Andy
Yes, I am here, and 'loops v verticals' is a very good idea for a project. I
am now formally retired from Academe, but ironically immediately have been
asked back to continue some activities. And so it is less easy to get a
student here for this project, but I will try. However it may have to be
elsewhere, perhaps at some other academic establishment - any offers?! I
will look at it anyway, but at the moment it will not be at the top of the
priority list.
I would like to start collecting evidence since the theory and simulations
in this frequency area are not particularly good for loops or for small
verticals in a real environment. At this stage theoretical proofs and
simulations only have a fifty-fifty chance of answering the question
correctly!
Even what might be regarded as anecdotal evidence on the topic is very
welcome from anyone. The type of environment is an essential part of the
equation and so results in different environments are particularly of
interest. I would prefer information via the reflector but direct to me is
OK if you have my email address from elsewhere.
Regards to all on the list
Mike U - G3LHZ
To: '[email protected]'
Subject: RE: LF: Loops v Verticals
Importance: High
I view of the continuing arguments about this issue, is there anyone who
knows,
or knows someone, with the mathmatical understanding of antenna theory as
well
as the common sense, to come up with a point at which loops will perform
better
than verticals, for given criteria. A useful criterion might be the same
amount of copper (include loading coil) in the antenna system, or a given
amount of ground area. Every parameter has to be taken into account so its
far
from trivial, but must be calculatable.
It would certainly make a suitable task for a PhD thesis (Mike U.. are you
there?)
Any deep analysis was way beyond me, but in the early days of 73kHz when we
had
a proper LF band rather than this high frequency stuff above 100kHz, I did
some some simplistic spreadsheets that did suggest that for VERY LARGE loops
(many tens or 100s of metres in effective diameter) there was an advantage
over
electric antennas of similar size, but for anything that would fit in a
typical
garden E field won every time.
If the loop could be made metres in diameter for example, or of Litz
conductors
to this diameter, then it copuld be made smaller for a given efficiency, but
the total of amount copper actually increased. Then there comes a point
where
the loop is of the same dimensions as the vertical, so what mode is then
radiating (Mike U, are you still there ?) etc etc.
This was borne out by G2AKV in Canterbury who used a huge loop of bog
standard
mains cable, quite low down and draped thorough trees. He was the strongest
signal on the band for a long time (unreceivable because of his chirp, but
that's another story).
Just making uninformed or sarky comments isn't going to solve anything.
Andy G4JNT (still lurking on this reflector, but 100% on microwaves these
days)
-----Original Message-----
From: Alexander S. Yurkov [SMTP:[email protected]]
Sent: 2004/07/21 16:04
To: [email protected]
Subject: Re: LF: Loops v Verticals
On Tue, 20 Jul 2004, hamilton mal wrote:
For those that do not know. Research around Europe has shown that
VERTICALS
are the only antennas suitable for Transmitting on LF. Loops are fine
for Receiving, little or large but the bigger the better. Who has ever
heard of a LF broadcasting station using loops for TX.
73 de G3KEV
Though loop has any advantage if there is very bad enviroment (trees,
buildings e t.c.) Antenna of a broadcasting station always is plased
in clear field. So there is no reason to use loop in this case in my
opinion.
73 de RA9MB/Alex
http://www.qsl.net/ra9mb
| 