DX Engineering RF-PRO-1B Manuale utente

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: [email protected]

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.

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 low-

noise, 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 electric-

field 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.

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.

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 Y-

adapter 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.

The relay’s actuation circuit is designed to operate with a typical transceiver’s “KEY” signal. The

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.

KEY INPUT

Switch 1

Switch 2

20 VDC ANTENNA POWER

Low

Off

Factory Default

Setting

High

Off

Low

Off

High

Off

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.

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.

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.

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.

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®Specifications

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.

Indice

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