Hermann Fri Sep 28, 2012 6:50 am
please let me give also some remarks concerning receiving aerials in submarine models.
In principle and independent of the model category routing of the receiving aerial has a major influence of the receiving quality and with bad routing the usable control range may be reduced dramatically ( just like on the transmitter side when the transmitter antenna is not expanded and only a stub).
But which kind of routing is poor an which is most useful? To receive the control signal the receiver needs a signal voltage at its input, this signal voltage develops between the aerial wire as one pole and the residual wiring such as supply cable, servo cables, speed controler cable etc. ; that residual wiring serves as a "counterweight" to the aerial, the second pole. A voltage means always a difference between the electrical potentials of two poles, in this case the voltage occurs between the aerial wire and the "counterweight" given by the residual wiring. To pick up as much radio frequency energy of the signal from the electromagnetic field, aerial wire and counterweigth should be layed out as far as possible apart from each other. They shouldn't be routed together. You can explain this circumstance by yourself when you remember that the measurement unit for the electric field stregth is defined as Volt per metre (V/m), so if you have a certain fied strength at the location of your model you will get more voltage if you increase the distance between aerial and counterweight (well, when submerged the voltages will be very low, in the range of microvolts). Of course separating aerial wire from the other cabling may be problematic in some cases, especially for small models, but in general it is useful to follow that rule.
It is not necessary to route the aerial inside the pressure hull, the aerial may be also in the flooded aeria. If your pressure hull contains additional conductive structures (e.g. thread rods of a technics rack) it is important to keep the aerial on distance to these elements and put it outside.
Of course it is also important to have an effective suppression of interference generated by sources within the model (e.g. brush type motors or switchmode voltage regulators for power supply). For good signal reception a good signal to noise ratio is essential. That means if the field strength of the signal is low (due to attenuation in water) the noise level must be consequently low to maintain a sufficient good signal to noise ratio.
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