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Receive Antenna Phasing
Controller
DXE-NCC-2
U.S. Patent No. 8,175,546
DXE-NCC-2-INS Rev 2
© DX Engineering 2022
1200 Southeast Ave. - Tallmadge, OH 44278 USA
Phone: (800) 777-0703 ∙ Tech Support and International: (330) 572-3200
Fax: (330) 572-3279 ∙ E-mail: DXEngineering@DXEngineering.com
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Table of Contents
Introduction
3
Features
5
Functions and Technical Description
6
Understanding Noise and Interference
10
Reducing Noise and Interference
10
Selecting Antennas
11
Receive Antennas
11
Antenna Polarization
12
Antenna Feedlines
12
Antenna Sensitivity
12
Antenna Bandwidth
13
Combining Antennas to Improve Signal-to-Noise Ratio
13
Use with a Receive Loop or Other Low Noise Antennas
14
Phased Verticals and Beverage Systems
14
Front Panel Controls and Switches
15
Rear Panel Connections
17
More on RADIO PTT - RX ENABLE Failsafe Feature
18
DXE-KWD-RTR Cable Information
19
Internal Jumpers
20
Bias Tee Enable
21
Force Ground
21
Bias Tee Always On
22
Installation
22
Connections
22
Operation
24
Using the NCC-2
25
Phase Nulling with a Transmit Antenna
26
Interconnection Diagrams
27
Appendix A
33
Internal Optional Modules
33
Removing - Installing Optional Modules or Bypass Plug-In Boards
34
Specifications
35
User Diagram
35
Technical Support
36
Manual Updates
36
Warranty
36
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Introduction
The DX Engineering NCC-2 Receive Antenna Phasing System Controller is a two-channel receive
signal phasing device with a special relay system that allows the user to combine and independently
adjust the phase and level between two antenna inputs. This essentially creates a fully adjustable
phased array. When combining two stationary antennas, an array pattern is created with signal
peaks and dips, called nulls. Adjusting the phase control has the effect of electronically rotating or
steering that pattern. The operator can steer the null direction to significantly weaken strong
interfering signals or noise, local or distant, and dramatically enhance the reception of weaker
signals from other directions. The NCC-2 is especially useful on low frequencies, where phase
nulling with small receive antennas can provide amazing benefits for almost all types of radio
operating enthusiasts: DXers, casual conversationalists, contesters, AM DXers and Short Wave
Listeners (SWL) throughout HF.
The NCC-2 Controller includes the RTR Receive Transmit Relay, which expands the exciting
benefits of antenna phasing for interference reduction in two ways. First, the NCC-2 can combine
signals from an HF transmit antenna and a separate receive antenna. Almost any Amateur, even
those with space-limitations for separating the receiving and transmitting antennas, can enjoy the
benefits of antenna phasing and noise-nulling to effectively notch-out strong stations or noise.
Second, the user of any standard HF transceiver, that does not have a separate receive antenna input,
can enjoy the enhanced reception of signal and noise nulling. The NCC-2 has rear panel SO-239, F
and BNC connectors, making it extremely versatile and easy to connect to almost any receiver or
HF transceiver as well as transmit and receive antennas.
The NCC-2 features three internal
slots per input channel for optional
Plug-In Modules that can also
improve reception. Receive
Preamplifier Plug-In Modules are
crucial for low-signal conditions.
Receiver Guard Plug-In Modules
offer front-end protection for the
NCC-2 and the receiver. Plus, the
Impedance Transformer Plug-In
Modules match the 75 ohm
receive-antenna feedlines to the 50
ohm internal impedance of the
NCC-2 and the Receive Preamp.
Optimal results with the NCC-2 are achieved with identical vertical receive antennas. The complete
package including the DXE-NCC-2 and DXE-RSEAV-2 is known as the Active Antenna Phasing
System. This receive only combination is shown in Diagram 3 on page 29. Bidirectional receive
performance is from 500 kHz to 15 MHz. The pair of Receive Short Element Active Verticals,
DXE-RSEAV-2, installed with a spacing of one-quarter wavelength on the lowest band, phased
together with the NCC-2, delivers an electronically steerable, optimized unidirectional pattern with
a single null. Operations on higher frequency bands results in a multiple null pattern that is very
useful. The NCC-2 front panel controls provide repeatable directional pattern adjustments. Properly
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spaced Active Receive Vertical antennas are useable over a wide range of frequencies, offering the
best possible nulling and peaking for enhanced weak signal reception.
The NCC-2 is also fully compatible with the DX Engineering Active Magnetic Loop; model DXE-
RF-PRO-1B, for phasing with a directional low-noise antenna. Although Active Verticals and
Active Magnetic Loops typically deliver the best results, the NCC-2 is ready for experimentation
with other combinations of receiving antennas including Single and Reversible Beverage and
Beverage On the Ground Antennas, Receive Four-Square and Eight Circle Arrays, K9AY Loops,
and more. The NCC-2 is primarily designed for 500 kHz to 15 MHz use, although the useful
operating range extends from below 300 kHz to 30 MHz. Typical applications include:
Combining two similar non-directional antenna elements to create a directional pattern
Combining two similar directional antennas to produce an enhanced pattern
Reducing overload or interference by removing or reducing a strong signal or noise
Reducing interference from distant signals or noise
The NCC-2 has four main advantages over typical directional phased array systems:
The NCC-2 array can be steered “electronically” even though the antennas are
physically stationary
The user can adjust the controls to obtain a null or a peak
The phased response can often be changed from a perfect null to the perfect peak with a
flip of a switch
Front panel adjustments compensate for less-than-ideal installations, making a
directional array possible in most situations
NOTE: A transceiver amplifier keying line must be connected, to activate a very important
feature of the NCC-2. The RTR Receive Transmit Relay has a unique Failsafe System, which
protects the unit and your receive antenna equipment when the NCC-2 is connected to a transceiver
RF output. When the NCC-2 is off, the transceiver RF output (RADIO) is connected by the relay
directly to the transmit antenna (MAIN ANT). This prevents internal RF damage and allows regular
station operations when not using the NCC-2. Conversely, reception of the phased antenna signals
on the RADIO is allowed ONLY when the NCC-2 is on, the RTR Switch is in the NORM position
AND a transceiver amplifier keying line is connected from the dual-purpose dual conductor
RADIO PTT connector, carrying the special RX ENABLE output signal on the keying line shield
to the transceiver chassis and back on the coaxial cable shield. The keying cable is the failsafe
interlock and the “Receive Enabled" condition is confirmed by the RTR LED change to BLUE.
When the transceiver is keyed to transmit, the transceiver amplifier keying line center conductor
carries the typical “Ground on Transmit” to the NCC-2 RADIO PTT input. The RTR LED changes
to RED and the high-speed RTR relay immediately connects the transceiver RF output to the
transmit antenna. Simultaneously, if enabled by internal jumper, DC power is disabled on the
receive feedlines to Active antennas. Toggling your transceiver to listen between phased antenna
receive and the transmit antenna is easy with the RTR Switch MAIN ON momentary and set
positions. Remember, the "no receive" MAIN ANT to RADIO transmit condition exists when the
RADIO PTT – RX ENABLE keying line is NOT connected or if NCC-2 power is turned off. See
more details in the manual sections entitled “See More on Radio PTT – RX Enable Failsafe
Feature” and “NCC-2 Functions and Technical Description.”
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DX Engineering NCC-2 Features
RTR system supports phasing a transmit antenna with a separate receive antenna
RTR system supports transceivers without a separate receive antenna input
Enhanced Phase control – adjusts through 360 degrees within primary design frequency
range 500 kHz to 15 MHz. Useable freq. range 300 kHz to 30 MHz.
Improved Balance control with easier adjustment for deeper nulls
Exceptional dynamic range – handles strong signals without overload
Low noise floor - operational balance and phasing system optimized for low signals
High Third Order Intercept – approaches, matches or exceeded many radios; +32 dBm
per channel, +38 dBm both inputs combined
Three internal option slots per channel for Plug-In Modules:
Receive Preamplifier (DXE-RPA-2-PM)
Receiver Guard (DXE-RG5000HD-PM)
75 to 50 ohm Impedance Transformer (DXE-IT-PM)
Internal 50 ohm impedance – rear panel SO-239 for RADIO and MAIN ANT
Receive Antenna Input Channels – BNC for 50 ohm and F connector for 75 ohm
feedlines (use 75 to 50 ohm Impedance Transformer Plug-In Modules - DXE-IT-PM)
RTR system automatically switches from phased antenna reception to transmit antenna
(when using a transceiver RF output)
Handles up to 200 watts (CW) of transmitted RF
Radio to amp keying line input RCA female (RADIO PTT) with RX Enable interlock
supports RTR failsafe to prevent RF damage to NCC-2
Accessory keying line output RCA female (ACC PTT) ‘ground on transmit’ Schottky
diode isolated pass-through from RADIO PTT transceiver amp keying for Amplifier or
Accessory
Multi-Color Status Indicating LEDs for Power, RTR Mode and Preamp Power CH A
and CH B
Internal jumper to enable DC injection onto receive feedline for Active Vertical or
Magnetic Loop Antennas
Screw-on version of the DC Power connector is provided to prevent accidental power
cable pull-out (any type 2.1 mm DC Power connector may be used)
Operates on +13.8 Vdc nominal, accepts and operates on any voltage from +13 to +21
Vdc input to power the NCC-2. Input DC line should be fused at 3 amps to protect
circuitry. For Active Verticals that are connected, the voltage may have to be +13.6 Vdc
or higher. Some loops may require +21 Vdc.
Note: Every radio manufacturer’s accessory interconnection scheme is different.
Consult your radio manufacturer’s manual for details and requirements for receive
signal inputs, outputs and switching voltages.
A new keying line cable assembly for most Kenwood transceivers with a 7-pin DIN Remote
connector, is the DXE-KWD-RTR. This custom cable allows proper operation of a Kenwood
transceiver with the NCC-2. See the section ‘More on Radio PTT – RX Enable Fail Safe Feature’.
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NCC-2 Functions and Technical Description
The DX Engineering NCC-2 is a multi-purpose two-channel phasing controller that features high
signal level handling and very low internal noise. Taking advantage of the time-delay of signal
arrival between two antennas spaced by a significant fraction (1/10) of a wavelength or greater, the
antenna array creates a directional pattern. Successful combinations of antennas and phasing
adjustments create a direction-rotating effect of the resulting array pattern. Changing the phase can
move the sharply reduced signal level of the pattern, known as the null, over the direction of an
interfering noise or signal. The result is the ability to hear signals from other directions that may not
have been heard otherwise.
Note: Effective and proper operation occurs when the same noise (for noise nulling) or the same
signal (for signal nulling or peaking) is present on both CH A and CH B receive antenna inputs.
Directly connected to the CH A and CH B Inputs are the NCC-2 Option Slots. Bypass Plug-In
boards are in place to carry input RF directly to the Channel A and Channel B phasing and
combiner systems. The DX Engineering Plug-In Modules function exclusively for the NCC-2
operational protection and enhancements. There are three option slots for each input channel. The
typical order of option installation is:
Option 1 - top slots are intended for 75 to 50 ohm Impedance Transformers (DXE-IT-PM)
when 75 ohm receive antenna feedlines are connected to either the F connectors or the BNC
connectors on the CH A RX ANT INPUT or the CH B RX ANT INPUT. Without these
transformers, both inputs are 50 ohms, the internal impedance of the NCC-2. Impedance
mismatch losses are acceptable if they are not installed; operations will not be adversely
impacted.
Option 2 – middle slots may be used for the Receiver Guard Plug-In Modules (DXE-
RG5000HD-PM) when high signal levels are anticipated to occur on an input.
Option 3 – bottom slots, switched and powered are reserved for Receive Preamplifier Plug-
In Modules (DXE-RPA-2-PM) as controlled by CH A Option and CH B Option switches.
When the NCC-2 is used with passive receive antennas the installation of the RPA-2 plug-in
modules is highly recommended to enhance low signal levels due to propagation. Optional
Preamplifier Plug-In Modules may not be needed when using or with Active Receive
Verticals (DXE-RSEAV-1 or -2).
See Appendix A for special information on removal of Bypass Plug-In boards and installation of
Plug-In Modules.
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NCC-2 Functions and Technical Description (continued)
Following the input modules slots, the NCC-2 maintains complete RF isolation between the two
channels, beginning with dual, voltage controlled attenuators. They maintain high-stability phasing
with low noise receive antennas, as the voltage controlled step attenuators and cross-channel
Balance control offers consistent operation for repeatable settings. High dynamic range operational
amplifiers buffer the input to the phasing system.
Voltages for phase adjustment are linearized through an active feedback system. Phase adjustment
is spread over a wide linear control range. This gives the phase control a smooth feel and improves
the ability to manually reset it.
The NCC-2 uses two exceptionally flat-response phasing bridge systems and a unique system of
mirrored bridges in each channel. When phase delay is increased in one channel, phase delay is
simultaneously decreased in the other channel. Any level changes while adjusting phase are
automatically compensated in the other channel. There is virtually no channel balance error over the
entire range of the phase control.
The NCC-2 has a dynamic range up to 30 dB (1000 times) better than other popular noise canceling
systems. It also has provisions for further improvements in exceptionally strong signal
environments.
The Channel B phase, normally at 180 degrees, can be inverted to 0 degrees with the B PHASE
Switch, to cover all phasing possibilities. This switch typically inverts a perfect null to a perfect
peak in signal response.
The phased signals from Channel A and Channel B are mixed in the final Signal Combiner. This
phased receive output is delivered only via the RADIO connector, as protected by the RTR Receive Transmit Relay.
The NCC-2 MAIN ANT IN and RADIO connectors that handle transmit RF, and the Phase
Combiner Output, are managed by the high-speed RTR relay. This is a reverse-logic relay which
prevents reception of the phase receive signals unless certain connections are met, thereby
preventing the transmitted signal from reaching the Phase Combiner.
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In Figure A, the NCC-2 is in MAIN ANT mode or transmit mode, the MAIN ANT IN is internally
connected to the RADIO when the power is turned Off.
The unit stays in the MAIN ANT mode and the RTR LED goes to Red when:
An antenna is connected to MAIN ANT IN
A coaxial cable is connected from the transceiver RF output to RADIO
The Power switch is set to On
The RTR mode switch is in Main On momentary or On position (not center position)
There is a keying line cable from the transceiver to the RADIO PTT – RX ENABLE
connector. Even when the NCC-2 is turned On the Red LED will be dark when no keying
cable is connected. This is a reminder to install the keying cable.
Figure A
NOTE: No reception of the Phase Combiner output is possible when the keying line is not
connected. Exception* - See page 9
When the NCC-2 is in the MAIN ANT mode, and even when independently jumper enabled, NCC2 input DC voltage (+13.6 to +21 Vdc) is interrupted and NOT fed onto either the CH A RX ANT
IN and/or CH B RX ANT IN to operate Active antenna(s) – See section on Internal Jumpers.
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In Figure B, the NCC-2 is in RX Enabled Mode and the RTR LED turns to BLUE, allowing the
RADIO to be connected to the CH A and CH B Phase Combiner output. This mode, the receiveenabled condition depends upon all of these items:
A coaxial cable is connected from the transceiver RF output to RADIO (or from
transceiver RX ANT IN)
The Power switch is set to On
The RTR mode switch is set to the Norm position
The transceiver amp keying line is connected to RADIO PTT/RX ENABLE, shield to
transceiver chassis, center NOT grounded
The properly connected transceiver is NOT in the transmit mode
When the NCC-2 is RX Enabled Mode, the Phase Combiner signals are sent to the transceiver
connected to RADIO. Also in RX Enabled Mode, these conditions are enabled, as shown in Fig B.
The MAIN ANT IN signal is connected to the MAIN ANT OUT.
When independently jumper enabled, NCC-2 input DC voltage (+13.6 to +21 Vdc) is fed
onto the CH A RX ANT IN and/or CH B RX ANT IN to operate Active antenna(s)
Figure B
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IMPORTANT NOTE:
There are three crucial uses of the NCC-2 MAIN ANT OUT:
1. When using the NCC-2 to phase the transmit antenna with a receive antenna, the included
BNC patch cable MUST be installed to connect the MAIN ANT OUT into the CH A RX
ANT IN. This is required to feed the transmit antenna’s received signal back in, to
accomplish phasing of that signal with the receive antenna signal that is connected to CH
B RX ANT IN.
See the warning below.
2. When using the NCC-2 MAIN ANT OUT to send the transmit antenna received signal to a
second receiver only, when phasing two receive antennas.
3. When using the NCC-2 MAIN ANT OUT to send the transmit antenna received signal to
an external splitter to share it between a second receiver and CH A RX ANT IN, when
phasing MAIN ANT with one receive antenna.
See the section System Connection Diagrams for details
Warning: DO NOT set “BIAS TEE ENABLE” jumper on RTR-2 PCB right board when the
MAIN ANT OUT is connected to CH A RX ANT IN as described above. See section entitled
Internal Jumpers.
The NCC-2 will immediately revert to MAIN ANT mode, Figure A, RADIO to MAIN ANT IN
as soon as:
The transceiver is keyed to transmit, with a ground on transmit on the keying line center
conductor
The keying line is removed
The POWER is turned Off
The MAIN ANT transmit mode cannot occur when the Exception* condition exists.
*Exception: A keyed condition can be set internally, if the NCC-2 is NEVER going to
be connected to a Transceiver RF OUTPUT, but ONLY to a dedicated
Receiver. For NCC-2 applications where ONLY receive antennas are used,
or for AM DX and SWL operations, the “Force Ground” internal jumper
can “semi-permanently” disable the MAIN ANT transmit and enable
NORM.
See the Internal Jumpers section.
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Understanding Noise and Interference
Before we can use the NCC-2, we need to understand the challenges for operations on HF. Noise
limits our ability to hear a weak signal on the lower bands. Noise is often an accumulation of many
unwanted signals. Noise from antennas is generally a mixture of local ground wave and ionosphere
propagated noise sources, although many locations suffer with dominant local noise sources.
Noise is generated by randomly polarized sources. Noise polarization is filtered depending on the
method of propagation:
Noise arriving via the ionosphere is randomly polarized. Noise arrives with whatever
polarization the ionosphere favors at the moment. Noise from a distant source has the same
characteristics as a "good" signal.
Sources within a few wavelengths of the antenna arrive randomly polarized. The noise does
not have a dominant polarization and it can either be electric or magnetic field dominant.
Local noise can also be random or directional in nature. Every effort must be made to locate
sources of noise that could be eliminated at the source. Dimmer switches, electric timers,
security lights, and many other items can be sources of unwanted noise. Plasma televisions
are becoming more popular and are a known generator of unwanted noise interference.
Ground wave noises arriving from a significant distance are vertically polarized. The path
along the earth "filters out" and removes any horizontally polarized signals. Horizontal
electric field components are "short circuited" by the conductive earth as they propagate and
are eliminated.
With the exception of ground wave-propagated noise, receiving antenna polarization effects are not
predictable. It is possible vertically polarized antennas may be quieter than horizontally polarized
antennas. Either may be true at different times.
It may be difficult to remove noise with any device when:
Noise and desired signals come from the same direction and elevation angle
Both antennas don’t hear the same noise
The noise source is moving around, or noise sources are coming from several directions at
the same time.
Reducing Noise and Interference
Unlike a conventional noise blanker, the NCC-2 is designed to reduce noise or interference before it
gets to the receiver. The NCC-2 can be effective on all types of noise, including interference
(QRM) from unwanted signals. The NCC-2 allows the user to continuously adjust both phase and
amplitude when combining two antenna inputs. The signal output to the receiver is the addition or
subtraction of signals from two separate antennas. Unwanted directional noise can be removed or
unwanted signals can be cancelled. Desired signals can be peaked or enhanced.
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The phasing method of signal enhancement or rejection has several advantages.
Interference much stronger than a desired signal can be completely removed without affecting
the signal.
The NCC-2 can be effective with all types of interference and all modes.
Signals can be peaked instead of nulled.
The number of cases where phase nulling can reduce or eliminate interfering signals cannot be overemphasized. The null can be steered to knock out overloading signals, stations with key-clicks,
splatter and intentional jamming noises. There will also be a time when the interfering pile-up can
be nulled to reveal the desired DX station signal coming from another direction.
Selecting Antennas
The NCC-2 generally works best when both antennas have similar patterns, polarization, and
Signal-to-Noise ratios. For the most effective nulling of noise, the antennas on both the A and B
inputs must hear the same unwanted noise and should have similar polarization. You may have to
experiment to find the best antenna, but successful operation more commonly occurs with similar
antennas.
Reducing of distant interference: Close element spacing is more desirable. Close spacing
produces a single null that is wider and more stable. Spacing of 1/4-wavelength or less is most
desirable when nulling distant interference or peaking distant signals. Spacing larger than 1/4wavelength can, at your operating frequency, causes multiple nulls in the patterns.
Reducing of a local noise source: Best performance occurs when the noise antenna "hears" the
noise much louder than it hears desired signals. The noise antenna needs to pick up the largest
amount of noise possible, so it should be located as close to the noise source as possible. In this
case the polarization is unimportant; whatever polarization hears the noise best. The spacing
between antennas, that are being phased together, can be any convenient distance within one
wavelength.
Receiving Antennas
The performance of the NCC-2 is largely dependent on the receiving antennas and their installation.
Please carefully read this section and make adjustments or changes to your antennas before using
the NCC-2.
The NCC-2 will function with almost any combination of antennas but it works best when antennas
have reasonably similar directional patterns. Optimum antenna spacing will vary with the
frequency band and what you are trying to accomplish. There are two general rules for antenna
spacing:
If antennas are too close together (less than 1/10-wavelength), a very stable deep null can be
produced but the system will lose gain or sensitivity.
If the antennas are too far apart (generally more than 1-wavelength) the nulls and peaks in the
pattern will become so sharp it might become impossible to maintain nulls or peaks on sky
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