Topband: 160/80 Sloping Inverted L

[Guy Olinger, K2AV]

Pat wrote: =============

I am contemplating the construction of a dual band sloping inverted L
for 160 and 80 meters ... I have modeled it in MMANA and am looking for 
advice...

You can see what the design ... here:
http://www.n0hr.com/Dual_band_Inv_L.htm

==============

>From the web page I can see that your model did not include the tower.  The 
tower is in play, and even though you may be feeding the "L" it is possible 
under some circumstances for the tower to carry the highest current. You need 
to add the tower to the model, including the boom and longest elements of the 
top yagi.

A one foot diameter wire can approximate the tower, and then convert to 1 inch 
conductors for the mast, boom and yagi.  If you do not have a radial system at 
the base of the tower, then add a series resistive load of  15 ohms to the 
lowest segment/node to approximate loss in the RF connection from the tower to 
dirt at the base.

Some modeling programs do not deal well or in a straightforward way with 
current-carrying connections to ground, or require certain techniques for 
approximation.  Use whatever convention the program documents for a vertical 
antenna with buried radials.

An extended discussion on these issues is on-topic on the antennaware 
reflector.

73, Guy.