I live in a area where the radio FM signals from various broadcasts are
quite weakly and coming from different directions. I was thinking to put on
my roof an omnidirectional vertical coaxial FM antenna (two elements of 1/4
wavelength), but I think that the losses through the coax cable could be
substantial. In order to alleviate this problem, I could put an in-line
amplifier just under the antenna. As an alternative, would be possible to
install multiple vertical coaxial antennas, perhaps 3 of them, forming a
triangle and connect them in parallel? But by doing, the characteristic
impedance would drop by a factor of three. Is perhaps a three way splitter
more suitable to maintain the correct output impedance? At what distance
should I install the antennas from each other to assure omnidirectionality?
I am not very knowledgeable about antennas, having just a degree in power
generation.
Many thanks for you help & advice.
Gene

On Wed, 13 Apr 2005 18:51:06 GMT, "EpsilonRho"
wrote:

I was thinking to put on
my roof an omnidirectional vertical coaxial FM antenna (two elements of 1/4
wavelength),

Hi Gene,

This has a good chance of working, even for a simple single element
antenna.

but I think that the losses through the coax cable could be
substantial.

You don't explain why, and an external antenna, up high can make a big
difference.

In order to alleviate this problem, I could put an in-line
amplifier just under the antenna.

This is also a good idea especially if the simple antenna does not
work well. More antennas probably will not give you as much gain as
the amplifier so if the simple antenna does not work, go straight for
an amplifier.

73's
Richard Clark, KB7QHC

Try 2 or 3 rabbit-ear antennas. Easy to adjust, etc - up in the attic.
use 300-ohm cable (its low loss).
use splitters to fan-out the 300-ohm cable from the radio to the several
antennas.
If this works, please apply for a patent in my name and copyright the
instructions.

:-)

"EpsilonRho" wrote in message
...
I live in a area where the radio FM signals from various broadcasts are
quite weakly and coming from different directions. I was thinking to put
on
my roof an omnidirectional vertical coaxial FM antenna (two elements of
1/4
wavelength), but I think that the losses through the coax cable could be
substantial. In order to alleviate this problem, I could put an in-line
amplifier just under the antenna. As an alternative, would be possible to
install multiple vertical coaxial antennas, perhaps 3 of them, forming a
triangle and connect them in parallel? But by doing, the characteristic
impedance would drop by a factor of three. Is perhaps a three way splitter
more suitable to maintain the correct output impedance? At what distance
should I install the antennas from each other to assure
omnidirectionality?
I am not very knowledgeable about antennas, having just a degree in power
generation.
Many thanks for you help & advice.
Gene

Hello Gene:

I once lived in little community over looking the San Fernando valley in
So California. I was surrounded by mountains and hills. I wanted to pick
up a FM Broadcast station several miles over the hills.

I installed a modest FM Broadcast Beam or directional Antenna on a small
mast with a rotor. I turned the beam antenna to the direction of the
transmitter, but heard only bleed over from other FM Stations. I was
disappointed about not being able to receive the FM Station almost 60
miles away. I turned the beam antenna now to all directions and to my
sup rise I could now here the FM Station with good audio quality!

I was pointed the beam antenna in the wrong direction, but hearing the
FM Station just fine. The Signal was bouncing off one of the mountains
and I was hearing a reflection off the mountain. I was impressed.

I listened to other FM Frequencies and heard all different kinds of
stations coming in from long distances. While listing to just one
frequency and then turning the beam antenna I could get different
stations coming in and other disappearing as the beam antennas was moving.

Using a beam antenna and rotor may save you a bunch of time and hassle.
Even if you just find one direction that it works in for your application.

Jay in the Mojave


EpsilonRho wrote:

I live in a area where the radio FM signals from various broadcasts are
quite weakly and coming from different directions. I was thinking to put on
my roof an omnidirectional vertical coaxial FM antenna (two elements of 1/4
wavelength), but I think that the losses through the coax cable could be
substantial. In order to alleviate this problem, I could put an in-line
amplifier just under the antenna. As an alternative, would be possible to
install multiple vertical coaxial antennas, perhaps 3 of them, forming a
triangle and connect them in parallel? But by doing, the characteristic
impedance would drop by a factor of three. Is perhaps a three way splitter
more suitable to maintain the correct output impedance? At what distance
should I install the antennas from each other to assure omnidirectionality?
I am not very knowledgeable about antennas, having just a degree in power
generation.
Many thanks for you help & advice.
Gene

Many thanks to you all for your replies. I built a coax vertical antenna
(two elements 1/4 wavelenght) using scrap water copper pipes. Only mediocre
results are abtained with the antenna alone, but with an in-line
amplifier...... thumbs up! A strong and useful signal.


Gene