Amps... How do they work?

JohnnyB · Jan 10, 2017

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Better? Lol ... Not giving up and moving forward for the sake of newbies...

Thanks for trying to answer an undefined question. Your answers still gave me direction towards what to research. Appreciated.
Found this video to be helpful and detailed, and answered questions I didn't know to ask...

Now I know why some readings are negative, and some are positive.

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JohnnyB · Jan 10, 2017

Or at least I think I do.. if power output is greater than power input, the dBm # will be in the negative? This correct?

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GrammatonxXXxCleric · Jan 10, 2017

Judging from what the magic marker scientist is saying: 0 (zero) dB is no loss, A negative number output = loss. A positive output number is gain. Example : -20dB =loss twenty times. +20dB= gain twenty times. That what I got from Mr. scientist with his magic eraser. I see a positive number is positively what I want... I'm positive of that... (Plants summer squash while typing).

JB63 · Jan 10, 2017

Well, dB is not really a unit. dB is the log (base 10) of the ratio between a given quantity and a reference value. When the quantity we're after and the reference are equal, their ratio is one, and log(1)=0. Thus, if there is no gain, we have zero dB.
Pushing this a bit more, in fact log(ratio) is expressed in 'Bels', we just multiply that by 10, and call that a deciBel.
In fact this does not apply only to amplifiers, it applies to sound as well as many other engineering quantities.

When a sound is 80 dB loud, it means it's 10^8 times louder than the 'reference' sound. Such reference is 20 micro-Pascals.

GrammatonxXXxCleric · Jan 10, 2017

You pushed your glasses up on your nose when you typed that didn't you.....

JB63 · Jan 10, 2017

GrammatonxXXxCleric said:
You pushed your glasses up on your nose when you typed that didn't you.....

Not sure ... I was not looking when I typed ... I work on sound for a living and dB is ... well .. I use that routinely. Granted, it is NOT the easiest of concepts to explain, especially to young engineers 'familiar' with only the linear scale.

GrammatonxXXxCleric · Jan 10, 2017

Seems fairly simple... 0= no gain, +Positive =gain, -Negative =loss

N017RW · Jan 10, 2017

GrammatonxXXxCleric said:
-Negative =loss

Not exclusively, in the RF context any value less that 1mW would be expressed as a negative.

For example, the GPS RF signal level on the earth's surface is about -130dBmw.

JB63 · Jan 10, 2017

GrammatonxXXxCleric said:
Seems fairly simple... 0= no gain, +Positive =gain, -Negative =loss

Fair enough. If you're only interested in and happy with that (little) amount of details, so be it. However, others might be interested in more, and hopefully what I wrote is of some use to them. If not, it's ok as well. You remind me of a classmate during a graduate course I took many years ago. The professor/lecturer was teaching some fundamentals in practical signal/image processing. This student however, kept on asking all the time: 'So what's a good rule of thumb for such and such parameter?'. Of course, the teacher (and some students) got very annoyed but in the end, there are those who want to understand how a car works, and those who just want to know which buttons to push. Whichever camp you're in, I sincerely hope you find what you're after in this forum. ***peace***

GrammatonxXXxCleric · Jan 10, 2017

And when we discuss Phantom to controller communication signal levels... we are discussing this? No, the simple bottom line is just that, simple. Either neutral level(No gain or loss) or gain OR loss. No need to Google technical terms that have no relevance in the discussion this post was created about. Right?

GrammatonxXXxCleric · Jan 10, 2017

Hmm, I smell adam henry unit odors... ( I remember your similar posts to others.. .good luck with that.)

JB63 · Jan 11, 2017

Wrote something not so nice but then removed it. Apologies to the community and especially to the OP. ***peace***

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