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Simple Broadband Antenna for the 40- meter Band

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ANTENTOP- 01- 2014 # 018

Simple Broadband Antenna for the 40- meter Band




Figure 4 Connection box


The resistor leaks the static from antenna wire to the ground. Antenna and ground wire went into the box from the down side. The wires had knot on it inside the box. The knot did allow the wires go off the box. Two ventilation holes (for removing condensed water) were drilled at the down side of the box.


Connection Box was placed on the fence at South- East side. So the most part of the day the box was shined by the Sun. At the autumn I discovered that tabs at the cover had cracks at the bending. The tags went away from the cover when this one was opened. Picture 6 shows the cover with cracked retaining tags. Take attention that one retaining tag had cutoff (the cutoff is near antenna socket). It was happened in 1.5 years from the antenna installation. However I had a spare cover to fix the box.



Picture 6 Cover with cracked retaining tags


 Picture 5 Coaxial Cable going into my Basement


Tuning the antenna to resonance is a simple matter. Connect an antenna analyzer (I use to a MFJ- 259B) to the antenna terminal (ground of the coaxial cable should be connected with antenna) or (that is better) to end of the coaxial cable going from the antenna. Measure the resonance frequency. The frequency would be lower the 7.0- MHz. Then do shortening of the antenna wire from the left side. I do not recommend cut the wire, just fold it like it is shown at Figure 5.


I got antenna impedance 75- 85- Ohm (at zero reactance) at 7.0- 7.350- kHz. The data is practically matched with data obtained from Antenna Simulator EZNEC for MMANA. The antenna should be simulated by this software. In spite of the antenna impedance is not strictly 50- Ohm at the 40- meter Band the antenna could match with my IC- 718 and K-1 without any ATU.

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Last Updated:

January 5, 2020 22:37