On Mon, 16 Apr 2012 10:15:29 +0200, "Szczepan Bialek"
wrote:
I am not arguing.
Very well. You are debating.
I agree with you that " they need a ground is to act as
the counterpoise for the monopole."
Not true. At higher frequencies, one can use the grounded coax cable
feed to act as a crude counterpoise.
I hope that you agree with me that monopole on the plane/satellite has the
counterpoise in form of chassis.
No. You claim that because the monopole requires a ground, therefore
all antennas require a ground. That's too general a claim and is not
true, even for a monopole. For example, a very common antenna type at
2.4GHz is a "meandering 1/4 wave" antenna, which uses no ground:
http://802.11junk.com/jeffl/antennas/laptops/slides/compaq-2120us.html
Another example is the metal rim of the iPhone 4G. It's an untuned,
ungrounded, end-fed, monopole in the form of parts of a metal frame.
There's also a large distinction between a "ground" and a
counterpoise. A counterpoise is a part of the antenna system and may
be earth ground in some situations. In RF, a ground is a connection
to the earth. While there is some overlap in these definitions, your
claim, that all antennas require a ground, was presumably referring to
the earth ground, as described by your examples of broadcast towers
and static buildups.
For a satellite, there's may be a counterpoise, but no (earth) ground.
The counterpoise is unlikely because most satellites use circular
polarization (to eliminate sensitivity to orientation), using spiral
wound or pyramid shaped antenna structures that are matched to
whatever the coax cable provides. The skin of the satellite is
crammed with other antennas, solar cells, and sensors, that finding an
area sufficiently large to be considered a metal counterpoise, is
impossible.
The only thing really necessary for an antenna to function is the
radiating element. Everything else is optional and depends on what
you're trying to accomplish.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558