The higher the Better right? In most cases this is true, but not always. It depends what you wanna do, do you want to talk local on 10 meters and just don't care about stations outside your local area? You'll say hello if they come in, but its not your primarily reason for being an amateur. Then antenna height shouldn't be that big of a concern to you. Do you wanna collect as many DX countries as you can on 20 meters? Then alot of stuff matters about your antenna including very importantly how high it is. Are you a linear amplifier or power freak? Well if you have your antenna whatever it is at 120 feet in the air instead of 30 feet in the air, your signal would be about 10X more powerful (from the ARRL Handbook).
What else happens at height? The amount of interference you might be causing (if your that power freak) goes way down the higher your antenna is. The amount of interference that shows up as random noise from your house or other noise generating problems, also goes way down or disappears completely. Quoting the ARRL again, doubling your height and or distance away from your house will reduce interference by 75% !!
AAH. Most importantly and usually forgotten: ( lets quote the ARRL again because most don't ever read that thick book anyway) "The angle of radiation of a signal launched from an antenna is one of the key factors determining effective communication distances. The ability to communicate over long distances generally requires a low radiation angle, meaning that an antenna must be placed high above the ground in terms of the wavelength of the radio wave being transmitted."
Okay we get it...what the ARRL says...The higher the better. Generally yes, but I don't think most realize the absolute importance of height in communications as much as they should. Again unless you are a rag chew guy on 10 meters, or maybe even 40 or 80 meters, and you do not care about anyone outside your local group, then height is very Important. How important? VERY IMPORTANT.....Let's see why;
OK, well here's a very typical example. This is the performace of a dipole at 25 feet, 45, 65 and 85 feet high. Lets hope you have some big trees in your yard. The scale going up the left side of the chart is the average db gain you will have at the shown heights Assuming Flat Ground. The takeoff angle along the bottom show the percentages that most of the angles will arrive at your antenna on the 20 meter band that will arrive at within the U.S. The takeoff angles on the left generally are the farther away signals. This chart represents stations located in NYC or generally the east coast of the US. So if you live on the east coast of the US, the lower takeoff angles 1-10 degrees would generally be signals coming in from the west coast. Generally signals arriving from 10-17 degrees would represent midwest signals arriving at your antenna, and anything higher would be short skip (dx) signals from within the east coast itself.
Astute readers may have noticed I am using the word generally quite a bit (generally speaking). Yes I am thats because these takeoff angles are not hard and fast rules. Because the reflection of your signal off of the atmosphere is not always at the same height it varies depending upon the height of the F layer at the time of your transmissions. I like to think of it like this: Look up at clouds in the sky, they form when the rising warm air condenses onto dust particles and form a cloud. This warm air does not always condense at the same point. Look at clouds they have a cloud base which is not exactly flat or at the same height thoughout the cloud itself. I imagine the atmosphere and its height base being similar to in ionization to clouds. This is why I need the term "Generally" in 50% of my sentences in this section of the website.
Notice on the chart above there is a long horizontal grey line going across the screen. That is the Zero DB gain level. So anything below that your dipole has no db gain advantage and if you have a dipole 25 feet high, most signals on 20 meters from the west coast will be difficult to hear well. Putting that antenna up 45 feet high and you will be able to make some headway to the west coast. Of course this is Generally speaking. My new favorite word for this page...Generally. Something else you may have noticed, look at the blue 85 foot high dipole pattern of signals coming to your antenna. Notice at that height signals coming into your antenna from the highest angles or the closer stations to your location, the db gain advantage of your high 85 foot dipole diminishes. So for stations near you, the 25 foot dipole does very well. So the highest dipole does well for the farther away stations, but no so good for the closer stuff. This applies to DX only.....NOT groundwave.
But lets say you like to contact the west coast United States stations on 20 meters, well is there an advantage to having a beam? Boy is there. The chart above compares the 25 foot dipole on 20 meters, compared to several beam types all at the average height of 45 feet for them. I assume that the beams are a bit higher then the dipole, because I assume you have a moderately sized tower if you bought one of these beams. So how much of a difference do these beams really make? One look at that Zero Db gain line and you can quickly see that having a beam at those heights versus a 25 foot dipole is a total mismatch for the west coast farther away stations, and even for the close in stations on 20 meters its a mismatch. Notice how great I said a Hexbeam works on one of the earlier page? Well now you can see why. Even just a Hexbeam can increase your capability greatly. Now you know why they have been recieved very favorably by amateur radio operators who have made the plunge to get one.
Ever wonder why you can't hear that rare weak island DX station on that rare 1 time only expedition? Or how come That guy with the big antenna farm can talk to and hear that Outer Mongolia station at S9 ? well here's your answer. HEIGHT and better antennas. Most of the rare DX stuff comes in at angles that would normally be very low to your antenna (thats why their rare). So sometimes your just gonna need a Bigger Gun. I put the Hexbeam up at 75 feet, most people probably have one up around 45 feet, and still at 75 feet you have virtually NO CHANCE at getting the signal to and from the lower angles as well as the top arc... The stacked Super Station. Even the mighty 30 foot boom 4 element Cubical Quad at 85 feet is more then 9-11 DB gain down from the Super Station. The Super Station might have to switch to a lower antenna to recieve the higher angle signals better, (which thats what they do) but if your gonna try to compete with the BIG GUNS....Bring a big wallet! Otherwise if one of these guys is on the air while you are, your going to have to wait your turn.
So how do I know you just didn't make all this stuff up? I didn't I swear I didn't. All of the above comes from a well known fact, the higher you get your antenna up in the air the lower the angle of radiation will be. The farther you antenna is above the ground the more it will generate most of its energy at a low angle along the ground. This is a fact, look it up at some real websites ( like the ARRL site and in the Big book of theirs) you'll see. So for Long Distance Ground Wave freaks only, if you can't be by the water to get a good ground or a lower angle of radiation, then get up on to a mountain top, or have your antenna up as high as possible. Period. Even more true for VHF and up.
So the saying Height is Might is true? Yes most times it is. And as you can see it makes a big difference in who you can hear and talk to. So let's say your not a freak (in the dx sense of the word only). And you just want to put some thing up that will give you relatively good performance across the HF bands, but you don't wanna go crazy. What should you do? Well I would (if I wasn't an antenna freak myself) put up a Hexbeam or a small Tribander Yagi at the very least. These will give you very good performance for all but the farthest DX contacts. All of the US, Europe, Middle East, and some Pacific stations will be easily within your grasp, put it up as high as you can at your location and I think you'll be for the most part entirely satisfied with your results. If you are stuck with a dipole or a wire antenna, use as much wire as you can and get it up as high as you can.
A word about Radiation angles and antennas: I don't want you to stress too much about radiation angles. Thats why I used the word Generally alot above. angles come in from everywhere. The above is a rough guide to where they occur, and each reception you have of that far dx station they are changing. In general the better antennas (beams) will have more gain at ANY angle then even higher inferior antennas. Get as good of an antenna you can and put it as high as you can, and you'll be happy.
Ok, so lets say you are on 40 or 80 or even 160 meters, and you are never going to get an antenna up high enough to get remotely anywhere near a radiation angle below 10 degrees. Don't worry your just like most lower HF operaters, and in this case you shouldn't give a rat's a** about radiation angles. Your friend for signals up to 1000 miles away on these band is called NVIS. This just means that your signal is going almost straight up bounces, off the Ionosphere and comes back down to earth. On these bands this allows your 20 foot wire antenna to talk to anyone within a 1000 miles of your location with very little signal loss. Have a beer and enjoy the ragchew. Now.... this doesn't mean you'll be killing it everynight to Japan on 80 meters, that would be unusual and probably out of your reach (that low angle thing), unless you are running 1.2 JIG A WATTS like in the "Back to the Future" movie. But lets assume your legal limit. You'll do just fine, with a wire, make it long as you can, and rock on.
Ok so whats this map about. It's just a simple propagation map that shows generally how signals propagate during the day versus the night. On the left side you have all the HF bands during the day. This shows that most of the lower bands 160,80,60 meters get absorbed by the D-layer of the atmosphere which is created at various intensities by the Sun. So for these bands most DX ( bounce off the atmosphere contacts ) are not available, and contacts are generally short regional, if at all.
The 40 & 30 meter bands during the day get weakened but most times not fully absorbed by the D-layer of the atmosphere. so some DX contacts may be possible in daylight although certainly not as strong as in darkness when the D-layer is no longer present after sundown. Anything that gets through the D-layer will have a chance to eventually reflect at a higher point in the atmosphere.
10 - 20 meter bands are happy as the D-layer does not effect the higher frequencys as much and these signals go up much higher into the atmosphere and reflect providing long DX contacts anywhere on the earth. Especially during sunspot maximums.
As night begins the lower bands become alive ....160-30 meters as the D-layer disappears, and signals travel all the way up to the higher atmospheric layers. There is still some ionization in the upper atmosphere layers ( the sun may have set where you are, but it hasn't in the upper atmoshere yet ), and the E & F-layers will still reflect signals of lower frequencys quite well, although the layers tend to lower as night goes on, and eventually disappear, and the cycle starts again at sunrise. For 10-20 meters the effect is almost the opposite, as the higher frequency layers do not reflect or bend in the weaker E & F layers at night like the lower frequencys do. They usually just pass through the atmosphere into outer space, never to return.
Now. This is the standard spleel about Atmospheric Layers and Propagation. However in reality there are NO LAYERS, just varying degrees of charged atmosphere at different heights for the day and the night. This changes not only day to day but hour to hour regularly. So the chart above is a rough guideline, but by no means the atmosphere bible by any stretch. Can you make DX contacts on 10 meters in the middle of the night with no sunspots whatsoever....... Sure, you just have to be there at the right time and moment, with the right size still energized ionization cloud passing over your QTH. Will that happen every day? NO. But it can happen and has countless numbers of times. The atmosphere is kind of like a soup that your mom made you that was thin at the top and thicker at the bottom. And this soup consistency changes from day to day, even hour to hour, minute to minute.
How far can you get Groundwave on 10 meters? Well how about this? Here's an easy 350 mile contact, only groundwave no enhancement. NY to Mount Washington NH.
