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10 watt or 25 watt slug?
- Thread starter 9Lives
- Start date
That is an RF sampler. The bnc carries the sampled RF out to whatever test hear you are using beit a scope, modulation monitor, or spectrum analyzer etc.
My advice would be to forget the Bird 43 and just buy a reasonably good quality ham power meter rated for the HF bands. This will be a lot cheaper for very little difference in performance on the 10/11m band.
The Bird 43 is one of the most over rated pieces of test gear out there. I don't own one myself but I have access to them and I've tested several of them.
On the plus side it is a very solidly built and versatile meter if you buy lots of expensive slugs but it is NOT some kind of industry standard meter for power measurement. It uses the same tech as a basic CB power meter for measuring power. eg a directional coupler and a simple (uncompensated) diode detector.
i.e. it isn't a proper power meter, it just reads peak RF voltage at the coupled port in a similar manner to how a $5 CB power meter does it. Obviously it is built better and the thru loss and the meter's own 'thru' VSWR will be better (it's good to use to over 1GHz with the right slugs) but there is no high tech magic inside.
Also, I don't really recommend messing with the x10 mods either and here is why.
On a standard Bird 43 the dial is calibrated for operating the diode partly in square law, partly in transition region and partly in the linear region. This makes the scale unique to this operating point of the diode.
Therefore, if you add the x10 mod then you will be operating the diode/meter in the linear region over most of the dial and the scaling will only be 'right' near the top end.
These old meters are bad enough for accuracy across the dial (away from FSD) and if you do the x10 mod this will get even worse on low and mid scale readings.
It's a dinosaur design that compromises the performance by operating the diode in the transition region and this makes it lose accuracy a LOT over temperature on the low to mid scale readings. Don't use it outside on a very cold day LOL!
By contrast a regular ham meter will operate mostly in the linear region and will be fairly immune to temperature changes unless operated on the lowest power range.
Don't waste your money and just leave the Bird 43 to the 'techs' who believe the BS about how good these meters are supposed to be
The Bird 43 is one of the most over rated pieces of test gear out there. I don't own one myself but I have access to them and I've tested several of them.
On the plus side it is a very solidly built and versatile meter if you buy lots of expensive slugs but it is NOT some kind of industry standard meter for power measurement. It uses the same tech as a basic CB power meter for measuring power. eg a directional coupler and a simple (uncompensated) diode detector.
i.e. it isn't a proper power meter, it just reads peak RF voltage at the coupled port in a similar manner to how a $5 CB power meter does it. Obviously it is built better and the thru loss and the meter's own 'thru' VSWR will be better (it's good to use to over 1GHz with the right slugs) but there is no high tech magic inside.
Also, I don't really recommend messing with the x10 mods either and here is why.
On a standard Bird 43 the dial is calibrated for operating the diode partly in square law, partly in transition region and partly in the linear region. This makes the scale unique to this operating point of the diode.
Therefore, if you add the x10 mod then you will be operating the diode/meter in the linear region over most of the dial and the scaling will only be 'right' near the top end.
These old meters are bad enough for accuracy across the dial (away from FSD) and if you do the x10 mod this will get even worse on low and mid scale readings.
It's a dinosaur design that compromises the performance by operating the diode in the transition region and this makes it lose accuracy a LOT over temperature on the low to mid scale readings. Don't use it outside on a very cold day LOL!
By contrast a regular ham meter will operate mostly in the linear region and will be fairly immune to temperature changes unless operated on the lowest power range.
Don't waste your money and just leave the Bird 43 to the 'techs' who believe the BS about how good these meters are supposed to be
Amen!
Many though, will not appreciate your blasphemous analogy of the Bird.
If I had a mobile radio service business and worked in the field under crappy conditions, I might buy one because of it's durable construction.
Actually, I probably wouldn't. I'd just buy a quality meter and treat it with care.
Many though, will not appreciate your blasphemous analogy of the Bird.
If I had a mobile radio service business and worked in the field under crappy conditions, I might buy one because of it's durable construction.
Actually, I probably wouldn't. I'd just buy a quality meter and treat it with care.
Yes, I can see the appeal of the rugged design
But on the technical side, you will see that Bird don't spec it for temperature (because the diode detector is uncompensated and its accuracy is woefully poor over temperature on low to medium dial readings)
Also they don't tell you that the accuracy is woeful if there are highish harmonics present. eg a -20dBc harmonics can introduce up to a +/-20% dial error on most of the scale.
This is despite the fact that a -20dBc harmonic is only 1% of the total power.
It suffers this alarmingly high error because it uses the same basic tech as a CB power meter. i.e. it is a peak voltage detector across much of the dial and this makes it suffer very high measurement uncertainty with harmonics depending on the phase of the harmonic.
But Bird don't tell you this in the manual...
But on the technical side, you will see that Bird don't spec it for temperature (because the diode detector is uncompensated and its accuracy is woefully poor over temperature on low to medium dial readings)
Also they don't tell you that the accuracy is woeful if there are highish harmonics present. eg a -20dBc harmonics can introduce up to a +/-20% dial error on most of the scale.
This is despite the fact that a -20dBc harmonic is only 1% of the total power.
It suffers this alarmingly high error because it uses the same basic tech as a CB power meter. i.e. it is a peak voltage detector across much of the dial and this makes it suffer very high measurement uncertainty with harmonics depending on the phase of the harmonic.
But Bird don't tell you this in the manual...
Pro. I have a Bird slug with a bnc for sampling the RF and it also has a tiny trim pot to adjust the sampled RF level. It is an attenuated sampler.
As for the Bird meters tbere is nothinh wrong witb tbem nor nothing special except they work well and can be recalibrated to ensure accuracy. They are rugged and for that reason are well suited for bench top work. As long as you inderstand the real truth about the accuracy all should be good.
You did. Just nothing magical nor mystical about it. It is a good solod meter with accuracy on par with other good meters. Too many people think Bird is super accurate and the meter to have.
If the thing works, then you didn't get hurt at all. Think of it like this, how often do you get a 'bird' and feel thrilled because of it? Or, how often can you get paid for giving someone the 'bird'? Hey, both of you are happy!
- 'Doc
- 'Doc
Especially if you want to sell the radio. Dosy watts are better for selling equipment.
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