A dipole antenna has a gain of 0 dBd. An isotropic radiator has a gain of -2.15 dBd. Ever notice how antenna ads always use the isotropic radiator as the reference since it will always be 2.15db more.

When ever I put up a new antenna I always check it compaired to my dipoles. Since conditions vary every minuite, this is the only way to get an idea about how it actually performs. To get an even better idea of how they compair you will have to have them at the exact same location. Believe me, only a few foot can make a huge difference. Just as moveing your ht around you get different results, its the same on hf, but not easily recognised since you can't easilly move your antenna. I have did this with ropes and pullies. I found that there is no "best" way to put up an antenna. Results vary acording to which direction the signal is coming from, the angle of radiation, soil resistance, proximity of objects, ect.

     A dipoles overall lenght can be found by 468 divided by the frequency in MHz.

Example: You have a dipole antenna cut for a target frequency of 7.200 MHz. 468 divided by 7.2 equals 65 feet exactly. Divide this by 2 and you get the lenght of each leg.

You will rarely hit the target frequency the first time. This is due to the fact that each instalation site will have so many variables that it is impossable to know the exact lenght the antenna needs to be. If you use a built in tuner there  is no reason to worry about a few KHz. If however you don't use a tuner then you should get it as close as possable. You should cut the antenna a little long if you plan on pruneing it.

The example below shows how to make pruneing an antenna much easier.

You check your antenna and find the lowest SWR is at 7.00 MHz. Do the math and you will find a length of 66.85 feet for 7. MHz. Subtract 65 feet from 66.85 feet and you come up with 1.85 foot. This is the amount you will need to take off to hit close to your target frequency of 7.2. Be sure to take off the same amounts off of each leg of the antenna.

This will get you real close. Insulated wire will be slightly shorter than bare copper wire. A neat trick is to make a loop at the end of each leg connecting the ends back to the antennsa a few inches from the end. To make the antenna longer you would just make the loop smaller.