Antenna Kohjinsha KA1-406S
Antennas
Dynamic Antenna HF 50 to 7 Mhz - Kohjinsha Mod. KA1-406S
Good Morning to all, after what happened the night between 21/22 December 2023 where an atmospheric event of exceptional magnitude, Foehn winds that reached a speed of 220 km per hour (140 miles) and destroyed my Antenna system that I was very fond of, see Antenna Disaster, consequently forced cessation of activity in Radio, I found myself having to decide what to do, which antenna to put to resume my activity in Radio, because it is clear, that for me the activity in Radio is so rooted that no one and nothing in this world will ever be able to make me give up continuing this wonderful and rewarding hobby. How to restore my Antenna park to the same level as the Quad 5 el. multiband + the two Yagi Antennas 3 elements in 30 and 40 m.? which is not exactly easy .... my choice was a careful and prudent choice on what the international market offers in terms of Antennas, to have the maximum performance in my opinion there are two choices, the first is to orient yourself towards monoband antennas or at most dual-band antennas, but the cost increases a lot considering that there are many bands (from 6 to 40 m.) and to do an excellent job you would need at least 2 Towers if not 3, to conveniently space all the Antennas, something to be excluded for me given the costs; so in my opinion there is only one solution left: the new Dynamic Antennas. There are many companies that produce them, see the American SteppIR, the Japanese Versa Beam by Kohjinsha, the Italian AD Antenna Dinamica and Ultrabeam. After a careful selection of the various models and based on my needs, my choice fell on the Japanese Kohjinsha Versa Beam, in the KA1-406S model. This antenna has a 10 meter long boom, 5 elements from 6 to 20 m. plus 3 elements in 30 and 40 m., on 6 m. i also added the kit of 3 passive elements which brings to 8 elements on this band, I hope I have made a good choice, I trust in Japanese products and from research done with several Versa Beam owners, the opinions that emerged on these Antennas were very very good, the Antenna arrives by air at the Turin / Caselle airport in the first ten days of September, after I will assemble it and test it, stay tuned, as soon as possible i will publish all details/install of this new Antenna KA1-406S, I hope I have chosen the best, Many Thanks Hiro San
Added Note September 16 / 2024
From September 10, 2024 to the resumption of my Radio activity, waiting for the new Kohjinsha KA1-406S Antenna to arrive, I installed a Rybakov vertical (fishing rod) length of 7.60 m. with 4 radials inclined at about 45 degrees, feed with a 300 Homs window line, tuned in the station with the Palstar AT2K, the antenna is placed on a mast about 7 meters from the ground and I must say that it works surprisingly well, I tune it from 50 Mhz to 5.357 Mhz, in 6 days of testing to date, I have made 340 QSOs all in FT8 on all bands, with excellent results, QSO with all the continents including the Pacific, well stay tuned guys, for now 73' and Good DX
Finally the antenna has arrived, after having completed all the customs procedures at the Turin/Caselle airport, the courier in charge delivered the antenna to me this morning at 08 AM, I immediately completed the unpacking operation of the 6 packages, all the pieces making up the antenna were very well packed in sturdy cardboard boxes, including the boom and the fiberglass rods, all the details such as brackets, screws supplied, supports etc. well divided and marked, the material used seems to be of excellent quality, now all that remains is to proceed with the assembly, but I want to do things slowly, so as to obtain the maximum without leaving anything to chance, it is my intention to brace the boom not only from above but also from below and laterally, and I will also see if it is the case to brace the fiberglass rods, you can never be too careful given the previous disaster of my antenna last December .........
I must say however that given the advanced season I do not think I will be able to install it before the weather conditions will no longer allow working outdoors, however as I said before there is no rush, considering the fact that I am about to make radical changes to my tower, such as automating it with a radio control in the ascent/descent of the antenna trolley, and proceeding to block the same trolley once it has risen in position where it will be blocked with mechanical pistons, so as to avoid my climbing to the top to bolt it to the tower (I am at an age that it is no longer the case to climb hi hi), for now this is everything, as the work progresses I will take care of informing you in detail with photos and explanations of everything, thanks for reading me, greetings to all and ... Good DX from Enrico IK1MNJ
Hello everyone, while I wait for better weather conditions this spring to assemble the Versa Yagi Mod. KA1-406S, I have done several tests on 5/8 wave vertical antennas for the frequencies 10/12/15/17/20/30 m. and 1/2 wave on 40/60/80 m. and I must say the results are extremely convincing, for the frequencies of 10/12/15/17 m. I used a 10 m. fishing rod which carries the respective 5/8 wave length elements made with 1.5 section insulated electric wire, duly spaced from each other on the rod itself and initially in the testing phase I fixed it on a 6 m mast. anchored to one of the three anchors of the braces of my tower, here I added 6 radials inclined at 45° for the lowest band (17m.), in a second phase of experimentation I said to myself: why not put the antenna on top of the mast of my tower at a height of about 30 m. and so I did, I did not put any radials, the power supply is made with 450 homs window line, tuned in the Shack with a Palstar AT2K, the results have improved, everything works wonderfully, especially on DX signals, often in FT8 the received signal as + 15 -25 db and more from far places as NA West coast and Pacific, but not only also the signals from Europe up to 2000/3000 Km are consistent.
We must say however that by raising one, two, three or more waves from the ground a vertical antenna of 1/4 wave will form a third lobe at a high angle, and therefore the radiated power will be divided among the three lobes, in the case of the 5/8 wave antenna I think the situation will be similar.
but let's get back to us, about 20/30/40/60/80 m. I proceeded in this way: considering that I have a lot of space available on my land of about one hectare including the house, the land used for grassland, has a perimeter of 160x40 m. my tower is 24 m high. and is located behind my house, I came up with the idea of stretching a steel cable from the top of the tower (24 m.) to anchor on a tall tree at the bottom of my property where the anchor point is at a height of about 7 m. (I can however further raise the anchor to about 12 m useful).
1°) The same steel cable is feed as 160 m. Long Wire Antenna.
2°) The same steel cable supports at a distance of 8 m. from the tower and duly spaced from each other and down to the feeding point on the ground of 4 antennas made with 1.5 mm square insulated wire, two of which are 5/8 wave for 20 and 30 m., the other two are 1/2 wave for 40 and 60 m (the one for 60 m. is linearly loaded), the last one of 80 m its always 1/2 wave that starts from the top of the fishing rod at 40 m. of height (the one that supports 5/8 of the wave of 10 > 17 m.) and goes down to the ground slightly inclined at a distance of 10 m. from the base of the tower, with a slight bend on itself it goes to the common feeding point of 20/30/40/60 m. always feed with 450 homs Window Line e tuned in the Shack; at the feeding point I put 13 radials of various lengths, in the future I try to increase their number, all antennas work very well.
3°) Not happy with all this (I'm always looking for improvements and testing new antennas) always hanging from the tension of the steel cable at a safe distance from the other vertical descents I built a Bobtail Curtain antenna for 60 m. a large antenna, essentially three 1/4 wavelengths connected together by two 1/2 waves always made with 1.5 mm square insulated wire, the central vertical 1/4 wave is the feed point where i put an home made antenna tuner at the base, the other two vertical 1/4 wave must be isolated from the ground, then i put four 1/4 wavelength radials at the base, the antenna is oriented south/west north/east, consequently it radiates North/West South/East, the results are exceptional, measured gain 5/6 db on the other vertical i have, unfortunately it is a very directional antenna and cannot be oriented hi hi (if only it could) the signals are consistent, among the other radio amateurs one that I always hear with very strong signals is Bob VE1YX who late at night on average I hear him in ft8 between + 20 and + 38 DB (+43 DB one night), for example this morning Mike ZL4OL at 07.16 UTC gave me + 10 DB and I gave him -10 DB, I don't know what antenna he uses and perhaps the conditions were via North Pole because my antenna is certainly not centered on his position indeed, I can't explain why this difference between received and transmitted signal, however it often happens, propagation does this and more hi hi, what can I say I'm very satisfied with what I've done.
4th) In 160 m. for now I use the same cable that supports the verticals and the Bobtail as Long Wire, or the 1/2 wave vertical of the 80 m. tuned in the Shack, it doesn't make me crazy ...
All the power supplies of the three solutions are feeds with Window Line at 300 or 450 Homs, which go to a four-position switch at the base of the tower, from here always with Window Line they go to the external wall of the house behind the Shack to a 4:1 Balun and from here with a piece of RG213 to the Palstar AT2K tuner, the Bobtail instead as I said above has a self-built tuner at the base and from here a coax RG213 to the Palstar tuner.
Well I think I'm not forgetting anything except that all these works are so to speak for experimental purposes, subject to improvements and definitive modifications once I have first assembled the Antenna Versa KA1-406S by Kojinsha, I will shortly publish some photos of all the antennas made, thanks for reading and greetings to all ... Good DX from Enrico IK1MNJ
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