Learn convert dBm to mW without calculator

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TheFreespaceloss

Күн бұрын

Пікірлер: 22

@civedm 6 жыл бұрын

OMG THANK YOU SO MUCH!!! I could cry man! My professor sucks at explaining this but you did a great job!!!

@TheFreespaceloss 11 жыл бұрын

Right Kevin. Very nice example.

@lynjazmin615 7 жыл бұрын

But in the www.rapidtables.com/convert/power/dBm_to_mW.htm says that 27 dbm is equal to 501 mW. you also got it wring in the 28,29

@TheFreespaceloss 7 жыл бұрын

That's correct. 27 dBm is 501.2 mW. But this is approximate calculation without calculator. And result 500 mW or 512 mW is good approximation of 501. Another thing, loss that you have in cable, connectors etc can easily be 1-2 dBm so you don't need to look 1mW difference if you can have 10, 20, 50 mW difference. You will never need that precision in practice. 27 = 3*9 => 2^9 = 512 27 = 30 - 3 = 10+10+10-3 => 10*10*10/2 = 500 mW Both are close enough and they are example how you can get result with any approach.. Choose what is easier for you in particular moment. (Mostly I'm using 2nd approach since * and / is easier than ^) 29 dBm is 794.32 Without calculator you get 800. That's 99.3% accurate... As I said, you don't need closer than that.

@germanmachado9830 9 жыл бұрын

hello Thefreespaceloss, Could you please explain me how could Kevin made that operation from 7+7+7 to obtain 5*5*5?????

@TheFreespaceloss 9 жыл бұрын

+German Machado Sure. 21 = 7+7+7 21 = (10 - 3) + (10 - 3) + (10 - 3) This can go in two directions: one is explained in video where you sum all 10's and all 3's and get: 30 - 9. I went with that approach because it's more common with other similliar values like 31 = 40-9 But you can also do as Kevin. 10 - 3 became 10 / 2 (remember: 10 became 10, - became /, 3 became 2) 10 - 3 became 10/2 = 5 (it's also explained how 7 dBm is 5mW at 4:21 of video) Now you have this: 21 = 7 + 7 + 7 7 became 5 + became * 7+7+7 became 5*5*5 = 125 mW Hope I've helped.

@NMETSGChan 6 жыл бұрын

There is a mistake in your calculation for 30 dBm. If you use the same method for all calculation, it should be read as follow. 30 dBm = 10 * 3 = > 10 power 2 = 100 mW so it should be read like that instead 30 dBm = 10 + 10 + 10 = > 10 * 10 * 10 = 1000 mW or 1 W As a rule of thumb if you can do the calculation with an addition you should.

@TheFreespaceloss 6 жыл бұрын

Yes, addition is easier... But it's not mistake... If you look carefully at 4:53 base is changing but exponent remains. Therefore: 30 dBm = 10 * 3 = > 10 power 3 = 1000 mW (because 10 remains 10)

@imjase-thisismylittleYTchannel 6 жыл бұрын

Could someone please explain to me (in friendly terms) how we work out 1dBm being equal to 1.25mW? I am struggling to figure out how we get there!

@reshmakrishnan511 6 жыл бұрын

Jason Kolmer 1dbm=10-9=10-3×3 =10/2^3=10/8=1.25mw

@TheFreespaceloss 6 жыл бұрын

Right.. Or just look 21 dBm: 1 dbm = 21 - 20 = 125 / 100

@gayathriciddamsetty4826 7 жыл бұрын

thank you soo much sir,

@asharatech 2 жыл бұрын

Thanks 🙏 jinx has been broken for me

@KTheeky 8 жыл бұрын

Hi, 21dBm=3*7 ==> 2^7=128mW.. but.. =125 what? I'm doing something wrong?

@TheFreespaceloss 8 жыл бұрын

+Sílvio Santos No, you doing fine. It's approximate calculation so you might get different result with different approach. Check video at 7:40 for 27 dBm (I got 512 and 500 mW). So it's AROUND 500mW. 26 is around 400 and 28 is around 600 - idea is to get close enough. Is that 500, 512, 520 or 480, really is not a big deal. Similarly for your calculation: 21 dBm is 125.89. Now, did you get 125 or 128 doesn't make difference. That's all within 2%. In different cases you'll use different approach. Take one that is easiest for you at that moment that give you close enough result.