DX Engineering DXE-TCB-FPK Instructions manual

Vertical Feedline Current Choke Kit

DXE-VFCC-H05-A
DXE-VFCC-H10-A

DXE-VFCC-H05-H10A-INS-Rev 6d

DX Engineering 2012

P.O. Box 1491 ∙ Akron, OH 44309-1491 USA

Phone: [phone] ∙ Tech Support and International: [phone]

Fax: [phone] ∙ E-mail: [e-mail]

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Introduction

The DXE-VFCC Vertical Feedline Current Choke kits are designed for use with coaxially fed, 50 Ω vertical
antennas such as the Hustler® BTV series, the DX Engineering family of verticals and many others.

The advantages of using a VFCC:

 Offers a substantially greater amount of isolation and current balance than coiled coaxial cable
 All power goes to the antenna system improving efficiency
 Prevents unwanted RFI by eliminating feedline current and radiation
 Reduces noise or unwanted signals picked up by the feedline
 Overcomes a less than optimal ground system

When quarter-wave vertical antennas are constructed over a good radial system, they have a feedpoint
impedance of about 36 Ω. When they are installed over an inadequate ground radial system there is a loss
introduced at the feed point that adds to the 36 Ω figure. This apparently improves the SWR but there is a
loss in the efficiency of the antenna. Transmitted and received signals suffer attenuation from this
inefficiency. Often, currents introduced on the feedline shield will cause unwanted transmit RFI and received
noise.

With a ground-mounted quarter-wave vertical, regardless of the radial situation, but especially with poor
radial systems, there is the need for a DXE-VFCC-H05-A Vertical Feedline Current Choke (VFCC) to keep
current off the feedline.

The VFCC kit comes in two power levels. The DXE-VFCC-H05-A rated at 2 kW continuous and the DXE-
VFCC-H10-A, rated at 5 kW continuous. Both kits include an insulated mounting plate used to mount the
choke to the base of the vertical and the necessary braid used to connect the choke to the vertical feed point
and ground system.

When a 1/4-wavelength vertical is mounted well above the ground and uses elevated radials, it is difficult to
keep current from traveling back to the operating position via the feedline. In this application, using an
additional feedline current choke like the DX Engineering DXE-FCC050-H05-A installed outside of the
near field of the vertical will further reduce feedline currents.

Additional Items Required

Mounting Clamp - Stainless Steel V-Clamp DXE-SSVC-2P, to mount the insulated plate to a 1" to 2" OD

(maximum) ground mounting pipe, usually the same one used to mount the vertical antenna.

Installation

Ground Mounted Vertical Antenna

The VFCC kit should be mounted to the same mounting pipe used to mount the vertical antenna. The

standard 1-1/2" galvanized water pipe (with its 1.9" OD) is just fine for this application and can
usually be found at your local home building supply store. It should be mounted horizontally as close to

the base of the vertical antenna as possible. If you are using a DX Engineering Tilt Base, sufficient clearance
is needed to ensure the antenna does not contact the VFCC when tilted. Proper orientation of the VFCC to
the Tilt Base also ensures good geometry of the feed connections during tilting.

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When using the DXE-RADP-3 Radial Plate, the VFCC shelf bracket should mounted so there is
approximately 1/8" to 1/4" gap between the insulated shelf bracket and the Radial Plate mounting tab. The
VFCC requires approximately 7” clearance from the radial plate to the bottom of the tilt-base to allow the
tilt-base to operate with no interference. Your set up may vary and dimensions may be adjusted. Use Figures
2 and 3 for orientation.

Mount the VFCC and the Mounting Bracket to the Insulated Shelf as shown in Figure 1.

Figure 1

Figure 2

After mounting the VFCC as shown in Figures 2 and 3, connect the 8.5"
braid to the bottom of the vertical antenna. Make sure you are using the
terminal closest to the Red "D" in DX ENGINEERING on the VFCC
label. Route the braid as shown in Figure 2.

Connect the 7.5" braid from the other VFCC terminal to the closest radial
wire bolt on the radial plate or ground system.

When making connections to the terminals, the braid should be placed
between the flat washers. The wing nuts should be hand tightened
only. Do not use pliers or other tools to tighten them as excessive force
may damage the internal connections or the ceramic insulators.

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