- Detta ämne har 3 svar, 2 deltagare, och uppdaterades senast för 5 år, 6 månader sedan av .
In our local radio club we had a presentation about the Grimeston radio station at 17,2 kHz..
Questions did come up about the alternator load by the antenna.
As expected the antenna is very short for the wavelength of 17,44 km. and so being tuned by a very high-Q network and antenna transformer (Q ca 350). This implying de-tuning by a small amount already means considerable dropping of power. Therefore the alternator is to be kept at a very accurate speed.
We understood the antenna is coupled to the alternator by a special transformer in the matching network, which in turn is getting de-tuned by a magnetic amplifier in the keying circuit, to modulate the antenna current.
To get a stable frequency also for keeping within the optimal antenna tuning range, the alternator should see a constant load, to keep a stable speed. Now de-tuning by keying means alternator load is constantly changing, which at 80 kW. is generating considerable force to the generator and also to the mechanics to and in the drive motor. We presume this to be avoided.
Can you tell us if, and if so by what means the alternator load is being kept constant during this keying action.