Topband: [Bulk] Best wire antenna for roof top location

Jim Brown jim at audiosystemsgroup.com
Sat Aug 8 00:22:31 EDT 2015


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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