"Roy Lewallen" wrote in message
...
Imagine that you have a highly directional transmitting antenna and you
spin it at, say, 100 revolutions per second. What would a listener at a
fixed location hear? He would hear a 100 Hz (but non-sinusoidal) amplitude
modulated signal rather than a constant amplitude CW tone. The shape of
the modulation envelope would be dictated by the shape of the antenna
pattern. The spectral content, i.e., sidebands, of the received signal
would be the same as if the wave had been amplitude modulated by
conventional means to produce the same waveshape.

I think that's what they mean.

Roy Lewallen, W7EL

Jimmie D wrote:
I was going through some FAA course material on Instument Landing Systems
and the term SPACE MODULATION was mentioned several times. What the heck
is this. From what I gather signals modulate each other out in space
without benifit of any nonlinear device. I personally beleave this cannot
happen but here is a reference to an FAA document.I assume they know what
they are talking about.

Abstract : The report describes an investigation into the cause of
incompatibility between ground and airborne measurements of VOR space
modulation when using the latest flight inspection receiver, FA-4165:3A.
The effort included a survey of the existing procedures and equipment
used throughout the FAA, an evaluation of the ground measurement
technique, and an evaluation of the airborne measurement technique. The
result of the investigation identified problem areas with both the ground
and airborne techniques.

I suspect that space modulation is more of a concept used to more easily
understand/teach the operation of ILS systems and that actual modulation
takes place in the receiver.

Jimmie
Roy I can kind of see this in a VOR with its rotating antenna but in ILS
systems(glideslopes and localizers) there is no moving antenna. They talk
about AM sidebands being formed due to space modulation.

On Sun, 17 Dec 2006 05:13:10 -0500, "Jimmie D"
wrote:

Roy I can kind of see this in a VOR with its rotating antenna but in ILS
systems(glideslopes and localizers) there is no moving antenna. They talk
about AM sidebands being formed due to space modulation.

Hi Jimmie,

I worked on this gear, and more, 30 years ago. Any discussion of
space was physical space. I was involved only with the
instrumentation, but the system specification is characterized in
terms of "signal-in-space." As such, the modulations vary by the
aircraft's position in airspace. This can be in terms of distance,
bearing, slope, or path. In some regions of space, the modulations
change from dash to dash-dot to dots. Shared with these are phase
relationships in both modulation and beam coverage. Testing of these
system parameters is tightly controlled so as to not create
hazardously misleading information to general aviation.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Sun, 17 Dec 2006 05:13:10 -0500, "Jimmie D"
wrote:

Roy I can kind of see this in a VOR with its rotating antenna but in ILS
systems(glideslopes and localizers) there is no moving antenna. They talk
about AM sidebands being formed due to space modulation.

Hi Jimmie,

I worked on this gear, and more, 30 years ago. Any discussion of
space was physical space. I was involved only with the
instrumentation, but the system specification is characterized in
terms of "signal-in-space." As such, the modulations vary by the
aircraft's position in airspace. This can be in terms of distance,
bearing, slope, or path. In some regions of space, the modulations
change from dash to dash-dot to dots. Shared with these are phase
relationships in both modulation and beam coverage. Testing of these
system parameters is tightly controlled so as to not create
hazardously misleading information to general aviation.

OM,

I'd appreciate any pointers you have to the FAA reference material that
defines "Space Modulation". Google shows only links to lists of training
courses that the FAA conducts, and references to "Pulse space
modulation", which I assume is a different thing.

TIA.

73,

William

(No cc: of ng posts needed, thanks)

--
A little learning is a dang'rous thing;
Drink deep, or taste not the Pierian spring;
There shallow draughts intoxicate the brain,
And drinking largely sobers us again.
-- Alexander Pope, Essay on Criticism

nonoise wrote:
Richard Clark wrote:

On Sun, 17 Dec 2006 05:13:10 -0500, "Jimmie D"
wrote:

Roy I can kind of see this in a VOR with its rotating antenna but in
ILS systems(glideslopes and localizers) there is no moving antenna.
They talk about AM sidebands being formed due to space modulation.


Hi Jimmie,

I worked on this gear, and more, 30 years ago. Any discussion of
space was physical space. I was involved only with the
instrumentation, but the system specification is characterized in
terms of "signal-in-space." As such, the modulations vary by the
aircraft's position in airspace. This can be in terms of distance,
bearing, slope, or path. In some regions of space, the modulations
change from dash to dash-dot to dots. Shared with these are phase
relationships in both modulation and beam coverage. Testing of these
system parameters is tightly controlled so as to not create
hazardously misleading information to general aviation.


OM,

I'd appreciate any pointers you have to the FAA reference material that
defines "Space Modulation". Google shows only links to lists of training
courses that the FAA conducts, and references to "Pulse space
modulation", which I assume is a different thing.

TIA.

73,

William

(No cc: of ng posts needed, thanks)

Do a GOOGLE search on "Space Modulation" You will find the occasional
pearl among the trash. There is an article about VOR's and Space
Modulation.
What follows is exactly what I understood about the contents: THE, AND, etc.
In other words nothing. HI HI...

Dave N

On Sun, 17 Dec 2006 13:59:08 -0500, nonoise
""william_warren_nonoise\"@speakeasy.(nonoise)net " wrote:

FAA reference material that
defines "Space Modulation"

Hi William,

There is no definition because it isn't part of the argot. The point
of my posting is that the Space of Space Modulation is physical space,
an area or volume in the flight path where all signals are targeted.
This is not about mixing, non-linear or otherwise. It is also not
about modulation waveforms except in how they are intercepted and
recognized by existing equipment (and thus giving rise to HMI,
hazardously misleading information).

It is not that there is anything "in" space that is doing any
modulation. There is nothing inherent "about" space that affects
modulation. Space itself does not modulate. There is no modulation
that requires space to complete it (except in the classic sense of
propagation).

There is VOR space.
There is ILS space.
There is TACAN space.
and on and on and on. Each is overlapping modulation in ostensibly
the same space. Thus we have VOR space Modulation....

73's
Richard Clark, KB7QHC