4el. Hentenna for 50MHz
still not completed

As for the antenna for the outdoor operation of JA7KPI, it is a modified 8el-Yagi, 9.2m in length.
However, according to the catalog, the weight of that antenna is 11kg, so heavy. It is highest Yagi about gain and frequency characteristic. But, because the weight of the cable joins, it becomes too heavy for QRV in the outdoors.

So a new antenna development plan has started.
The design policy is as follows. :-)

Structure of 4el-Hentenna
1. It should be hentenna.
Hentenna has the gain 3dBd with the unit as consented. And it wins by 2dB compared with mere quad (one element loop). As for hentenna, the merit about its gain decreases by becoming to a long boom. However, assuming for the outdoors operation on 50MHz, this is designed short boom.

Therefore, the merit of hentenna is energized.
Of course, a certain kind of hope for the loop antenna which might be unscientific is considered enough. ;-) hi.

2. A large gain is more necessary than 5el-F9FT.
To tell the truth, though the element data of Create Design's 6el at which was aimed was not able to be acquired, I thought it was equal in gain if this hentenna had higher gain than 5el-F9FT.

3. The characteristic of gain-to-frequency should be broad.
Of course, this is an ideal. When a high gain is obtained by few elements, the bandwidth may be sacrificed.
If actual manufacture is considered, it is needless to say that characteristic of gain (and SWR) should be broad in the band.
First, I began simulating by using MMPC which was the antenna analysis software by JA1WXB. The number of elements was increased from 3el to 6el one by one, and the calculation was done tens of times respectively. As the result, the promising one was 4el-hentenna.
Neither the gain nor the F/B ratio were enough in 3el. In 5el and 6el, the gain has not increased although comparatively I expect that the boom is long.
Moreover, 4.44m and 2.94m length boom 4els ware calculated.
About the latter, two types of width (he4kpi_S max1.49m) and (he4kpi_N 1.00m) were tested, so that I simulated three types of the hentenna.

Refer to upper right figure for the structure (unit=m) of the short boom and narrow width type. The height is 3.02m, and it's equal in all elements. As for the horizontal element is fixed to the boom, the "L" type aluminum material is assumed. And Input to MMPC is as 15.6mm in the diameter. If you use the one of 20mm+20mm or 12.5mm+25mm for "L", it might be OK. Other parts are plain copper wires of 2mm in the diameter.
Two booms are 3m aluminum pipe which can be easily obtained at DIY shop.

f9ft-5el vs 4el-Hentenna
Dat he4kpi_N he4kpi_S he4kpi_L

The table above is the characteristic with frequency by the calculation of MMPC. Right figure is the beam pattern of this antenna compared with 5el-F9FT (50.3MHz, above real-ground). In this simulation, the mast 7.5m in height is assumed.
The unit of the gain is dBd as gain to dipole in free-space. The beam pattern in the one of short booms are mostly same.

Well, my 8el-Yagi is too heavy to lift up to top of the mast. It is utmost 6m high above the ground. However, the front gain is 15.89dBd, strong enough, in the calculation by MMPC.

On the other hand, the gain of he4kpi_N is 14.41dBd, 7.5m from the ground. If 9.4m mast is used, its gain reaches 14.74dBd but is defeated by 8el-Yagi about 1.2dB.
What a indescribable difference 1.2dB! It can be explained if the antenna has been actually manufactured and compared. A certain person says there's no difference, and another person says that is great difference.

It is difficult to increase the gain 1.2dB for this class of the boomlength. The difference of the gain is only 1.2dB though the difference of boomlength is as long as three times. May it be permitted?
Yes, so I decided to design and calculate about the short boom antenna.

8el.Yagi vs 4el-Hentenna
Left figure is a comparison between 4el-Hentenna and 8el-Yagi on top of the mast 9.4m height.

he4kpi_L(LongBoom) is a version which has extended boomlength to make the gain approach 8el-Yagi even in some measure. Its gain on 7.5m mast is -0.78dB compared with 8el-Yagi though the bandwidth is narrow, and -0.33dB on 9.4m mast. It fights bravely, don't you think so?
If it has 5 elements, this hentenna may completely defeat 8el-Yagi on the same mast. However, the structure of this antenna is more complex than Yagi. In this band, it is not desirable situation that increasing the element.

I can do nothing but admit the Yagi is excellent. As for the structure, it is so easy, and the calculation time is so short. :-)
Therefore, many company-made-Yagi is marketed. And a lot of people buy it more easily and QRV, though its easiness is definitely good.

Well, this antenna has not been completed yet. I've already found materials for this antenna in the DIY shop, but have the problem that how make it. Anyway, there is not a meaning without actually manufacturing. Because we're amateur radio engineer, you know.

I planed which type making, and finally decided to make a short boom and narrow width one (he4kpi_N).
Why narrow? Because a wide type one exceeds the width of my automobile. :-p
Of course, the weight of the antenna is lighter a little. This is exactly the one because of outdoor-QRV.
Recently I obtained the data of Create Design's 6el.-Yagi and had calculated it. The output for result of its gain in the free space is 11.2dBi. And my he4kpi_N has 11.4dBi, so joyously it win in simulation. However in actual??


This hentenna has not manufactured still actually.
if you use the data published in here, please take the same material for the elements as this article, or correct the diameter and length of elements properly.
For instance, if you don't use a plain copper wire for elements but use the vinyl coated wire, the resonance frequency of your hentenna turns down to 46MHz.
Please note there is a possibility that characteristics of the antenna changes.
Tnx to JH7VHZ