Multiple transmitters can cover the area you need if one transmitter
won't do the job. The most common method people are using to cover a
larger area with multiple transmitters is place RangeMaster
transmitters around town and link them by Internet, see
this link. When using this method there
are some important things to know. First you need to keep your audio
in sync, even a few tenths of a second delay of audio between the
transmitter s will cause a noticeable echo as a person drives
between transmitter zones. Second, the RF carrier is not in phase
sync using this method, the transmitters will not heterodyne (you
must use the crystal controlled model) but the PHASES of the
carriers will not be synced. Normally you will have a short zone of
"flutter" as you drive between zones, not too noticeable, like
driving under a power line. However if you don't do a good job of
planning transmitter locations and get the transmitters to close
together then the flutter will become worse. Do not try to use other
(PLL) type transmitters with this method, you can get into all kinds
of heterodyne problems.
See this FCC Publication addressing Multiple Part 15 Transmitters
We have other various communications from the FCC and Enforcement
allowing the use of Multiple Part 15.219 transmitters
The way to design a system would be to generally plan a coverage
are, put up the first unit and determine your coverage area. If you
are getting 1.5 miles range then the next transmitter would need to
go approximately 3 miles away. All the cells would be planned
depending on the range attainable by the other cells and of course
available locations. The idea is not to get the transmitters to
close together and not to far apart. To close together and you have
to much overlap, phase flutter and wasted coverage. To far apart and
you have hole in you coverage. This is the Zerobeat method. With our
system your coverage areas CAN overlap.
The Barix (see this link) product has
provisions for audio synchronization.
Seek locations with a good ground when you are planning your site.
Typically if you see antennas and such at the site there is already
a good ground there.
See this link for an example system for
2 transmitters, linked audio and radio carrier by microwave.
Here is an inexpensive microwave system
prairietech
We recommend first of all using a good technical person that has
worked with radio before. A good technical person can get more legal
range just because they understand radio. What we recommend when
setting up to cover an area is to put in one unit first to get an
idea of what kind of range you will be able to get. Then design the
location of the other units with the range of the first in mind.
Range will vary widely according mostly to ground quality, installer
skill, height, noise floor, ect.
Here is a link that describes many
different methods of linking transmitters.
sync instructions Sync
guidelines New Sync
Manual
Using an Radio station type audio processor like an
Innovonics 222 will make you signal
sound louder and get you more range legally, however most audio
links won't support the asymmetrical modulation output of the 222 so
you will need a 222 for each transmitter. You can also you an old
Audiomax or Volumemax audio processor.
Some customers have suggested that using a standard phone line to
deliver the audio is acceptable, especially for talk radio.
Another method of expanding is to receive the signal of the first
transmitter in the second location with a good quality selective AM
radio, send the audio to another transmitter and rebroadcast the
audio on a different frequency. The transmit and receive frequency
have to have some good separation for this to work. The disadvantage
of this setup is that you will be broadcasting on two different
frequencies. Basically what you would be doing is using a
Rangemaster Am transmitter to distribute your audio.
See www.comrex.com for
information on phone line STL links,
www.audiotx.com says they can
make your computer a phone line STL using software.
See this link for the Barix network MP3
player that will play audio right from you internet stream into the
transmitter.
Here are some e-mails from tech support
in response to us about the Barix Gold unit.
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