DX Engineering NCC-1 User manual

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Receive Antenna Phasing
Controller
DXE-NCC-1
DXE-NCC-1-INS Rev 7b
© DX Engineering 2017
1200 Southeast Ave. - Tallmadge, OH 44278 USA
Phone: [phone] ∙ Tech Support and International: [phone]
Fax: [phone] ∙ E-mail: [email protected]

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Table of Contents
Introduction
3
Features
4
Receiving Antennas
5
Antenna Polarization
5
Antenna Feedlines
5
Antenna Sensitivity
5
Antenna Bandwidth
5
Combining Antennas to Improve Signal-to-Noise Ratio
6
Use with Beverage or Other Low Noise Antennas
7
Phased Verticals & Beverage Systems
8
Noise
10
Reducing Noise and Interference
10
Understanding Noise
10
Removing Noise
11
Front Panel Controls and Switches
12
Rear Panel Connections
13
Internal Jumpers
14
HD1 & HD2 - Antenna Power Enable/Disable
15
HD4 - Antenna Power Source
15
HD5 - TX Muting
15
Installation
16
Connections
16
NCC-1 Dimensions
17
Typical Connections to a Transceiver
18
Phase Nulling with a Transmit Antenna
19
Using two Active Receive Antennas and the RTR-1
21
One Active Receive Antenna, RTR-1 and Transmit Antenna
22
Operation
23
Using the NCC-1
24
Technical Description
25
Specifications
26
Appendix A
26
NCC-1 Connection Diagram for High Power Operation
27
NCC-1 Connection Connections for Remotely Powered Receive Antennas
28
Optional Items
29
NCC-1 Receive Filters
32
Receive Filters Graphs
33
Receive Filter Installation
42
Technical Support
44

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Introduction
The DX Engineering NCC-1 Receive Antenna Variable Phasing Controller is a two-channel receive
antenna phasing system. This sophisticated controller allows the user to combine and
independently adjust the phase and level of two antenna inputs, essentially creating a fully
adjustable phased array out of two similar receive antennas.
It can be used with existing or new
receiving antenna systems to improve or
enhance desired signals by adding
desired signals. It can also eliminate or
greatly reduce unwanted signals or noise
by phase nulling the unwanted signal
regardless of the signal or noise type.
The NCC-1 is fully compatible with the
DX Engineering Active Receive
Antennas. Using 102" whips as antenna
elements, these antennas can provide
excellent receiving performance from
100 kHz to 30 MHz. Two ARAV3-1P active receive vertical antennas can be phased to form a
vertically polarized array. The minimum useable spacing varies with local noise floor, but is
typically 1/10-wavelength. Maximum spacing for true unidirectional patterns is just over 1/4-
wavelength, although wider spacing is still very useable. Two ARAH2-1P active receive horizontal
antennas can be configured as horizontally polarized dipoles to form a two element horizontally
polarized receiving array.
The NCC-1 front panel controls provide repeatable directional pattern adjustments. Properly spaced
Active Receive antennas are useable over a wide range of frequencies, offering the best possible
phase nulling and peaking.
The NCC-1 can be used with many other combinations of receiving antennas including Single
and Reversible Beverages, Receive Four-Square Arrays, K9AY Loops, and more. It will
increase the directivity of any properly spaced combination of two similar antennas.
The NCC-1 is primarily designed for 500 kHz to 15 MHz use, although the useful operating range
extends from below 300 kHz to above 30 MHz.
Typical applications include:
Combining two similar non-directional antenna elements to create a directional pattern.
Combining two similar directional antennas to produce a better pattern.
Reducing overload or interference by removing or reducing a strong signal or noise
Reducing interference from distant signals or noise
Direction finding

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Features
Phase adjustable through at least 360 degrees in the primary design area
(500 kHz to 15 MHz)
Exceptional dynamic range - able to handle strong signals without overloading
Low noise floor
Provisions for optional internal high pass and band pass filters
DC controls with smooth repeatable action. Expandable for remote or external control
Provides power and transmit muting for external active antennas
Antenna and Receive Outputs use RCA phono and Type F connectors to help prevent
accidental connection to live transmit feedlines
The NCC-1 has four main advantages over typical phased antenna systems:
The array can be electrically "steered" or directed using physically stationary antennas
The user can adjust direction and wave angle of either a null or peak
The response can change from a signal null to a perfect signal peak with a flip of a single
switch
Front panel adjustments compensate for less-than-ideal installations, making a directional
array possible in most situations
NOTE: The NCC-1 is a Receive-Only phasing system. It is designed to go between
the receiver input port of a radio or transceiver and two receiving antennas.
Do NOT transmit through the NCC-1 
If transmitted energy is ever allowed to reach the antenna or receive output ports of the
NCC-1, serious damage may result in a burned out unit.
If this occurs either by intermittent misuse, neglect, or accident, any warranty would be
voided and your NCC-1 may not be repairable.
Operation of the NCC-1 with Active Receive Antennas in close proximity to transmit antennas (1/10-
wavelength minimum) and high power operation with a linear amplifier requires additional optional
equipment. See Appendix A for details.
The NCC-1 is not a Digital Signal Processor (DSP) unit and it is not a Noise Blanker. The NCC-1 is a
receive signal RF phasing controller with exceptionally low noise, high dynamic range, level control and
phasing range.

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Receiving Antennas
The performance of the NCC-1 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-1.
The NCC-1 will function with almost any combination of antennas but it works best when INPUT
Aand Bantennas 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 wave signals. With very wide spacing, signals will fade in and out more rapidly with
ionospheric changes.
Antenna Polarization
It is generally not a good idea to mix polarization of antennas. Although this scheme can work
when nulling a ground wave signal or noise, mixing polarizations generally makes nulls or peaks
more difficult to find and maintain. When receiving skywave propagated signals, mixing a
horizontal antenna with a vertical antenna almost always increases fading.
Antenna Feedlines
It is not necessary to use any special length of feedline with antennas used in this system or for
antennas to be "resonant" or physically large. The front panel controls will compensate for feedline
lengths. You should still use a good feedline and make good connections. DX Engineering
recommends DXE-F6 75 Ω CATV style cable with weather-tight connectors such as DXE-SNS6
Snap-N-Seal, both available from DX Engineering.
Antenna Sensitivity
Receiving antennas should not have excessive signal level or gain. They only need enough gain or
signal level to have very weak signals limited by external noise. Too much signal level from
antennas is actually not good. Normally we should just hear a slight increase in noise (or weak
signal) from no antenna connected to having one connected. We would then clearly hear a noise
floor increase. For best weak signal reception, background noise of antennas should be around 5 dB,
or about 1 S-Unit, above the NCC-1 noise floor.
The NCC-1 is a very good match for DX Engineering Active Antenna arrays and closely matches
their dynamic range. Higher noise floor antennas can be also be successfully used due to the built-in
front panel adjustable attenuators.
Antenna Bandwidth
Wider bandwidth antennas produce the most stable and reliable performance. Very narrow
bandwidth antennas do not work as well. A small resonant loop will be very narrow in response and

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will shift phase rapidly with frequency changes. This means temperature changes and frequency
changes will both require more frequent readjustment of the NCC-1 controls. (Exceptionally wide
spaced antennas also produce a similar effect, as will mixing of antenna polarizations in one
system.)
Combining Antennas to Improve Signal-to-Noise Ratio
If your location is limited by noise coming from many directions, you can still use the NCC-1 to
enhance signals. The following guidelines apply when enhancing signals:
Both antennas must hear the desired
signal with similar signal-to-noise ratios.
Don’t combine an antenna that hears the
signal with one that can’t hear it at all.
Adding desired signals from a "quiet
antenna" to a "noisy antenna" only
makes the quiet antenna noisy.
The most reliable and consistent
performance occurs with antenna
spacing less than 1/4-wavelength when
antennas are in line with the desired
direction, and less than 1-1/2-
wavelengths apart when antennas are
spaced at right angles to desired
directions.
Best sensitivity occurs when antennas
are more than 1/10-wavelength apart
when the antennas are in line with the
desired direction, and more than 1/2-wave apart when broadside to the desired direction
When enhancing desired signals, it is preferable to locate both Aand BINPUT antennas as
far from local noise sources as possible.
Using a vertically polarized antenna in combination with a horizontally polarized antenna
almost always increases fading over an ionospheric path.
Note: In cases where one antenna is significantly noisier than the other, it is often possible
to use the quieter antenna for the signal and cancel noise with the noisy antenna.
The same noise must appear on both antennas.

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The NCC-1 generally works best when both antennas have similar patterns, polarization, and S/N
ratios. You may have to experiment to find the best antenna, but successful operation occurs more
often with similar antennas.
Use with Beverage or Other Low Noise Antennas
The NCC-1 is probably most useful when used to enhance reception on lower frequencies. The
NCC-1 is often useful even if the station already employs low noise directional receiving arrays.
A suggested method follows:
Connect one Beverage or other similar low noise receiving antenna to INPUT A
Connect another Beverage or another low noise receiving array to INPUT B
Connect the NCC-1 RECEIVER connector to the receiver's input line.
If you are using a Reversible Beverage, run two feedlines back to the NCC-1 INPUT
connections. Then use the NCC-1 to control the directivity and nulls.
A Reversible Beverage system, like the DX Engineering DXE-RBS-1, is ideal to use when both
feedlines are run to the NCC-1. It can reduce interference, strong signals or noise from one
direction, while peaking reception in the other, improving the Signal-to-Noise Ratio in the desired
direction.

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Phased Verticals & Beverage Systems
This unit is an adjustable phasing network that combines two antenna input ports. Antennas can be
combined to change or improve directional patterns. Pattern changes can be used to improve signal-
to-noise ratio even in the absence of strong noise.
It is possible to combine almost any type of receiving antennas into a large array.
For example:
Two verticals or dipoles can be combined to produce a steerable array capable of peaking or
nulling signals.

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Two parallel Beverage antennas spaced an eighth to quarter wave apart with an eighth to
quarter wave stagger in the desired direction can be combined to improve front-to-back ratio
or steer nulls to the direction of unwanted signals or noise.
The best system is often found by planning, although it is often worth experimenting.
Using this type of directional phased antenna array you may record phase settings to null stations
from known directions. It is then possible to make a direction chart. With optimal antenna spacing it
is possible to tell direction within several degrees.

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Noise
Reducing Noise and Interference
Unlike conventional noise blankers, the NCC-1 is designed to reduce noise or interference before it
gets to the receiver. The NCC-1 can be effective on all types of noise, including interference
(QRM) from unwanted signals. The NCC-1 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.
Unlike conventional noise blankers, 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-1 can be effective with all types of interference and all modes.
Signals can be peaked instead of nulled with a flip of a switch.
Note: Failure to follow guidelines outlined in sections below will often result
in reduced nulls or reduced enhancement of distant signals
Understanding Noise
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 at whatever
polarization the ionosphere favors at the moment. Noise has the same ratio of electric to
magnetic fields 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.

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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. The opposite is also true.
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
Removing Noise
The NCC-1 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.
Removal 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 1/4-
wavelength can, at your operating frequency, cause multiple nulls in the patterns.
Removal of a local noise source: Best performance occurs when the noise (B INPUT) antenna
"hears" the noise much louder than it hears desired signals. We want the noise antenna 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 can be any convenient distance within one wavelength.

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Front Panel Controls and Switches
POWER: Turns power off and on. When powered-off, INPUT Bis disconnected and
INPUT A is connected directly to the receiver, removing antenna power.
 Two Attenuator switches reduce gain in ten dB steps. The steps are 0, -10, -20, and –30 dB.
The left switch sets INPUT “A” attenuation (primary antenna), the right switch sets
INPUT “B” (secondary antenna) attenuation.
BALANCE: Provides fine adjustment of gain. It is used to balance or equalize signal levels
from INPUT Aand B. The BALANCE control provides anywhere from zero to 12 dB
attenuation on either Aor B. This control has the same “feel” and operation as the balance
controls on conventional stereo systems. Maximum gain on both channels occurs when the
BALANCE control is positioned in the center of the range, and gain is reduced as the knob is
rotated away from a particular channel. If you rotate the BALANCE control clockwise, the
gain of INPUT Ais reduced. Without precise signal or noise level balancing between
INPUTS A and B, noise nulling or canceling will not be as deep as possible.
PHASE: Changes the phase delay relationship between INPUT Aand B. The resulting phase
shift will change the position of nulls or directions of peak signal response.
INPUTS: Reverses A(primary) and B(secondary) antenna inputs. This is done after
attenuation adjustment. Changing this switch is the electrical equivalent of physically
swapping antenna element locations.
BAND: Optimizes phase range and selects the filter boards used. "L" selects the low optional
filters. "H" selects the high optional filters. See page 32 for optional filter information.
B PHASE: Moves B INPUT phase by exactly 180 degrees.
NORM is 180 Degrees or no phase reverse, REV is 0 Degrees.

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Rear Panel Connections
INPUT A: Primary Receive Antenna –Phono and F style connector. Phono and F style
connectors are used to prevent accidental connections to transmitting equipment.
INPUT B: Secondary Receive Antenna –Phono and F style connector. Phono and F style
connectors are used to prevent accidental connections to transmitting equipment.
The NCC-1 can supply T/R Controlled DC power to active antennas through the INPUT A
and B coaxial lines. DC power can come from either the NCC-1 supply or through a separate
rear panel power connector. The NCC-1 has an internal high-speed solid-state switch that will
switch up to 30 Volts DC Positive voltage at 150 mA per input channel for powering receive
antennas. (See Appendix A for special instructions for remotely powered receive antenna
systems that require 15 to 30 Vdc)
RX OUT: Receive Signal output to receiver –Phono and Type F connector. These types of
connections work well with most transceiver and receiver RX ANT Inputs.
Main Power: The NCC-1 requires well-filtered +13.8 to +15 Vdc @ 1A minimum. The NCC-
1 should be connected to a well filtered and regulated +13.8 to +15 Vdc @ 2 A power
source. A 2.1 mm plug, center positive power plug is included with the NCC-1. External high
current and well filtered sources, such as station power supplies, should be appropriately fused
at the power source. The use of switching power supplies is discouraged due to the presence of
noise in their output.
ANT PWR: –2.1 mm jack. Supplies external voltage to INPUT Aand INPUT Bfeedlines to
power active antennas or other devices. Allowable voltage range is +13.8 to +30 Vdc with 300
mA maximum load current, well filtered & fused for both INPUTs combined. A 2.1 mm plug,
center positive power plug is included with the NCC-1.
T/R CTRL: –Phono connector. Activated by pulling to ground or by external application of
voltage (internal jumper selectable). When activated INPUT A is bypassed directly to receiver
and INPUT B disconnects. Activation also removes antenna power from both INPUTs.
The T/R CTRL line can be configured to disable the NCC-1 and remove power from antennas
attached to the NCC-1 when pulled either low or high. The normal switching threshold voltage

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is +3 Vdc. A valid T/R CTRL input disconnects INPUT Band bypasses INPUT Adirectly to
the RX OUT. Antenna voltage is also removed from input ports when T/R CTRL is activated.
This reduces chances of damaging the NCC-1 when the receiving antennas are located close to
transmitting antennas and allows the DX Engineering ARAV series active antennas to mute,
protecting them from transmitted energy.
Internal Jumpers
The NCC-1 motherboard has jumpers that configure the antenna jack power and transmitter muting
options. With the unit unplugged and no power connected, remove 6 screws on each side of the
cover and lift it off.
To configure the jumpers, turn the NCC-1 so the components match the orientation of Figure 1.
The Default jumper positions as shown:
HD1 –Antenna A Power: OFF
HD2 –Antenna B Power: OFF
HD4 –Antenna Power Source: 13.8V
HD5 –TX Mute Polarity: NOR or Low (Most transceivers) Both Jumpers Installed.
Figure 1: NCC-1 Jumper Locations
The jumpers are small plugs that fit over and connect two of the pins on the associated header. The
jumper is removed by pulling straight out and installed by aligning with two pins and pushing
straight in to fully seat the jumper.

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HD1 & HD2 - Antenna A and B Power - Activate/Disable
Jumpers HD1 and HD2 (both three pin headers) activate or disable power on the feedline to
INPUTs A and B.
HD1 is in the front corner of the circuit board directly behind the PHASE control and BAND
toggle switch. This header controls power to the INPUT A port. When this
jumper is on the middle and forward pins, power is OFF to INPUT port A as
shown in Figure 1. When this jumper is moved and connects the middle and
rearmost pins, power is applied to INPUT port A.
HD2 is along the edge of the board directly towards the rear from HD1. This header controls
power to INPUT port B. When this jumper is on the middle and forward pins,
power is OFF to INPUT port B as shown in Figure 1. When this jumper is
moved and connects the middle and rearmost pins, power is ON to INPUT
port B.
Note: During TX Mute activation, power to the active antennas is disabled
regardless of the Antenna Power jumper settings.
HD4 - Antenna Power Source
The HD4 jumper determines the source of active antenna power, either through the NCC-1
power supply or the ANT PWR jack on the rear panel. HD4 is a three pin header located at the
rear of the main circuit board near the power jacks and the two large power
transistors that are bolted to the main circuit board. When the jumper on
HD4 is positioned on the middle and 12V pins (factory default position), as
shown in Figure 1, antenna power comes from the NCC-1 main power supply. When the
jumper on HD4 is positioned toward EXT, the antenna port power comes from the ANT PWR
jack. Only when an alternative power source is used for active antenna devices powered via
feedline connected to INPUT A and B, should the HD4 jumper be set to EXT.
HD5 - TX Mute Polarity
HD5 controls the logic state that activates the TX Mute polarity function and is located just
below the rear panel Ext Control connector. HD5 is a four pin header.
When HD5 has two pin jumpers in both positions completely filling
the header, operation is normal. A logic low activates the TX Mute.
This means any voltage above 3 volts positive or an open circuit allows the NCC-1 to function
normally. Power is available for use at antenna ports.
Anything below 1 volt positive (including a "Ground on Transmit") causes the NCC-1 to mute.
Power is removed from the antenna ports and the INPUT Aport is connected directly to the
receiver port. Switching time is about 2 ms.

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If one shunt on HD5 is installed on the center two header pins, logic is reversed. Positive
voltage over 3 volts applied to the TX Mute will force the NCC-1 into
standby and disable the antenna power feature. Any voltage below one volt,
including a grounded condition, will allow the unit to function normally.
Installation
Please read the following section carefully.
The best location for this unit is at the operating position with easy access to the controls since you
will be using the S-Meter on your receiver while adjusting the NCC-1.
Connections
Make connections to the NCC-1 as follows:
Connect a fused power source of +13.8 to +15 Vdc @ 2A, well filtered &
fused to the 2.1 mm center-positive MAIN PWR jack using the included 2.1
mm plug. Well filtered and fused station power is recommended.
Connect a receiving antenna to the INPUT A F style or Phono connector.
Connect a second receiving antenna (or local noise source antenna) to the INPUT B F style or
Phono connector.
Connect a standard shielded audio style cable between the T/R Control Phono connector and
an external transmit control source.
oBy default, the NCC-1 is set to mute when the T/R Control line is pulled LOW.
This is normal station wiring. Many modern transceivers have a rear panel amplifier
control jack typically labeled as "TX", "AMP", "Send”, “Control" or "TX GND" that
pulls low when the transceiver is keyed. (Check the user manual for your radio)
Note: Internal jumpers (HD5) can be changed to allow the NCC-1 to use an
inverted + 5 to +50 Vdc amplifier control line. This is an unusual configuration.
oT/R Control line on the NCC-1 can be paralleled on the same control line used for
the amplifier provided the amplifier does not load the line when not transmitting. If
the amplifier does load the line, you will have to add a blocking diode.
oThe DX Engineering TVSU-1A programmable sequencer can also be used to
provide the proper transmit/receive switching for an amplifier, transceiver, and the
NCC-1. Refer to Appendix A for the high power installation connection diagram.

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Connect the RX OUT jack to a receiver or the transceiver receive-only antenna port.
Do not connect the RX OUT connector of the NCC-1 to a transceiver RF output!
If desired, connect a fused external power source to the ANT PWR 2.1
mm center-positive jack if you are not using the NCC-1 supply to power
antennas (HD4 Jumper Selectable). The allowable voltage range is
+13.8 to +30 Vdc (well filtered & fused) with 300 mA maximum load
current for both INPUTs combined. The DX Engineering DXE-
ARAH2/V3 Active antennas typically require a nominal 13 Vdc @ 50
mA each. See Appendix A for special instructions and a diagram for
remotely powered antennas that require +15 to +30 Vdc.

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Typical Connections to a Transceiver
Figure 2 shows the normal default connection of the NCC-1 to a typical Transceiver with Receive
Input. Antenna Inputs A and B may be connected to any receive antennas as discussed in the
Introduction, and in the following pages.
Power is supplied to the Active Receive Antennas by setting the NCC-1 internal jumpers according
to instructions setting in Figure 2.

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Phase Nulling with a Transmit Antenna
As described throughout this manual, the primary advantage of using receiving antennas for phase
nulling of unwanted signals is to enhance the signal to noise ratio (S/N) of the desired weak signal.
Wherever possible, the use of low signal, low noise receiving antennas will generally produce
superior results, especially with the NCC-1.
HF and Low Band (160, 80, 40 meters) transmitting antennas usually receive high levels of noise
and when used for phasing, the result is a noisy signal.
However, there are cases where phasing with a transmit antenna is desired. Some fortunate
Amateur Radio Operators reside in locations where the ambient noise levels on their transmit
antenna is low enough that their benefits from phase nulling and peaking will be maximized.
Many radio enthusiasts live in areas where some type of noise or strong signal interference is
preventing normal or weak signal DX receive operations. Some Amateur Radio Operators must use
a transmit antenna for nulling out undesired signals because receive only antennas will not 'hear' the
desired signal. Many of the low noise advantages of the NCC-1 will be hidden by strong ambient
noise if a transmit antenna is used as a receive antenna for the NCC-1.
If your transceiver has both Receive Antenna Input (RX IN or RX ANT) and a Receive Output (RX
OUT), you may use the transmit antenna receive signals that are available from that port for phasing
the transmit antenna against those from a receive antenna. Figure 3 demonstrates the connection
scheme for phasing a receive antenna against a transmit antenna. Special adjustments to the
attenuator and balance may be required. Additional attenuation of the RX Out to INPUT B may be
required in certain conditions, so the signal or noise level coming from the transmit antenna does
not override the signal or noise level coming from the receive or noise "sense" antenna.
If used, active antenna power may be derived internally from the NCC-1 and is automatically
disconnected during transmit by setting jumpers HD1 and HD4 per the chart listed in Figure 3.
If a non-powered, passive receive antenna is used, jumpers should be in the default position as
supplied. Refer to Figure 1.

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Phase Nulling with a Transmit Antenna and a single Active Receive Antenna