50 fo —90 VDC potentiometer bias cd just
Unconditionally guaronfeea against defects in materials and workmanship for a period o^ 6 months
A Broad Band
Coax, Folded Dipole
Ray Abraczinskas W3HJR/^ 412 Elm Grove Lane, Apt. 7
Haze I wood, Missouri
I have heard numerous comments on the bands lately such as, "Don't work any CW here on 80 meters because my antenna is tuned for the phone band and won t load up down there." "I can't talk to him because he works on 3810 and my antenna is cut for 3950." "I'm using an inverted V antenna and the apex angle is sharp causing the bandwidth to be narrow/' "I want an antenna that will perform well with a low SWR across the whole 20 meter band." "I can t put up a low frequency dipoie because haven't got the room/' This article is presented for these persons' benefit.
Many oldtimers who have used the folded dipoie antenna will recall that shorting the two wires of the ribbon a distance out from the center equal to the velocity factor of the ribbon times a free space quarter wavelength, see Fig. 17 will cause the antenna to have a more constant impedance match over a wider range of frequencies thereby giving better bandwidth characteristics. This is the theory on which the material presented here is based with minor variations to suit ones need and fancy.
Since most new commercial transmitters have a relatively small variation in output impedance, 52 ohm coax is a natural choice for a transmission line. When connected to an ordinary wire dipoie antenna* coax will match adequately over a relatively narrow range of frequencies provided the dipoie is at the proper height
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