Model DX-OCF Off-Center-Fed 7 Band Antenna
75/80, 40, 20, 17, 12, & 10 meters, NO TUNER REQUIRED!
DX-OCF Installation Instructions
One leg is 45 ft., the other is 90 ft. (135 ft. Overall) and the antenna is fed between the two legs to an SO-239 connector on an integral 6:1 balun with 50 ohm coax. It installs like an inverted-V or straight dipole. Completely assembled and ready to go. No counterpoise or ground lead is required.
Our test conditions are: center feed point 30 ft. high, ends at least 8 ft. high, installed in an inverted-V configuration in "the clear". Antenna wires 180 degrees from each other (like a dipole, top view) and included angle 120 degrees, side view as an inverted-V. It can be installed higher for even better DX performance. The feed point must be at least 12 inches offset from a metal mast or support (not required for fiberglass masts) to minimize coupling. Antenna must be in the clear of surrounding objects and other antennas, roof tops, gutters, wall fascia, tree limbs or guy wires. The antenna should be at least 15 ft. from any of these objects. Keeping the antenna in the clear is extremely important for minimum SWR and best performance! Attic installations not recommended due to attic wiring and HVAC ducting.
If your installation site is not "in the clear" of surrounding objects, or if you cannot attain the proper height (30 ft. or more), the built-in tuner in your transceiver may be able to tune the system to an acceptable SWR. In more severe cases, it may be necessary to use an external wide range antenna tuner. However, when the antenna is installed as per the installation conditions outlined above, you will find low SWR across all 6 bands, and the low end of 6 meters, and a tuner is not required.
Attach a good quality 50 ohm coaxial cable (e.g. RG8X or RG213) to the SO-239 connector sealed in the precision designed 6:1 balun (auto-transformer) at the feedpoint of the antenna. Run the feed line at 90 degrees away from the antenna wires.
The Model DX-OCF is completely assembled and no adjustments should be necessary if installed as outlined above. The antenna (Model DX-OCF) is rated at 300 watts CW/SSB within the designated bands. It is ideal for the new higher powered transceivers. The Model DX-OCF-HP is rated at 3 kW CW/SSB within the designated bands. See details below.
These instructions are simple because there is no assembly, wire stripping, soldering or trimming required. Also, it does not use coils which could complicate installation. It is completely assembled and "good to go".
Instructions to modify the Model DX-OCF/OCF-HP to a limited space antenna only approx 67 ft. long overall (the size of a single band 40 meter dipole), covering 40, 20, 10 and the low end of 6 meters.
A. The OCF antennas, as delivered, have two legs, one 45 ft. long, the other 90 ft. long. A 68 ft. Section of the 90 ft. leg will be removed, making an antenna which now has two legs, one still 45 ft. long, the other leg approx 22 ft. long (90 minus 68= 22).
B. About 22 ft. Down the 90 ft. leg from the feed point you will find an insulator with a removable cable clamp on one side of the wire and a jumper across the insulator with a quick disconnect connector in the center of the jumper, covered by heat shrink.
C. On one side of this connector you will find a "cut mark" (yellow band around the side to be cut). Using a very sharp knife, like an X-ACTO knife, cut circularly all the way around the yellow band "cut mark" so the heat shrink is cut all the way through in a complete circle. Do not try to cut the heat shrink along the length of the wire across the connector, as this will not work to remove the heat shrink due to its thermosetting properties. Cut the circle wide enough so the two sides of the connector can be pulled apart. The connector is a spade and receptacle device.
D. Once you have separated the connector, the next operation will be to loosen the two screws on the removable cable clamp near the insulator and connector, and remove this clamp from the wires. Keep the clamp for future use.
E. Pull the wire (68 ft. length) and connector through the enlarged hole on the insulator and store for future use. The insulator is now the "new" insulator where the support rope will be attached. The approx 6 inch "pigtail" with the other end of the connector on it should be laid back on the "antenna" wire and taped with black outdoor rated electrical tape.
F. You now have an OCF antenna with one leg approx 45 ft., and the other leg approx 22 ft. This configuration will cover 40, 20, 10 and the low end of 6 meters with the same broad band characteristics as the longer version. No further tuning or adjustments should be necessary.
G. If you wish to put the removed leg back on, reverse the procedure as outlined above. Where the two connector ends are reinserted, just cover the "split" in the heat shrink with outdoor rated black electrical tape.
Unique Features of the Model DX-OCF Multiband Antenna
Unlike many antenna designs, the Model DX-OCF covers the ENTIRE 80/75 meter band with low SWRs. Its broad band design makes moving from band edge to band edge quick and easy. It also offers excellent DX performance across the ENTIRE 40, 20, 17, 12 and 10 meter bands, and the low end of 6 meters with low SWRs. No More Fiddling with Tuners. The unique broadband OFF-CENTER-FED (OCF) design makes this possible.
No external hardware to loosen or corrode. No external splices, connectors or soldering in the antenna wire. It survives severe weather environments with ease.
The custom designed integral 6:1 balun is permanently potted in a special epoxy potting compound for moisture and corrosion free operation. It is internally crimped and hard soldered to a Teflon barrel high quality SO-239 coax connector. An integral PVC moisture drip ring around the connector shields and protects the coax connection. A heavy duty ¼ inch stainless lock nut eyebolt supports the center insulator/balun for your support rope. There is no other design like it.
The antenna is unique not only because of the extremely high quality engineering, design and construction, but also because the antenna wire is something you've probably never seen before and provides AMAZING severe weather performance. It is a flexible, 65 strand 12 Ga. PVC coated wire, with EVERY strand tinned to prevent corrosion. You can put this antenna up and forget it! It is actually inexpensive compared to having to replace other antennas after several winter storms.
The antenna is custom designed for Alpha Delta by Buckmaster Antennas, and versions of it have been providing excellent DX performance for many, years. This antenna is the culmination of all the best design features of an OCF antenna.
To look at the DX-OCF SWR chart thru 6 meters, Click Here.