Broad Band Terminated Dipoles (BBTD), Tilted Terminated Fold Dipoles (T2FD) and Balanced Termination Folded Dipole BTFD) antennas can be designed to cover a large range of frequencies between 1.8 30 MHz. Longer length antennas generally provide better low frequency efficiency but take up a larger footprint of land. One BBTD that has worked well at the AK6R antenna farm is shown below. Many other designs are available and can be found at www.HFLINK.COM as well as other internet sites. Your mileage may vary using this antenna, but as a general coverage antenna for ham and shortwave broadcast, the simplicity can’t be beat even though an individual dipole on a specific band may out perform this broad band dipole. Palomar Engineers has all the parts you need to build this antenna, so why not give it a try?
Depending on the source of the antenna design, different value baluns are specified. Our Bullet(TM) baluns in ratios of 9:1, 12:1 and 16:1 are excellent for this type of antenna as they are broadband from 1.8-61 MHz and will take up to 500 watts PEP.
After many requests we have created a compact, special balun for single band loop (Sky loop or Delta loop) antennas with specific dimension that present a feedpoint of 70-75 ohms. The CB-1.5-1-1500/5000 is a CUBE(TM) enclosure containing a multi-core, broadband 1.5:1 impedance transformer (50 ohm coax input to 75 ohm balanced output) in series with a 1:1 current balun for extra common mode current choking to keep RF current off the outside of the coax braid and on the antenna where it belongs. The extra choking action also means that the coax feed line will not act as a radiator causing unnecessary RF interference (RFI). Rated for full 1500 watts PEP and 1500 watts CW (ICAS), 1KW Digital. 1.8Mhz – 61 MHz.
CB-1.5-1-1500EB is housed in a 4” x 4” x 2” waterproof housing with SO-239 input and stainless steel eye bolts on the side for ease of connection to your wire antenna (or top studs as desired). Top eye bolt acts as an antenna hoist. Also available with top studs for post or wall mounting (Model # CB-1.5-1-1500/5000TS). 5KW models are in a 4 " x 4" x 4" housing.
Loop antennas should be cut for 1005/F(MHz) in total length, where F (MHz) is the lowest frequency to be used. For 3.5MHz this equates to 288 foot perimeter (square, delta, multi-side ok). Vertiucal loops with pointy side up and longer bases and fed 1/4 wavelength down one side have a feedpoint impedance near 75 ohms for which this balun is well suited. A very good DX antenna!
For unbalanced 50 ohm input to unbalanced 75 ohm output use the CU-1.5-1500 or CU-1.5-5000.
Display Note: Product picture is 2:1 balun, 1:1 Unun but actual delivered product is CB/CU-1.5-1-1500/5000 as selected.
Likewise Termination Resistor values vary from 500-1250 ohms and we have a good selection shown HERE: