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ANTENTOP- 01- 2015, # 019

Insulation RX Transformer



Figure 3 Advertising of the Coaxial Antenna Switch Protax from 73- Magazine # 1, 1967


Please, take attention that a 50- Ohm dummy load is switched there. Why? The switch has position when the antenna is grounded. It is very useful at lighting time or time when static could copy on to antenna wires. It is time of strong winds, snowfall or before lighting period. When antenna is grounded the static goes to the ground and could be not damaged devices that are switched to the Coaxial Switch. However it is worked well when antenna does not contains a ferrite transformer (s) in the design. If antenna had ferrite transformer in the design and the antenna is grounded to the natural ground, antenna current caused by static or lighting discharge may be strong enough to destroy the ferrite transformer.


I use to the switch with Beverage Antenna that is described at that issue (Antentop 01- 2015, pp.: 35- 41). My Beverage Antenna has ferrite matching transformer at the end. So theoretically the transformer may be damaged when switch grounded the antenna directly to the ground. 


At professional radio communication an antenna that has ferrite parts in the design newer being directly grounded to the natural ground. Such antenna is grounded through a low ohm resistor that as usual has nominal equal to surge impedance of the transmission line. In this case the current going through the antenna ferrite parts would be limited by the resistor and the ferrite parts would not be destroyed by the lighting and static electricity. I use 50- Ohm coaxial cable so I turn on my antenna to a Dummy Load 50- Ohm when the antenna is not in use.


The main lack of the Coaxial Antenna Switch Protax CSR- 5G is that one position rotary switch is used at the device. So grounds of all devices connected together at the switch. It may be caused that interferences catching by one device may penetrate to another one having common ground. Professional Antenna Commutator as usual has 2 position rotary switch that commutate simultaneously input and ground of antenna or used device.



Figure 4 Design of the Insulation Transformer



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Last Updated:

May 1, 2016 22:20