Beverage Feedpoint Matching System
BFS-1
User Manual
PATENT PENDING
P.O. Box 1491 ∙ Akron, OH 44309-1491
Phone: (800) 777-0703 ∙Tech Support and International: (330) 572-3200
Fax: (330) 572-3279 ∙ E-mail: DXEngineering@DXEngineering.com
Introduction
The BFS-1 is a single-wire, single direction Beverage Feed System. This W8JI design is immune to strong signal overload and core saturation common in multi-transmitter contesting environments, and is used by winning contest stations and low-band DXers. The unit uses an isolated-winding, matching transformer system to significantly increase the signal-to-noise ratio in Beverage and other high impedance antennas.The BFS-1 works with antenna impedances from 400-500 Ω. Included with the BFS-1 is a 470 Ω, 2-Watt non-inductive termination resistor that withstands nearby lightning strikes significantly better than hard to find carbon composition resistors. DX Engineering has replacement resistors available, part number DXE-ECM-R470-2.
The feedline impedance of the BFS-1 is optimized for 75 Ω, however, any feedline between 30 Ω and-100 Ω can be used. While not intended for transmitting, the BFS-1 can withstand power levels of 20 watts continuously, 200 watts for 5 seconds or the power rating of the termination resistor, whichever is less. The BFS-1 uses an industry standard CATV F type connector.
The BFS-1 sets itself apart from competitive products by combining quality components and superior technology inside a compact metal housing, and offers the following advantages:
Features
- • 100 kHz to 30 MHz operating range
• Spark gaps minimize damage from lightning
• Wing nut terminals eliminate soldering
• Metal housings used for superior shielding and improved life
• Flange-mount holes for easy mounting
• Ground isolated secondary essential for building beverage arrays and can be connected with normal or reverse phase
The BFS-1 is an isolated-winding, matching transformer system that significantly increases the signal to noise ratio in Beverage and other high impedance antennas. This unit is immune to strong signal overload and core saturation common in multi-transmitter contesting environments, and is used by winning contest stations and low-band DXers.
Coax and Connectors
The feedpoint matching system is optimized for 75 Ω feedline. This allows the use of readily available 75 Ω CATV type cable and F style connectors. We recommend using high quality “flooded” 75 Ω RG-6 type coax DX Engineering part number DXE-F6-SPL. Flooded cables have the distinct advantage of automatically sealing small accidental cuts or lacerations of the jacket. Flooding also prevents shield contamination and can be direct-buried. To ensure weatherproof connections, use Snap-N-Seal connectors. (DX Engineering part number DXE-SNS6-25 contains 25 Snap-N-Seal connectors). The Snap-N-Seal connectors cannot be installed with normal crimping tools or pliers, so an installation tool like the DXE-SNS-CT1 is essential for proper connector installation.Additional Requirements
Please note you will need the following items (not included in this package) to install and operate the BFS-1 antenna:- Antenna Wire:You will need a minimum of 3/8 wavelength of wire of any gauge between #8 and #20. Refer to Performance Factors on the following page for details.
- Ground Rods: Use at least one 5-ft copper rod. Refer to the Grounding section for complete information.
- Insulators and Supports: Insulators and supports are required to mount the antenna wire 5 to 10 feet above ground. Supports can be metallic but the antenna wire must be insulated from them.
Specifications
- Operating Frequency: 100 KHz to 30 MHz
- Input Impedance: 400-500 (The impedance presented to the matching system by the antenna wire
- Output Impedance: 30-100 Ω (75 Ω recommended
- Common Mode Isolation: 20-30 dB (feedline and antenna) (The attenuation or loss when measuring transmission of a 50-ohm test signal between the coax shield and ground
- Power Handling: 20 watts continuously or 200 watts for 5 seconds (The power this antenna safely handles. This power handling value is primarily dependant on the rating of the termination resistor
- Termination Resistance: 400-500 (The value measured at the termination resistor)
Installation
Isolation
The BFS-1 operates on the principle of a transformer with isolated antenna and feedline connections. This prevents the feedline from contributing unwanted electrical noise or signals to the receiver. Many antenna enthusiasts unwittingly connect their feedline to their matching system housing, not realizing that the practice simply makes the antenna longer and increases unwanted signals. The BFS-1 solves this problem by insulating the connection lugs from the housing, which also isolates the antenna from the feedline.We strongly suggest that you read the entire BFS-1 manual before installing the antenna, and make sure you understand the concepts outlined in the sidebar (below) that are critical to proper operation.
Performance Factors
For an effective Beverage antenna, you will need at least 3/8 wavelength of wire. Acceptable wire types include galvanized or cadmium-plated steel electric fence wiring, stranded or solid copper wire, and steel-core wires like copperweld. Avoid wire designed for welding applications. The line with the best mechanical and electrical characteristics is generally #16 gauge copper clad steel (copperweld) wire. Aluminum wires will work, but connections and splices are problematic due to the formation of aluminum oxide.Antenna Length
The chart below shows relative performance of Beverage antennas based on wire length:
The antenna can be any length between 3/8 wavelength through multiple wavelengths, although we recommend using lengths similar to those in the table above. In most cases, the BFS-1 performance is excellent even when the antenna is not cut to the ideal length.
Location
Beverage antennas work well and are easy to install; you can make reasonable height changes, drape the antenna over tree branches, and deviate orientation by as much as 10 degrees. Metal poles will not affect the antenna’s performance as long as the wire is insulated from the pole. Avoid placing the antenna near transmitting antennas, power lines, large metal fences, or over buried cables. Install the antenna wires 5-8 feet above the ground. It is not necessary to follow the contour of the land because small hills, ravines and ditches generally do not affect the antenna. Contrary to popular belief, sloping the antenna does not improve performance.Connections
The BFS-1 Feed Point unit has antenna terminals marked + and ─ . Normally, the + side goes to the antenna wire and the ─ .terminal goes to the antenna ground as shown in the drawing below. When building Beverage arrays, phase can be reversed by simply reversing the connections. The BFS-1 also has ground-isolated secondaries which are essential for array construction. Do not ground the case of the BFS-1 to the antenna ground system.
Grounding
Ground the ends with at least one five-foot copper rod. ¾ inch copper water pipe is ideal. A five-foot rod typically has 50-150 ohms RF resistance on 160 meters. For most soil types, you should use two or more rods spaced at least five feet apart. Longer rods generally do not improve RF grounding because RF skin depth prevents deep ends from having much effect. Do not connect the coax shield to the antenna ground. Isolating the feedline and antenna grounds will prevent the feedline shield from becoming an unintentional antenna ground and introducing unwanted signals and noise. Caution: Be sure to use the wing nut terminal on the case for the antenna ground. The metal case is NOT connected to the antenna ground, and should not be connected to the antenna ground. Refer to the “Grounding” (Critical Installation Information) section above fro more information.
Feedline
The BFS-1 uses standard CATV “F” connectors. We recommend using CATV connectors and cables because they are generally high quality and have excellent shielding. CATV cables and connectors are inexpensive and easy to install, they are well suited for outdoor use, and direct burial cable is inexpensive and readily available. Be sure to use a coax sealant or install a rain hood over cable connections, and follow all appropriate wiring codes for grounding where cables enter a building. Bury the feed cable for 10 feet or more when approaching the feedpoint, or ground the feedline shield to a separate ground rod.Termination
The far end of the antenna must be terminated, typically at 450 to 500 ohms, or the antenna will not have the optimum F/B ratio. Failure to terminate the antenna always results in a reduction of S/N ratio. S/N reduction can be as much as twenty dB, depending on the noise arrival direction.A special termination resistor is included in this package. This high-energy, metal composition resistor has stable electrical characteristics, almost no inductance, and withstands severe overloads.
Lightning
This unit features small air gaps and wide foil trace areas, as well as entrance gaps at all feedthrough terminals. The gaps act as safe, short paths for lightning discharges. The BFS-1 is normally immune to nearby lightning, although a direct strike might cause component failure. For additional lightning protection, consider using a one-foot link of #26 wire between the antenna terminals and the antenna. This wire will act like a fuse link and help protect against severe lightning energy.Simplified Testing
The BFS-1 feedpoint matching system is not only easy to use, it can also be tested in its operating configuration. Just attach a standard SWR analyzer to test the antenna, the termination and the BFS-1 as a single entity. Properly functioning systems will show a reasonably constant SWR value over several bands. The SWR does not have to be low (it is typically under 1.8:1) but it should change gradually over large variations in frequency.Technical Support
If you have questions about this product, or if you experience difficulties during the installation, contact DX Engineering at (330) 572-3200. You can also e-mail us at DXEngineering@DXEngineering.com.For best service, please take a few minutes to review this manual before you call.
Warranty
All products manufactured by DX Engineering are warranted to be free from defects in material and workmanship for a period of one (1) year from date of shipment. DX Engineering’s sole obligation under these warranties shall be to issue credit, repair or replace any item or part thereof which is proved to be other than as warranted; no allowance shall be made for any labor charges of Buyer for replacement of parts, adjustment or repairs, or any other work, unless such charges are authorized in advance by DX Engineering.If DX Engineering’s products are claimed to be defective in material or workmanship, DX Engineering shall, upon prompt notice thereof, issue shipping instructions for return to DX Engineering (transportation-charges prepaid by Buyer). Every such claim for breach of these warranties shall be deemed to be waived by Buyer unless made in writing.
The above warranties shall not extend to any products or parts thereof which have been subjected to any misuse or neglect, damaged by accident, rendered defective by reason of improper installation, damaged from severe weather including floods, or abnormal environmental conditions such as prolonged exposure to corrosives or power surges, or by the performance of repairs or alterations outside of our plant, and shall not apply to any goods or parts thereof furnished by Buyer or acquired from others at Buyer’s specifications. In addition, DX Engineering’s warranties do not extend to other equipment and parts manufactured by others except to the extent of the original manufacturer’s warranty to DX Engineering.
The obligations under the foregoing warranties are limited to the precise terms thereof. These warranties provide exclusive remedies, expressly in lieu of all other remedies including claims for special or consequential damages. SELLER NEITHER MAKES NOR ASSUMES ANY OTHER WARRANTY WHATSOEVER, WHETHER EXPRESS, STATUTORY, OR IMPLIED, INCLUDING WARRANTIES OF MERCHANTABILITY AND FITNESS, AND NO PERSON IS AUTHORIZED TO ASSUME FOR DX ENGINEERING ANY OBLIGATION OR LIABILITY NOT STRICTLY IN ACCORDANCE WITH THE FOREGOING..
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