Question on antenna Power Multiplication

[firerunner]

So I am going to use a Maco M104c as a reference. I know antenna manufactures exaggerate the specifications of their antennas. That being said Maco rates the power multiplication of the m104c as 28x. Now does this mean that if I put 10 watts out of the radio into the antenna is now putting out 280 watts?
I know it's really not putting out that many watts so whats really up with this spec?

 

[wavrider]

Every 3db. Doubles you transmitted power. Erp. Effective radiated power

4. Element yagi may have 8 Dbd gain

 

[The DB]

So I am going to use a Maco M104c as a reference. I know antenna manufactures exaggerate the specifications of their antennas. That being said Maco rates the power multiplication of the m104c as 28x. Now does this mean that if I put 10 watts out of the radio into the antenna is now putting out 280 watts?
I know it's really not putting out that many watts so whats really up with this spec?

The words "power multiplication" is not a good way to describe what is happening. Your antenna cannot "multiply" the power that it gets from the feedline.

What an antenna can do is take the power that it does get, and focus it in a smaller area. A better way to describe what is happening is "Power Focusing".

Here is a question, what is this "Power Multiplication" being compared to? There is no "Power Multiplication" standard, and nothing is referenced for a comparison. Further, I see nothing on their web site which explains this figure. All it appears to be in reality is a number that makes their antenna look good to prospective buyers, much like the "Audio Gain" figure you see on some antennas.

Also take a look at their gain figures, again they have numbers that, on their own, don't mean anything. All of their antennas range between 11 and 18 dB in gain, but compared to what? To have a given decibel of gain you also need a reference, or what that gain is being compared to. When a company posts incomplete gain data like that I just assume that it is dBdl, or decibel gain over a dummy load. Again nothing on their site explains what that figure is based on in any way.

Note, I am not trying to say their antennas are crap, that is a decision that you the user have to make on your own. I know several people who own them and use them, but some of the data given is little more than fluff.


The DB

 

[Justme]

Compare the isotropic antenna as an lightbulb hanging in free space radiating in all directions equally poor.
Now look a the 5/8 antenna, and the main lobe will be directed more to the earth or in a low angle for more dx, the same power is put into that antenna as the theoretical isotropic antenna, but through bundling your power in a certain direction more of that same power is directed to where you want it to go.
A beam antenna you can compare with a flashlight, that bundles the same power in one direction only, hence the "gain" of the beam, goes from reception as well.

In all these cases if we put 10 watts into the antenna the antenna's will radiate 10 watts, the isotrope mostly used as comparison is a theoretical antenna that will radiate 360 degrees all around, we as hams use the dipole as reference antenna.
But gain figures look 3 dB better using the theoretical isotrope antenna, hence a less reliable antenna manufacturer will use the isotrope as reference antenna......

Compared to a 1/4 wave antenna the 5/8 will have 2.7 dB gain in the direction of the main lobe, a 3 element beam will have 4,5 to 5 dB gain over a dipole, but add another beneficiary point, a deaf backside that lets you filter out unwanted stations by turning the backside to them.

There are no miracle 5/8 wave antenna's with 12 or 20 dB gain, yes, over a dummy load.....
For a round table talk with friends around you a good 5/8 antenna will be the most practical antenna to use, for DX a good beam is more practical.

One reason you won't find these wild gain claims for Ham radio antenna's because most hams know the truth, and any antenna maker that claims unrealistic gains won't sell any stuff.

The average starter on 11 meters won't have that knowledge and will fall for those unrealistic claims as intended by the makers of those fantasy claim antenna's.

The words "power multiplication" is not a good way to describe what is happening. Your antenna cannot "multiply" the power that it gets from the feedline.

What an antenna can do is take the power that it does get, and focus it in a smaller area. A better way to describe what is happening is "Power Focusing".

Here is a question, what is this "Power Multiplication" being compared to? There is no "Power Multiplication" standard, and nothing is referenced for a comparison. Further, I see nothing on their web site which explains this figure. All it appears to be in reality is a number that makes their antenna look good to prospective buyers, much like the "Audio Gain" figure you see on some antennas.

Also take a look at their gain figures, again they have numbers that, on their own, don't mean anything. All of their antennas range between 11 and 18 dB in gain, but compared to what? To have a given decibel of gain you also need a reference, or what that gain is being compared to. When a company posts incomplete gain data like that I just assume that it is dBdl, or decibel gain over a dummy load. Again nothing on their site explains what that figure is based on in any way.

Note, I am not trying to say their antennas are crap, that is a decision that you the user have to make on your own. I know several people who own them and use them, but some of the data given is little more than fluff.


The DB

 

[firerunner]

Thanks to all of you guys for the great answers. I wasn't trying to bash any antenna builders and I don't own any Maco antennas, I just used as a reference. I think the light bulb and flashlight explanation is the easiest way for the average person to look at it. I thought I understood what it meant and i did just wanted to make sure. It would be great if there was a set way to measure these antennas so that the buyer could compare and know pretty much what you were buying. I know there are a lot of variables also and one antenna may work better than another in the same location.

 

[M0GVZ]

dBd, reference to a dipole.

It would be great if there was a set way to measure these antennas so that the buyer could compare and know pretty much what you were buying. I know there are a lot of variables also and one antenna may work better than another in the same location.

dBd, reference to a dipole.