude measurements - because they are handy. Before I could afford the
Birds, I designed and built my own - and calibrated them. In fact, I wrote
an article for QST in 1973 on how to build your own using ordinary plumbing
parts. They were hand calibrated and as accurate as any Bird meter.

If, you want your meter to be calibrated like Bird would do it, send it to
them.

Colin K7FM