I really like the method Jim outlined here -- I've been using it on my
Tee vertical ever since I moved to W6 ten years ago! I use a parallel
combination of small doorknob caps to tune it.
73, Jim K9YC
On Sat,11/20/2010 6:51 PM, Jim Thomson wrote:
## Install a capacitor in series with the feedpoint of the vertical, right
at the base. Make the horizontal wire long enough, so the resistive component
is 50-60 ohms on the freq you are interested in. At that point you will have
some XL. Then tweak the cap so the Xc of the cap will cancel out the XL on
160m. Presto, flat swr on 160m. On 80m, the cap has to be shorted out. No
big deal with a suitable spst relay.
A buddy used a motor driven 2500 pf cap... and a 100' tall vertical, with an
inverted vee type capacity hat on top. This entire mess was suspended on a
catenary line, between 2 x trees. It's flat swr across the entire 200 khz.
Note, on some vac caps, they have a feature on em, whereby when the cap is
fully meshed, and then some, the plates will short out. This saves you
having to install a relay across the cap, in cases where you want it shorted
out.... as in your dual band set up.
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