DL7JV
Self's building of an antenna changeover switch operated by remote control
Quadruple the antenna changeover switch operated by remote control with relays, introduced here, stands a transmitting power of 1kW. The system consists of the relay change over switch in the HF and waterproof housings of aluminum injection moulding, the 5-pin control cable with DIN plugs and the controller in the plastic housing with rotary switch and LED position display. HF of connections are PL. Supply voltage is = 12V. Material costs are with self's building around 50 Euro. Comparable systems cost at least the three-way.
The condition for a troublefree enterprise over years is that only low impedance antennas (Yagiantennen, mono volume dipoles, Groundplane) with approx.. 50 ohms input impedance to be used. The reason is, the used map relays by "finder" (KR1U-12-220/16A) stood a high river of 16 ampere, is however only for tensions up to 250 V to be used.
With a multiband antenna and Antennatuner the relay contact is attached before the tuner and co-ordinatedonly only with small transmitting power.
Both devices possess a plate even corroded. Since corroding at home, after which "cucumber glass method" brings only poor results with iron three-chloride, are both plates completely tinned: -)
In the relay change over switch the resting contacts are put on mass. This increases the signal-to-noise ratio.
The heart of the remote maintenance is the 6 change over switch with 2 switching levels. I use only the necessary 4 contacts in the center of the first switching level S1a around the control voltage from = 12V over the control cable to the relay selected in each case to switch. 1. and the 6. Contact are the position "out"(Aus) . The 4 light emitting diodes are connected by a pre-resistor 2K2 with the second switching level S1b and indicate, which relay is switched at present.
In the practical radio enterprise the antenna changeover switch operated by remote control brings advantages with relays only. I use the part for years and am very content. It saves antenna cables to the roof and in the station. There the relays work is wear-free contactlessly it.
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Christian, DL7JV - July 2007