Our HAM Station

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Thanksgiving Weekend NPOTA Fun

Posted: 27 Nov 2016 10:18 AM PST
https://stationproject.wordpress.com...end-npota-fun/

Fred, AB1OC, Operating Mobile in Minuteman National Historical Park, HP27

With only 1 month to go in theÂ*ARRL NPOTAÂ*event and some free time this
Thanksgiving weekend, Fred and I decided to hit the road with our Mobile HF
Station to activate some new parks. Â* Â*We activatedÂ*two nearby parks, each
less than 1 hour away from our home, Â*Lamprey Wild and Scenic River,Â*Â*WR23,
near Epping, NH, andÂ*Minuteman National Historical Park, HP27, near
Concord, MA. Â* Â*There were close to 900K QSOsÂ*made overall in the NPOTA
program as of Thanksgiving day and we also wanted to help the cause to get
to 1 Million NPOTA QSOs by years end.
Map of Lamprey Wild and Scenic River

On Saturday, we drove to Epping, NH, where we activated Lamprey Wild and
Scenic River. It was a rainy day, but we still enjoyed the scenic drive
along the river. We drove along the river until we found a place by the
river to park and operate. The bands were not great, with a K-index of 4
and a high A-index. Despite the conditions, our activation was a success.
We operated on both 20m and 40m SSB and made a total of 307 QSOs over 3
hours.
View of Countryside in Minute Man National Historical Park

I work in Burlington, MA and often travel between Burlington and Waltham,
MA for meetings. Â*Each time I passed by Lexington on I-95 I saw the sign
forÂ*Minute Man NHPÂ*and thought it would be fun to do a NPOTA activation
from there. Â*We activated the park on Saturday. WeÂ*entered the park
fromÂ*the Concord, MA endÂ*and were pleasantly surprised to see some nice
countryside in the middle of a suburban area of Massachusetts, not far from
Boston.
AB1QB logging for AB1OC/M during the NPOTA activation.

WeÂ*operated from a parking lot in the park from mid afternoonÂ*until
dark. Â*The bands were a little better on Saturday and we were able to get
239 contacts into the log, mostly US but also worked stations from Spain,
Jamaica, Aruba and Puerto Rico.

We have enjoyed activating 8 National Parks so far in the NPOTA event. Â*We
are planning another activation between Christmas and New Years of multiple
parks before the end of the event on December 31.
Filed under: Mobile HF, NPOTA

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Fall Antenna Projects - A New Low-Band Receive Antenna System

Posted: 27 Nov 2016 08:34 AM PST
https://stationproject.wordpress.com...enna-projects/

NCC-1 Receive Antenna System Control Unit and Filters

Anita and I like to take advantage of the mild fall weather to do antenna
projects at our QTH. We have completed two such projects this fall the
installation of a Two-Element Phased Receive System and a rebuild of the
control cableÂ*interconnect system at the base of our tower.
NCC-1 Receive Antenna System Components

Our first project was the installation ofÂ*aÂ*DXEngineering NCC-1 Receive
Antenna System. This system uses twoÂ*receive-only active vertical
antennasÂ*to create a steerable receive antenna system. The combination can
work on any band from 160m up to 10m. We set ours up for operation on the
80m and 160m bands.
NCC-1 Receive System Antenna Pattern

TheÂ*NCC-1 SystemÂ*canÂ*be used to peak or null a specific incoming signal. It
can also be applied to a noise source to null it out. The direction that it
peaks or nulls in is determined by changing the phase relationship between
the twoÂ*Active Antenna ElementsÂ*via theÂ*NCC-1 Controller.
NCC-1 Filter Installation

The first step in the project was to open theÂ*NCC-1 Control UnitÂ*to install
a set ofÂ*80m and 160m bandpass filter boards. These filters prevent strong
out-of-band signals (such asÂ*local AM radio stations) from overloading the
NCC-1. The internalÂ*switches were also set to configureÂ*the NCC-1
toÂ*provide power from an external source to the receive antenna elements
through the connecting coax cables.
Installed Active Receive Antenna Element

The next step in the project was to select a suitable location for
installing theÂ*Receive Antenna Elements. We choose a spot on a ridge which
allowed the two Antenna Elements to be separated by 135 ft (for operation
on 160m/80m) and which provided a favorableÂ*orientationÂ*toward both Europe
and Japan. The antenna elements use active circuitry to provide uniform
phase performanceÂ*between eachÂ*elements 8 1/2 foot whip antenna and the
rest of the system. The antenna elements should be separated by a 1/2
wavelength or more on theÂ*lowest band of operation from any towers or
transmit antennas to enable the best possible noise rejection performance.
Received Antenna Element Closeup

The twoÂ*Antenna ElementsÂ*were assembled and installed on 5 ft rods which
were driven into the ground. To ensure a good ground for the elements and
to improve their sensitivity, we opted to install 4 radials on each antenna
(the black wires coming from the bottom of the unit in the picture
above).Â*The Antenna Elements are powered throughÂ*75 ohm flooded coaxÂ*cables
which connect them to theÂ*NCC-1 Control UnitÂ*in our shack. The coax cable
connections in our setup are quite long Â*the longer of the pair being
approximately 500 ft. The use of flooded coax cable allows the cablesÂ*to be
run underground or buried. Should the outer jacket become nicked, the
flooding glue inside the cable will seal the damage and keep water out of
the cable.
Receive RF Choke

It is also important to isolate the connecting coax cables from picking
upÂ*strong signals from nearby AM Radio stations, etc. To help with this, we
installedÂ*Receive RF ChokesÂ*in each of the twoÂ*coax cables which connect
the Antenna Elements to the NCC-1. These chokes need to be installed on
ground rods near the Antenna Elements for best performance.
Underground Cable Conduit In Our Yard

We ran the coax cables underground inside cable conduits for a good portion
of the run between the antenna elements and our shack. TheÂ*conduits were
installed in our yardÂ*when we built our tower a few years back so getting
the coax cables to our shack was relatively easy.
Receive Antenna Coax Ground System

The last step in the outdoor part of this project was to install a pair
ofÂ*75 ohm coax surge protectorsÂ*near the entry to our shack. An additional
ground rod was driven for this purpose and was bonded to the rest of our
stations ground system. We routed both of theÂ*75 ohm coax cablesÂ*from the
two Antenna Elements through surge protectors and into our
shack.Â*Alpha-Delta makes theÂ*copper ground rod bracketÂ*shown in the picture
for mounting the surge protectors onÂ*theÂ*ground rod.
Antenna Equipment Shelf In Our Shack (The NCC-1 Control Unit Is At The
Bottom)

The installation work in our shack began with the construction of a larger
shelf to hold all of our antenna control equipment and to make space for
theÂ*NCC-1. The two incoming coax cables from the Antenna Elements were
connected to the NCC-1.
microHAM Station Master Deluxe Antenna Controller

Antenna switching and control in our station is handled by aÂ*microHAM
System. Each radio has a dedicatedÂ*microHAM Station Master Deluxe Antenna
ControllerÂ*which can be used to select separate transmit and receive
antenna for the associated radio.Â*The microHAMÂ*system allows our new
Receive Antenna System to be shared between the 5 radios in our station.
Antenna Switching Matrix

The first step in integrating theÂ*Receive Antenna SystemÂ*was to connect the
output of theÂ*NCC-1Â*to theÂ*Antenna Switching MatrixÂ*outside our shack. We
added aÂ*low-noise pre-ampÂ*(shown in the upper left of the picture above) to
increase the sensitivity of the Antenna System. The blue device in the
picture is aÂ*75 ohm to 50 ohm matching transformerÂ*which matches the NCC-1s
75 ohm output to our 50 ohm radios. The other two pre-ampsÂ*and transformers
in the picture are part of our previously installedÂ*8-Circle Receive
Antenna System.
Multi-Radio Sequencer

The Antenna Elements must be protected from overload and damage from strong
nearly RF fields from our transmit antennas. In a single radio station,
this can be handled via a simpleÂ*sequencer unitÂ*associated with ones radio.
In a multi-op station such as ours, it is possible for a different radio
than the one which is using theÂ*Receive Antenna System to be transmitting
on a band which would damage the Receive Antenna System. To solve this
problem, we built aÂ*multi-radio sequencer using one of the microHAM control
boxesÂ*in our station. TheÂ*062 Relay UnitÂ*shown above has one relay
associated with each of the five radios in our station. The power to the
Receive AntennaÂ*SystemÂ*is routed throughÂ*all 5 of these relays. When any
radio transmits on a band that could damage the Antenna Elements, the
associated relay is automatically opened 25 mS before the radio is allowed
to key up which ensures that the systemsÂ*Antenna ElementsÂ*are safely
powered down and grounded.
NCC-1 Controls

So how well does the system work? To test it, we adjusted theÂ*NCC-1Â*to peak
and then null a weak CW signal on 80m. This is done by first adjusting
theÂ*BalanceÂ*andÂ*AttenuatorÂ*controls on the NCC-1 so that the incoming
signal is heard at the same level by both Antenna Elements. Next, theÂ*B
PhaseÂ*switch is set toÂ*RevÂ*to cause the system to operate in a signal
nulling configuration and theÂ*PhaseÂ*control is adjusted to maximize the
nulling effect on the target signal. One can go back and forth a few times
between theÂ*BalanceÂ*andÂ*PhaseÂ*controls to get the best possible null.
Finally, the incoming signal is peaked by setting theÂ*B PhaseÂ*switch
toÂ*Norm.
Peaked And Nulled CW Signal

The picture above shows the display of the targetÂ*CW signal on the radio
using the NCC-1 Antenna System. If you look closely at the lower display in
the figure (nulled signal) you can still see the faint CW trace on the pan
adapter. The difference between the peak and the null is about 3 S-units or
18 dB.
NCC-1 Used For Noise Cancellation

The NCC-1 can also be used to reduceÂ*(null out) background noise. The
picture above shows the result of doing this for an incoming SSB signal on
75m. The system display at the top shows anÂ*S5 SSB signal in the presence
of S4 S5 noise (the lower display in the picture). Note how clean the
noise floor for the received SSB signal becomes when the unit is set to
null the noise source which comes from a different direction than
theÂ*received SSB signal.

We are very pleased with the performance of our new Receive Antenna System.
It should make a great tool for DXing on the low-bands. It is a
goodÂ*complement to ourÂ*8-circle steerable receive systemÂ*which we use for
contesting on 160m and 80m.
Tower Control Cable Interconnects (Bottom Two Gray Boxes)

Our other antenna project was a maintenance one. We have quite aÂ*number of
control leads going to our tower. When we built our station, weÂ*placed
surge protectors at the base of our tower and routed all of our control
leads through exposed connections on these units. Over time, we found that
surge protection was not necessary and we also became concerned about the
effects that sunlight and weather were having on the exposed connections.
To clean all of this up, we installed twoÂ*DXEngineering Interconnect
EnclosuresÂ*on our tower and moved all the control cable connections inside
them.
Inside View Of Interconnect Enclosures

We began with a pair ofÂ*enclosures from DXEngineeringÂ*and we mounted screw
terminal barrier strips on the aluminum mounting plates in each enclosure.
The aluminumÂ*plates are grounded via copper strap material to our tower.
Closer Look At One Of The Interconnect Enclosures

The picture above shows one of the interconnection boxes. This one is used
to connectÂ*our twoÂ*SteppIR DB36 Yagi AntennasÂ*and some of the supporting
equipment. The barrier strips formÂ*a convenientÂ*set of test points for
troubleshooting any problems with ourÂ*equipment on the tower. There are
almost 100 control leads passing through the two enclosures and this
arrangement keeps everything organized and protected from the weather.

With all of our antenna projects complete, we are looking forward to a fun
winter of contesting and low-band DXing.

73,

Fred,Â*AB1OC


Filed under: Antennas and Feedlines, Shack Design and Construction,
Station, Station Automation, Station Design, Station Performance, QSOs and
QSL'ing, Tower Construction and Maintenance Tagged: Antennas and Feedlines,
Pan Adapter, Shack Design and Construction, Station Automation, Station
Design, Station Performance, Tower Construction and Maintenance, Yagi