ANTENTOP- 01- 2013 # 017

Modifications for the Multiband UB5UG Antenna

Oleg Safiullin, Kazan, UA4PA

Credit Line: Radio # 9, 1969

Anyway any ham wants to have a separate antenna for each of HF-Bands. But, very often the person has only one antenna that compromised for several bands. The same is for the author of the article. He tested lots compromised antennas. However the best one was the Five Band Antenna designed by UB5UG (References 1, 2).

The antenna may be modified with some improving in the overall antenna performance. See below the improvements.

OK1MC recommended tune the antenna on the used band with help of a variable capacitor that is connected to bridge on to the coaxial stub L3. Figure 1 shows the method of the tuning.

Capacitor gives possibility to reach SWR less the 1.5:1.0 for all of the working bands of the antenna. Capacity of the capacitor is close to 450- pF on the 80- meter Band. Others bands require less capacity. Capacitor should

Oleg Safiullin, UA4PA

has gap between the plates not less the 2- mm if used TX with100- wtts output RF power.

UA4PA discovered that the efficiency of the antenna may be improved on 40 and 80- meter Bands. It should be done by lengthening of the vertical (and all counterpoises) part of the antenna (L1) to length of 11.2- meter. Length of the coaxial part L2 should be shortened (for coaxial with dielectric with epsilon =1.51) to 20.6- meter.

Overall improving of the efficiency may be made by adding one resonance counterpoise (length lambda/4) for the each working band of the antenna.

Next improving of the antenna was the added Antenna Tuning Unit that was installed at the end of the stub L2.

Front Cover the Radio # 9, 1969

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