The S9v31 can be mounted on the ground or on your roof. Permanent ground-mount installations require a 40-inch long, 1-1/4 to 1-5/8 inch OD max. galvanized steel pipe. The S9v31 base tube simply slips over the pipe for a simple and elegant deployment. A mechanical connection from the antenna base tube to the pipe is neither required nor desired. Because the S9v31 is so light, you can roof-mount the antenna using a simple 3 foot tripod normally used for TV antennas. In this configuration, the S9v31 functions as a ground plane antenna and four, half wavelength radials are required for each band of operation.
When used with a good RF ground, the S9v31 is a serious 40 meter DX antenna. The natural resonant frequency of the antenna is just above the top of the 40 meter band - around 7.4 MHz and it is extremely broad banded. Depending on your ground system and proximity to nearby objects, the S9v31 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 primarily operate SSB on 40, you may be able to use the S9v on 40 meters without an antenna tuner. In this configuration, the coax feed line can be directly connected to the antenna. Radials and a 1:1 current choke balun are recommended. There are several commercially-available 1:1 choke baluns available (Balun Designs being one of the best) or you can create a simple choke balun using your coax feed line. Internal rig tuners will easily tune the S9v31 anywhere on 40 meters. But if you want to use the S9v31 as a multi-band antenna, you will need a quality antenna tuner in your shack or remotely located at the antenna feed point. Internal rig tuners do not have adequate range to match the higher impedance presented by the antenna on bands above 40 meters.
For multi-band use, a 4:1 Unun is recommended at the antenna feed point for coax runs over 50 feet long. A 4:1 unun lowers the higher impedances presented by the antenna on frequencies above 40 meters. If you are using a quality antenna tuner and have a coax run under 50 feet, a 1:1 current choke balun located outside of the radial field will suffice.
In lieu of an antenna tuner in your shack, you can use a weatherproof remote antenna tuner at the S9v31 feed point for absolute lowest loss and best over-all multi-band performance. When a remote tuner is used at the antenna feed point, a 4:1 unun is not required. However, a 1:1 current choke balun may be needed 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.
For optimum performance, a ground-mounted S9v31 should be used with at least 16 radials (32 preferred), with each radial at least 26 feet, 9 inches long (0.2 wavelength at 7 MHz).
Copyright 2011-2014 Universal Radio, Inc.