S9v 31’ M K II Installation Guide
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4
Balun/Unun
For 40 meter monoband use
, a 1:1 current choke balun is recommended. It
should be located outside of the radial field (between your transmitter and the
antenna) 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 on-line 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 18 to 21 feet
of your coax feed line 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
, 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).
