Topband: Shunt feed vs sloper

[2]

>My apologies for revisiting this thread, which was discussed briefly last
>month.
>
>I am tempted to try a sloper as the first Topband antenna from my new QTH
>here in ZL, as it will be quicker to get going than a shunt feed to my mast,
>but there were a couple of negative comments last month.  

//  As well there should have been.  The intrinsic problem with a 1/4 
wave sloper antenna is that two currents of opposite polarity are 
traveling pretty much in the same direction -- i.e., toward the ground.  
Thus, some H-field cancellation is unavoidable,  

>These were mainly
>to the effect that they (slopers) act more like low dipoles.  

//  Indeed.  The E-field produced is much like that of a low inverted V 
dipole - i.e., close to the ground.  .  

>Can anyone elaborate on this?  My first intuition is that a sloper should 
behave
>in very similar fashion to an inverted L with the feed at the top of the
>vertical section.
>
>My antenna simulation software predicts very little difference in
>performance between a sloper and a shunt fed vertical.  Has anyone compared
>them on the air?
>
//  I listened to a tape recording made by SM4CAN of Western United 
States 80m signals received via longpath into N. Europe.  None of the 
clearly audible signals came from 1/4 wave slopers.  Two of the most 
audible signals came from directional verticals.  

//   My free, unsolicited, advice is to try a Hertz, either full-size or 
shortened, supported at mid-point by your tower and a halyard.  Typical 
feed-Z is 1000 to 5000 ohms, so an L-network is needed at the surface fed 
end of the antenna.  To maximize the E-field, the far end should be as 
high off the ground as possible.   To prevent H-field cancellation, the 
enclosed angle of the wire at the top of the tower needs to be >90º.   On 
average, my 160m Hertz beat my 70-foot vertical by about one S-unit.  

cheers, Greg, ZL3IX

-  R. L. Measures, 805.386.3734, AG6K, www.vcnet.com/measures.  
end