Broad Band Terminated Dipoles (BBTD, T2FD)

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?

BBTD at AK6R 1024x726 - Broad Band Terminated Dipoles (BBTD, T2FD)

 

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.

2302699123 - Broad Band Terminated Dipoles (BBTD, T2FD)
+3

Snap On RF Choke - 1/2"/12.7mm cable -5/10/15 Bead Option, 100 KHz - 5 MHz, Excellent in AM Broadcast Band

SNO75-1/2-5
$64.75
In stock
1
Product Details
Brand: Palomar Engineers
MPN: SNO75-1/2-5, -10, -15
Country/Region of Manufacture: United States
Effective Frequency Range (MHz): 100 KHz - 30 Mhz
PEP Power Rating (watts): same as coax cable rating
Common Mode Attenuation (db): see graph
Estimated Insertion Loss (db): .025

Use for 1/2″ Cable – RG8, RG213, LMR-400, AC/DC and signal cable for suppression of common mode current (RFI) from 100 KHz to 30 MHz

Typical common mode suppression up to 22 dB depending upon the number of beads and frequency. Quite often 20 dB is considered the minimum effective reduction.

A minimum impedance of 500 ohms is needed for 50 ohm cable or 10 times the cable impedance for other cables to make a measurable difference in common mode current suppression.

The beads clamp to the cable and may be operated as is for indoor use. However, it is strongly suggested that they be covered to protect the plastic covers from weathering – use electrical tape for best results or heat shrink to ensure longer life. All kits come with instruction manual which covers assembly and application tips.

As you can see from the impedance vs frequency graph, you can very effectively increase the choking impedance by increasing the number of beads on the cable.

Snap On and Slip on Feed line chokes available in sizes to fix cables with outside diameters of 1/4", 3/8", 1/2", 3/4", 1" - check website for other size options.

Tech note: For RFI frequencies over 3.75 MHz, choose SNO31-1/2-5, 10 or 15 for improved common mode rejection (see graph for comparison)

Note: Ferrite beads may be hexagonal or square shape depending on inventory on hand at time of order.
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Likewise Termination Resistor values vary from 500-1250 ohms and we have a good selection shown HERE: