Introduction OM0A Adjusted Yagi antenna for 10 meters

Adjusted Yagi antenna for 10 meters

Yagi at 10 meters
Yagi na 10m
Yagi at 10 meters

10 m band are due to low solar activity, and hence the small number of possible stations, riešili v contestoch len nenáročnou anténou, CB as a vertical. In the spring we installed a 4el. yagi, which lay a long time in the cellar. The original owner was happy with it (during solar maxima), We liked, however, little. One of the tasks before the next race was the aerial Reconnaissance.

The original antenna had a boom with a length of 4 m. Program MMANA-GAL calculated, that the frequency 28.5 MHz in free space the antenna impedance 40 -j2 ohms, profit 4,5 dBd and before-back ratio of just over 10 dB.

Based on documents G0KSC I did the conversion of this attractive design antenna for 10 meters band. G0KSC yagi is very easy due to the direct power supply, antenna coaxial cable with a member of adjustment. MMANA-GAL shows these parameters: impedance 50 + j3 ohmy, profit 6,2 dBd and before-back ratio of about. 20dB. Moreover, the boom is about thirty centimeters shorter.

These parameters are now much more interesting than the original antenna. Editing involves the removal betamatch-in, shorten the boom, drilled new holes for handles elements and adapting the length of elements. Modification of our yagi was difficult because, that the previous owner too shortened elements and so I had to replace the pipe end or redundancy thinner tube, to achieve the desired size. T?the dimensions are adjusted 4el.yagi antenna:

Element Length Position the boom-e
Reflector 5,30m 0m
Žiarič 5,14m 1,29m
Dl 4,88m 1,78m
D2 4,66m 3,7m

After changing the dimensions of the antenna is subjected to the measurement antenna analyzer. The measurements were performed at app. 5m coaxial cable RG-213 of 3.5 m. To reduce the impact of the second antenna near the yagi was against it turned 90 °. Here are the results of measurements:

Frequency Impedance SWR
27,8 MHz 67 + j0 1,35
27,9 MHz 62 + j0 1,26
28,0 MHz 59 + j0 1,18
28,1 MHz 55 + j0 1,10
28,2 MHz 52 + j0 1,06
28,3 MHz 50 + j0 1,00
28,4 MHz 48 + j0 1,08
28,5 MHz 47 + j0 1,09
28,6 MHz 47 + j0 1,09
28,7 MHz 49 + j0 1,02
28,8 MHz 50 + j0 1,00
28,9 MHz 54 + j0 1,10

The imaginary component of the frequency analyzer appeared under 27,6 MHz and at 29.2 MHz, which is growing rapidly with distance from the center of Gaza. The antenna is therefore likely, nasimulované parameters that are confirmed and work on 10m band.