converting antenna dbi to watts and amp watts to dbi what are you really getting for output!

[droneuser]

I think this may help when comparing antennas or amps transmitting power! receiving dbi is usually less just a fyi!

This conversion will work on antennas (omni directional or directional antenna) or amps! this is NOT the calculation of a amp with antenna!

NOTE: directional antenna has more "pin" pointing/aiming concentration of signal Thus may give more range depending on surrounding environment meaning trees,wifi, building etc

the stock remote output is FCC 26 dBm = 0.398 watts (US)

CE：<=20 dBm = 0.1 watts
SRRC: <=20 dBm = 0.1 watts
MIC: <=18 dBm = 0.063 watts



Also this is calculated numbers in the real world there is loss that comes from connectors, cables, wire, etc

dbi to watts

5dbi = 0.0032 watts

10dbi = 0.01 watts

15dbi = 0.0316 watts

20dbi = 0.1 watts

25dbi = 0.3162 watts

30dbi = 1 ( one full watt)

watts to dbi

2 watts = 33.01 dbi

4 watts = 36.02 dbi

8 watts = 39.03 dbi

10 watts = 40 dbi

Notice you don't see much of an increase from 8 watts to 10 watts!!! so its it worth the extra dollars for that small amount? no but also notice there is not much difference as you go up in wattage hence why you may have seen threads on people saying I didn't get that much more distance with a 8 amp compare to a 4 amp! but of course the antenna type being used would help with that too!

sooo lets do some math and find out how more difference is there

2 watts is 33.01 dbi and 4 watts is 36.02 dbi the difference in dbi is 3.01 dbi which is only 0.002 watts!

 

[droneuser]

I should also add the "i" in dBi stands for "isotropic", meaning uniformly radiating in all directions. Such an antenna doesn't really exist, cause there is no such thing as a perfect antenna! but the theoretic model can be used as a reference. just a fyi on that

ok so what is the calculated output of an amp WITH antenna?

That will be the next post

 

[droneuser]

NOTE: watts output is ERP watts ( Effective radiated power) which means, the RF power supplied to an antenna multiplied by the antenna gain in a given direction.

as I said before this is a calculated number! connectors, cable, etc has an affect and no antenna is made "perfect" cant be done! but these numbers will give you an idea!

I pick the following antenna gains (dbi) and amp size by what is used mostly with this hobby for mods!




2 watt amp into a 5 dbi antenna = 3.85 watts

2 watt amp into a 6 dbi antenna = 4.85 watts

2 watt amp into a 9 dbi antenna = 9.68 watts (1)

2 watt amp into a 12 dbi antenna = 19.32 watts (2)

2 watt amp into a 15 dbi antenna = 38.56 watts (3)



4 watt amp into a 5 dbi antenna = 7.71 watts

4 watt amp into a 6 dbi antenna = 9.70 watts (1)

4 watt amp into a 9 dbi antenna = 19.37 watts (2)

4 watt amp into a 12 dbi antenna = 38.65 watts (3)

4 watt amp into a 15 dbi antenna = 77.128 watts (4)



8 watt amp into a 5 dbi antenna = 15.425 watts

8 watt amp into a 6 dbi antenna = 19.41 watts (2)

8 watt amp into a 9 dbi antenna = 38.74 watts (3)

8 watt amp into a 12 dbi antenna = 77.31 watts (4)

8 watt amp into a 15 dbi antenna = 154.25 watts


do you see a pattern? if not you can see I marked them 1 goes with 1 and 2 goes with 2 , etc! as you can see with the right gain (dbi) of a antenna you can Achieve the same ERP out of a higher wattage amp with a small dbi antenna! of course there is a trade off and that is the size of the antenna that is need to achieve this!

 

[efowler]

NOTE: watts output is ERP watts ( Effective radiated power) which means, the RF power supplied to an antenna multiplied by the antenna gain in a given direction.

as I said before this is a calculated number! connectors, cable, etc has an affect and no antenna is made "perfect" cant be done! but these numbers will give you an idea!

I pick the following antenna gains (dbi) and amp size by what is used mostly with this hobby for mods!




2 watt amp into a 5 dbi antenna = 3.85 watts

2 watt amp into a 6 dbi antenna = 4.85 watts

2 watt amp into a 9 dbi antenna = 9.68 watts (1)

2 watt amp into a 12 dbi antenna = 19.32 watts (2)

2 watt amp into a 15 dbi antenna = 38.56 watts (3)



4 watt amp into a 5 dbi antenna = 7.71 watts

4 watt amp into a 6 dbi antenna = 9.70 watts (1)

4 watt amp into a 9 dbi antenna = 19.37 watts (2)

4 watt amp into a 12 dbi antenna = 38.65 watts (3)

4 watt amp into a 15 dbi antenna = 77.128 watts (4)



8 watt amp into a 5 dbi antenna = 15.425 watts

8 watt amp into a 6 dbi antenna = 19.41 watts (2)

8 watt amp into a 9 dbi antenna = 38.74 watts (3)

8 watt amp into a 12 dbi antenna = 77.31 watts (4)

8 watt amp into a 15 dbi antenna = 154.25 watts


do you see a pattern? if not you can see I marked them 1 goes with 1 and 2 goes with 2 , etc! as you can see with the right gain (dbi) of a antenna you can Achieve the same ERP out of a higher wattage amp with a small dbi antenna! of course there is a trade off and that is the size of the antenna that is need to achieve this!

Great Post - Thank You! At what point does any of this become harmful to nearby electronics (like the controller you are holding) or to your self??

 

[droneuser]

not sure what you mean by "harmful to nearby electronics" as in damaging them? or as in interference? if you are asking can you damage the stock remote with RF power using a 8 watt amp? NO


can RF power be harmfully to you? if you get high enough wattage and you grab the antenna you could get a RF burn. but the takes more wattage then what is listed here.

RF = radio frequency

here two links if you what to read about it ( if you want more info just search google)

Radio frequency - Wikipedia

Radiation burn - Wikipedia

 

[efowler]

not sure what you mean by "harmful to nearby electronics" as in damaging them? or as in interference? if you are asking can you damage the stock remote with RF power using a 8 watt amp? NO


can RF power be harmfully to you? if you get high enough wattage and you grab the antenna you could get a RF burn. but the takes more wattage then what is listed here.

RF = radio frequency

here two links if you what to read about it ( if you want more info just search google)

Radio frequency - Wikipedia

Radiation burn - Wikipedia

Thank you. You answered my question perfectly. Your math discussion helps me to understand the difference between a Titan Cyclone (9dbi antenna with a 3 watt amp) & a 4Hawks XR (14dbi panel with a 3 watt amp)

 

[Kilrah]

You're kinda mixing dBi and dBm.

Transmitter powers are typically indicated in dBm (referenced to 1mW).
dBi is used to describe antenna gains (as it is referenced to an isotropic antenna).

As to harmful there still is no definite answer to this. Some still say a watt could in theory be harmful (the range in which mobile phones transmit and we have mandatory power absorbtion number publication in some places), others refute it.

 

[droneuser]

You're kinda mixing dBi and dBm.

Transmitter powers are typically indicated in dBm (referenced to 1mW).
dBi is used to describe antenna gains (as it is referenced to an isotropic antenna).

As to harmful there still is no definite answer to this. Some still say a watt could in theory be harmful (the range in which mobile phones transmit and we have mandatory power absorbtion number publication in some places), others refute it.

I used a formula that lets you enter in TX watts and antenna dbi which gave me the ERP watts. so it should be right unless the formula is wrong

 

[Kilrah]

Probably got something wrong in the conversions, it's too easy to need such a thing.

10dBm TX power + 5dBi antenna gain = 15dBm EIRP. If you want watts then convert that.

There's a reason we use dB for RF stuff, it's becasue it makes the calculations much easier. Only convert the final result.

 

[droneuser]

but you have to take it one step further and that is to convert dbm to watts. the reason for the watts that is the output that is listed for the amps. my output is in watts in ERP

here is the screen shot , of the calculator ( unless the site has their formula wrong)

 

[droneuser]

So if I was using your example it would go like this



Then




So the answer for yours would be

0.01928 watts in ERP ( unless the sites have their formula wrong)

I picked the ERP because that compares the actual antenna to a half-wave dipole antenna, while EIRP compares it to a theoretical isotropic antenna. I didnt want to post a "theory" I wanted to post practical. so that is why I picked the ERP

So if my thinking is wrong? it seems to do it this way is the Logical way of doing it? but iam no RF engineer so I could be wrong?

 

[droneuser]

As to harmful there still is no definite answer to this. Some still say a watt could in theory be harmful (the range in which mobile phones transmit and we have mandatory power absorbtion number publication in some places), others refute it.

you are correct on that, but I though the op was asking if it harmfully if you touch it???? hence why I mention RF burn of course this would require alot more wattage then we are dealing with here

 

[Kilrah]

I picked the ERP because that compares the actual antenna to a half-wave dipole antenna, while EIRP compares it to a theoretical isotropic antenna.

But what matters in most things we deal with like RF regulations and is what gets calculated straight from the info you have about the gear you're working with is EIRP. Antenna gains are specified in dBi, not in dBd so the difference is taken into account there.

ERP is 2.1dB less, and of course the numbers match.
10dBm + 5dBi = 15dBm EIRP = 0.0316W.
10dBm + 5dBi - 2.1dB = 12.9dBm ERP = 0.0194W

 

[droneuser]

But what matters in most things we deal with like RF regulations and is what gets calculated straight from the info you have about the gear you're working with is EIRP. Antenna gains are specified in dBi, not in dBd so the difference is taken into account there.

ERP is 2.1dB less, and of course the numbers match.
10dBm + 5dBi = 15dBm EIRP = 0.0316W.
10dBm + 5dBi - 2.1dB = 12.9dBm ERP = 0.0194W

yes antenna gain is in dbi that is what I used, if I recall the 2.1bd is based on a half-wave dipole antenna? so EIRP is 2.1 less then ERP, but I used ERP

 

[droneuser]

so you saying POST the EIRP due to the it being less compared to ERP due to 2.1 ?

I guess either way people can still see the linear increase over wattage and/or antenna gain

 

[Kilrah]

No, EIRP is 2.1dB MORE than ERP, as the capture you posted shows.

 

[droneuser]

No, EIRP is 2.1dB MORE than ERP, as the capture you posted shows.

yes sorry I got them mixed up when I post that... that's why I posted ERP I thought it was the "right" number cause its not a theory

but you are saying post that instead? or I am misunderstanding what you are saying?

 

[Kilrah]

Regulations and most documentation refer to EIRP, not ERP. And that's what you get most "naturally" using the power and gain as specified on pretty much everything, so just more convenient for everybody.

 

[fileophile]

I'm beginning a project to lengthen the leg length of the Mavic Pro so that the bird sits higher off the ground. I'm planning on adding some shock absorption capability also, but that will of course be all mechanical.

What I'd like to do on the electrical side is use longer send/receive antennas inside the front legs (this is where the stock antennas for those who didn't know). If I can get those little 4W Dragon amps in there without overheating anything I will add those too. My question is what would be a good antenna for this?

Needs to be flat like the stock ones, I assume about twice as long (to stay with the wavelength of 2.4 GHz, and able to pair well with the 3W amps. Any good ideas?

Will the length twice as long buy me anything in terms of radio performance?

 

[droneuser]

check this thread out if I recall some one was talking about that

Aircraft Antenna Mod