Dipoles for all directions

 


The good thing about a dipole is it has good gain off the broadside with a broad beamwidth, almost 90 degrees. This bandwidth is between the 3 dB points. Can’t hardly tell 3 dB. After that the signal drops maybe 10 dB directly off the ends. Other antennas can get a couple more dB off the front but that is ALWAYS at the expense of beamwidth and creates more or deeper nulls. In my opinion there is no single antenna better for general purpose amateur operating than a dipole. A better antenna requires a tower and a rotator. Such an antenna would be a Yagi, but a two element Yagi only has a few dB gain over a dipole. The rule of thumb being that you have to double the size of the array to get 3dB of gain. So the big deal with Yagi antennas is you can rotate them to focus your power where you want it. Again at the expense of beamwidth. I found myself always turning my antenna to point it in the right direction because it had such a narrow beamwidth! Some years ago after working a 10 meter contest up in Richmond with extremely high gain and very high Yagis I came home and decided not to put up a tower and Yagi again because I thought I could do almost as well with my dipoles.  I had been doing good for several years with only dipoles so I decided to just improve on that.
Below is a plot of my 20 meter single dipole. Notice that I have drawn a circle at the -3dB point. I have a 90 degree beam width off the front and off the back where the signal is very strong. Off the ends the signal drops by about 10 dB. That’s very noticeable. So instead of putting up a tower I added two more dipoles. The result is in the second plot. My signal is only down by 1 dB everywhere except in two narrow directions where it is 4 dB down! For practical purposes what I have is probably not any different that being able to rotate the antenna. That rotation is instantaneous as I just flip a switch and do not have to wait for the antenna to actually turn. This may not have the gain of my 4 or 6 element Yagis that I had in Hampton but it’s a lot more convenient and infinitely less maintenance. Also if I lose one antenna I still have two in operation. No climbing a 70 foot tower in cold weather is definitely a plus. Nothing every goes bad in good weather. 
These pattern only apply to 20 meters and above because we are looking at dipoles that are half wave high or higher. Lower antennas tend not to be so directive and therefore there is usually less to gain with an additional 40 meter antenna like on the higher bands.
On 80 most dipoles are not high enough to have much directivity.

I plan to build a tri band fan dipole (20/15/10) next and put it up pointing East/West to replace my single band 20 meter East/West dipole. 


























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