The half-10 Meter and 6 Meter Rotatable Half-Wave Dipole Antenna
The half-wave center-fed dipole is one of the most popular antennas in use today. In free space the center-fed half-wave antenna has an input impedance that is a close match to 50 ohm coax and to most radios that have a 50 ohm output impedance. (The actual impedance depends on the height of the antenna above ground and many other factors.)
The Frequency Devices 10N6RDB take the half-wave dipole a step further by working on two bands with one feed line: The 10 Meter and 6 Meter ham Bands.
In the pictures the bottom horizontal Aluminum tubing is a half-wave dipole tuned to 10 Meters that is all set to be fed with your 50 ohm coax. Inside the box is a 50 ohm 1:1 Balun. One of the problems with feeding and half-wave center-fed dipole directly with coax without a Balun is that the dipole is a balanced device while coax is unbalanced. A Balun should be used to convert the unbalanced coax to a balanced output to connect to the antenna1. Not using a Balun can affect the directional pattern of the antenna and can also result in having RF in your shack. This antenna has a 1:1 Current Balun based on the W2FMI design inside the center isolator and the antennas should be good for the legal limit in power provided the SWR is not over 2:1. (Note that the vertical pipe shown in the picture is not supplied.)
The upper horizontal Aluminum tubing that is shown in the pictures is a half-wave dipole that is tuned to 6 Meters. It uses parasitic coupling between the 10 Meter dipole and the 6 Meter dipole to allow the antenna to work on 6 Meters. This antenna is built using stainless steel hardware, all nuts are self-locking, and all holes are sealed with RTV sealant.
The half-wave antenna has maximum gain off of both sides of the antenna (see the figure). Off of the ends of the antenna the gain is the lowest. Usually the antenna is mounted using a rotator so that you can rotate the antenna for maximum gain. However, a rotator is not necessary as you can install it on a pole fixed in one direction the direction you expect to work the most. This does not mean that the antenna will not work at all off the ends but the gain will be less.
The figure shows the ideal free space radiation pattern of the half-wave dipole. This pattern will vary depending on how high you install the antenna, what kind of ground is located below the antenna, what buildings and structures are close to the antenna, etc. Please note that this antenna is bi-directional. It will work equally well in both directions.
The antenna is shipped almost completely assembled. All you need to do is install the 1/2 inch Aluminum tubing at both ends of the 10 Meter and 6 Meter antennas, adjust them to the proper length and tighten the hose clamps that hold them in place. The antenna is then ready to install on your vertical pipe and Rotator.
Antenna Power Rating: 1500 Watts P-E-P
Impedance: 50 ohms
Gain: 2.15 dBi
Front to Back Ratio: 0 dB
Weight: less than 6 pounds
Turing Radius: 8 foot 2 inches
Maximum Mast Size: 1.5 inches
Wind Surface Area: 1.4 square feet
Maximum Wind Speed: 100 MPH
10 Meters: <3:1 28 MHz - 29.7 MHz
6 Meters: <3:1 over any 2 MHz portion of the band
(dimensions for 50-52 MHz provided by the factory)
Price $199.95 (includes free shipping anywhere in the continental United States)
1. The ARRL Antenna Book is a good reference on Baluns.
Bill Franklin, K9EIF
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||10 And 6 Meter Rotatable Antenna with Balun R
1. Rudy Severns, N6LF, “Conductors for HF Antennas,” QEX Magazine, November/December 2000, pp 20-29, see Table 6.
2. The ARRL Antenna Book is a good reference on Baluns and if you need them or not. Most any edition will work.