There is one thing I don t understand. This is your diagram from initial post.
It is showing us upper right and upper left quadrant. What about lower right and lower left quadrant? Can you moddel it?
It would be interesting to see 360 degrees of vertical diagram. Here is the example of yagi antenna
After a little bit of thinking I came to conclusion. Maybe I am wrong.
Lower right and lower left quadrants are mirror picture of upper quadrants. So, energy radiated into the sky is wasted. For qso, on the summit, the lower lobes are important.
Correct me if I am wrong
A great question. The elevation plot is presenting the gain (dBi) in relation to the ground. The x-axis on the plot represents the ground. Most of the radiation directed at the ground is reflected, contributing to the the gain shown above ground in the plot. This is why ground conditions are so important.
The elevation pattern that you presented as an example of a Yagi is a model of an antenna in free space.
I have some hunches on what might happen if the ground is not flat and level. If the ground is perfectly flat but inclined I think that the entire far field plot will be inclined. If the antenna is on an area of land that is inclined in an otherwise level landscape I suspect that the far field plot will be inclined to a lesser extend that the angle of the ground. If the antenna is sat on top of a cone of ground I suspect that the far filed plot will be pulled down towards the ground in all directions. This leads me to believe that it may be possible to place an antenna too high.
The real world is complex, and SOTA summits doubly complex. I will never be able to create a model for a real summit, let alone all summits.
I have assumed that I want to maximimse the RF at an angle near the horizon. What goes on once the RF leaves the antenna is even more unpredictable and may proove this assumption to be wrong in certain conditions.
I was on [SOTLAS](https://GW/SW-035 Myarth) yesterday, on 145.450mhz fm. This is a difficult summit for VHF. A helicopter flew over and suddenly I could hear @M0TRI on [SOTLAS](https://G/SC-006, Periton Hill) in a QSO with MW0SAW on my frequency. The helicopter left and they were gone, a great pity as I was struggling for a 4th contact. It would be easy to attribute this to a reflection from the helicopter, but who knows.
SOTA is about far more than antenna modelling, or even the perfect antenna. One of my ambitions is to have a summit to summit with Fraser one day.
I have watched your videos and you do far more than ‘just climb hills and try to make contacts’.
Yesterday I had a summit to summit with Gerald MM0EFI, who I had met on Mickle Fell earlier in the year. @M5RJC walked up a hill specifically for a summit to summit with me. There were lots of other people who made my day so pleasant that I have not mentioned.
The antenna helps, but untimately, for me, its about people.
I never model the antenna. Now I think that all plots are not accurate to the degree to be useless. Sometimes.
I do not believe that any antenna, expecialy yagi on summit is not radiating below boom. And plots are not showing that radiation. I do not believe that ground cancels lower radiation.
Plots without lower radiations are good for hf. You are interested in reflections from ionosphere. VHF/UHF punches ionosphere. So on the summit low angles are important. On low lands upper angles are important.
There is no way that energy radiated at any degree up in the sky reach me lower. Line of sight. We are talking about frequencies that are not reflected from ionosphere. That energy is lost in space
The plot shows the yagi radiating below the boom. The ground does not cancel radiation below the boom or antenna centre, in fact the plots show that the ground enhances the radiation at these low angles.
The absence of a mirror image to the plot is because this is below the ground. The bottom axis of the plot is ground level, not the antenna centre line.
Thank you for your clarification.
I am interested in antenna radiation, 360 degrees vertical (or horizontal). That radiation exist. It gives me real world data.
Models are models. They are good. After your nice and simple explanation I will look every diagram twice. I learned a lot. Thank you
Hi Kevin,
The answer to the original question in simple terms is the higher the better. No contest. You will run out of mast before the coax losses negate the height gain.
I see some are questioning your findings on the basis it does not align with what they believe.
Well it’s partly because they can’t read graphs. A basic pattern can easily show signal radiated vs angle.
At zero degrees the radiation is likely to be zero. But at 1 degree it’s not zero, albeit a long way down on the lobe maximum. What it lacks in antenna gain at low angles is made up by the lower losses on the path. This may explain some of the “I don’t believe it” crowd.
Those who mistrust simulations should stay home as aircraft, bridges and tall buildings are now all simulated and tested in software before being built.
Keep simulating.
73
Ron
VK3AFW
I am not native English speaker and sometimes is very hard for me to say what I think.
For those who do not believe in simulations, I think that goes to me. I am not offended.
But
If your antenna is radiating like this and 1000 metres higher than mine in this plot there is no energy going my direction. Are we able to make a contact?
I am tired of writing and it is time to go to the forest and rest on fresh air
Modeling only part of diagram is good but not complete. Give me 360 degrees vertical diagram. That would be useful.
If you model an airoplane you model whole airoplane. Both wings, not only one. Tail included
Damir,
These are great questions and the very questions that lead me to start modelling the antennas.
Now that is a big question. I would like to answer a slightly different question so that I do not have to consider modes of propogation.
If I am on a plateau at 1000m with and antenna radiating like this (the plot in your post), and you are at the base of a cliff 1000m below me it will be difficult to make contact (ignoring edge diffraction).
If I am 1000m up on the side of a hill and you are at the base of the hill, with no obstructions, we should be able to make contact. I believe that the angle of ground will cause the radiation pattern from the antenna to be tipped down the hill.
If I walk to a flat summit of our imaginary hill it is likely that our signal will deteriorate as the pattern tips back up.
This is exactly the phenomean that I would like to understand more thoroughly.
I suspect that it is possible to raise my antenna to a height where I point the null towards your station?
This is not easy stuff and I had to go for a walk in a forest yesterday.
I have great respect for anyone who can read technical subjects in a second language.
Damir,
First and important point I do not want to upset you. You are not on my list of people I want to annoy
When the graph shows an infinite null at zero degrees then the software probably has been pushed beyond its resolution capability and the default for not much signal is zero.
A black cloud in the sky does not necessarily mean it’s going to snow nor does a clear sky mean no rain. We need to take other factors into account, to read the weather properly. The same with simulation graphs.
Evidence that the average yagi has poor gain at zero degrees as per simulation can be obtained by listening to a big gun eme station. You won’t hear him at moonrise but you will hear him as the moon moves into the first and second lobe and maybe more. But zip at zero elevation and in between the first two lines.
So how come you work people at apparently zero degrees? I suggest that apart from the residual radiation at zero degrees, it’s enhanced by los troppo scatter and environment scatter from the lowest lobe.
73
Ron
VK3AFW
There are as many perfect solutions to this problem as there are hills and mountains.
Quite correct. Good enough is often the perfect solution 
I started modelling to gain some insight. I haven’t seen a challenges to the validity of the modelling so I will stick with what I have got and take my role up dipole and 6m pole unless I am trying for something special.
I will see if I can replicate the modelling on a hill at some point by setting up on a slope facing a willing station and hoisting my antenna to different heights to see if I can find a reduction in signal at the first null. When I did some antenna shootouts on The old man of Conniston with GW6WBS it highlighted how few data points can be obtained and how coarse our measurement in S points was. We ‘prooved’ that the Yagi at 7m offered about half an S point improvement over a dipole at 10m for the 3 stations that joined in our test. On reflection what we prooved was that on that day there was no benefit to be had from half an S point as we were not able to work any additional stations!
One counter intuitive result from modelling was the effect of tilting a colinear. The far field plot really didn’t change to any significant extent. I may investigate this further.
If you don’t want an upwards pointing set of lobes from your vertical why don’t you mount it upside-down ?
Hello Kevin,
Interesting thread, thanks for sharing your simulation results.
As Andrew recalled, there was an event devoted to test VHF FM long distance qso ran for three times here in EA.
We choose to do it in VHF FM as we wanted to get reports for as many chasers as possible. Not everybody has a yagi beam at home, but instead, lots of ham have a vertical antenna at home.
We know that horizontal polarization adds a bit of improvement due to ground reflection enhancement, but we did the event in FM vertical.
We tried using some vertical antennas in the summits and also some small yagi.
Of course, distances are improved when using yagi beams.
As we could expect, maximum distances were longer than usual between two operators placed on high mountains end to end.
Line of sight in these cases were overcome by far. Having no tropospheric duct within the large EA land, we got a large number of S2S qso at a range of 300 - 400 Km: quite a long distance and unusual qso! The higher the mountain the longer distances were achieved.
Some ops in summits by the sea shore did find marine tropo enhancement and had qso in the range 500 - 1000 km.
Antenna height?? My proposal is to look for a highest mountain with unobstructed views all 360º aroung and you are gonna enjoy with a great experience!
Don’t really worry too much if you elevate your aerial at 5m or 10m over ground, just look for a reliable support over ground, as going too high makes it difficult to support.
See all data from our two past editions here:
73 de Ignacio EA2BD
Thanks for the invite. Honestly, I don’t consider myself to be an antenna expert and I certainly have not spent much time doing antenna modeling. I have spent quite a bit of time working 2m FM, SSB and CW from SOTA summits. Yes, most of those contacts were using FM with vertical polarization.
I have compared the signal strength of omnidirectional antennas at different mast heights. I have found essentially no difference in signal strength when raising a 1/2-wave vertical on a mast. (Other people have reported different results.) I think a major factor is the shape of the summit and the type of soil. I am almost always operating from a pointy summit made of rocks or rocky soil. (There is a reason they call them the Rocky Mountains.) The conductivity of these rocks is low, so it does not have a great effect on the antenna performance. This may not be true for a very broad summit that is covered with wet, conductive soil. I don’t know.
My 3-element handheld Yagi always outperforms an omnidirectional antenna at any mast height. So I have stopped worrying about antenna height above ground and just make VHF radio contacts.
On another topic, I have been trying to educate folks that VHF is NOT limited to line of sight. If that were true, we would not be making long-distance contacts from SOTA summits using 2m FM. Here’s my simplistic model to try to communicate this point:
https://www.k0nr.com/wordpress/2019/02/the-myth-of-vhf-line-of-sight/
73 Bob K0NR
Thanks for the link Bob, it is a great read and very helpful. Your observations agree with Fraser’s:
I chose to use ‘average ground’ in my model, which may be a poor fit for many summits, most of the summits in South Wales are wet peat or grassy pasture. The RF ground is probably some distance below the rock surface of your Rocky mountains and Frasers highlands giving the antenna a significant height above RF ground, reducing the effect of raising the antenna further.
To quote your linked article ‘All models are wrong, but some are useful’ I have found this exercise useful, a model may shed light on a complex problem, but it is no substitue for experience.
Hi Kevin
The profile of the hill is also important - and many of our local ones are round or flat topped without a cliff to launch the RF from. Flatter hills definitely see a benefit from raising the height of a VHF antenna.
Cheers
Rick
And unless the profile is the same in all directions, you will need multiple solutions on each hill.
I have been using a handheld moxon 2 el for VHF contests (as I have been too lazy to make something better)
It is interesting that I can sometimes usefully increase signal by moving the antenna in Z (up and down), or by adjusting the pitch slightly from horizontal (tip downwards ~5-10 degrees).
These are exactly the effects modelled.
Also by roll (adjust the polarisation from horizontal) perhaps up to 20 degrees for stations that I know have a horizontal antenna, but have a path to me that is bending over hills.
I may be doing better with being able to easily maximise the signal, than any gain from fixing my antenna on a pole, at the (bound to be) wrong height.
Since this is also the maximal-laziness solution, I’m running with it.
