[TowerTalk] Coil across feed point of dipole

[K9MA]

See the N9NB article in QST a little while ago on chokes to shunt 
isolated elements to the mast for shunt feed. It works fine on two of my 
antennas. I can provide details on the choke design.

73,
Scott K9MA


On 10/16/2019 07:42, Stan Stockton wrote:
> 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
>
>
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-- 
Scott  K9MA

k9ma at sdellington.us