Topband: Shunt fed T

[Herb Schoenbohm]

John, G4EIM wrote:


Am I on the right lines, what if I use 4 wires the reason been its better for guying and I thought the 4 shorter ones mean less cancellation of the vertical radiator!! Obviously I can use 2 rope for the missing guys but I thought 4 wires may be better

I have not seen any info on using more than 2 wires at least not unless we look at a horizontal capacity hat constucted with rods and wires.




John,

Your on the right track!

If you go to a four wire top hat, lets say 25 feet each, don't worry 
about the exact base impedance.  If the top hat is a four wire sloping 
affair shorter top hat  wires will mean less cancellation and that is 
good especially if your guy angle is acute.  Pulling the current node up 
the pole, so to speak is beneficial and the base match you can take care 
of with a simple L network.  Some AM radio installations run a perimeter 
wire abound around connecting the ends of the 4 wires which is supposed 
to gain another 8 to 10 per cent top loading.  I would think it would 
help but have not modeled this nor have the capability of doing so.  It 
is a gem that John Mulleny, an superb FCC engineering firm use to 
recommend in the 60's.


73,

Herb Schoenbohm, KV4FZ

j