[Lf] G3LDO antenna and TX details]

[Andre' Kesteloot]

Peter Dodd wrote:

> A few days ago I promised to give details of my antenna and
> transmitter, which was used during the 136kHz/14MHz crossband QSO
> with VE1ZJ on 29th Sept.
> The antenna comprises two wires connected at the feedpoint about 2m
> high with each separate wire connected to the ends of a  3m long
> crossboom fixed to the top of a 16m tall steel mast (located 15m from
> the feedpoint). The wires continue in the horizontal direction for
> 24m but drooping to 10m high with the spacing maintained with a 1m
> spacer at the end. The crossboom at the top of the mast is insulated
> from the mast. This antenna configuration minimises the coupling to
> the steel mast.
> A loading coil is located at the feedpoint which in turn is fed with
> a series variometer.
> The antenna radiation resistance is calculated at 0.037ohms and the
> antenna current was about 6amps. If we take the erp to mean the power
> dissipated across the radiation resistance then it is about 1.33Watts.
> The transmitter is a modified Decca 5501. The input power to the
> transmitter modules was 60v @ 19amps, which is just over  1100 watts.
> These units are around 90% efficient so the power to the antenna must
> have been about 1KW.
> The transmitter driver comprises two 10MHz variable crystal
> oscillators (actually 136kHz apart) followed by a mixer.
> The transmitter system is located at the bottom of the garden in a
> shed and remotely controlled from the shack in the house. The QRSS
> computer and the main Spectran computer, and the receivers are
> located in the shack in the house.
>
> --
> Regards, Peter, G3LDO
>
> <g3ldo at zetnet.co.uk>