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@sdellington.us
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