A Portable Satellite Station Part 4 – 2.0 Station First Contacts!


Station Packed and Ready for Transport

Station Packed and Ready for Transport

With our new 2.0 Satellite station built, tested, and packed; we were ready to try it in a portable environment. Fortunately, the Nashua Area Radio Club had a Technician License class coming up and we thought that the new station test would be a great way for our students to learn about Amateur Radio Satellites.

Satellite Status from AMSAT Website

Satellite Status from AMSAT Website

Final preparations included checking the operational status of potential satellites on the AMSAT website. The page shown above is like a spotting cluster for LEO Satellites – it shows satellite activity as reported by HAM satellite operators. Using this information, we configured MacDoppler to track the active satellites.

Satellite Pass Predictions

Satellite Pass Predictions

Next, we used MacDoppler to generate pass predicts for the weekend of our Technical Class. We assembled this data for all of the potential satellites and color-coded the available passes to identify those which had the best chance of producing contacts.

With this done, we loaded our portable tower, antennas, and all of the rest of the gear into our pickup truck and transported it to the class site.

Sateliite Antennas Setup Portable

Satellite Antennas Setup Portable

The first step at the class site was to unload all of our gear and move the portable tower to a suitable location. We used a compass to orient the tower to true north and leveled it. We used the weight bags that we made up to anchor the tower securely and then installed the antennas, rotator loops, and control cables. The antenna system worked out very well in the portable environment and was easy to set up.

Satellite Antenna Details

Satellite Antenna Details

Here’s a closer to look at the LMR-400 UF coax cables which connect the antennas to the rest of the system. The loops just behind the antennas are necessary to keep the coax from effecting the pattern of the antennas. The coax cables shown were made long enough to allow the antennas to be rotated through their full travel in the azimuth and elevation directions without binding.

Satellite Station Portable - Radio and Supporting Equipment

Satellite Station Portable – Radio and Supporting Equipment

The final step in the portable setup was to put the IC-9100 Transceiver and Supporting Equipment together in the building and check everything out. As soon as we got everything hooked up and working, we heard an ON4 station through FO-29 which was near the end of a low angle pass. A very good sign!

We took some time to fine tune the calibration of our rotators and to check the operation of the computer controls – everything checked out fine. The video above shows MacDoppler controlling the Azimuth/Elevation rotator and the IC-9100 Transceiver during the testing.

First Contact using New 2.0 Station (AO-85)

First Contact using New 2.0 Station (via AO-85)

With all the setup done, it was time to try to make our first contact. Fortunately, we did not have long to wait. We caught a medium angle pass of AO-85, a U/V Mode FM Easy Sat. With MacDoppler setup and tacking, we immediately heard contacts being made through AO-85. I gave a whistle and adjusted my uplink VFO until I heard my signal coming back through AO-85. I gave a quick CQ call and immediately got a response from Jonathan, NS4L in Virginia, USA! It took on a few seconds to exchange call signs and grid squares and our first contract with our new station was in the log.

Explaining Satellite System to License Class

Explaining Satellite System to License Class

Our Technician License Class students were very interested in the station. We spent some time explaining the setup and demonstrating how it worked. We made more contacts between our class sessions using AO-85 and FO-29 (a V/U Mode Linear Transponder Satellite). Our most interesting contact was with Burt, FG8OJ in Guadeloupe through FO-29. It was great to work DX using the new station during the first time we used it.

We learned several things during our first use of the new station. First, while the 35 ft. maximum separation allowed between the antenna system and the rest of the station is adequate in many applications, the antenna system’s close proximity to the building we were in blocked passes to the west of us with this separation. We are going make up a second set of feed lines using a pair of 100 ft. long 7/8″ hardline coax cables to allow for a greater separation in portable deployments such as this one.

We were glad that we had the Heil Pro 7 Headset with us and we used it for most of our contacts. The separate speaker allowed our students to hear the contacts well and the boom microphone on the Pro 7 Headset eliminated feedback due to our own voice coming back through the satellites. We improvised a mono to stereo converter cable to connect the Heil Pro 7 Headset to one of the two speaker outputs on the IC-9100 Transceiver. This allowed the radio to drive the separate speaker and the headphones at the same time.

We were glad to have the low-noise preamps available. These were especially useful during low-angle satellite passes and the sequencing setup that we built worked well.

All in all, our first test of our new 2.0 Portable Satellite station was a success. Our license classes students enjoyed learning about Amateur Satellites and had fun along with us making contacts through a few of them. Our next goal will be to get packet modes and APRS working with our setup. We plan to do another article in this series when this part of our project is completed. Other articles in this series include:

You may also be interested in the satellite station at our home QTH. You can read more about that here.

Fred, AB1OC

A Portable Satellite Station Part 2 – 2.0 Station Goals and Antenna System


M2 Antenna Systems LEO Pack On Display at Dayton 2016

M2 Antenna Systems LEO Pack on Display at Dayton 2016

We came upon the M2 Antenna Systems booth while walking around the exhibit halls at Dayton last year. M2 had one of their LEO Pack satellite antenna systems on display there. This got us thinking about building a new, more capable version of our portable satellite station. The LEO Pack is a relatively lightweight circularly polarized antenna system for working satellites using the 2 m and 70 cm bands. It turns out that AMSAT members can purchase the LEO Pack at a discount. Starting with the LEO Pack in mind, I began to lay out some goals for a new, 2.0 Portable Satellite Station:

  • Be capable of working all active Amateur LEO Satellites including those using linear transponders and digital modes
  • Be portable and manageable enough to be setup in an hour or less
  • Be simple enough to operate so that HAMs who are new to satellites can make all types of satellite contacts with a relatively short learning curve
  • Be manageable to transport and store
  • Utilize computer controlled antenna tracking to aim the antennas
  • Utilize computer control to manage radio VFOs to compensate for doppler shift
  • Be easy to transport and store
Computer Controlled Satellite Station Via MacDoppler

Computer Controlled Satellite Station via MacDoppler Software

We decided to take a computer controlled approach for both antenna aiming and Transceiver VFO management to meet our goal of making the station simple to operate for new satellite operators. After some research on the available options, we choose MacDoppler from Dog Park Software Ltd. for this purpose. MacDoppler runs under Mac OS/X and works well on our MacBook Air laptop computer which is very portable. This program also has broad support for many different rotator and transceiver platforms and is very easy to understand and use. Finally, the program features high quality graphics which should make the station more interesting to folks with limited or no experience operating through Amateur Satellites.

With the satellite tracking software chosen, we made selections for the other major components in the 2.0 Portable Satellite Station as follows:

I will explain these choices in more detail as our article series proceeds.

Glen Martin Roof Tower

Glen Martin 4.5′ Roof Tower

Our solution to making the antenna system portable is built around a Glen Martin 4.5′ Roof Tower. This short tower is a high-quality piece made of extruded aluminum parts. The tower is very sturdy when assembled and is light in weight. We added a pair of extended “feet” to the tower which are fabricated from 36″ x 2″ x 1 /4″ strap steel. This gives the tower a firm base to sit on and allows us to use sandbags to weight it down (more on this later).

Our chosen Yaesu G-500 AZ/EL Rotator is a relatively inexpensive Azimuth/Elevation rotator which is suitable for light-weight satellite antennas such as those in the LEO Pack. This rotator can be installed as a single unit on the top of a tower or separated using a mast. We choose the latter approach as it is mechanically more robust and helps to keep the center of gravity for our portable antenna system low for improved stability.

Yaesu G-5500 Elevation Rotator

Yaesu G-5500 Elevation Rotator

Separating the Yaesu AZ/EL rotator requires as short mast and a thrust bearing to be used. The mast was made from an 1-3/4″ O.D. piece of EMT tubing from our local hardware store. The thrust bearing is a Yaesu GS-065 unit. Both of these pieces fit nicely in the Glen Martin Tower. The thrust bearing provides support for the LEO Pack and G-500 elevation rotator and greatly reduces stress on the azimuth rotator. We also added a Yaesu GA-300 Shock Absorber Mount to the azimuth rotator. This part provides shock isolation for and reduces strain on the azimuth rotator during the frequent starts and stops which occur during satellite tracking.

LMR-400 Feed-lines And Antenna Connection Jumpers

LMR-400UF Feed-lines and Antenna Connection Jumpers

We decided to use LMR-400 UltraFlex coax throughout our antenna system. LMR-400UF coax provides a good balance between size, flexibility and loss for our application. To keep feed-line losses reasonable, we choose to limit the total length of the coax from the transceiver output to the antenna feed point to 50′. This results in a loss of about 1.3 dB on the 70 cm band. The result is that our planned IC-9100 Transceiver which has a maximum output of 75W on 70 cm will deliver a little more than 50W maximum at the feed point of the 70 cm yagi. This should be more that enough power to meet our station goals. Allowing a total of 15′ for antenna rotator loops and transceiver connections, we settled upon 35′ for the length of our coax feed-lines between the tower and the station control point.

Portable Tower Cable Connections and Base Straps

Portable Tower Cable Connections and Base Straps

We added some custom fabricated plates to the tower to act as a bulkhead for feed line and control cable connections and to mount our low-noise preamplifiers. The control connections for the rotators and preamps were made using 6-pin Weatherpack connectors and rotator control cable from DXEngineering. The control cables are also 35′ long to match the length of our coax feed lines. This length should allow the tower and the control point to be separated by a reasonable distance in portable setups.

Low-Noise Preamplifiers From Advanced Receiver Research

Low-Noise Preamplifiers from Advanced Receiver Research

We added tower-mounted Low-Noise Preamplifiers from Advanced Receiver Research to improve the receive sensitivity and noise figure for our satellite antenna system. Two preamps are used – one each for the 2 m and one for 70 cm antennas. While these units can be RF switched, we decided to include the preamp control lead in our control cable to allow for control of the preamp switching via sequencers. This was done to provide an extra measure of protection for the preamps.

Levels And Compass For Tower Setup

Levels and Compass for Tower Setup

We added a compass and pair of bubble levels to the tower assembly to make it easier to orient and level it during setup. This picture above also shows the Yaesu shock absorbing mount for the azimuth rotator.

Weight Bags To Anchor Portable Tower

Weight Bags to Anchor Portable Tower

Finally, we added a set of weight bags to securely anchor the tower when it is set up in a portable environment. These bags are filled with crushed stone and fasten to the legs of the Glen Martin tower with velcro straps.

LEO Pack Antenna Parts

LEO Pack Antenna Parts

With the tower and rotator elements complete, we turned our attention to the assembly of the M2 LEO Pack. The LEO pack consists of two circularly polarized yagis for the 2m and 70 cm bands. The 2m Yagi is an M2 Systems 2MCP8A which has 8 elements (4 horizontal and 4 vertical) and provides 9.2 dBic of forward gain. The 70 cm Yagi is an M2 Systems 436CP16 with 16 elements (8 horizontal and 8 vertical) and provides 13.3 dBic of forward gain. Both Yagi’s are meant to be rear mounted on an 8.5′ aluminum cross boom which is included in the LEO Pack. The picture above shows all of the parts for the two antennas before assembly. It took us about a 1/2 day to assemble and test the antennas and both produced the specified SWR performance when assembled and test in clear surroundings.

Assembled LEO Pack On Portable Tower

Assembled LEO Pack on Portable Tower

The picture above shows the assembled LEO pack on the portable tower. We attached a short 28″ piece of mast material to the cross boom as a counterweight to provide better overall balance and to minimize strain on the elevation rotator. The antennas and the two outer sections of the mast can be easily removed to transport the antenna system.

2m Circularly Polarized Yagi Feed Point

2m Circularly Polarized Yagi Feed Point

The LEO Pack yagis achieve circular polarization via a matching network which drives the vertical and horizontal sections of the antennas with a 90 degree phase shift. The phase shift (and a final 50 ohm match) is achieved using 1/4 wave delay lines made of coax cables. We configured our antennas for right-hand circular polarization. The choice between right and left hand circular polarization is not a critical one in our LEO satellite application as most LEO satellites are not circularly polarized. The advantage of circular polarization in our application is the minimization of spin fading effects.

Green Heron RT-21 Az/El Rotator Controller

Green Heron RT-21 AZ/EL Rotator Controller

The final step in the construction of our antenna system was to add the rotator controller and test the computer aiming system. We have had very good results using Green Heron Engineering rotator controllers in our home station so we selected their RT-21 AZ/EL rotator controller for this application. The RT-21 AZ/EL rotator controller is really two rotator controllers in a single box. The rotator control parameters such as minimum and maximum rotator speed, ramp, offset, over travel and others can be independently set for each rotator.

Rotator Test Using MacDoppler

Rotator Test Using MacDoppler

The RT-21 AZ/EL Rotator Controller connects to our computer via a pair of USB cables. We run Green Heron’s GH Tracker software on our MacBook Air laptop to manage the computer side of the rotator controller and to provide a UDP protocol interface to the MacDoppler tracking software. The picture above shows the test setup used to verify the computer controlled antenna pointing system.

Mixed OS/X and Windows Software Environment

Mixed OS/X and Windows Software Environment

One challenge associated with selecting a Mac OS/X platform for computer control is what to do about the inevitable need to run Windows software as part of the system. In addition to the GH Tracker software, the WaveNode WN-2 Wattmeter and digital modem software for satellite/ISS APRS and other applications require a Windows run-time environment. To solve this problem, we use a virtual machine environment implemented using VMware Fusion and Windows 10 64-bit on our MacBook Air Laptop along with Mac OS/X. Using the Unity feature of VMware Fusion allows us to run windows apps such as GH Tracker as if they were native Mac OS/X apps. The picture above shows an example of this.

Rotator Controller and Software Configuration

Rotator Controller and Software Configuration

With the antennas removed from the cross boom, we tested the operation of the computer controlled tracking system. The Yaesu G-5500 AZ/EL Rotator have some limits as to its pointing accuracy and backlash performance.  Experimentation with the combination of  the RT-21 AZ/EL rotator controller, GH Tracker and MacDoppler setups was required to achieve smooth overall operation. We finally settled on a strategy of “lead the duck” tracking. The idea here is to set up the rotators so that they over-travel by a degree or so when the computer adjusts them and couple this with a relatively wide 2-3 degree tracking resolution. This maximizes the overall accuracy of the pointing system and minimizes the tendency towards constant start-stop operation of the rotators during satellite tracking. Our current configuration for all of the elements involved in the tracking system is shown above.

With the antenna system complete and tested, we can move onto the next step in our project – the construction of a computer controlled transceiver system. We will cover this element in the next part  in this series. Other articles in the series include:

You may also be interested in the satellite station at our home QTH. You can read more about that here.

Fred, AB1OC

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


NCC-1 Receive Antenna System Control Unit and Filters

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 cable interconnect system at the base of our tower.

NCC-1 Receive Antenna System Components

NCC-1 Receive Antenna System Components

Our first project was the installation of a DXEngineering NCC-1 Receive Antenna System. This system uses two receive-only active vertical antennas 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

NCC-1 Receive System Antenna Pattern

The NCC-1 System can 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 two Active Antenna Elements via the NCC-1 Controller.

NCC-1 Filter Installation

NCC-1 Filter Installation

The first step in the project was to open the NCC-1 Control Unit to install a set of 80m and 160m bandpass filter boards. These filters prevent strong out-of-band signals (such as local AM radio stations) from overloading the NCC-1. The internal switches were also set to configure the NCC-1 to provide power from an external source to the receive antenna elements through the connecting coax cables.

Installed Active Receive Antenna Element

Installed Active Receive Antenna Element

The next step in the project was to select a suitable location for installing the 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 favorable orientation toward both Europe and Japan. The antenna elements use active circuitry to provide uniform phase performance between each element’s 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 the lowest band of operation from any towers or transmit antennas to enable the best possible noise rejection performance.

Received Antenna Element Closeup

Received Antenna Element Closeup

The two Antenna Elements 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). The Antenna Elements are powered through 75 ohm flooded coax cables which connect them to the NCC-1 Control Unit in our shack. The coax cable connections in our setup are quite long –  the longer of the pair being approximately 500 ft. The use of flooded coax cable allows the cables 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

Receive RF Choke

It is also important to isolate the connecting coax cables from picking up strong signals from nearby AM Radio stations, etc. To help with this, we installed Receive RF Chokes in each of the two 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

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. The conduits were installed in our yard 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

Receive Antenna Coax Ground System

The last step in the outdoor part of this project was to install a pair of 75 ohm coax surge protectors near the entry to our shack. An additional ground rod was driven for this purpose and was bonded to the rest of our station’s ground system. We routed both of the 75 ohm coax cables from the two Antenna Elements through surge protectors and into our shack. Alpha-Delta makes the copper ground rod bracket shown in the picture for mounting the surge protectors on the ground rod.

Antenna Equipment Shelf In Our Shack (The NCC-1 Control Unit Is At The Bottom)

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 the NCC-1. The two incoming coax cables from the Antenna Elements were connected to the NCC-1.

microHAM Station Master Deluxe Antenna Controller

microHAM Station Master Deluxe Antenna Controller

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

Antenna Switching Matrix

Antenna Switching Matrix

The first step in integrating the Receive Antenna System was to connect the output of the NCC-1 to the Antenna Switching Matrix outside our shack. We added a low-noise pre-amp (shown in the upper left of the picture above) to increase the sensitivity of the Antenna System. The blue device in the picture is a 75 ohm to 50 ohm matching transformer which matches the NCC-1’s 75 ohm output to our 50 ohm radios. The other two pre-amps and transformers in the picture are part of our previously installed 8-Circle Receive Antenna System.

Multi-Radio Sequencer

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 simple sequencer unit associated with one’s radio. In a multi-op station such as ours, it is possible for a different radio than the one which is using the Receive Antenna System to be transmitting on a band which would damage the Receive Antenna System. To solve this problem, we built a multi-radio sequencer using one of the microHAM control boxes in our station. The 062 Relay Unit shown above has one relay associated with each of the five radios in our station. The power to the Receive Antenna System is routed through 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 system’s Antenna Elements are safely powered down and grounded.

NCC-1 Controls

NCC-1 Controls

So how well does the system work? To test it, we adjusted the NCC-1 to peak and then null a weak CW signal on 80m. This is done by first adjusting the Balance and Attenuator controls on the NCC-1 so that the incoming signal is heard at the same level by both Antenna Elements. Next, the B Phase switch is set to Rev to cause the system to operate in a signal null’ing configuration and the Phase control is adjusted to maximize the null’ing effect on the target signal. One can go back and forth a few times between the Balance and Phase controls to get the best possible null. Finally, the incoming signal is peaked by setting the B Phase switch to Norm.

Peaked And Null'ed CW Signal

Peaked And Null’ed CW Signal

The picture above shows the display of the target CW signal on the radio using the NCC-1 Antenna System. If you look closely at the lower display in the figure (null’ed 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

NCC-1 Used For Noise Cancellation

The NCC-1 can also be used to reduce (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 an 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 the received SSB signal.

We are very pleased with the performance of our new Receive Antenna System. It should make a great tool for DX’ing on the low-bands. It is a good complement to our 8-circle steerable receive system which we use for contesting on 160m and 80m.

Tower Control Cable Interconnects (Bottom Two Gray Boxes)

Tower Control Cable Interconnects (Bottom Two Gray Boxes)

Our other antenna project was a maintenance one. We have quite a number of control leads going to our tower. When we built our station, we 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 two DXEngineering Interconnect Enclosures on our tower and moved all the control cable connections inside them.

Inside View Of Interconnect Enclosures

Inside View Of Interconnect Enclosures

We began with a pair of enclosures from DXEngineering and we mounted screw terminal barrier strips on the aluminum mounting plates in each enclosure. The aluminum plates are grounded via copper strap material to our tower.

Closer Look At One Of The Interconnect Enclosures

Closer Look At One Of The Interconnect Enclosures

The picture above shows one of the interconnection boxes. This one is used to connect our two SteppIR DB36 Yagi Antennas and some of the supporting equipment. The barrier strips form a convenient set of test points for troubleshooting any problems with our 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 DX’ing.

73,

Fred, AB1OC

 

Summertime Station and Antenna Projects At AB1OC/AB1QB


Summer is the time of year that many of us work on our antennas and improve our stations. Anita AB1QB and I did both of these things at our QTH this summer.

Removing Lower SteppIR Yagi From Tower

Removing Lower SteppIR Yagi From Tower

Our SteppIR DB36 Yagis were due for some maintenance so we took them off our tower. A special thanks to all the members of the Nashua Area Radio Club who helped us remove, recondition and reinstall our antennas! Matt Strelow, KC1XX of XX Towers and Andrew Toth provided equipment and know how to safely remove our two large SteppIR DB36 Yagis with help from the rest of us.

Lowering Antenna With Electric Winch

Lowering Antenna With Electric Winch

The SteppIR DB36 Yagis weigh almost 200 lbs each and Matt made good use of his electric winch to lower them.

Antenna Coming Down The Tram Line

Antenna Coming Down The Tram Line

The picture above shows the lower antenna coming off the tower. We used a Tram Line system to lower both antennas to the ground so that we could rebuild them.

SteppIR DB36 Antenna On The Ground

SteppIR DB36 Antenna On The Ground

The SteppIR DB36 Yagis are quite large. They have 36 ft booms and the driven elements are almost 50 ft from tip to tip! They completely fill up our back yard when they are both off the tower.

Element Pole Sun Damage

Element Pole Sun Damage

The rebuild process began with a careful inspection of both antennas. They were both in good overall condition with some sun damage to the paint on the fiberglass element poles.

Disassembled SteppIR DB36

Disassembled SteppIR DB36

We removed all the element tubes and sweeps from both antennas for rebuilding. The picture above shows the disassembled upper antenna.

Reconditioned Stepper Motors Installed

Reconditioned Stepper Motors Installed

All four Stepper motors on both antenna were replaced. These motors move metal tapes inside hollow element tubes to adjust the length of each antenna’s 4 movable elements. These adjustments are done automatically by controllers in our shack which receive frequency information from the radios which are connected to each antenna.

Reconditioned Element Sweep Poles

Reconditioned Element Sweep Poles

All of the element housing poles were cleaned, prepped and painted with a UV resistant clear coat to protect them from further sun damage. The poles cleaned up like new.

New Element Sweeps Ready For Installation

New Element Sweeps Ready For Installation

The assembly of all the new element sweep tubes (shown above) was done next. Each antenna has six sweeps.

Element Pole Preparation

Element Pole Preparation

The end of each element pole must be prepped with a tape system which ensures that the poles are seated properly, sealed to and firmly attached to the sweeps. This process and the associated assembly and tightening of the element couplers was the most time-consuming step in the rebuild process as it had to be repeated a total of 24 times.

Rebuilt Element Assembly

Rebuilt Element Assembly

Here’s a picture of one of the rebuilt element tube assemblies. The ropes support the element tubes and keep them aligned when the antenna is up in the air. These elements are attached to the antenna motors with couplers and clamps.

SteppIR DB36 Yagi - Rebuild Complete

SteppIR DB36 Yagi – Rebuild Complete

The picture above shows the lower antenna with all the element tubes reattached. There is quite a bit of additional prep work associated with adjusting all the supports and taping all the exposed areas of the antennas which are susceptible to sun damage. Also, all the electrical wiring on the antenna must be checked to ensure good electrical connections and good overall condition of the wiring.

Ground Test Setup

Ground Test Setup

The final step in rebuilding the antennas is to test their operation on the ground. This ground test is done to ensure that all the motors are working correctly and that the element tapes move smoothly inside the rebuilt element tubes.

Ground Test Results

Ground Test Results

Another important part of the antenna Ground Test is to confirm that the antennas have a consistent resonant frequency and SWR on all bands. The resonant frequencies and SWR levels are far from those that would be measured when the antennas are on the tower at operating height. The idea here is to confirm that a resonance exists and that its frequency and SWR readings are repeatable as the antenna is adjusted to different bands.

With both antennas rebuilt, its was time for Matt and Andrew to return and, with help from folks from our club, reinstall the rebuilt antennas on our tower. The video above shows this process. It is quite something to see! The installation took about 3 1/2 hours.

Updated SteppIR Controllers

Updated SteppIR Controllers

The last step in the SteppIR DB36 rebuild process was to install the latest firmware in the associated SDA100 Antenna Controllers. There are some integration issues between the updated SteppIR Firmware and our microHAM system but we are getting those worked out with help from the folks at both SteppIR and microHAM.

Icom IC-7851 With Display Monitor

Icom IC-7851 With Display Monitor

I recently had a major birthday milestone and Anita surprised me with a new radio – an Icom IC-7851. This radio is an upgrade/replacement for our Icom IC-7800. While the two radios are quite similar in their operation and interfaces, I did not want to install the IC-7851 until the SteppIR antennas were reinstalled and all of their upgrades were working properly with our current radios. With the antennas done, it was the finally time to install the new radio!

Icom C-7851 Transceiver

Icom C-7851 Transceiver

The Icom IC-7851 has several important performance upgrades. The most impactful one is a new low phase noise oscillator which significantly improves RMDR performance compared to the IC-7800. The IC-7851 is in the top-tier of Transceivers in Sherwood Engineering’s tests. The receivers in the IC-7851 are very quiet, have excellent Dynamic Range and perform great in when close-in interference is present.

Icom IC-7851 Display Monitor

Icom IC-7851 Display Monitor

The Icom IC-7851 has a higher resolution and faster display. It also supports higher resolution external monitors so we installed am upgraded display monitor along with the new radio. The IC-7851 has a number of new networking features and supports stand-alone remote operation over a LAN and the Internet. We are planning to use these capabilities to add a second remote operating gateway to our station. More on this in a future article.

The combination of the rebuilt antennas and the new IC-7851 Transceiver has our station performing better than ever. The antennas are working as well or better than when they were new and the IC-7851 has significantly better receive performance compared to its predecessor and is a pleasure to use.

We will be hosting the ARRL Rookie Roundup RTTY contest for our club members who have received their first license in the last 3 years next weekend and we’re going to use the new radio and rebuilt antennas for the contest.

This project was completed in a little over two weeks and was a lot of work. I could not have done the project without the help of the many folks in the Nashua Area Radio Club. Again, a big Thank You to all the folks in our club who helped me with this project! I hope that many of you will be able to find some time to operate from our upgraded station.

73,

Fred, AB1OC

2016 ARRL Field Day!


2016 Field Day Site Layout

2016 Field Day Site Layout

I had the privilege of acting as the Field Day Incident Commander for the Nashua Area Radio Club this year. Field Day is the most important operating event for the Nashua Area Radio Club each year. We operated under our club callsign, N1FD and we were 7A here in New Hampshire, USA. We included some new antennas including a Three Element 40m V-Beam, a Satellite Station and a 70cm Digital ATV Station in our operation this year. You can see some of the details which went into the planning of our 2016 Field Day Operation on our Club’s Tech Night Page.

The video above shows highlights from our 2016 Field Day Operation. As you can see, we had a lot of fun at Field Day this year. Our club has 120+ members and we had a large turnout for Field Day. You can see more about our 2016 Field Day operation on our Field Day Page including photos, a score summary and a recap presentation shared at a recent club meeting. I hope that you enjoy sharing our memories from 2016 Field Day.

73,

– Fred, AB1OC

Building a 40m Delta Loop Antenna


40m Delta Loop Antenna

40m Delta Loop Antenna

Several members of the Nashua Area Radio Club recently got together to help one of our members, Ralph N1UH, put up a 40m Delta Loop antenna. Delta loop antennas are some of the best performing wire antennas and have the advantage that they can be easily supported via a single elevated mounting point such as a mast or tall tree.

40m Delta Loop EZNEC Model

40m Delta Loop EZNEC Model

The location that Ralph choose for his 40m Delta Loop already had a radial field under it and we decided to take advantage of this to try to improve ground quality under the antenna. He built a detailed EZNEC model of the planned antenna and radial field under it to evaluate the best approach to the design. The antenna was modeled and build with its apex around 50 ft and designs resulting in Horizontal Polarization  (feed point in the center of the bottom leg) and Vertical Polarization (feed point 1/4 wavelength down a vertical leg) were considered.

40m Vertically Polarized Delta Loop Pattern

40m Vertically Polarized Delta Loop Pattern

The graphic above shows the EZNEC modeling result for the Vertically Polarized 40m Delta Loop. This design tends to concentrate the radiated energy at the lower takeoff angles which optimizes the antenna for long DX contacts.

40m Horizontally Polarized Delta Loop Pattern

40m Horizontally Polarized Delta Loop Pattern

This graphic shows the modeled pattern when the antenna is fed to create Horizontal Polarization. On first look, one might conclude that this version of the antenna would only be useful for short-range communications. The point to consider here is that the Horizontally Polarized version of the antenna has much higher overall gain.

40m Delta Loop Gain Comparison

40m Delta Loop Gain Comparisons

The table above helps to better understand the real difference in performance between the two versions of the 40m Delta Loop. Columns 2 – 4 compare the gain of the two versions of the antenna at various elevation angles. We can see that the Horizontally Polarized version of our 40m Delta Loop has higher gain down to elevation angles of about 20 degrees. At lower elevation angles, the Vertically Polarized version has an advantage. Also note that both antennas begin to exhibit less than -1.0 dBi of “gain” at angles below 10 degrees of elevation. The net of this is that the Vertically Polarized antenna does have an advantage for DX signals which arrive at low angles in the 20 – 10 degree range. Such low angles would be typical for very long DX contacts or in conditions of marginal propagation which might occur toward the bottom of the sunspot cycle. For many typical DX contacts (ex. DX contacts with Europe from here in New England) which would have arrival angles in the 20 – 30 degree range, the Horizontally Polarized version of the antenna will probably perform better. Ralph lives in a residential neighborhood with many potential noise sources close by; most of which will tend to be vertically polarized. The Horizontally Polarized version of the antenna will be less sensitive to the local noise sources which gives it a further advantage in this situation.

It’s also interesting to note the effect of the radial field under the antenna in the table above. The benefit of radials is pretty limited in the Vertically Polarized configuration averaging less that 0.5 dB. The gain from the radials is more significant in the Horizontal configuration averaging close to 1.5 dB. This is enough to expose an addition “layer” of weaker stations.

40m Horizontally Polarized Delta Loop Azimuth Pattern

40m Horizontally Polarized Delta Loop Azimuth Pattern

There is a common misconception that a Delta Loop Antenna is directional towards the open side of the loop. This is not the case at typical heights above ground. The plot above shows the pattern of the Horizontally Polarized version of the loop to be omnidirectional.

40m Vertically Polarized Delta Loop Azimuth Pattern

40m Vertically Polarized Delta Loop Azimuth Pattern

The graphic above shows the equivalent pattern for the Vertically Polarized version. Note that this antenna is actually slightly directional off the ends of the antenna, not towards to open side of the loop. This is a result of the fact that the two vertical legs of the Vertically Polarized Delta Loop antenna behave somewhat like two independent vertical antennas in a phased array.

The net of all of this analysis was that Ralph decided to build the Horizontally Polarized version of the 40m Delta Loop.

Finished Radial Field Under The Antenna

Finished Radial Field Under The Antenna

The first step in constructing the antenna system was to expand the existing radial field under the antenna.  We next put up a 50 ft guyed mast to support the apex of the loop. The result is shown above.

Feed Point and Balun on Mast

Feed Point and Balun on Mast

The antenna’s bottom wire element is about 10 ft above the ground and the bottom corners are anchored to the ground via Dacron guy ropes. After trimming the antenna to be resonant in the center of the 40m band, we found the final impedance to be around 80 ohms. We used a custom 1.5:1 Balun from Balun Designs to create a 50 ohm match at the Delta Loop’s feed point. The picture above shows the Balun mounted on the mast about 10 ft up from the ground. The antenna’s 2:1 SWR bandwidth with the Balun covers the entire 40m band. The antenna is fed with a relative short run of LMR-400UF coax inside underground conduit.

40m Delta Loop in use with FlexRadio-6700 SDR

40m Delta Loop in use with FlexRadio 6700 SDR

The final step of the project was to hook up the completed 40m Delta Loop system to Ralph’s FlexRadio 6700 SDR. We made several QSOs with the new antenna to verify that its performance across the band was as expected. Ralph has been receiving good signal reports with his new antenna further confirming that it is performing as expected. I have built several 40m Delta Loops at my home QTH at as part of our club’s 2015 Field Day Operation this past year. All have been good performers.

– Fred (AB1OC)

2015 Nashua Area Radio Club Field Day Recap


We had the opportunity to be part of the Nashua Area Radio Club’s 2015 Field Day Operation. Ed, K2TE was our incident commander and he helped to club to put together a great Field Day Operation. We operated under our club callsign, N1FD as 8A. John, W1MBG put together the video above which is a really nice recap of our operation.

Field Day Tower and Beams

Field Day Tower and Beams

The club was very active in WRTC 2014 and, as a result, was able to purchase several of the tower and station kits from the WRTC operation. The heart of our Field Day antenna system was built around two of these towers. One was used for CW and 6m and the other was used for SSB. Both towers had tri-band beams and we used Triplexers and Filters to allow our stations on 20m, 15m and 10m to share the beams on each tower. The towers got us a long way towards our status as an 8A operation.

Wire Antenna Construction

Wire Antenna Construction

My role in the setup part of our Field Day operation was to build our wire antennas. We began with a class covering how to build and tune Delta Loop antennas and we used the newly gained information from our class to build 40m and 80m delta loops at our Field Day site. We also put up a 75m inverted-V antenna in one of the tall trees at our site.

Operating Tents

Operating Tents

We made good use of our WRTC station kits and other gear that our members brought to setup comfortable tents to operate from as well as a public information tent and a food tent.

Operators For The Nashua Area Radio Club

Some Of Our Operators For The Nashua Area Radio Club

Despite the rainy weather on Saturday evening and Sunday, we all stayed comfortable and dry. Shown above is Dave, N1RF, Mike, K1WVO and Mike, K1HIF in our 40m SSB tent.

Field Day 20m SSB Station

Field Day 20m SSB Station

John, W1MBG and I shared a tent which we used for both 10m and 20m SSB operations. The picture above shows our 20m station which was built around an Elecraft KX3 with a PX3 Panadapter and 100w outboard amplifier.

Young Person Operating During field Day

Mikayla Operating With Her Dad During Field Day

Our club has been doing a great deal of work on bringing young people and other new HAMs into the hobby via license classes, outreach to schools and other activities. We carried this work into our Field Day operations with a GOTA station and lots of opportunities for new HAMs and young people to get on the air. Shown above is Wayne, AA9DY helping his daughter Mikayla to make some contacts on 20m SSB phone.

Field Day Feast

Field Day Feast

Anita, AB1QB made us great meals and snacks during our Field Day operation. The food provided all of us a great opportunity to take a break from operating and enjoy each other’s company. Anita and John, W1SMN organized our public information and outreach activities which were very successful. we had over 30 visitors from the general public during our operation this year.

We all had a great time during Field Day this year and we’re looking forward to doing it again next year.

– Fred (AB1OC)