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:[email protected]] On Behalf Of Jim Brown Sent: Saturday, August 08, 2015 11:23 AM To: [email protected] 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) _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband
