Summer 2012

Dedication:  This collection of technical information is dedicated to Part 15 low power radio broadcasters who erect indoor transmission antennas for reasons of their own.
In some cases an outdoor antenna is not possible because the necessary ground space is not available. In other cases the operator may be prohibited from mounting antennas on land or structures because of deed restrictions or building rules of various kinds.

A testing facility has been dedicated inside the Internet Building utilizing an AMT3000 transmitter from and a part 15 station established with call letters KHZ, operating at a frequency of 1640 kHz, expressly for the development, testing and documentation of many indoor antenna designs. In some cases other frequencies or transmitters may be utilized, this will be stated.

This collection of antenna information will be posted in the public domain, except that special designs from contributors and external sources will be properly attributed and those inventors made part of this record.



Submitted by Rich on August 9, 2012 - 08:09.

NEC will calculate the radiation pattern of an antenna, but it is not the best tool to determine the effect of the passage of radiation from indoors to outdoors.

Such effects vary considerably depending on the construction of the building, the operating frequency, and other factors.

I have a Tecsun PL310 receiver, which displays the strength of the received signal in "dBµ." When I tune it to a local station on 1530 kHz, it reads the same maximum value no matter where I am in my house as when I am outside the house.

On a local FM station, the radio reads about 3 dB lower inside the house than outside, in general, but there are some places on the first floor of the house where it reads 5-6 dB lower.

My house is a typical ranch style, brick veneer structure. Houses with aluminum siding, stucco over a metal grid, buildings with steel beams etc all behave differently. In some cases they can make radio reception inside them almost impossible.