More Cage Monopole
Posted on February 6, 2011
The present experimental antenna mounted on an indoor bamboo tower is a 4-element cage monopole at 107.1 FM. The antenna output from a Wholehouse 2.0 connects to four wires that are hung vertically, each wire 3″ parallel to the one next to it. This indoor antenna sends the signal about 50-feet to a Technics FM tuner which provides audio to an SStran at 1550kHz. This antenna replaces a simple 1-wire vertical antenna, which suffered from frequent multipathing as I walked around the room space and through the doorway.
What I have found so far is that the 4-element cage monopole increases the power received at the FM radio by only a small increment as seen on the S-meter, but the multipathing problem no longer exists. Therefore it seems that the cage-monopole is providing a much more stable indoor coverage, allowing human movement within the space without interference.
Now we move on to another question. What if one wire of the four was disconnected from the antenna output and connected to transmitter ground… would this create a null on one side of the radiation pattern, putting the main signal toward a particular direction with some side lobes, like a cardioid microphone pattern?
Perhaps if that works there could be any comination of patterns achieved, depending on which wires of the four were grounded… figure eight, sharply directional, for example.
Please tell your expectations based on your knowledge; experience, and I will post the results here as I go ahead with testing.
The first problem will be finding a ground point on the transmitter, which probably will be the shield side of the audio input, since there doesn’t seem to be a way of opening the Wholehouse.