I have been in Jakarta and also a number of places in China trying to
operate
from a city environment, you cannot believe the noise, S9 if your
lucky, and its
360 degs, impossible to null,
Operating from BY1QH building top, the best was a dipole stretched
between two buildings roofs.
At times the noise would go below S9, was there two weeks trying to
pull 160
signals out.
If you have never been there and heard that, its hard to grasp. Putting
out a
signal was never a problem, hearing any one was.
We complain about plasma TV noise and other noise from Chinese made
appliances
just think of trying to operate in the center of 5 or 10 million of
these devices all around
you, and an the same care taken for the infrastructure of electric lines
etc, coated
with coal and smog dust and pollution, arcing at every juncture.
I bet the space station can hear the "buzz" on their electronics as they
pass over
these areas.
73 Merv K9FD/KH6
If the noise level is too high, perhaps you could use a separate receive
antenna.
A pennant, flag, or coaxial loop, might help null noise from certain
directions.
Art NK8X
ᐧ
On Sat, Aug 8, 2015 at 6:18 AM, Nuradi <yb0unc@gmail.com> wrote:
Thankyou verymuch to Grant KZ1W, Greg ZL3IX, Mike W0BTU, Garry NI6T and Jim
K9YC for all the suggestion.
As suggest by Grant KZ1W and Jim K9YC, I will install a half-lambda dipole
on 160M with both ends were 90 degrees bent due to the size of the building
,and find out what will be the Tx / Rx performance...
To Mike W0BTU, it is slightly difficult to install the radial for the
vertical antenna or inverted L as
the roof top is not empty flat, hi hi
Regards,
Nuradi, YB0UNC / KU2B
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Jim
Brown
Sent: Saturday, August 08, 2015 11:23 AM
To: topband@contesting.com
Subject: Re: Topband: [Bulk] Best wire antenna for roof top location
And remember -- the roof of this building is 110m, so a horizontal
antenna is high enough to have pretty good low angle radiation! See
http://k9yc.com/VertOrHorizontal-Slides.pdf and double the heights for
the graphs of 80M performance. When you're thinking height, consider
the building a tower -- it's mostly the far field reflection that
determines the vertical pattern.
As to "ground" for a vertical antenna -- let's not confuse the word
"ground" with counterpoise or "radial system." An end-fed current-fed
vertical needs a counterpoise or radials, NOT a connection to earth.
I strongly concur with the advice to spend some serious time LISTENING
on that roof before doing anything else. It's pretty common for the
stuff described on that roof to be MONDO NOISY, and it's unlikely that
you can do much about most of it unless the guys who maintain it are HF
hams.
73, Jim K9YC
On Fri,8/7/2015 8:02 PM, Garry Shapiro wrote:
And Bob Brown used a monograph by J.A. Ratcliffe--"The Magneto-Ionic
Theory and its Application to the Ionosphere" which says the same
thing. It has to do with the angle between the E vector and the
Earth's Geomagnetic Field, which is horizontal at the geomagnetic
equator. Bob borrowed my copy of the book when he was writing the Big
Gun's Guide.
Garry, NI6T
On 8/7/2015 6:24 PM, Greg - ZL3IX wrote:
Careful Mike! Jakarta is close to the equator, and power coupling is
likely to be better from a horizontally polarised antenna, especially
in an E-W direction. Ref The Big Gun's Guide to Low-Band Propagation
by Bob Brown, NM7M (SK)
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