Indoor Antennas
Posted on October 11, 2011
The fascinating experience of learning how to use the new AMT5000 transmitter from sstran.com has brought the question of antennas foremost to mind, for the obvious reason that the antenna is so essential in disseminating a radio signal into the surrounding air.
The perfect starting point for me is this description of the Ultimate Part 15 Installation, written by PhilB earlier in the year:
http://www.part15.us/index.php?q=node/2728
In his posting, Phil is talking about classic antenna practice for AM radio, a proven and standard set of practices.
The trouble for Part 15 is that the typical setup is in a home or apartment, and the more industrial step of devoting real estate and somewhat of a big dig to locate an ideal 3-meter stick on cleared ground is not often an option.
Therefore something less than ultimate is needed, something of a compromise.
Indoor antennas are a common reality for many Part 15 radio stations, and this brings the question: what are the best designs for indoor AM antennas?
When I first started Part 15 about 6-years ago I used a glue stick to run the “white wire” 3-meter antenna up the same corner of the room where the transmitter and audio source were located (computer). Typical room height in most homes is less than 3-meters, about 8.5-ft.
The corner was chosen for proximity to the equipment, and neatness, because a white wire in the corner of a white room is very inconspicuous. But would the antenna have served better moved away from the corner, farther toward the middle of the wall?
The wall is the most likely place for a vertical indoor antenna, but would it work better moved into the room, away from the wall, perhaps by hanging from the ceiling alongside a floor lamp or other furniture?
Basement transmitter locations usually utilize horizontal antennas, and there are attic installations.
No full power radio station would ever place its antenna indoors, therefore no standards have been developed for such practice, but Part 15 is an exceptional circumstance, and indoor antennas are part of the game.
The question is, what are the best designs for including a 3-meter vertical antenna within home furnishing.
