For reasons I have never completely understood NEC states that neutral and ground cannot be connected except at the main panel and all sub panels have to keep the neutral isolated from local and service ground at that panel, also think there is something about not being allowed to return any current on the ground being that’s only a safety connection. The RCA transmitter is designed for 240 volt operation being that all the transformers, the fan and all the control relays are 240 volt. So the connection to the transmitter is a three conductor cable brought out to a twist lock plug that has two wires for the 240 volt input and a safety ground. No neutral! So there is no neutral available in the transmitter to connect one side of the HV transformer to.
The "safety" ground is not supposed to carry any of the load current. The neutral is supposed to be treated the same as a hot, everywhere past the entrance where neutral and ground are bonded together. One of the reasons is that without the separate safety ground, if the neutral connection were lost, the entire unit, case and all could become hot with 115v. The same could occur if one of the hots shorted to a case left floating with no safety ground. Keeping ground and neutral separate beyond that one bonding point also reduces the tendency for ground loops to occur.
Some older 230-volt appliances like electric kitchen ranges make no distinction between neutral and ground. The same goes for broadcast transmitters. I separated the two in my BC1-T by lifting the original ground/neutral from the cabinet, and running a separate ground wire from the transmitter cabinet to the shack ground. The shack ground is connected to a 8' ground rod, some ground radials at the point where the rod is driven in, plus a #6 wire, buried a couple of inches in the soil in the same manner as a radial wire, bonds the shack ground to the main service entrance ground at the house.
I have noticed that when I temporarily short the neutral wire in the shack to ground, there is enough current sometimes to cause a visible spark. There may be a volt or so measured difference between ground and neutral. With the short in place, the hum level in my audio equipment increases by several dB.
If you pull a heavy 115v load off one leg of the line, a voltage drop will occur in both the hot and neutral. That will cause the voltage to sag. But the voltage drop in the neutral is additive to the other side of the line. Assuming the same size wire is used for the hot(s) and neutral, the voltage at a 115v outlet on the opposite leg will
increase by approximately one-half the voltage sag on the side under the load. I take advantage of that phenomenon in my HF-300 rig, in which everything runs off 115 volts (the transformers in the rig have 115v-only primaries). The filament line is connected to the opposite leg of the power mains as the plate transformers. So when I transmit, and draw plate current, that causes the filament voltage to increase slightly, rather than to sag. That helps maintain emission from the tube filaments under heavy plate current load. OTOH, the modulator bias supply connects to the same side as the plate transformer right at the transformer terminals, so that the grid bias voltage sags in step with the plate voltage, reducing distortion and maintaining more constant static plate current under variations in line voltage.
Because of the slight variations in potential of the neutral wire as the circuit is placed under load, if the ground and neutral were bonded together at the appliance in use, the safety ground would share some of the load current with the neutral wire, which it is not supposed to do.
http://en.allexperts.com/q/Electrical-Wiring-Home-1734/Neutral-vs-ground.htm
