Understanding dB Math

One of the "Wireless LAN Design Rules" is, as a designer you need to understand dB math because you're going to be using it for many things. So, in this video, we're going to talk about some quick ways you can learn to do dB math, even in your head and we'll finally end up with am Excel spreadsheet you can play with so you can reinforce the knowledge.

Chapters:
00:00 - Start
00:46 About dBm (decibels compared to 1 milliwatt)
01:28 Easy dB Math in 5 minutes (Rules)
03:07 Easy dB Math in 5 minutes (Trial)
05:53 dB Math Cheat Sheet
08:02 Excel Spreadsheet (dBm to mW Conversion)

[KK-rgnj]

Thanks for this video! Pretty systematic way of doing this mentally. We can also modify this to the voltage log/dB expression of YdB = 20log(x) by changing the values in the dB column to 2x ie, 20 dB => 10 and 6dB => 2.
So for example:
60dB would become: 20+20+20 = 10^3 = 1000 times
And 26dB would be: 20+6 = 10*2 = 20 times
Appreciate your effort to simplify this!

[pauloche]

'You are such a great cheat'. 🤣. Anyways, thanks for the trick. Works like magic.

[isolinear]

Thanks a lot Sir. This will be really useful as a template for me to teach other people. A shame nobody taught me this method decades ago. I've been doing it the "way you're supposed to" mentally (with my personal shortcuts developed over the decades, so there's no point in me using your methodical shortcuts now), but it would have been easier on me if I'd been taught this from the beginning. I remember struggling to do the math in my head when I was a kid. Ah well, at least I get to use this method in teaching others which seems a LOT easier to articulate and demonstrate.

[wongalex]

Thank you, I struggle for so long of this

[victornjoroge]

Magical! Great video..Thanks Keith for sharing this

[mahendrachavan]

No idea why it took so long to get this video, Sir...Thank you a Billon Tons!!!! 😀

[joelourenco]

Thank you so much!! I appreciate this.

[qzorn]

very nice for an esp32 arduino wifi project... now to remember this great info 6 months from now and longer... 👍👍 thanks a lot...😉

[jspaceboy]

How would you go from normal to db? For example 500 Watts? I think I figured it out but want to make sure (10*10*5 --> 10+10+7 = 27)

[theofanisc.karagiorgos]

what about dBm =-110 i.e? should add the "-" after the calculation? or start with

[dinyarbuhariwalla]

Hello Sir, how will you convert a decimal mw to dbm? for eg if i want to convert from 25 milli watt to dbm?

[Dylan-nitc]

Hello, I have a question.
I learned an equation which simplifies converting dB to dBm (by using this following eq, dBm = dB + 30) at college in my freshmen year. But now, fast forward almost 4 years later, I found that this method is highly debateable amongst telecom engineer. And right now, i'm in a desperate situation about this converting dBs stuff. I need to finish an eq which involves dBm and dB. My eq problem is Rx (dBm) = Tx (dBm) - Pathloss (dB), I have the data for Rx and Tx in dBm, but I need to know whats maximum distance in the PL equation (Cost231-Hata model). Is it allowed to use this methods? If not, how can I find the maximum distance? Thank you.

[phillipkluttz]

Keith, The link to the resources returns "No results found".

[MrGeronimo]

Prof. -48dbm is it good or not good for 100Mbps internet fiber optique 😂 or shouldn’t be like that 🙃

[c.danielpremkumar]

5.56 couldn't understand any thing in this cheat sheet. Perhaps a different explanation will help.