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When a remote tuner is used at the S9v feedpoint, a 4:1 unun is not required. A
1:1 current choke balun may be required between the tuner and your transmitter
if you experience RF current in your shack. (Burying your coax cable also helps
minimize RF current from flowing back into your shack.)
Balun/Unun
For 40 meter monoband use, a 1:1 current choke balun should be located as
close as possible to the antenna feed point to isolate RF currents from flowing
back into your shack over the coax shield. There are several commercially-
available 1:1 choke baluns (Balun Designs offers some of the best – see them at
www.balundesigns.com) or you can create a simple choke balun using your coax
feed line.
To create a 1:1 choke balun using your coax feed line, simply wind the last 18 to
21 feet of your coax feed line before the antenna evenly around a 4-inch round
form such as a PVC pipe. You can use zip lock cable ties to secure the windings
and to maintain the coil form. Additional information about constructing an
inexpensive 1:1 choke balun using your coax feedline can be found on-line at:
http://www.hamuniverse.com/balun.html.
For multi-band use and coax runs over 50 feet long, a 4:1 "unun" from Balun
Designs is recommended at the antenna feed point. A 4:1 unun lowers the
higher impedances presented by the S9v on frequencies above 40 meters.
Balun Designs manufactures two 4:1 ununs specifically for the S9v, depending
on the amount of power you expect to run. These ununs may be purchased on-
line at www.balundesigns.com:
• If you are running 300 watts or less, use the Balun Designs "Model 4130sv
for S9 Vertical".
• If you are running more than 300 watts, use the Balun Designs "4:1 Unun
for Verticals" (Model # 4134).
For multi-band use and short coax runs (50 feet or less), a quality antenna
tuner and a 1:1 current choke balun at the antenna feed point will suffice.
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S9v 31' Installation Guide
4
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