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Bird 43 slugs

Discussion in 'General Ham Radio Discussion' started by lerch256, Jan 24, 2017.

  1. lerch256

    lerch256
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    Well i have a new questions

    I purchased a 1000w 25-60mhz element and a purchased a 1000w 2-30mhz slug



    I have a 3 transistor amplifier for 11 meters 1-1446 driving 2-2879 toshiba on red dot

    The 2-30mhz will read 60 watts higher than the 25-60mhz on average I've used 2 bird 43's same results 200 bird watts vs 260 bird watts can anyone explain that to me
     

  2. 543_Dallas

    543_Dallas
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    Like most test equipment the slugs can be calibrated. A 60 watt difference on a 1000 watt scale isn't that big of a deal.
     
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  3. n8fgb

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    A 60 watt difference at 200 watts is a pretty big deal. I have heard of some counterfeit bird slugs.
    Rich
     
  4. StrangeBrew

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    Meters and slugs are generally rated for accuracy by percentage of full scale, how many watts you're actually trying to measure isn't really a factor. 60 watts is only 6% of 1000. If the amp is putting out 230 watts each element would be off by 3% of 1000 watts, to the best of my knowledge this would be within spec for a bird. With meters bigger isn't always better.
     
    #19 StrangeBrew, Mar 19, 2017
    Last edited: Mar 19, 2017
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  5. 543_Dallas

    543_Dallas
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    It is but that's not the point. If he is measuring 200 watts he needs a smaller slug. 60 watts on a 1000 watt scale is a 6% difference. Bird's tolerance spec is +/- 5%. It is very possible that both slugs would pass a calibration test.
     
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  6. n8fgb

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    if your cars speedo is of by 5 mph ant 25mph, it will be of by 20 at 100. If your watt meter is off by 60 at 200 watts, it may be off by 300 at 1000 watts.
     
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  7. lerch256

    lerch256
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    I have a 250 2-30mhz slug I'll give it a try when I make it home thanks
     
  8. 543_Dallas

    543_Dallas
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    The company that manufacturers the slugs say +/- 5% at full scale. They make no mention of automobiles.
     
  9. lerch256

    lerch256
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    I was just wondering if any of yall have seen that much of a difference before from the different mhz rating between slugs

    Now one is a coaxial dynamics and the other a bird

    Coaxial dynamics is 25-60mhz
    Bird is 2-30mhz
     
  10. 543_Dallas

    543_Dallas
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    I don't own more than one slug with the same rating and all of mine are bird 2 to 30mhz. Going from a 1k to a 2.5k slug etc I do see minor differences. For a more accurate measurement I would use the 250.
     
  11. Captain Kilowatt

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    The accuracy is stated as a % OF FULL SCALE not of what is being measured so therefore being off 60 watts is only 6% of full scale which in this case is 1000 watts. Meter accuracy is always speced as a % of full scale deflection. It is for this reason you always want to use a meter or slug that will result in the meter deflection being as far as possible without going off scale.
     
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  12. 543_Dallas

    543_Dallas
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    Thanks. I was beginning to think I mixed this drink too strong.
     
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  13. lerch256

    lerch256
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    Lol
     
  14. Captain Kilowatt

    Captain Kilowatt
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    LOL I was beginning to think I didn't mix mine strong enough. :ROFLMAO: Seriously......an Appleton Rare Blend rum on the rocks before I head to bed. LOL
     
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  15. nomadradio

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    Comparing one element at the bottom end of its frequency range to another one at the top end of its frequency range will maximize the error difference you see between them.

    The tricky stuff inside the Bird element is the frequency compensation. Making a RF measurement stay the same at widely-different frequencies is not as easy as it sounds. Bird elements typically covered a range of about 2.5-to-1, starting with the "A" elements at 25-60 MHz.

    The "H" elements cover a range more like ten or fifteen to one from highest to lowest. 27 MHz is nearly at the top end of that element's coverage. And it's just above the very-lowest frequency for the "A" element. Seeing a 6 percent difference is normal, since your test conditions have been set up for maximum error, at the top of one coverage range and at the bottom of the other.

    They're still within the 8 percent number I remember for Bird elements.

    73
     
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