The HY GAIN 105 and 27 Mhz


When planning a new antenna or playing with an old one, I think the computer analysis can offer a good starting point. At least you avoid to blunder ;-)

I have not a 105 BAS handy but I received by Tony 102 the 105 CA measures for 28.5 Mhz.
The elements are split into 3 piece, with tapered diameters of *around* 22mm, 16mm, 11mm. I suppose the actual diameters are 7/8", 5/8", 7/16"

dia. 22 mm.dia. 16mmdia. 11 mm
reflector at 0.000 m.112 cm 54.6 cm 105.4 cm
driver at 1.473 m.061 cm 59.7 cm 137.8 cm
1st directorat 2.616 m.061 cm 59.7 cm 133.4 cm
2nd directorat 4.737 m.061 cm 59.7 cm 116.5 cm
3rd directorat 7.277 m.061 cm 59.7 cm 097.2 cm

And, for the "aficionados" here the Eznec card.

Frequency = 28.5  MHz.
Wire Loss: Aluminum -- Resistivity = 4E-08 ohm-m, Rel. Perm. = 1 

              --------------- WIRES ---------------

Wire Conn. --- End 1 (x,y,z : m )  Conn. --- End 2 (x,y,z : m )   Dia(mm) Segs

1           -2.720,  0.000,  0.000  W2E1  -1.666,  0.000,  0.000 1.11E+01  10
2     W1E2  -1.666,  0.000,  0.000  W3E1  -1.120,  0.000,  0.000 1.59E+01   6
3     W2E2  -1.120,  0.000,  0.000  W4E1   1.120,  0.000,  0.000 2.22E+01  22
4     W3E2   1.120,  0.000,  0.000  W5E1   1.666,  0.000,  0.000 1.59E+01   6
5     W4E2   1.666,  0.000,  0.000         2.720,  0.000,  0.000 1.11E+01  10
6           -2.585,  1.473,  0.000  W7E1  -1.207,  1.473,  0.000 1.11E+01  14
7     W6E2  -1.207,  1.473,  0.000  W8E1  -0.610,  1.473,  0.000 1.59E+01   6
8     W7E2  -0.610,  1.473,  0.000  W9E1   0.610,  1.473,  0.000 2.22E+01  13
9     W8E2   0.610,  1.473,  0.000 W10E1   1.207,  1.473,  0.000 1.59E+01   6
10    W9E2   1.207,  1.473,  0.000         2.585,  1.473,  0.000 1.11E+01  14
11          -2.541,  2.616,  0.000 W12E1  -1.207,  2.616,  0.000 1.11E+01  14
12   W11E2  -1.207,  2.616,  0.000 W13E1  -0.610,  2.616,  0.000 1.59E+01   6
13   W12E2  -0.610,  2.616,  0.000 W14E1   0.610,  2.616,  0.000 2.22E+01  12
14   W13E2   0.610,  2.616,  0.000 W15E1   1.207,  2.616,  0.000 1.59E+01   6
15   W14E2   1.207,  2.616,  0.000         2.541,  2.616,  0.000 1.11E+01  14
16          -2.372,  4.737,  0.000 W17E1  -1.207,  4.737,  0.000 1.11E+01  12
17   W16E2  -1.207,  4.737,  0.000 W18E1  -0.610,  4.737,  0.000 1.59E+01   6
18   W17E2  -0.610,  4.737,  0.000 W19E1   0.610,  4.737,  0.000 2.22E+01  12
19   W18E2   0.610,  4.737,  0.000 W20E1   1.207,  4.737,  0.000 1.59E+01   6
20   W19E2   1.207,  4.737,  0.000         2.372,  4.737,  0.000 1.11E+01  12
21          -2.179,  7.277,  0.000 W22E1  -1.207,  7.277,  0.000 1.11E+01  10
22   W21E2  -1.207,  7.277,  0.000 W23E1  -0.610,  7.277,  0.000 1.59E+01   6
23   W22E2  -0.610,  7.277,  0.000 W24E1   0.610,  7.277,  0.000 2.22E+01  12
24   W23E2   0.610,  7.277,  0.000 W25E1   1.207,  7.277,  0.000 1.59E+01   6
25   W24E2   1.207,  7.277,  0.000         2.179,  7.277,  0.000 1.11E+01  10

              -------------- SOURCES --------------

Source    Wire      Wire #/Pct From End 1    Ampl.(V, A)  Phase(Deg.)  Type
          Seg.     Actual      (Specified)           

1           7     8 / 50.00   (  8 / 50.00)      1.000       0.000       I   

No loads specified
No transmission lines specified
Ground type is Free Space
Now the radiation pattern in free space: and the impedance *should* be 17.77 -J17.04 ohms.



Why I spent so a lot of time over the 28.5 Mhz project? But to verify how the software can deal with such an antenna. Now I think the known real performances of 105-BAS and the software predicted one are quite similar. Btw I ran the same card for Yagi Analyser by K6STI Brian Beezley, with quite equivalent results. So why to fear the 11m project would be not OK? Better result can be obtained rearranging the element spacing too, but Tony likes to stay with the original ones. So I scaled the antenna from 28.5 to 27.555 Mhz, rearranging only the tip's length.

dia. 22 mm.dia. 16mmdia. 11 mm
reflector at 0.000 m.112 cm 54.6 cm 114.7 cm
driver at 1.473 m.061 cm 59.7 cm 146.7 cm
1st directorat 2.616 m.061 cm 59.7 cm 142.1 cm
2nd directorat 4.737 m.061 cm 59.7 cm 124.6 cm
3rd directorat 7.277 m.061 cm 59.7 cm 104.7 cm

Here the new radiation pattern in free space, note a little low gain and F/B: and the impedance *should* be 18.24 -J18.21 ohms. If true, the match will be the same as for 28.5 Mhz.



The above setting is for max F/B: here a project derived by the CA setting for 28.200 Mhz.

dia. 22 mm.dia. 16mmdia. 11 mm
reflector at 0.000 m.112 cm 54.6 cm 113.3 cm
driver at 1.473 m.061 cm 59.7 cm 143.7 cm
1st directorat 2.616 m.061 cm 59.7 cm 141.5 cm
2nd directorat 4.737 m.061 cm 59.7 cm 136.9 cm
3rd directorat 7.277 m.061 cm 59.7 cm 127.2 cm



Waiting for Tony ... Cheerio. Paolo 1839




Later I received a message by Tony:

So I think the measures already used by Tony are as below:

dia. 22 mm.dia. 16mmdia. 11 mm
reflector at 0.000 m.112 cm 54.6 cm 109.3 cm
driver at 1.473 m.061 cm 59.7 cm 141.1 cm
1st directorat 2.616 m.061 cm 59.7 cm 137.9 cm
2nd directorat 4.737 m.061 cm 59.7 cm 133.4 cm
3rd directorat 7.277 m.061 cm 59.7 cm 123.9 cm

Now that's Eznec response for the above measures :-)
If we trust Eznec, a better arrangement can be found. But software is not all, in the life. So if I was Tony, I'll stay with it some time and I'll test it ...



Here the antenna in the real environment, 15m over Tony's roof. Look at the very low take-off angle; with this antenna you can *open* the propagation, i.e. heard stations before others can. Look also to the null from 14 to 18 degree. When the propagation is strong, a big can sometime be outperformed because ... he's got too a low take-off :-)