low power FM TX and multiple antennas?
 

Greetings.

If we are using one low power FM transmitter and we want to use a 2-bay
FM antenna configuration, will using a power splitter at the
transmitter output be sufficient?

The FM TX utilizes a type N connection to the FM antennas. .... So if I
split the power output and just have two outputs to handle each of the
two antennas, then that would work right?

What other considerations should I have in mind? Do I need to worry
about phasing issues?

Thanks!

low power FM TX and multiple antennas?
 

MRW wrote:
Greetings.

If we are using one low power FM transmitter and we want to use a 2-bay
FM antenna configuration, will using a power splitter at the
transmitter output be sufficient?

The FM TX utilizes a type N connection to the FM antennas. .... So if I
split the power output and just have two outputs to handle each of the
two antennas, then that would work right?

What other considerations should I have in mind? Do I need to worry
about phasing issues?

Thanks!


You need to move the splitter closer to the antennas in order to save
power losses. You you need to worry about phasing but that is taken care
of when you run the coax from the antennas to the splitter cut the coax
to approx. 1/2 wave. See the ARRL antenna book.
You will have a change in impedance in this configuration from the
splitter to the antennas. Look at about 70 ohms to the antennas and use
50 ohms from the transmitter to the splitter.
I am sure that other helpful assistance will be forthcoming from others.
Turn your BS filter on.

Dave WD9BDZ

low power FM TX and multiple antennas?
 

"MRW" wrote in message
ups.com...
Greetings.

If we are using one low power FM transmitter and we want to use a 2-bay
FM antenna configuration, will using a power splitter at the
transmitter output be sufficient?

The FM TX utilizes a type N connection to the FM antennas. .... So if I
split the power output and just have two outputs to handle each of the
two antennas, then that would work right?

What other considerations should I have in mind? Do I need to worry
about phasing issues?

Thanks!


MRW -

Start with Radio World - for industry info
http://www.rwonline.com/

You need to understand more about antennas. Please look at (and learn from)
the methods used by commercial broadcasters - that have been at this for
decades -- they have taken the road of "least cost" and best economics".

2-bay and 4-bay designs are common is FM broadcasting and even used in the
Land Mobile Radio (LMR) Service. Amateur radio references can be invaluable
in learning the proper theory.
http://members.tripod.com/AMN92/cp_ant.htm

gb

low power FM TX and multiple antennas?
 

Dear MRW:
Do not do what you are proposing - assuming that I understand what you
are proposing.

It sounds as if you propose to connect in parallel, near the
transmitter, two transmission lines with each transmission line running to
one bay of a two bay antenna. You are not too clear about what you propose.

It is very difficult to have two transmission lines that are many
wavelengths long (as expected) that are so equal (including the termination
impedance) as to have the phases of the two signals at the antennas be equal
(as required by the normal two bay antenna). It is possible to maintain
close phase equality with short pieces of coax that are near the antennas.

Tell us more about what you wish to do. Mac


"MRW" wrote in message
ups.com...
Greetings.

If we are using one low power FM transmitter and we want to use a 2-bay
FM antenna configuration, will using a power splitter at the
transmitter output be sufficient?

The FM TX utilizes a type N connection to the FM antennas. .... So if I
split the power output and just have two outputs to handle each of the
two antennas, then that would work right?

What other considerations should I have in mind? Do I need to worry
about phasing issues?

Thanks!