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S9v 31' M K II Installation Guide
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Configurations
When used with a proper RF ground, the S9v is a serious 40 meter DX antenna.
The natural resonant frequency of the S9v is just above the top of the 40 meter
band - around 7.4 MHz - and the 2:1 SWR curve is broad. Depending on the
efficiency of your RF ground system and proximity to nearby objects, the S9v
may exhibit an SWR well below 2:1 in the upper, SSB portion of the 40 meter
band without an antenna tuner.
So, if you operate a lot of SSB on 40, you may be able to use the S9v on 40
meters without using an antenna tuner. In this configuration, the coax feed line
can be directly connected to the S9v. Radials and a 1:1 current choke balun are
strongly recommended. As a 40 meter monoband antenna, the S9v can be
mounted on the ground or as an elevated ground plane antenna on a pole.
If you want to use the S9v as a 40 meter monoband vertical in the lower, CW
portion of the band and do not own (or want to use) an antenna tuner, consider
our optional 40 meter monoband conversion kit – please see our web site for
details. The monoband conversion kit is also useful to tune the S9v to a specific
40 meter frequency when you want to phase two S9v antennas together on 40
meters for 3 to 4 dB of directional gain over a dipole.
Antenna Tuner
Internal rig tuners will easily tune the S9v anywhere on 40 meters. But if you
want to use the S9v as a multi-band antenna, you will need a more robust
antenna tuner. (Internal rig tuners typically do not have adequate range to match
the higher impedances presented by the antenna on bands above 40 meters.)
For multi-band use, we recommend the LDG Electronics series of auto tuners for
use with the S9v. LDG tuners easily handle the wide-range of impedances
presented by the S9v over the higher HF frequencies and also cover 6 meters.
Using a weatherproofed, remote antenna tuner at the antenna feed point ensures
absolute lowest signal loss and best overall multi-band performance. 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 your transmitter and the antenna
(outside of the radial field) if you experience RF current in your shack. (Burying
your coax cable also helps minimize RF current from flowing back into your
shack.)
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