[TowerTalk] Coil across feed point of dipole

[Stan Stockton]

I am leaving this weekend for ZF and don't have a lot of time for experimentation.  Just starting to focus on radio after 6 months of golf.  Retirement is fun!  

I want to put a 40m dipole above a Tribander which I already know from experience will beat my salt water vertical by several S units in directions over land.  I am aware of interactions between the dipole and the Tribander.  The dipole will likely consist of about 24 feet of tubing that will be parallel to the ground with another ~23 feet of wire on each end that will slope to the least extent possible.  Figured I would have a collar on the mast and attach the dipole boom-mast plate to a larger size of tubing above the collar so the Yagi can turn without moving the dipole.

I want it to add to top loading so I can shunt feed the tower for 160m.  In order to electrically connect both sides of the dipole to the mast above the Tribander I propose to connect a coil across the feed point and connect the shield of the coax to the mast.  Unlike the hairpins I use on the near salt water verticals to raise the R from very low to 50 ohms, I don't want this coil to have any affect on R at all.

I need to know some approximate dimensions of what that coil should be and also whether there are other concerns I may have not considered.

Thanks... Stan, ZF9CW