I decided to try to adapt this type of design to 1090 mhz.
I had 16 gauge copper wire in hand, so I formed it into the 1/2 wave 1st element 137 mm long,then into a 10mm single coil ( bent around an F connector barrel which is close enough in diameter ) then the 3/4 wave 207mm second element, another 10mm single coil, ending with the last 3/4 element of 207mm.
I knew that I would be trimming the last element, so I found that a final length of 200mm worked well and I wasn’t willing to keep trimming- although it appeared that the article I borrowed the design from the final element was reduced nearly 10% from the 3/4 wave length. I have no way to verify this other than “destructive test”, so maybe I’ll create another to fiddle with trimming/ tuning
Certainly not a new concept, and I’m sure that folks like @abcd567 have already tested versions of this design. I found that despite being nearly 12 feet lower in elevation in a tree-infested property, the reception results were nearly on par with the FA stick.
Only takes a little more time than building a 1/4 wave spider.
Ha- me in search of facts is a lot like a blindfolded person swinging at a Pinata- once in a while I strike something, it could be a useful fact, some random person’s head, or a priceless Ming vase. All result in the same stunned reaction from onlookers
I am an amateur but the more I read about RF in this context, the more I see evidence that the best science leads to a greyish area where results in the real world are not wholly explainable.
I think I’m going to start charging myself a higher fee for solving problems
In the early 1960’s my father did a lot of radio experiments, mostly with CB radio. He was not well-educated in RF but self taught in most electronics of the era. We had bins of tubes , resistors and transistors stripped out of junk electronics that I had to help sort. Sadly most of that stuff leaked out of my head over the ensuing 55+ years.
His best antenna ? I think it was a ground plane just like the spiders we use for 1090mhz.
A few days ago I suddenly realized that the smell of a hot soldering iron was a direct link to some very primal childhood memories. So much has changed yet the tiniest of components today are still soldered in one form or another.
You have adjusted the lengths of vertical elements to 1090 MHz, but did NOT adjust the diameter of coils to 1090 MHz. If 10mm dia is recommended for 2.4 GHz, then for 1090 MHz, the coil dia should be 22mm.
Good point. I ‘ll try that on the next one I make. I’m having issues using the F connector as the 16 gauge copper is too heavy and hard to keep from falling over in the connector since its just a push in.
Doing some head-scratching on how to enclose it as well once I settle on a final version.
I always use core wire of RG6 coax, which is 18 AWG (1mm dia) copper-covered steel, and lighter than 16 gauge copper. Your antenna is very tall and 18 gauge wire may be too thin to stand upright.
So I built a 18Ga ( RG6 core) version using 20mm coils. It sort of worked, but three problems:
Its not able to support itself in a way that it stays centered and plumb to the can ( ground plane/ decoupling )
The thinner wire makes it difficult to have consistent gaps for the coil entry/ exit points…springy and the whole assembly hard to keep aligned as intended.
Performance was not as good as the original. Maybe 20% less contacts and planes with the best tweaking of the antenna.
Coincidentally I tried varying the gaps/ overlap and even partially shorting the 20mm coils in an effort to force a change in result but wasn’t able to cause a change large enough to be of note. I tried varying the length of the last element from 207mm down to 190mm also without significant impact on reception.
I reinserted the original 16 gauge copper with 10mm coils and it performed better in the same orientation and height.
I cannot tell if this was due to coil size, dimensional stability or wire diameter itself factoring in. Since I left the insulation on that copper wire, it helps maintain a very close coil entry/ exit gap without any risk of shorting the coil.
Next I will take a piece of 1/2 wave copper and the can to test just in case most of my antenna isnt doing a darn thing and its really the can and first element thats doing most of the work
Plans for Wi-Fi collinear antennas abound on the web. One of the most common designs is shown in the photograph below.
The instructions often provide the exact information shown above and include the suggestion that you can add as many center sections as you want for increased gain. Some builds include a provision for a waterproof housing made from PVC pipe. Apparently anyone can successfully build one…except yours truly.
Multiple different construction attempts did not produce an acceptable result. The tries included the three-element version seen above, a six-element version (with and without insulation,) and finally a nine-element version built with 18 AWG wire, the lower three elements of which are shown below.
Variations were built with and without ground planes. Laird Product Manager, Ted Hebron, provided the following advice regarding ground planes on collinear antennas:
Typically, collinear arrays are designed to be self-resonating structures and will not need a ground plane. In fact, for this type of design a metal ground plane would be seen as a metal obstruction in close proximity to the antenna and as such both the radiation patterns and impedance will be perturbed. The end result may be unexpected nulls in the radiation pattern due to reflections/scattering or mismatch issues because of possible impedance changes. [However,] to make an antenna smaller in length it may be possible to use a ground plane. In this case, the ground plane is intentional and is part of the antenna design.
Thank you for the links. I am having trouble reproducing my first result with this type antenna, and taking a pause to change hardware. One reason I am chasing my tail is that the F connector I was using apparently was damaged by inserting the thicker gauge wire and changing back and forth sometimes it would make connection and sometimes not. Essentially I wore it out…so, going to a soldered BNC bulkhead ( for no reason other than: its what I have in stock )
I still may find that although it “works”, it may prove to be only effective at closer ranges than I am interested in.
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