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Recently I bought three antenas from some well known shop. One was 5/8 3Dbi construction, second described as Collinear Phased Coil with gain 5 Dbi and third as Collinear Skirted Dipole Array 10Dbi gain CC1090/8-P. Before mounting them on mast and tested how they perform in my setup, checked them on nanoVNA, first two looked very good and had swr on 1090mhz around 1,4 this 5/8 and 1,1 the colinear,CC1090/8-P looked weird and have swr around 3,0. After mounting them on mast first two outperformed my DIY spider antenna; the third, which has more than 1m and supposed to have the highest gain from all three (costed also two times more) was significantly worse than two others in every possible aspect signal, range etc, even my spider had much better performance. Definitely there was somthing wrong with it. But insted returned it as defective and get money back or new good antenna, I decided to see how it is made and whats inside motivated that maybe is some simple problerm like broken conection betwen elements etc and ofc ended with nothing, besides my curiosity was fulfiled . Now what I don’t fully understand in this construction and maybe someone with better knowled in antenas can explain me this construction more professionally.
So after removed radome as I expected find more or less typical well made colinear made from coaxial cable, wasnt able to find any defect and only notice that when I touched by fingers between first and second element on nanovna antena had proper swr less than 1.2 on 1090mhz but as I’m completly noob i have no idea why it behaved like that and if its have anything common with problem at all. So only what I could was to messured all elements but it was even more confused after all also fact that it was made from two types of coax (H155 and probably H1000) and have something made from aluminium thin foil attached using tape to copper tape soldedred to bride of thisthicker coax (foil was removed with original strong black tape and placed back so thats why looked like that, orginaly was nice and straight) Any idea whta is for? Also lenght of elements (5 of them have around 102-103mmm, top is 125mm plus this shorting element. to better ilustrating see photos. I assumed the lengths of most elements are correct and were chosed on purpose and that why compared to the dimensions typical for this cable in the case of theoretically calculated lenght of 1/2 or 1/4 elements. Most users of this antenna find them very good or even one of the best available in the market, especially for the very competitive price.
Since I dont know what’s wrong exactly was with my antena and cant be sure it;s matter of mistake of design or just in asembly of elements maybe some one can do simulation in software of such construction and see results, any way i I’m planing to build exact copy using the same material and dimensions and see what i get. My previous two or three attemps of making this type antena wern’t fully successful, so maybe copy of product which has good review finaly gives better results. If not I will order one more and will have pricy lesson.
PS The thicker coax is one pice only with cating of shell and soldered coper tape to which is conect thin alu foil. The thin black element is a fiberglas rod, probably as support to keep it straighter and less flexible N connector is directly soldered to this thicker coax on the end.
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