Free Yagi Antenna Designs for Ham Radio
- Written by G0KSC
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The team at OL7M spent one year building and installing a monster 28MHz OWA array designed by G0KSC. The array consists of 4 x 6 element OWA Yagis and built the entire system and H-frame on site.
2 photos of the finished project are below but certainly, it is worth taking a look at the 10m YouTube video at the bottom of this article whcih takes you through the build from concept to completion.
4 x 6el G0KSC OWA Yagis for 28MHz at OL7M
A second, closer short of the same array
The below like is the YouTube video which takes you through the project start to finish, Enjoy!
If you need help designing and building an array, contact me directly via this site.
Project photo gallery can be found here: http://ok2zaw.blogspot.cz/
- Written by G0KSC
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These rumours extend from you and your friend in Belgium who markets the same brand as you, no one else. Perhaps you can give details of the undiscovered theory that suggests that such phenomena could occur? You won't because there is none.
Applying common sense and being in a position where I am not looking to start a witch hunt I would suggest the following to you -
Most people looking at EME are misguided into using DL6WU stacking formula (or variations of) and configurations for maximum gain to achieve their EME goals but unlike you, most live in locations where there is far more than warm earth beneath the antenna to create noise. Ironically, the result generally is a system that they can be heard on but they cannot hear as well as they would have, if receiver tuning considerations (tune for minimum noise, not maximum gain) had been applied to their antenna system, as it has been in every other part of their receiver chain.
When 4 antennas are placed in a H-frame, large side lobes occur in a forward direction beneath, above as well as to the sides of the array. Inevitably, when a ham elevates his array and there is a noise source in the far or near field, the lower lobe will move through it and cause an increase in noise which increased then decreases with the size of the lobe. This point at which this happens depends upon the distance of the noise source and the size of the array. This will occur on any Yagi and if you had a conversation with someone with such an issue, I would have hoped you would have been knowledgeable enough on the subject to have known and communicated the above.
Again, the above will occur on any Yagi, and in summary, the more gain they have configured their spacing between the antennas for, the less they will be able to hear at these elevation angles due to the increased size of these side lobes. Ironically, the increase in noise will be more pronounced on an LFA system than if using traditional Yagis that have a 'blown pattern' simply because the 'blown pattern' antennas have a far bigger rear bubble to start with so ambient noise is far higher at all elevation angles including being parallel to the ground.
I know you have moved from 2m to 6m but have you taken a look at and spoken with any of the hams using LFA on 2m EME systems including X-pols? Heard about the huge differences in performance they have seen over and above what they had before even when the previous arrays were similar or larger in size?
If the truth be known Lance, I don't think you would want to hear it would you? ''Never let the truth get in the way of a good story'' - statement I heard once relating to tabloid news reporting years ago which really did sum up what had been written in the press at that time. I was reminded of that statement again this afternoon.''
"Can Yagi-Uda style antennas as a single antenna or as part of an array produce more noise when
elevated at all?
I have been monitoring and designing lower noise Yagis for quite a while now
and did a handful of publications on this topic in Dubus magazine and on my website.
The answer is NO, they can not. It does not matter if the antenna is a low noise design or not.
Once the main and first side lobe have left 'hot earth' there is no way
additional noise could be received or generated. Analysing Antenna Temperature and G/T over elevation angles
from 0 to 90 degrees with TANT software might not resemble real world settings
for all occasions or environments, but it is a good indicator. Antenna Temperature goes down
as the elevation angle increases.
Yes, there is ground gain and with that an increase in forward gain and so
with noise picked up by first and maybe second side lobes are possible but this will vary with
elevation angle. To the subjective operator this might occur as swelling
up and down of any background noise, especially when a major noise source on the ground is located
in the beam direction. But this is NOT an issue of a certain design but comes
with whatever directive antennas that produce a first side lobe is facing. And
any noise swelling up and down picked up by first side lobe enhanced by ground
gain at lower elevation angles will still be less than at zero elevation.
It is virtually impossible to have higher noise with an elevated Yagi-Uda
unless beaming at an object as a near by sky scraper full of plasma TVs.