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.
Model BA-1-1000 is a 1:1 balun kit used to translate a 50 ohm
unbalanced input to 50 ohms unbalanced at power levels up to 1000 watts
PEP/100 watts continuous when used with a matched load. With a matched
load the SWR will not exceed 1.5 over the frequency range 1.8 to 61 MHz.
1,000 PEP watt rating on a 25% duty cycle. Will sustain about 100 watts RTTY or FT8 at 6 meters. (for higher power use the BA-1-1500 with 6-8 turns for higher frequencies).
Common mode impedance peaks
around 3,500 ohms at 10Mmhz.
With a matched 50 ohm load the SWR over the frequency range 1.8 to 61
MHz is shown in the following table measured with an AIM 4170 network
analyzer. Notice that the conversion from 50 to 50 ohms is very
consistent from 1.8-61 MHz and SWR is less than 1.3:1 over the range
allowing easy tuning by most radio internal antenna tuners or an
external tuner.
Ba-1-1000 1:1 Balun/Unun 1KW PEP 1-61 Mhz
The kit consists of a F140 ferrite toroidal core, enamel insulated
wire, a SO-239 connector with stainless steel hardware, and an
illustrated instruction manual with directions to connect the kit as a 1
to 1 balun/unun (unbalanced coax to unbalanced antenna or balanced
antenna like a dipole). Balun assembly time takes about an hour and is a
fun learning process.
Add a SO-239 Kit on output side to create a 1:1 unun (coax to coax line isolator) or add studs for a balun for use with dipole or beam antenna.
Use the recommwnded CB-Box-1 for a convenient enclosure.
Likewise Termination Resistor values vary from 500-1250 ohms and we have a good selection shown HERE: