wrote in message
...
On Fri, 4 Dec 2009 02:39:00 -0000, "Arfa Daily"
wrote:


wrote in message
. ..
On Tue, 01 Dec 2009 02:46:53 -0500, mm
wrote:

One more antenna question: Antenna pitch?

That is, my attic has a pitched roof and the antenna for channels 7 to
60 that I'm thinking of now is almost 13 feet long.

It would fit more easily in the attic if I pointed it down a little
bit just like the roof pitches down from the center. Does the angle
of the axis matter that much if the individual elements are all
horizontal?

After all, if the tranmitter is higher than the antenna, it's as if
even a horizontal antenna is pointed down, from the pov of the
transmitter.

I've been reading but nothing has addressed this. All outdoor
antennas are of course horizontal, and I don't get to see people's
indoor antennas.

A small amount of tilt won't make a significant difference. Those that
suggest tilting the antenna will increase the gain are misguided. The
antenna can take advantage of ground reflection up to a theoretical
6db of gain. This gain is seldom reached but the in phase reflected e
field that causes this gain is best achieved when the antenna is
horizontal.

It depends on how close in you are to the transmitter mast. Look at cell
phone sites beside roads. The flat panel antennas on those masts are
angled
down significantly to avoid shadowing around the mast. As I said earlier
in
this thread, I experienced a real life example of the effect of antenna
tilt
at the bottom of a hill, close in to a transmitter that was on the top of
the hill. Nothing will affect the actual 'gain' of the antenna when it's
mounted in reasonably free space. However, tilting, under *some*
circumstances, may improve its ability to interact with the radiated field
from the transmitter, resulting in an increase in the received signal
level,
relative to a no-tilt situation.

Arfa

If tilting the antenna made a difference then the receiver is very
close to the transmitter.

If the proximity was that close you could use rabbit ears.

Yes, I'll go along with that. In the case that I cited, the receiver *was*
close to the transmitter, which was an amateur TV repeater with a 10 watt
input (less cable losses) to the antenna. All of this discussion is pretty
academic anyway, and I was just indicating that as well as on paper, in the
real world, antenna tilt *can*, under some unusual circumstances such as
this, have a significant effect, the implication being that if you extend
that out across the board, it *is* a real effect, allbeit of no significance
in the vast majority of cases.

I think it is highly unlikely that it would be a noticeable effect for the
OP, but may be visible on a signal strength meter, given that he is
proposing using a very long multi-element antenna (at VHF I think ?) - which
I guess he must be thinking of using because of potentially marginal
reception conditions - and which will have a comparitively narrow beamwidth
in both the horizontal, and vertical planes.

Arfa