Topband: T loaded vertical

[Herb Schoenbohm]

Rich,  Try to get the current loop to appear at the connection to the 
flat top T.  This can be done by modeling or in the old days we would 
just tape a small 6 volt bulb on a loop at the T. While running just 
enough power at night to get the bulb to illuminate, keep pruning the 
wire until you get the maximum illumination. When you finally go QRO the 
light will burn out and you won't have the neighbors calling 911 because 
of the flashing light they see in the sky. This will require raising and 
lowering the wire ends at night and  if you have a forest of trees may 
not be a feasible means of tuning your T to maximum performance. Try to 
keep the flat top wires equal in length

 If you have a 60 foot vertical drop a 75 foot to 80 foot each side of 
the T connection should work well as a starting point if you plan to 
tune it in the field. Even a smaller flat top will also work if you are 
prepared to deal with the increased reactance and lower feed point 
resistance at the base.  However it is best to match the feed point with 
a simple L network and put down as many radial as possible.  I have 
found this out to be true, that a well designed T design always beats an 
inverted L for a long angle DX path. I believe this is due to the 
cancellation of much of the horizontal radiation component .

I hope this information will help you.

73

Herb, KV4FZ


Rich, W1TSP wrote:

>     Thinking about erecting in it's place a T loaded vertical and wonder if you have any suggestions on calculating the dimensions of the T if used with a 55 foot or hopefully a 60 foot radiator. 
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>  Finally, any suggestions on a matching? If it comes out at ~20 ohms can I direct feed with the RG213 that is in place and use the tuner in the shack or is it best to construct an L/C circuit at the base?
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