Halfsquare antenna

If you follow G3TXQ's suggestion, you can remove the vertical wire at the driven end and replace it by using the coax shield of the feed - you just relocate the balun down to the quarter wave point where the first vertical wire ended - mechanically much simpler.

Mike
AF7ON

 

I use one mix-77 and one mix-43 in series on the same piece of coax.
For higher frequencies I use one mix-43 and one mix-61 if nessecary.

 

Back in 2010 when I first heard about G3TXQ's (SK) suggestion, I thought a sleeve over the coax would work better than just the coax braid. We could have a quarter-wavelength of aluminum tubing insulated from ground by a short non-conducting support. The coax could be routed up the inside of the tubing and the tubing becomes one of the two required supports.

 

Draw it. The verbal description makes no sense to me.

 

That would make more sense, because a choke at the top would be in a better position. A choke at the bottom would be at a high voltage point on the radiator---where it is expected to serve as an insulator between the 1/4λ of outer braid and the rest of the cable.

 

Mike (ARK), Could you be prompted to share the nec file? I'd like to play with it.

 

As soon as I get dressed, and walk over to the "lab"

 

Remove the .txt after saving it to your disk.

 

Tnx. Dave

 

Using a tubing element as a quarter-wave stub is perhaps a better alternative than just trying to choke the coax at the high-voltage point! Of course, you then have the high voltage at the bottom end of the tube to insulate from the coax shield where it exits the tube. However, properly done, this should eliminate most current on the coax shield and reduce the necessity for choking.

Mike
AF7ON