RF-PRO-1B®
Active
Magnetic
Loop
Antenna
DXE-RF-PRO-1B
DXE-RF-PRO-1B-INS Revision 0c
1200 Southeast Ave. - Tallmadge, OH 44278
Phone: (800) 777-0703 ∙ Tech Support and International: (330) 572-3200
Fax: (330) 572-3279 ∙ E-mail: DXEngineering@DXEngineering.com
© DX Engineering 2017
Introduction
The DX Engineering rotatable DXE-RF-PRO-1B Active Magnetic Loop Antenna is designed for
reception of signals over the range of 100 kHz to 30 MHz. The RF-PRO-1B® can be mounted to a
pole, mast or any flat surface. The included very high dynamic-range low-noise preamplifier is
designed for minimum intermodulation distortion in the presence of very high-level signals that
would normally overload most preamplifiers. This rotatable loop antenna is receive ONLY.
Features
Same technology and quality as Pixel Technologies and InLogis loop antennas
Unique Loop architecture provides enhanced
performance
Magnetic loop that rejects near field electrical noise
Up to 30 dB rejection of locally radiated noise
compared to whip antennas
Figure eight directivity and deep nulls to further
reduce interference from local or distant signals
Very low IMD, 27 dB Low-Noise Clifton
Laboratories Norton Preamp insures good
performance in both strong and weak signal
environments
Useable coverage range: 100 kHz to 30 MHz
Rejects power line noise
Rugged construction, easily mounts to a pole or flat
vertical surface, 3/4 inch dia. aluminum loop,
supplied with preamplifier, power inserter and DC
power supply
No manual tuning necessary
No Home Owners Association problems; low
profile, easy to camouflage and works at a few feet
above ground level
Modular design for easy installation and maintenance
Internal transmit / receive relay disconnects the antenna / preamplifier from receiver when
transmitting
Antenna Design
The RF-PRO-1B® Loop Antenna consists of a rigid 3/4 inch diameter light-weight aluminum loop
and a balanced broadband preamplifier that is housed in a separate enclosure mounted close to the
antenna on its mast bracket. A 20 volt DC regulated power inserter unit is provided. The antenna
and preamplifier has been designed to permit the use of 75 ohm cable (RG-6 is recommended and is
available from DX Engineering). For best results the antenna should be positioned a minimum of 15
feet away from any buildings or other sources of interference. The loop antenna may be rotated to
take advantage of the directional properties of this type of antenna.
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Not Your Father’s Loop Antenna
Based on the work of Dr. Carl Baum for the U.S. Air Force his “Moebius Strip Shielded Magnetic
Loop Antenna” architecture outperforms much larger antennas. Dr. Baum was a Senior Scientist at
the U.S. Air Force Research Laboratory and is the recipient of several awards from the IEEE
(Institute of Electrical and Electronic Engineers) for his work.
Developed for a classified U.S. Air Force project involving the measurement of EMP (Electro
Magnetic Pulse) from nuclear weapons, this loop design has wide application to antennas for lownoise, interference-free radio reception over a wide frequency range. The designer of this magnetic
loop antenna version coupled this antenna to a custom made low-noise preamplifier originally
developed by Clifton Laboratories.
Magnetic Loop Antenna Advantages
Most active antennas are the whip type and respond mainly to the electrostatic-field portion of an
electro-magnetic radio wave. This Magnetic Loop responds primarily to the magnetic-field and this
ensures high rejection of nearby
electric-fields. The intensity of the
electric field is usually higher than
the magnetic-field when an antenna
is close to interference sources such
as TVs, florescent lamps, power line
wiring, etc. By rejecting the electricfield there is a reduction in local
interference compared to other types
of active and passive antennas.
Interference reduction is further
enhanced by the deep nulls of the
antenna’s 'Figure-Eight' directivity
pattern that can be used to null out or
reduce interference coming from a
specific local or distant direction. The electrical field is often much stronger than the magnetic field.
When lined up properly the loop will enable better copy for weak signals which could not be copied
by other antennas.
Intermodulation
Some active antennas generate intermodulation products which can appear as spurious signals
interfering with reception. This interference or second and third order intermodulation is caused by
non linearity in the preamplifier, producing signals which are usually the sum and difference of
strong stations and their harmonics. The RF-PRO-1B® Loop (DXE-RF-PRO-1B) has been
specifically designed to reduce intermodulation products to a minimum. The third order intercept
point is typically +48 dBm (OIP3) and the second order intercept point is greater than +100 dBm
(OIP2 typically 110 dBm). The 1 dB compression point of this preamplifier is +27 dBm making the
levels of the intermodulation products generally far below the atmospheric and man- made noise.
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Cautions:
This is a Receive-Only Rotatable Antenna. Do not connect it to a transmitter as it will be
damaged and void your warranty
Do not inadvertently connect the (To Preamp) +20 VDC output of the power inserter
to your receiver’s antenna input as your receiver may be damaged
When operating with nearby transmitting antennas, follow the instructions to avoid over-
driving (or damaging) your receiver’s input or damaging the loop’s low-noise preamplifier
General Information
Positioning the Antenna
This antenna has a directional
‘Figure Eight’ pattern with two
deep 25- 30 dB nulls, so for
maximum daytime low-angle
ground wave reception of a desired
signal it should be oriented so that
the plane of the loop rests
perpendicular to the ground and
should, if extended, pass through
the general location of the signal’s
transmitter. At night, for reception
of high- angle sky waves this
antenna is less directional and the
nulls are far less prominent.
To take advantage of the directivity of this antenna, it should be mounted on a light duty rotator. For
best results it should be located as far away as possible from any metal objects that could distort or
shield the antenna’s reception like gutters, downpipes, metal plumbing and aluminum foil backed
thermal insulation. It can be positioned indoors or outdoors at least 5 feet above ground level, but
for best results it should be as far as possible from sources of interference such as AC power cables,
cat 5 network cables, fluorescent lights, light dimmers, computers and flat panel TV’s. If located
outdoors it can be camouflaged with shrubbery. Ideally, a location outdoors at least 20 feet away
from any buildings will yield superior results. It can be mounted to a pole or attached to a flat
surface or wall via the included L-bracket and clamps.
Cable
For best results the coaxial cable run from the indoor power inserter to the external preamplifier
should be shielded RG-6 cable with male F connectors on each end. RG-6 cable is available from
DX Engineering along with high-quality compression fit water-proof F-connectors that have
internal O-rings to keep moisture out.
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Use with Near-By Transmitting Antennas
The antenna’s low-noise preamplifier will withstand RF input levels of at least 30 dBm without
failure. In tests with a 1,500 Watt transmit RF amplifier and a ¼-wave vertical transmitting antenna
it was found that the worst- case loop output power into the preamp was 10 dBm when the antenna
was located 25 ft from a vertical radiator and adjusted for maximum coupling. This would indicate
that at 25 ft separation, there is a 20 dB safety margin for the preamplifier. The other factor to
consider is, with this kind of input signal (+10 dBm), the preamplifier’s 27 dB gain will cause it to
saturate and output 1.3 watts into the connected receiver. This high saturated output level is a
byproduct of the excellent intermodulation distortion performance of this preamplifier.
While most receivers have some sort of input protection and possibly an internal transmit / receive
switch that disconnects or shorts the input when transmitting, we cannot be sure of the radio’s
protection limits and DX Engineering cannot be responsible for any damage that may result.
Therefore, included in the loop’s power inserter is a relay “KEY” jack that can be actuated by the
amplifier keying output of a typical transceiver. When actuated, the relay disconnects power to the
antenna preamplifier. A green LED on the power inserter is illuminated when power is applied to
the preamplifier. An RCA-plug to RCA-plug cable is included with the accessories to connect the
KEY output of your transceiver to the RCA jack on the side of the power inserter. An RCA Yadapter is also included to enable connecting the KEY signal from your transceiver to other
equipment. It is the user’s responsibility to ensure proper keying line connections.
The diagram below shows an Icom IC-7600. Your radio set may differ. Consult your radio
instruction manual for details when using a separate receive antenna input.
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The relay’s actuation circuit is designed to operate with a typical transceiver’s “KEY” signal. The
KEY INPUT
Switch 1
Switch 2
20 VDC ANTENNA POWER
Low
Off
On
Off
Factory Default
Setting
High
Off
On
On
Low
On
Off
On
High
On
Off
Off
power inserter has internal DIP switches that can be programmed to harmonize relay actuation with
the proper state of the transceiver’s KEY signal.
The default setting is such that when the KEY output is “low” (less than 0.7 VDC) the relay turns
on and disconnects the preamplifier’s power and the connection to your receiver is grounded
through a resistor. If the KEY signal is “high” or greater than 1.2 VDC the relay is not actuated and
power is applied to the preamplifier and connection is made to your receiver. If the KEY input to
the power inserter is left open or disconnected, then power is always applied to the preamplifier. If
your transceiver has a “KEY” output that goes high on transmit, then you can reverse the polarity of
the power inserter relay actuation by removing the power inserter’s base plate and programming the
DIP switches on the PC board in accordance with the table shown.
A simplified schematic of the relay
interface circuit is shown. Note that the
KEY input is pulled up internally via a
10K ohm resistor to the “high” state.
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The loop antenna aluminum tubing must not be grounded. It must remain electrically isolated from
its metal L-bracket mount via nylon shoulder washers. Do not remove these insulating shoulder
washers.
Mounting to a Rotator
The picture shows the RF-PRO-1B® Magnetic
Loop Antenna mounted to a customer supplied
rotator using customer supplied mast.
Many users utilize this configuration to take full
advantage of the antenna’s directional
characteristics.
Because of the antenna’s low weight and wind
loading a very low power rotator can be used
typical of the type used with TV antennas (A light
duty rotator is available from DX Engineering).
Hint: When installing the one foot jumper with F
connectors (or any cables with F connectors), the optional
DXE-CIT-1 F Connector Tightening Tool is handy to
have in your tool box.
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Overall Diagram
This diagram shows the overall wiring scheme. Once familiar with this set up, assembling the
antenna and making the actual cable connections is easy.
Be extremely careful to avoid inadvertently connecting the 20 VDC antenna output of the
power inserter to the antenna input on your receiver. Although the power inserter has a self-
resetting internal fuse that will trip at a current draw above 400 milliamps. Making this connection
error will put 20 VDC on the input of your receiver momentarily that could damage some receivers
and is not covered by warranty.
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Mounting the Preamplifier to the Loop Antenna L-Bracket
The preamplifier is mounted to the L-bracket that is attached to the loop antenna
using the included saddle clamp and mounting hardware which also connects the
antenna to a short 1-1/4” diameter customer supplied mast (that would then normally
go into the rotator). Nylon shoulder-washers and nylon flat washers are used to
electrically isolate the metal case of the preamplifier from the mounting pole as shown below. This
is required to avoid ground loops. The upper saddle clamp uses the regular hardware (serrated
flange hex nut) as shown in the pictures below. The use of Jet-Lube SS-30 anti-seize (JTL-12555)
is recommended for all hardware to avoid galling.
The loop antenna and the preamplifier have small weep holes in that face downward to drain any
condensation that may accumulate internally. A one foot RG-6 jumper cable is supplied to connect
the output of the loop antenna to the input of the preamplifier. When looping this RG-6 jumper,
ensure the loop does not rub against the saddle clamp hardware.
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Waterproofing F Connectors & Weather Proofing
The included one foot long RG-6 coaxial cable jumper is used to connect the output of the loop to
the preamplifier. This cable uses specially designed F-connectors to eliminate moisture ingress. A
package of coax seal and electrical tape is supplied for additional
weatherproofing.
The coax seal can be cut into strips to make it easier to wrap around
the connectors. It is suggested that the electrical tape be used first,
then wrap and kneed together the coax seal to provide a complete
water resistant seal. The reason for using the electrical tape first is
when a cable has to be removed, the coax seal can be completely
removed and not leave sealing residue on the connector threads.
Power Inserter
The preamplifier’s output is connected to the 20 VDC output of the power inserter via the customer
supplied lead-in RG-6 cable. If a lightning protector is used in this coaxial line, it must be capable
of passing DC. The power inserter contains a highly filtered linear DC regulator with an internal
self resetting fuse that provides protection from short circuits. It is designed for indoor use only.
The wall mount transformer provides 24 VAC for the power supply. A PL-259 to type F Connector
adapter is provided for the radios that may require it.
®
RF-PRO-1B
Frequency response: 100 kHz to 30 MHz (Nominal Gain: 27 dB ±3 dB)
DC power: 20 volts at 240 mA
OIP3: typically +48 dBm
OIP2: > 100 dBm (typically 110 dBm)
1 dB compression point: +27 dBm
NF: typically 2 dB (at 10 MHz)
Antenna Diameter: 38 inches
Antenna Weight: 3 lbs.
Specifications
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RF-PRO-1B® Parts List
QTY Description
1 Loop Antenna with L-Bracket
1 Preamplifier
2 Saddle Clamps with U-Bolts and
Mounting Hardware
1 Package of Preamplifier
Mounting Hardware
1 Coax Seal package
1 Roll of Electrical Tape
1 24 VAC Wall Mount
Transformer
1 3 foot F-male to F-male jumper
cable
1 1 foot F-male to F-male jumper
cable
1 PL-259 to F Connector Adapter
1 20 VDC Power Inserter
1 RCA to RCA cable
1 RCA-Y adapter cable
Manual Updates
Every effort is made to supply the latest manual revision with each product. Occasionally a manual
will be updated between the time your DX Engineering product is shipped and when you receive it.
Please check the DX Engineering web site (www.dxengineering.com) for the latest revision manual.
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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.
©DX Engineering 2017
DX Engineering®, DXE®, DX Engineering, Inc.®, Hot Rodz®, Maxi-Core®, DX Engineering THUNDERBOLT®, DX
Engineering Yagi Mechanical®, EZ-BUILD®, TELREX®, Gorilla Grip® Stainless Steel Boom Clamps, Butternut®,
SkyHawk™, SkyLark™, SecureMount™, OMNI-TILT™, RF-PRO-1B®, AFHD-4® are trademarks of PDS Electronics,
Inc. No license to use or reproduce any of these trademarks or other trademarks is given or implied. All other brands
and product names are the trademarks of their respective owners
Specifications subject to change without notice.
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