Spike wrote:
On 08/03/15 09:33, Jeff wrote:
Spike wrote
I think you are coming at this from the wrong view point.
Perhaps the question that you should be asking is what take-off angles
are required to produce maximum ground wave, and how do you maximize
that for a MF mobile installation.
I'm really after figures for the proportions of the RF power fed to that
antenna, that finish up in whatever 'they' are called (the use of the
well-known word 'waves' seem to upset people despite their having been
used for the specifics I mentioned, for about 100 years).
Yes, there is wide use of the word "waves", but not as you are using it.
To answer your question, all you have to know is the frequency, antenna
pattern, the current state of the ionosphere, ground conductivity,
terrain roughness and the dielectric constant in the area in question.
I'm aware that reconfiguring the set-up might affect these proportions,
but I did refer the original query to a typical /M (mobile) set-up of a
short rod antenna not connected to ground and operating over average
conductivity in the MF/low-HF bands.
Well, to start with, you get little to no surface wave propagation
above about 3 MHz.
For example, does 40% power the sky (redacted), another 40% power the
space (redacted), and the other 20% power the surface (redacted)?
Clearly, 100% of the RF power goes somewhere, and the various parts of
it must add up to 100% - so what are the proportions?
Once again, all you have to know is the frequency, antenna pattern,
the current state of the ionosphere, ground conductivity, terrain
roughness and the dielectric constant in the area in question.
If the /M (mobile) set-up was changed to a /P (portable) one with a 5/8
lambda ground-mounted antenna, the sky (redacted) proportion would lower
and the surface/space (redacted) would increase - but from what to what?
I'm beginning to think that this topic is either so simple or so complex
that most Amateurs have either forgotten it or have never heard of it.
No, you simply do not understand how propagation works.
First read all of this:
http://en.wikipedia.org/wiki/Radio_propagation
Read the section on Modes very carefully.
Follow the links under Modes and read them:
http://en.wikipedia.org/wiki/Surface_wave
http://en.wikipedia.org/wiki/Skywave
http://en.wikipedia.org/wiki/Line-of-sight_propagation
http://en.wikipedia.org/wiki/Sporadic_E_propagation
http://en.wikipedia.org/wiki/Tropospheric_propagation
--
Jim Pennino