The higher the antenna 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 ham radio propagation and 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% !! So does this mean you have to have your antenna a million feet in the air/ No. DB gain increases with height yes, but it slows down and even levels off after a while. So what is the minimum height that you should look to put your antenna at and still get decent results. The bare minimum is one wavelength in height. This height will give you distance from the ground and most likely from your house, to get both good gain and eliminate some noise. In fact anywhere from 1 wavelength or 1 1/2 wavelengths is a good height. It turns out that at 1.5 wavelengths of height the db gain after this starts to slow down in smaller increments. At 1.5 wavelenghts the antenna db gain actually levels off for a while. Meaning the difference between 1.5 and 2 wavelengths is not that much. After that the gain continues onward and upward at a fairly regular pace.
Before you get too excited about this...... realize that 1.5 wavelengths at 20 meters is around 110 feet high! Right. Its still no cakewalk. So if you could possible do around 70 feet for your 20 meter antenna (1 wavelength) you'll still be okay, not as good as 110 feet, but very decent. Now if your on 10 meters...Now you got something. 1.5 wavelengths on 10 meters is 54 feet! Entirely doable in most cases, even without a giant tower, depending on what kind of antenna you have. Ever wonder why antenna towers are usually 100 feet high? Well thats why, tower manufacturers figured with the mast your at 110 feet, and your 20 meter beam and all other bands higher than that you will be kicking butt.
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. 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 not so great 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. Think of it this way. Your at a NFL sports arena, there are 50,000 fans.... a referee just made a terrible call, you are in the upper deck, you and everyone else in the stadium starts yelling at the referee! What are the chances he hears you? Thats your chances against one of the Super Stations.
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 Ham Radio Propagation, 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.
As far as height is concerned, there is another major factor that determines your communication effectiveness, and its related to antenna height. Its Prominence above the surrounding area. Its great if you are 4000 feet above sea level, but if you are surrounded by mountains that are 6000 feet above sea level, then your location is not so great after all. You may get out decently on some DX contacts, but your local communications ability or groundwave is really going to stink. So does this mean that you have to be at the top of a tall hill with nothing around your height for many miles? , not necessarily, but it sure wouldn't hurt! There are other antenna height factors that determine just how well you get out. Lets say again that your on the east coast of the US. and you live near the shore ( let's say Virginia ) and there is a large hill to your west that effectively blocks alot of the signals from that direction. UGH right? Well maybe not. If you like to talk to Europe most of the time , those signals coming in from Europe will be heard nicely on your recieve. Why? Because that big hill to your west will gather up those signals like a satelite dish and bounce them back down to you and your antenna by the shore. The Big Plus.... Europe will come in better than if you were on top of a large hill at your location. Bad News....Asia in the west direction is going to be tough to hear consistently, as well as any local groundwave stuff most times.
The bottom line is this, you may think your location stinks if you happen to be the location on the east side of the photo on the left. But the reality in your local situation is you will be getting some reflection even behind the big hill as in the right photo. And the reality is there are reflections happening everywhere as in the photo below. These are impossible to predict. You can't really count on reflections as a positive to your station because they are random and unpredictable. You may be in a spot like mentioned in the prior paragraph, where a big hill to your west helps your reception to the east. But don't count on it. However as a rule, try to get your antenna up as high as possible and as far away from not only your house but any other obstructions around your immediate area and you should have a decent recieving station.
HF Antenna Propagation is extremely complicated. Other places or software programs that predict or tell your otherwise are wrong. Just follow the above guidelines and do the best you can.
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Near Vertical Incidence Skywave:
Ok, so lets say you are on 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 operators, and in this case you shouldn't give a rat's ass about radiation angles. Your friend for longer signals up to 500 miles away on these band is called NVIS. Near Vertical Incidence Skywave , this just means that your signal is going almost straight up bounces, off the Ionosphere and comes back down to earth. On these bands a mixture of groundwave and your new buddy NVIS allows your 20 foot high wire antenna to talk to anyone within a 100-500 miles of your location with very little signal loss. Have a beer and enjoy the ragchew. Now when it does get dark and 80 meter signals get to the upper atmosphere.... it doesn't mean you'll be killing it everynight to Japan, that would be unusual and probably out of your reach (it's that low angle thing), but it does happen occasionally.... 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.
How and why does all this stuff happen?
The ionized part of the Earth's atmosphere is known as the ionosphere. Ultraviolet light from the sun collides with atoms in this region knocking electrons loose. This creates ions, or atoms with missing electrons. This is what gives the Ionosphere its name and it is the free electrons that cause the reflection and absorption of radio waves.
When the sun is overhead during the day, most of the ionosphere is ionized due to the large amount of ultraviolet light coming from the sun. As radio waves enter Earth's atmosphere from space some of the waves are absorbed by the electrons in the ionosphere while others pass through and are detectable to ground based observers. The frequency of each of these waves is what determines whether or not it is absorbed or able to pass through the atmosphere. Low frequency radio waves do not travel very far through the atmosphere and are absorbed rather quickly. Higher frequency waves are able to pass through the atmosphere entirely and reach the ground.
This process also works in reverse for radio waves produced on the earth. The very high frequency waves (mostly VHF and UHF) pass through the ionosphere and escape into space while the lower frequency waves (HF) reflect off the ionosphere and essentially "skip" around the earth. These 3 paragraphs above directly from NASA, which is why there are no spelling errors.
Ok so whats this map about. It's just a simple radio 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 groundwave and short regional contacts. As the day goes on, even those contacts will be tough. antennas here are very low per wavelenght, most signals are going up at angles of 70-90 degrees making short regional contacts in early mornings before the sun takes out the band completely.
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 short DX contacts and some groundwave 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. Here the Ham Radio Antenna Propagation is slightly different. So 40 meter signals can pass through the D layer but usually only at high angles so daytime communications are similar to the earlier 80 mornings, during the day.
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 off of the E and F layers 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 atmosphere 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 what so ever....... 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. Just like someone is stirring it with a spoon from up above. Okay lets not get too deep....you get what I mean.
If this is confusing, and I can see how it is, being that I obviously wasn't born a natural writer, I will try to simplify the lower bands here. Elsewhere on this page and others I talk about the Higher HF bands at lenght. These 3 bands below have separate different characteristics than the higher bands. So here we go.
160 meters:
This is a short distance communications daytime band, because of D layer absorption during the day. Daytime communication is limited to relatively short ground wave coverage, just like when you listened to your Am radio. At night, when the D-layer in the ionosphere disappears, communication distances increase and it may be possible to hear stations several hundred or thousand miles away. During grey line zone have an increased chance of making long-distance QSOs, especially if the other station is also in a grey line zone. Signals long-distance propagation for this band is often better around sunspot minimum when solar activity is low and noise levels are lower. As a general rule, the probability of long-distance contacts improves in winter because of the longer hours of darkness and lower levels of static. December through March nighttime is best time for this band. This band is popular in rural ares, where electrified fence wire and just LONG random wires and loops can hear just about anything with with no noise especially in winter.
80/75 meters:
On 80 meters during the night, contacts up to a few hundred miles away can be had. At night, you can pull in ham radio stations from distances of 1,500 miles or more. As always greater distances can be achieved with good HIGH antennas. The 80 meter band opens up during the years of the sunspot minimum, but is workable anytime of year during the night, better in the winter when there are no thunderstorms. Early mornings this is a great band for regional contacts , this will fade out as the sun come up. Sometimes you will run across some loose cannons, former CBer's and LIDS (rude operators). These are operators who never made the jump to the higher HF bands where some antenna knowledge is needed, and do not know how to talk politely to people, so they found a wire, realized they can be heard and end up here. This is not the norm but it occurs here and on 160 to some extent. Others are more polite former Cber's whose local CB contacts have dried up, they got their license, found a wire and think that talking 300 miles is just amazing. They usually insist on having a 1KW of power, even though most times 100 watts will be fine on this band. This band and 160 for that matter are very forgiving as far as antennas go. You don't need much to hear and talk to people within 100 miles. Think of the size of the antenna that your transistor radio had as a kid. You are only a little over 2 MHZ away from AM radio. However if you want to get away from noise, and also would like to play DX in nighttime, if you can raise your dipole, loop or end fed wire up to 50 feet your experiences on the band will be rewarding.
40 meters:
This band is most useful for inter-continental communication for one or two hours before sunset, during the night and for one or two hours after sunrise. This band does exceptionally well around the time of greyline for worldwide contacts. At night distances improve greatly and around the world communications are possible. It is extremely useful for short to medium distance contacts from local contacts out to a range of 300–1,000 miles or more, during daytime periods. This band is not affected much by sunspots as all the the HF bands above it 30-10 meters are. So it can be good day and night. There is also less stations with multiple element beam antennas on 200 foot towers, so you have a better fighting chance in that dx pileup as most stations are using wires. Lots of Nets on this band helping you to get WAS (worked all states award) if you want it. Winter is still quieter than summer, thunderstorms will still be an issue in summer. But overall a very good band and you can always find someone or someplace unusual.
Shortly after sunrise and during the early morning the band conditions "go short" as the D layer is getting stronger and absorbing more signals, reflections off the atmosphere are less likely at longer distances. So "the band is going short". You will often hear claims of the band is going long or short at all times of the day or night, disregard this chatter. On the lower bands 40/80/160 that get affected by D layer absorbtion, when daylight gets stronger in the morning, the band "goes short" , when its sunset and it becomes night time, the band "goes long" this is because the D layer of the atmosphere is weakening and more signals will bounce farther up in the atmosphere leading to longer distances being attainable. The opposite happens during the morning.
20 meters: The Grandaddy of them all. This is the go to band if your into long distance DX contacts during the day. Who wants to stay up all night when you can make contacts during the day? Although sunspots are starting to affect this band ( more sunspots the better ) you can still almost talk across the world most any day. In times of solar maximums like now in 2024, this band is on fire! Noise is much less than 160-40 meters even in the summer. Sure you can talk a bit local like 200 miles maybe during the daytime, but it's almost exclusively a DX band. Want to get that hard to island expedition contact, at some point he'll be on this band more likely than all others, except for maybe FT8. But I don't personally consider that a challenge. You think your a big gun? With alot of un neccessary wattage with a new hexbeam or tri bander you just got? Well sit yourself down son, you ain't nothin on this band! The superstations with stacked Yagi's or big Cubical Quad antennas are here waiting to eat your lunch. My point is this band is SO popular getting through the pileup make take a while. Good Luck and keep trying, you'll get them once you figure out the dx stations timing and cadence.
17 meters: similar in propagation to 20 meters, but no contesters here (YAY), no 59 and good buys, maybe even a decent conversation across the world with someone you just met on the radio, imagine that! You'll have a better shot at that rare DX contact on this band than 20 meters, since not everyone has a decent 17 meter beam. This band is slightly more affected by sunspots than 20 meters, meaning better at solar maximums then minimums. One of my favorite bands, less crowded. Hexbeams do well here.
15 meters: 3 MHZ up 17 meters, similar again in description, except contesting allowed, more popular than 17 meters, good dx possibilities during periods of maximum sunspot activity. less noisy than the lower bands. The band can be closed during solar minimums, strickly a dx band, very little if any local groundwave traffic. Most everyone who decided to put up a 3 element or more beam has one that includes 15 meters, so dx pileups are still prevalent here. So if you don't have at least a tribander beam, you may be waiting a bit to make that rare dx contact.
12 meters: No contesters, great during solar maximums and daylight hours, open to the southern hemisphere most days. The least popular of all bands. During periods of low solar activity the band is completely dead. There is zero local groundwave traffic. Hexbeams do well here.
10 meters: AAAH, The band that a whole book could be written about. This is the band of unexpected activity. Large variations in its groundwave and skip/dx activity, and intensity. During high solar activity virtually any part of the world can arrive at your reciever from short, long and everything in between paths and distances all at once. Why, well this band is the middle ground between upper HF and lower VHF and consequently is affected greatly by both. Like the lower frequency daytime bands maximum sunspot activity means alot fo people to talk with. But even when sunspots are not super high, you can chat day or night locally and sometimes much much further. Also anyone with a CB radio antenna ( yes I mentioned a bad word ) and an HF radio can get on the air and chat locally or across the world. So there are just lots of people who know zip about HF antennas, and they discover that their Antron 99 and Imax 2000's can do fantastic here. To top it off Sporadic E propagation is very common here like on VHF from 400 to 1500 miles in spring and early summer time. This means all sorts of big stations and even small qrp stations from all over the US can come in with rather large unexpected signals. This is the band that you can get your WAS (worked all states) award rather easily in times of just decent solar activity. 10 meters is also greatly affected by the weather (tropo), this means if its foggy out or before a big storm, the band will also be open regionally to great groundwave distances. Want to talk to Rochester NY from NY city? didn't think its possible? Wait for bad weather you'll find out you had a cousin you didn't know about in Rochester soon enough. Don't like snow? If you get it where you live you'll be surprised to see how it effects your groundwave talking distance especially when its foggy ( temperture inversions ). Hundreds of miles of territory is now open to you under these conditions, that normally falls in the skip zone, which is the place where local communications end and dx begins. Not on this band, think of fog and rain as your new radio friend and enjoy talking to station a few hundred miles away.
Ever heard of backscatter? Well this is the main band for that. How can you tell? Signals coming in with echoes, weird changes in signal strength, complete dissappearing acts every few seconds. If you have a beam point it south and you hear stations behind you hundreds of miles away. All the crazy propagation stuff is here, including TEP, Meteor scatter, Aurora, Aurora E at night, and more propagation modes you never knew existed. So the band has excellent potential to keep you busy all year with or without sunspots. When your at a solar maximums for a few years, you'll have plenty to do and maybe forget that your radio has other bands on it! At the very least you'll meet alot of local guys you never knew existed. All your CB radio junk antennas will work on this band, as well as any wires you have hung in trees. However you'll meet amateurs with all kinds of antennas from World Wide Superstations to 100 watt mobiles with 48" whips. The most un predictable and fun band in my opinion to play on. And easiest to test your antennas true signal strength on. There's less fading between signals on groundwave, similar to the VHF bands where your signal is either heard easily or its not. Admit it you've been waiting years to fire up that old Texas Star 500 linear in your truck haven't you?? Don't lie, you know you have. Well this is the band to do it. Have fun.
Grey Line and Long Path Propagation
Shortpath – Straightest communications path between two locations
Longpath – Longest communications path between two locations
Grey Line is the band around the Earth separating sunlight from darkness. This Grey Line provides a low loss path of varying size and duration for signals to travel much further distances then they normally would during daylight or darkness. This is due to changes happening while the sun is rising or setting in the atmosphere. Related to "ducting" discussed below. Puzzling but true, the Grey Line propagation works best around the solar equinoxes, greyline happens best towards the end of September and the end of March. To a lessor degree in late June and December. You might have heard of someone or some book calling the Grey Line "The Terminator" ...this is actually an astronomers term referring to twilight ruining your astrophotography in early morning. I know this because I am also an avid astronomy photographer. In my opinion the only "Terminator" is a great 1980's mvie starring Arnold Schwarzenegger! This term is not needed in Amateur Radio so don't confuse it with the Grey Line. It is the same thing. The Grey line propagation happens when your in relative darkness and so is the dx station on the other side of the earth. It only effects the 10-40 meter bands. It is also happens every day of the year, but is more prominent during solar equinox. There is also alot of confusing nonesense about where to point your antenna, etc, disregard it, and try getting on the radio right around early morning twilight and you maybe surprised about the contacts you can make.
LONG PATH: related to the above grey line
This happens again on the 10-40 meter bands. Only noticeable if you have a beam antenna. Lets say you're on 20 meters on the east coast of the U.S. and you see a station on the dx cluster that is in South Africa and you want to try a contact with him. Early morning just past twilight , you will probably only be able to make contact with him if you point your antenna 180 degrees AWAY from him! WTF you say? This is long path, its related to the changing atmospheric conditions just past your morning twilight and his later afternoon good conditions. Sometimes the stronger path is the opposite direction through darkness around the entire earth rather then the early morning short path. WHY? possibly the atmosphere where you are is not energized enough to refract signals to his part of the earth yet. So the stronger signal is had going by the long path around the earth. Sometimes both paths are open and you hear yourself via echo! Like alot of things in this scientific hobby, you will read no shortage of theories as to why this occurs. But my opinion is they are ALL JUST theories. Don't worry about it much and enjoy the dx no matter how you get it.
Example once again: Lets say you on 10 meters and you are looking for DX stations. I mean real DX, not stateside skip or European stations if your in Europe. You want to speak with India, Australia or South Africa. So you naturally point your beam antenna to the direction that you think is the proper direction, or the one that qrz.com tells you it is. ( in the details portion of qrz.com ) You listen for some chatter and you hear nothing. Well what if you turned your antenna in the completely opposite direction and gave another listen? Well you might be pleasantly surprised at now being able to hear Australia quite well, or whatever DX you were looking for. WHY? HOW? WHEN?
So called experts are somewhat baffled just like you and me, but that didn't stop them from coming up with some theories as to why this has happened. And to be fair some truths as well. Here's what we do know:
1. This is called Long Path propagation.
2. It usually happens between HF stations that are opposite sides of the earth or, one in nightime and one in daylight.
3. It usually happens when the long path is above 5000 miles or 10,000 kilometers between the two stations.
4. Conditions for this are sometimes but not always better near grey line. ( Its near or close to sunrise where you are and near or close to sunset where they are, or vice versa.) It also can happen when just one of the stations is near grey line and the other is not.
5. If you live near a large ocean the prospects of a long path for you occuring are even higher.
6. If your short path, direct signal ot the DX station is loud, you can forget any possibility of long path happening. Most times.
7. Long Path works best with low A and K indexes ( discussed in the space weather page ).
Theories and Observations by people smarter than me
Why does this happen: There are lots of theories about grey line and long path, and no shortage of websites and books attempting to convince you that they alone know what they are talking about. So I'll stick with the biggest most recognized main theory. This theory is called the "Chordal Hop". Chordal hop propagation is when you have much less attenuation due to the fact the signals does not reflect against Earth’s surface. In this mode your signal travels through the atmosphere bouncing from ionized cloud to ionized cloud until it eventually comes down to earth. When taking this path the "hops" are through the atmosphere and not bouncing off of the earth like normal DX propagation and thus end with a stronger signal than the short path. Which would have earth hops and more attenuation of signal. Other names for this currently being madeup, ahem used for this are: whispering galley, Pederson ray, etc.etc. Its all the same thing. These are all theories, in reality no one is quite sure whats happening.
This theory is similar to what I am going to discuss a few paragraphs down from here about Groundwave Ducts. Except the "duct" is in the upper atmosphere and not close to the earth. To add some juice to this theory and backing it up is the fact that stations on either side of the grey line, or one in nightime and one in daytime, the atmosphere at this time is changing from a solid F2 layer daytime layer and a nightime F1 layer. There are at different heights and therefore the theory goes in "Chordal Hopping" that the signal is trapped between these two layers for a long distance and therefore has less signal loss, then heads down to earth. To a long distance station.
The theory states: "During night time the F layer loses it’s ionization density, and it’s ability to reflect signals back to Earth. But sometimes the F-layer is just dense enough to reflect the signal back, but with a less steep angle, causing the signal to be directed to another part of the ionosphere thousands of km’s ahead, not touching the ground." Hmmm. maybe like I said its a theory. I'll buy it until a better explanation comes along.
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Here's one you probably never heard of: Transequatorial propagation
Transequatorial propagation ( TEP) is propagation between two mid-latitude points at approximately the same distance north and south of the magnetic equator. The approximate maximum range for signals using transequatorial propagation is 5000 miles. The best time of day for transequatorial propagation is afternoon or early evening. Care to explain it? trust me no one really knows why. Basically highly charged clouds form along the equator and reflect signals along the equator on others sides of the earth. Stations usually have to be within 15-45 degrees of the equator for this to happen. Valid theory? maybe. In any case this supposedly has something to do with the earth's magnetic field and its placement. Don't worry don't feel like you have to throw yourself down a flight of stairs just yet! I am not going to go deep into the theory, the main point is communications from the northern hemisphere's Europe / USA with contacts to the southern hemisphere in the afternoons are quite common on all bands from 10-20 meters. My opinion is because that's just when the sun is highest and most likely energizes the atmosphere strongest around the equator, so signals heading north or south into this area from both hemisphere's do rather well bouncing off of the F layer. But somebody decided they need a new name for this, so TEP propagation is the winner.
Groundwave Radio Propagation
The most important properties of Groundwave propagation is that it propagates parallel to the surface of the earth. The distance you can communicate using it is very dependent on the terrain constants such as, soil conductivity, antenna polarization, antenna height, distance, and frequency. All HF frequencys have Groundwave Propagation. On 10 meters this is a challenging fun activity, on 80 meters it is more of an afterthought. Groundwave propagation largely depends on currents that are flowing in the ground. Factors include moisture content and ground and air temperatures. The general geological structure of the soil, ( is it salt water or dry desert?). And the many terrain obstructions along the way and the absorptions or reflections they create relative to the signal path.
The morning hours where the sun itself has not dried up the morning dew, or where there might be a temperture inversion still in effect, or has not changed the atmosphere dynamics are usually when the best conditions for extended noise free groundwave conditions occur. Vegetation differences between summer and winter depending upon where you live also make for changes in groundwave propagation.
Groundwave happens for hundreds of miles daily in the evening and early mornings when the tempertures are stable and more importantly the Sun has not energized the atmosphere so much as to cause variable drying and ground heating yet. Most noise sources have been put to bed or are not yet awakened. This includes not just man made noise sources but also atmospheric noise sources like thunderstorms. As the sun rises higher it also energizes the D-layer of the atmosphere which will absorb most signals from the band, preventing any short skip(dx) and hinders groundwave as well. Think of your AM radio when you were a kid, did you hear it better and further at night or during the day?
Groundwave on 10 meters is similar to 160 and 80 meters as far as when is the best time for extended communications or noise free communications. However things are a bit different regarding the sun getting higher in the sky in the mornings. The sun here is energizing all of the atmosphere of course just like on 160 and 80 meters, but 10 meter signals do not get blocked from rising through the lower atmosphere by the D-layer so Skip or even DX distant stations can be heard. BUT signals can also be refracted in between lower levels of the atmosphere. This often brings stations on the band that are within a couple hundred miles of you calling the same dx station as you. These are groundwave stations with weak steady signals you didn't know existed! They can also be gotten as well as the dx stations. Many operators find this very enjoyable. Kind of like a two for one propagation band.
There is a growing number of 10 meter amateur radio operators who enjoy this activity. Operators are having frequent groundwave events that see how far one can transmit and be heard just through this means of communications. Somewhat more common on UHF and VHF, but also on 10 meters
This enhanced groundwave phenomenom occurs is also on 6 meters and also on 2 meters. And its not caused by reflections off the Ionosphere! Its caused by the Weather. Yup that sneaky suspicion you've always thought maybe the weather has something do with the band conditions is true. Sometimes in winter but certainly more so in summer it happens quite frequently. Surprise ! Its called FOG. (in simple terms). It happens when warm humid air is cooled overnight usually on clear nights (with lots of radiation cooling) and early in the morning a layer of trapped very humid (hence the fog) air exist. The day before the close to ground warm air now cools below the dewpoint and the fog forms. It usually burns off by noon, depending upon how thick the layer is. Or the day before the warm air rose and cooler air replaced it underneath it and got trapped, either way ...same result..... FOG ....known in snooty weather geek nerd circles as a Temperture Inversion. There are websites and phone apps that can tell you when these temperture inversions are supposed to happen in your area. If your into it, check them out. https://www.dxinfocentre.com/tropo.html
Guess what a layer of trapped humid air does to radio signals? It prevents them from escaping into the higher atmosphere and disappearing, but BENDS them along the layers length, so that stations within this trapped (Tropospheric Inversion) can communicate with one another for hundreds of miles. Depending on local weather conditions. This is kind of like when you put a stick into a body of water and notice how the stick now looks bent, it is a similar effect with high humidity moisture, like in a Fog. The denser the better. No wind usually accompanies Fog and this no wind occurance is what keeps the Fog and high moisture intact, thus keeping the communications alive until it burns off.
Fog is not the only time it happens, sometimes during storms approaching, like cold fronts, again warm rising air gets trapped from rising any further and is eventually cooled at some height in the approaching storm, and provides a "DUCT" for signals to travel through, sometimes these " Ducts" are quite long, like 100's of miles long! This affects 10 meters and above. The VHF guys LOVE this stuff.
Other summer days when the air is still, the sky is clear, but there is really high humidty, the kind where mosquitos have a feast on you outside. And generally when the weather is unbearable to stay outside for too long. This condition when it happens on the east coast is called a "Bermuda High" , basically it is when you have a high pressure system (above 30.10 mb of pressure) sitting above you pumping hot humid air up from the south, but yet the skies are clear,... well overnight as the air cools by early morning often before sunrise you will have a nice temperture inversion which......You can almost bet this is a good day for Ground Wave. This happens usually in my experience just when the High Pressure system overhead is just about to leave the area, in other words the last good day of nice weather before it changes.
This also happens in Spring and many times over the ocean, as the water is still cool from Winter, and quickly cools the air above it after sunset. It again becomes a"duct" of cool very humid air close to the coast. Want to know how you heard that guy from Delaware in Boston that night on 10 meters? Thats how. A natural fog occurred over the ocean up and down the east coast and WaH La! (walla, wala, wallah, or however the hell you spell it).
Now as far as Winter goes, there is fog although its certainly not as common as in summer but the same type of weather conditions do occur so in can happen as well. In winter often not during stormy or cloudy weather but during clear weather where there is high pressure overhead, and snow on the ground, the air near the surface again becomes cooler then the air above it and a Tropospheric Inversion occurs. Next thing you know you're talking to your cousin 250 miles away, with a weak signal BUT no fade and with 100 watts on a Antron99 antenna. (crappy antenna btw).
Okay, a bit of technical jargon (ie: backup) This groundwave/tropospheric propagation occurs very near the ground. When you think of the word troposphere, you tend to think of air 5 -10 miles above the earth. What I am mentioning weather wise for 2-6-10 meters and what has certainly been noticed by VHF/UHF operators are weather conditions 0 FEET to 4 miles above the earth maximum. Not really tropospheric. There is something known in technical circles called the refractive index, this is an index of how refractive the air is near the earths surface. Refractive meaning how much can it bend radio waves. Under normal conditions the air as it gets farther away from the earth is less refractive. Under WEATHER conditions where the cooler air moist air is trapped below warmer air which has been pushed aloft the refractive index becomes very high, due to the dense heavy moisture laden air close to the earth. This allows radio signals to be bent along the surface of the earth (Groundwave) much further then they normally would be. Like hundreds of miles farther. The fog does not have to be present at both stations, this is based on alot of observational evidence both by 10 meter geeks and it is very widely known as fact in VHF circles. High pressure just starting to wane with the above conditions present is a very high indicator that you've got some enhanced Groundwave conditions. These conditions happen almost every morning, when the sun comes up and it warms the atmosphere, the air near the ground is cooler. A Temperture Inversion is taking place. These early morning HF propagation conditions will be your best long distance 10 meter groundwave contacts. Think: " The early bird gets the worm" Little or no wind certainly helps keep these conditions in place early mornings. Myself and others most notable N2DXT have noticed these exact conditions and the resulting extended 10 meter propagation groundwave contacts over the past 20 years, hundreds of times, Believe it. It happens.
Learn about even more Groundwave conditions from this guy:
https://www.dxinfocentre.com/propagation/tr-modes.htm
What about no fog or any weird conditions at all, is there really any Groundwave communications possible on 10 meters?
Yes of course there is. I happen to hail from the NYC area. On 10 meters we have a very diverse group of operators who get on the air every night of the year and talk to each other routinely 20 - 60 miles away from each other. Nobody is running 1.5 KW's, Not everybody has beam antennas, although there certainly are some. These operators have low height dipoles and low height above ground Vertical antennas. Like Imax 2000's and Antron 99's. Basic 1/2 and 5/8 wave verticals. At 20 feet in the air. Most with 100 watts and hardly anyone has any height advantage over one another. In fact the area is hardly above sea level for most stations. AND get this, this is NYC. There are MANY BUILDINGS in the way! So don't give me any of that line of sight story..... No line of sight in the New York City area trust me. AND guess what else we have here in NYC? Lots of NOISE. Yet still every night dozens of 10 meter operators talk to each other over distances that apparently "can't be done."
When some slight conditions come in, like fog or a weather front, these distances extend to hundreds of miles for many stations. As an example I own a home in Vermont as well, it is 250 air miles to New York City. I do have a beam antenna. In talking with any so called propagation expert you would think there is no way I can talk to any stations back in the NYC area 250 miles away. Groundwave. Not possible. WRONG I can make the contact almost everytime I go to Vermont and get on the radio on 10 meters, with ZERO special conditions. And I have been doing it for 20 years!
We have a few guys in the NYC area that travel to far away places on purpose to see if they can get back to the NYC area with their mobiles! I am talking 100's of miles away, no special tropo or other conditions. Can they make the contact back to guys even with just simple vertical dipoles? The answer is surprisingly YES THEY CAN. SO the moral of this long story is.......... GET on the air on 10 meters and say hello to someone. You'll be surprised just how far you can talk, with your simple antenna. And don't listen to stuff on the internet like " there really isn't any groundwave at all on 10 meters". Those are people like many things in life, are people who have never tried to do it, and yet on the air they are "groundwave propagation experts".
I personally and hundreds of others have communicated on pure groundwave ( no signal fade, no echo, no choppy audio, or any other weird audio stuff ) for hours on end, to stations over a hundred miles away, day & night , summer or winter, Sunspots or No Sunspots, almost every day of the year. ( Ok maybe not Christmas, when everyone gets a new radio under the tree,...... don't they?). 10 meters is almost VHF like in that it is almost line of sight, but not quite, it is also low enough in frequency that the radio waves can still be bent towards the surface of the earth and travel distances well beyond normal line of sight. In any case distances you wouldn't normally think possible are indeed possible on 10 meters on pure groundwave. So get on the band, make a new friend and have some fun on 10 meters.
How far can you get Groundwave propagation on 10 meters? Well how about this? Here's an easy 300 mile contact, only groundwave no enhancement. NYC to Mount Washington NH. This is a few years ago, notice the questions I am asking about the weather. I know these greatly affect the conditions and can change abruptly. These Inversions usually happen best in early morning times, even before the sun has a chance to wake up and ruin everything. But they can also happen at sunset when the air is cooling to dewpoint or even overnight! So listen early in the AM, like you did when you first got CB radio (go ahead admit it to yourself) and maybe you'll be surprised at what you hear hundreds of miles away.
What about real DX on 10/12 meters? Is it ever really open?
The biggest thing to remember is on 10 meters your antenna is probably close to 1 wavelength high (36 feet). Your antenna is at a height where the far away dx stations are coming to your antenna at an angle which is not too hard for you to hear and contact. If you get your antenna up to 50 feet high its at a optimum height for 10 meters. On 20 meters the optimum height is 110 feet! Although the 20 meter band has more consistent dx, if your antenna is not alot higher then it is at 10 meters it doesn't matter, your not likely to hear them anyway. So when the dx runs it is easier to reach on 10 meters. This is especially true if you have a wire antenna or a lower height vertical.
10 meters has very different characteristics then the bands 15, 17 & 20 meters. Lets compare : On 15-20 meters DX signals come in of varying strength depending upon band conditions mostly in the daytime. Its common to hear a station at S9 who then 30 minutes later its S6, then as the band changes goes to signal 1. Then they are gone, below the noise.
However on 10 & 12 meters...this scenario is entirely different. Since these bands are much closer to VHF or 6 meters, their characteristics can sometimes be very similar to VHF. Ionospheric propagated Sporadic E is common most spring and summer and even some winters (around Christmas...no kidding). When a signal comes in on 10 meters for example. it is IN , meaning its S9 period. It can begin from nothing heard to Signal 9 stay at Signal 9 for a few minutes, then the signal is gone. No fading over 30 minutes of time its either S9 or...Gone...period. They rarely slip below the noise level because on 10 meters the noise level is non-existant! Unless for some man-made noise around your home. If you live in any area that is remotely considered rural, you have no noise. ZERO. Like VHF & UHF you have less noise. There aren't many signals you have to pick out of the noise, because there isn't any noise. And the signals you do hear when they come in from Europe or anywhere else will most likely be strong signals, easily heard and there are no pile-ups to break through because everyone thinks the band is DEAD !! Sound good? It gets better.
Here's what else happens on this band. Lets say your talking to Alaska and he's signal 8, you may get a station trying to break in from Antarctica at the same time. After that you might hear Europe followed by Hawaii all with strong signals. 10 meters has an uncanny knack of signals coming in from multiple directions at a time, and if you have an omnidirectional antenna with little to no gain it doesn't matter, because all the DX is coming in at signal 8 or above and usually at a high angle, or your antenna is high enough to catch the angle! Unlike other bands, like on 20 meters where if your antenna whatever it is isn't high enough, you can forget about hearing or talking to that guy in Vietnam. On 10 meters myself and others had experienced talking to Alaska from NY, and heard Antarctica CQing to the frequency. We then spoke with Antarctica and eventually Alaska and Antarctica were talking to each other! Lets see you do that on VHF or anyplace else!
Typical HF noise levels
The bigger the - minus number the better
160 meters -87 dbm ....... about S7 on your meter
80 meters -92 dbm ....... about S6 on your meter
40 meters -100 dbm ....... about S5 on your meter
20 meters -109 dbm ....... about S3 on your meter
15 meters -114 dbm ....... about S2 on your meter
10 meters -120 dbm ....... about S1 on your meter
So this means the noise level on 10 meters is at least 10 db lower than on 20 meters and as much as 30 db lower than on 80 or 160 meters!
I should note that the noise levels on 40-160 meters are highly variable and during the summer could be much worse! Depending on the time of day.
As I am writing this sentence in 2024, 10 meters has been open since February, even to Europe and Asia. All coming in with strong signals even when the king of the DX bands...20 meters right now is so noisy its having trouble supporting communications even midday to Europe from the US!
As I mentioned above, as quick as they come (the DX) its as quick as they're gone. So making DX contacts on 10/12 meters can be exciting because you never really no how long they are going to last or be 'in there" . As much as I like 20 & 40 meters, don't under estimate 10 meters, it has alot to offer the ham radio operator.
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