Hello everybody. I have a question about dbi. Whats the difference between an antenna with a 17dbi gain and a 48 degrees beamwith compared to an antenna with 18dbi gain and a beamwith of 42 degrees, or can you see any changes on the recieving end with 1 dbi of gain? Thanks in advance for your response.
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17dbi vs 18dbi
- Thread starter shoemaker
- Start date
"can you see any changes on the recieving end..."
or
"will you see any changes on the recieving end..."?
The receiving station isn't going to know the difference. You might notice the difference 6 degrees of beamwidth will make, though, especially if you're trying to null out interfering stations, or get the antenna right on the other station.
or
"will you see any changes on the recieving end..."?
The receiving station isn't going to know the difference. You might notice the difference 6 degrees of beamwidth will make, though, especially if you're trying to null out interfering stations, or get the antenna right on the other station.
SORRY CORRECTION (WILL). THANK YOU MOLECULO, I WANTED TO KNOW IF IT MAKES ANY SENCE TO BUILD A BIGGER ANTENNA WITH ONLY A GAIN OF 1 DBI BETTER.
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The smallest difference a human ear will notice is about 2..3 dB.
However if you start "compromising" for example 1dB less in gain...a half db in cable another halve in lowpass construction/amplifiers etc... well you know where i am going at.
Besides that moleculo is spot on regarding the beamwidth (this is where gain comes from the smaller the more gain you have).
So if you have the possibility to produce a single dB more.. please do.. we all work to get the maximum form your station.
And dont forget heigth..and ground conductivity. It migth be wiser to put up a smaller beam higher
For example a small 3el yagi at 60 feet (boomlength 7feet) would produce the same signal as a large 4el yagi at 40 feet(boomlength 14 feet) for communication about 5000-10000km.
So 20 feet higher equals in THIS situation half a boomlength.
Ofcourse this is al dependable on your ground situation etc...
PS...from wich antenna are you expectiing 17dBI ?...that equals a boomlength of at least 150 feet...unless you stack two 100 feet boomlength beams...(for 11 meters).
If you are going for any manufacturer wich is saying they have that many gain from a shorter boomlength beam, i wouldnt go for it at all...i dont like those who cheat.
73 Henry
19SD348
(all writing mistakes can be changed with: abcdefghijklmnopqrstuvwxyz1234567890.,?!@#$%^& )
(sorry, not my native language)
However if you start "compromising" for example 1dB less in gain...a half db in cable another halve in lowpass construction/amplifiers etc... well you know where i am going at.
Besides that moleculo is spot on regarding the beamwidth (this is where gain comes from the smaller the more gain you have).
So if you have the possibility to produce a single dB more.. please do.. we all work to get the maximum form your station.
And dont forget heigth..and ground conductivity. It migth be wiser to put up a smaller beam higher
For example a small 3el yagi at 60 feet (boomlength 7feet) would produce the same signal as a large 4el yagi at 40 feet(boomlength 14 feet) for communication about 5000-10000km.
So 20 feet higher equals in THIS situation half a boomlength.
Ofcourse this is al dependable on your ground situation etc...
PS...from wich antenna are you expectiing 17dBI ?...that equals a boomlength of at least 150 feet...unless you stack two 100 feet boomlength beams...(for 11 meters).
If you are going for any manufacturer wich is saying they have that many gain from a shorter boomlength beam, i wouldnt go for it at all...i dont like those who cheat.
73 Henry
19SD348
(all writing mistakes can be changed with: abcdefghijklmnopqrstuvwxyz1234567890.,?!@#$%^& )
(sorry, not my native language)
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When comparing two or more antenna's gain specs, you compare them by using db. Leave off the i at the end. The i means "isotropic radiator", which means you're comparing the gain of the antenna to an isotropic radiator, not another real antenna.
THIS ANTENNAS WERE DESIGHN ON EZNEC PLUS BY ME. BOTH ARE 6 ELEMENT QUADS AT 60FEET, 6 ELEMENT 31FT BOOM= 17DBI(14.85DBD)/ AND 6ELEMENT 48FT BOOM 18DBI(15.85DBD).(I SHOULD OF DONE THIS FROM THE BEGINNIG). THESE ARE THE REASON I ASKED THE QUESTION. IS IT WORTH IT?
This is where you have to ask yourself if adding an extra 17 feet of boom is worth an extra 1 dB. In a nutshell NO! A 31 foot boom is a monster in itself much less a 48 foot boom. One db is the minimum discernible difference that the human ear can hear but that is irrelevant because we are talking antennas and not audio. The difference that we hear is not the same as signal/noise ratio in the receiver and the effects of automatic gain control circuits etc. One extra dB of gain will not be noticed on either end. It takes 6 dB to increase the signal one extra S-unit so 1 dB is about half the width of the S-meter's needle.
Not to mention the mental stress involved when watching that thing in a wind storm.
I started to mention about the wind AND ice problems but then I noticed where you are located. Not too much worry about icing in Nassau. LOL
I used to talk to a fellow a lot many many years ago down in Nassau Bahamas. His name was Tyrone unit 2008. Called himself the Pink Sand Base.
Hello people,
Just wanna have it said that my english just migth be not as smooth it is not my native language..but i mean everything in a very polite way. Just here to help each other
@captain kilowatt:
I realise we are speaking about signal/noise etc etc but exactly that is irrelevant.
The receivers signal/noise ration remains the same if you use those different kind of antennas.
The difference in noise picked up by the antennas with such "small" beamwidths is nill.
So in my opinion the fact remains that about 3dB is the first you will be able to notice.
You could trest it with a few radio-stations.
Ask a distance station to lower his power until you just can not hear him anymore.
Then ask him to add power just as long as you just can hear him...say stop to him and ask him how much power he has added..now you can easily calculate the dB..
You will end up with about 3.
It is not intresting the signal to noise ratio cause that is not a number that will changes.
And you can probarbly turn your AGC off.
Although we are talking about antennas it does come down to audio wich you will hear comming from the speaker and your abbility to detect any difference. It is the 3dB difference that will allow you to copy a station or not.
As you say yourself it takes 6dB to add 1s-unit wouldnt 3dB be a half s-unit and just the difference in being able to notice?
And i dont believe you are rigth when saying: 1dB can be noticed in audio by the human ear.
Ask a local DJ to add 1dB on the volume...i am confident you will not be able to notice the difference.
You need measurement equipment to notice 1dB.
Therefor it is relevant cause that was the question..is 1dB noticable?
If you can confince me otherwise please do, always happy to learn!
@ Shoemaker
Thank you for the explination about 60 feet so that would leave about +/-12dBI in normal words..you certainly got my attention with that gain numbers hihi.
Then im my humble opinion the wise descision (probarbly not what you want to hear)
I would go for a Yagi..
As you migth know beyond 5el the quad versus yagi battle is lost and the yagi comes out as the winner.
Just taking a look at eznec here and i have some older designs wich produce higher gain with a litlle less boomlength. And i am certain we could optimes it beyond that since those are already a 10years old.
Another disadvantege of the quad would be the windloads it will be much higher compared to a yagi.
Ofcourse the weigth of the quad is higher.
There is more room for ice and snow to "sit" on a Quad antenna wich doubles the problems again..
Believe me i have designed/construct lots of beams (quad/yagi upto 75 feet boomlength for 11 meter and..above 4..5.. elements i would always go for a yagi type.
Back to your design on a 48 feet boomlength..Have you thought about that this might be too long for a 6 elements ?
You could be better of with a 7el yagi on such a boomlength. T
This will probarbly expand your bandwidth and will produce a "cleaner"pattern.
More a like a "owa" design.
For the larger beams i often use sailing boot rope (this wont stretch will not held water and can handle enorm intens forces).
You can use ironwire aswell but dont forget to insert them in eznec, putting isolaters in them can help you for not making them resonant.
73 Henry.
19SD348
Just wanna have it said that my english just migth be not as smooth it is not my native language..but i mean everything in a very polite way. Just here to help each other
@captain kilowatt:
I realise we are speaking about signal/noise etc etc but exactly that is irrelevant.
The receivers signal/noise ration remains the same if you use those different kind of antennas.
The difference in noise picked up by the antennas with such "small" beamwidths is nill.
So in my opinion the fact remains that about 3dB is the first you will be able to notice.
You could trest it with a few radio-stations.
Ask a distance station to lower his power until you just can not hear him anymore.
Then ask him to add power just as long as you just can hear him...say stop to him and ask him how much power he has added..now you can easily calculate the dB..
You will end up with about 3.
It is not intresting the signal to noise ratio cause that is not a number that will changes.
And you can probarbly turn your AGC off.
Although we are talking about antennas it does come down to audio wich you will hear comming from the speaker and your abbility to detect any difference. It is the 3dB difference that will allow you to copy a station or not.
As you say yourself it takes 6dB to add 1s-unit wouldnt 3dB be a half s-unit and just the difference in being able to notice?
And i dont believe you are rigth when saying: 1dB can be noticed in audio by the human ear.
Ask a local DJ to add 1dB on the volume...i am confident you will not be able to notice the difference.
You need measurement equipment to notice 1dB.
Therefor it is relevant cause that was the question..is 1dB noticable?
If you can confince me otherwise please do, always happy to learn!
@ Shoemaker
Thank you for the explination about 60 feet so that would leave about +/-12dBI in normal words..you certainly got my attention with that gain numbers hihi.
Then im my humble opinion the wise descision (probarbly not what you want to hear)
I would go for a Yagi..
As you migth know beyond 5el the quad versus yagi battle is lost and the yagi comes out as the winner.
Just taking a look at eznec here and i have some older designs wich produce higher gain with a litlle less boomlength. And i am certain we could optimes it beyond that since those are already a 10years old.
Another disadvantege of the quad would be the windloads it will be much higher compared to a yagi.
Ofcourse the weigth of the quad is higher.
There is more room for ice and snow to "sit" on a Quad antenna wich doubles the problems again..
Believe me i have designed/construct lots of beams (quad/yagi upto 75 feet boomlength for 11 meter and..above 4..5.. elements i would always go for a yagi type.
Back to your design on a 48 feet boomlength..Have you thought about that this might be too long for a 6 elements ?
You could be better of with a 7el yagi on such a boomlength. T
This will probarbly expand your bandwidth and will produce a "cleaner"pattern.
More a like a "owa" design.
For the larger beams i often use sailing boot rope (this wont stretch will not held water and can handle enorm intens forces).
You can use ironwire aswell but dont forget to insert them in eznec, putting isolaters in them can help you for not making them resonant.
73 Henry.
19SD348
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I would put the experiment the other way around. Everyone seems so obsessed with the transmitting station and forget their ears...
Put the 17dBi antenna up, and then ask the other station to lower his power until they just cannot be heard. Then replace your antenna with the 18dBi gain antenna. Can you hear me now? I think so...not only will the noise go lower, but signal will also go up. you'd need to look at the other factors to quantify that. I think for the same reason, the quad is a good choice, but also agree to stay within practicle range. That is a big antenna and too unweildy for my tastes...I'd be quite happy with a 4- or 5-element quad. If I wanted more, I'd look at something else
Put the 17dBi antenna up, and then ask the other station to lower his power until they just cannot be heard. Then replace your antenna with the 18dBi gain antenna. Can you hear me now? I think so...not only will the noise go lower, but signal will also go up. you'd need to look at the other factors to quantify that. I think for the same reason, the quad is a good choice, but also agree to stay within practicle range. That is a big antenna and too unweildy for my tastes...I'd be quite happy with a 4- or 5-element quad. If I wanted more, I'd look at something else
Almost spot on.
Perhaps i was not clear in preview post but that is what the experiment is though.
If you can HEAR a difference..for example 4 watts or 16 watts it is 6dB.
These antennas are reciprocity so please do use your ears as earlier stated fully agreed!
But you will probarbly not lower your noise, as there will not be any difference in antenna temperture.
You will however have an extra dB wich on its own just migth not be the effort.
Though if it is the last you can do to improve your station (and you are a real fanatic) it is.
73 Henry
Perhaps i was not clear in preview post but that is what the experiment is though.
If you can HEAR a difference..for example 4 watts or 16 watts it is 6dB.
These antennas are reciprocity so please do use your ears as earlier stated fully agreed!
But you will probarbly not lower your noise, as there will not be any difference in antenna temperture.
You will however have an extra dB wich on its own just migth not be the effort.
Though if it is the last you can do to improve your station (and you are a real fanatic) it is.
73 Henry
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GENTS THANKS SO MUCH FOR YOUR IMPUT. I THOUGHT IN WOULD BE VERY INTERESTING TO POST THIS QUESTION BECAUSE I ASSUME OTHERS MY HAVE THE SAME QUESTION IN MIND. I AM SATISFIED AND WILL GO WITH THE 6 ON 31FT BOOM, BOTH OF THE ANTENNAS IN QUESTION I OPTIMIZE FOR SWR. THE FRONT TO BACK ON BOTH IS 36DB AND THE SWR IS 1.02 ON 27.025, INCREASE TO 1.7 ON 27.385 AND DECREASES TO 1.1 ON 27.605. I LOVE THE SWR CURVE BECAUSE I TALK ON 27.025AM AND 27.555USB. THANKS AGAIN FOR THE INPUT. (I LOVE THIS HOBBIE)
ON THE SUPERBOWL(27.025) IM KNOWN AS 73 AKA SHOEMAKER.
ON 27.555 USB= 121IR073.
73'S.
ON THE SUPERBOWL(27.025) IM KNOWN AS 73 AKA SHOEMAKER.
ON 27.555 USB= 121IR073.
73'S.
Antennas are reciprocal as mentioned. Unless something heats up due to conductor losses anything done to improve transmit will improve receive by the exact same amount.
My feeling is the longer boom length antenna modeled was not maximized for forward gain. There should be a little more additional gain from all that extra boom length. Maybe model a 7 element.
In answer to the original question the 1 dB isn't worth the extra metal unless it comes along with other things useful to you like better low SWR bandwidth.
My feeling is the longer boom length antenna modeled was not maximized for forward gain. There should be a little more additional gain from all that extra boom length. Maybe model a 7 element.
In answer to the original question the 1 dB isn't worth the extra metal unless it comes along with other things useful to you like better low SWR bandwidth.
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