ANTENTOP- 01- 2013 # 017

RA3AAE Antenna for the 10- and 2- meter Band

By Vladimir Polyakov, RA3AAE

Credit Line: Radio # 5, 1971, p.: 26

The antenna works on the 10- and 2- meter Bands. Antenna does not require any switching in ATU when the band is changed. Antenna radiates radio wave with vertical polarisation. Antenna is fed by 75- Ohm coaxial cable. The cable is very chip compare to 50- Ohm coaxial cable. It is possible to buy 30- meters good 75- Ohm cable intended for underground placement for 10... 20 dollars. Practically any transceiver (designed for 50- Ohm antenna) could work with 75- Ohm antenna. Figure 1 shows design of the antenna.

At the2- meter Band the radiated part of the antenna is a Vertical Dipole (item 1). Physically the dipole is simulated by two tubes (item 1). Vertical radiator (that serves at the 10- meter Band) (item 2) is going through the upper tube. The vertical is connected with the upper tube at the bottom of the tube. Coaxial cable (item 4) is going through the lower tube. Central core of the coaxial cable is connected to the upper tube. Braid of the coaxial cable is connected to the lower tube. Radials (item 3) for the 10- meter band antenna are connected to the braid of the coaxial cable a little lower of the lower tube. The tube (item 1) is quarter-wave sleeve (serve like an RF choke) for the 2- meter Band. The choke does not allow the leaking of the RF current of the 2- meter Band to the others parts of the antenna.

Radio # 5, 1971. Front Cover

Hereby the vertical (item 2) and coaxial cable (item 4) going through the vertical and lower tube (item 1) is insulated on RF at the 2- meter Band from the Dipole Vertical antenna (item 1). The Dipole Vertical antenna (item 1) has input impedance close to 75- Ohm at the 2- meter Band.

At the 10- meter Band the antenna is a Vertical antenna with 3 slope downward radials. All parts of the antenna from the top of the vertical (item 2) to the ends of the radials (item 3) are radiated.

Vertical antenna with 3 slope downward radials (as it is shown on the Figure 1) has input impedance near 40... 60- Ohm when the antenna is fed at the terminals "Vertical- Radials." The input impedance is less the 75- Ohm. To match the antenna input impedance with the 75- Ohm coaxial cable the feeding terminals are risen up. It is going to increasing of the antenna input impedance in proportional with:

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