[TowerTalk] Matching 3 band Vertical

[Robert Seymour]

I am planning improvements to my 160/80/40 TX vertical to improve efficiency and bandwidth.  Today it is mounted on a 4.5 ft post in a salt marsh and has a 44 ft long radiator.  I remotely switch bands by shorting out parts of the base coil.  I want to increase height to 60 ft and top load it.  I can not get beyond 60 ft. and properly guy everything.

My main question is the following:  As antenna height is increased to improve efficiency and bandwidth, I get into the situation where feedpoint impedence on 40M becomes very high.  As I pass over 1/2 wavelength, but stay under 5/8 wavelength, the impedence decreases somewhat, so that on 40M EZNEC predicts  1245 - j370. Most of what I read suggests feeding such an antenna with a tapped parallel tuned circuit, but when I calculate a standard L/C L network, the components seem practical -  80 pf shunt across the antenna and 5.8 micro-h in series with the feedline.  According to EZNEC the bandwidth should be OK.  

1. What determines the choice of a parallel curcuit over an L-network.  Is there any reason NOT to go the L network route?  Maybe the losses the deciding factor.

2. What can you suggest about the form factor and wire (copper tubing maybe) size for the L-network coils for all three bands - especially 160M where I need 25 micro-h in the series element.  I want to handle 1500W max.

Thanks for any input - Bob  AF4OX