Multi lobes
 

I haven't been on the air for a long time but I don't remember any
conversations
as to the upper lobe being used for communication. I always assumed
that
I was using the main lobe. Today I was messing around with some
antenna designs
and I arrived at one where there was only the lower single lobe to the
front
with the upper lobe somehow being removed.
I have no idea what the ommission of any upper lobe would have of any
consequence.
Anybody had experience with this sort of thing?
I suppose that in the early stages of propagation the lower lobe
could make
a connection where as the upper lobe transmission may well be absorbed
by the upper layers that had not yet obtained reflected powers, but
that is
just conjector on my part.
Art

Multi lobes
 

"art" wrote in message
ups.com...
I haven't been on the air for a long time but I don't remember any
conversations
as to the upper lobe being used for communication. I always assumed
that
I was using the main lobe. Today I was messing around with some
antenna designs
and I arrived at one where there was only the lower single lobe to the
front
with the upper lobe somehow being removed.
I have no idea what the ommission of any upper lobe would have of any
consequence.
Anybody had experience with this sort of thing?
I suppose that in the early stages of propagation the lower lobe
could make
a connection where as the upper lobe transmission may well be absorbed
by the upper layers that had not yet obtained reflected powers, but
that is
just conjector on my part.
Art

Someone once explained antenna lobes and gain is like taking a balloon and
putting some water in it and put it on the table.
If you squeeze it from 2 sides, then 'lobes' would extend the other 2 sides.
The water in the balloon would represent the available RF. Since water is
not not compressable, pressing in on one side would require the water to
bulge into other lobes.
And they said about omni gain (like a 5/8 wave vs a 1/4-wave vertical) is
like pressing down on the top of the balloon so the total area of coverage
on the table is increased.

So to answer your question - if one of the lobes gets lost, then some other
lobe will gain. If the lobe lost was not being used, I would hazard to guess
the ones that are being used would benefit (gain).
....and they lived happily ever after

Multi lobes
 

"art" wrote in message
ups.com...
I haven't been on the air for a long time but I don't remember any
conversations
as to the upper lobe being used for communication. I always assumed
that
I was using the main lobe. Today I was messing around with some
antenna designs
and I arrived at one where there was only the lower single lobe to the
front
with the upper lobe somehow being removed.
I have no idea what the ommission of any upper lobe would have of any
consequence.
Anybody had experience with this sort of thing?
I suppose that in the early stages of propagation the lower lobe
could make
a connection where as the upper lobe transmission may well be absorbed
by the upper layers that had not yet obtained reflected powers, but
that is
just conjector on my part.
Art


The upper lobes may participate in local (non-skip) comms. The mode is
near-vertical incidence skywave, NVIS.

See http://www.tactical-link.com/field_deployed_nvis.htm, among others.

We have a local 10m net every week and some of the stations experience a
slow fade or flutter which we have taken to be returns of NVIS that are
arriving with a slight doppler shift off a layer whose height is changing.
I won't swear to this; I am also engaging in conjecture. However, when the
10m DX is in, the distant stations don't ever have this flutter. I use a
horizontal antenna and the station that has the most variation most often is
also horizontal. (The clues keep piling up.)

BTW, the articles about NVIS seem NOT to address freqs as high as the 10m
band. Make of this what you will.

73,
"Sal"