EME II Tech Night – Station Construction and Operation
We recently did a second Tech Night Program on EME as part of the Nashua Area Radio Society’s Tech Night program. I wanted to share the presentation and video from this Tech Night so that our readers might learn a little more about how to build and operate an EME station for the 2m band.
January 2021 Tech Night – EME II: Station Construction and Operation
A key part of optimizing our EME Station was to reduce RFI from the network in our home. You can read about the installation of Fiber Optic Networking to reduce RFI and improve our EME station’s performance here.
The next step in our EME project is to assemble the four M2 Antenna Systems 2MXP28 Yagis. These antennas are large, cross-polarized yagis. They feature 28 elements each on 34 1/2 foot booms. The design operates as an independent horizontal and vertical Yagi on a shared boom and each plane have an independent feed point.
EME Antenna Array Assembly on H-Frame
We are building four of these antennas to be mounted on an M2 Antennas 2X2 H-Frame. It is important that the four antennas be identical so they operate properly as an array. This includes things like symmetrical mounting and alignment of each antenna’s vertical and horizontal elements and the associated feed points. We will cover the assembly of the H-frame and Elevation Rotator systems in the next article.
Preparation
NOALOX Assembly Compound and Sharpie Pen
M2 Antenna Systems instruction manuals are very good and they specify the tools and procedures to properly assemble the associated antennas. A few additional items were helpful in our project. These included:
The assembly steps and procedures are similar for most M2 Antennas 2m and UHF Yagi antennas so I’m going to share some details and a few tricks that we’ve used successfully to build a number of their Yagis. You can see some of these other projects via the following links:
We successfully built all of these antennas using similar components and techniques.
M2XP28 Yagi Sorted Parts
The first step in assembling each antenna was to inventory and arrange all of the parts. I also took the time to wipe the boom elements with a solvent soaked cloth to remove dirt and aluminum dust that results from the manufacturing process. This makes assembling the antenna a much cleaner process.
2MXP28 Yagi Dimension Sheet
M2 supplies detailed dimension sheets and boom layout diagrams with their antennas and we took the time to carefully identify each element and boom component according to the diagrams.
Element Measurement and Marking
This step included careful measuring, sorting, and marking each element with its location and polarity (horizontal or vertical). This step makes the somewhat difficult step of getting all of the elements in the correct polarity and orders much easier. The marks allowed me to check and confirm the correct installation of all of the elements on the antenna boom before locking them in place.
Mast Clamp and Boom Truss Attachment Pre-assembly
We also pre-assembled things like the Mast Clamp and the Boom Truss Clamp during the parts inventory process.
Boom Assembly
Boom Assembly Details
The first step in assembling the antenna boom was to arrange all of the boom segments in the correct order and confirm their front/back orientation. This took some time to get right on the first of the four antennas. Each Boom segment was marked with the Sharpie to indicate its location and orientation in the final assembly.
We also installed the T-Brace Clamp to attach the rear of the antenna to the H-Frame’s T-Brace. It’s essential to do this step before assembling the Boom as the clamp cannot be attached once the antenna’s elements are in place. The correct location for the clamp was established via a careful measurement and the location was marked on the boom using the Sharpie.
Assembled Boom
The next step was to assemble the boom sections paying careful attention to the markings made earlier. We did not tighten any of the bolts that hold the boom sections together at this stage to allow us to re-clock each boom section for the best alignment of the elements later. A generous coat of NOALOX was used at the joint of the two largest diameter Boom sections to facilitate easier assembly and potential re-clocking later. NOALOX was also used on all bolts to provide anti-seize lubrication.
Once the boom is assembled, a 40-foot tape measure is used to carefully confirm that all of the holes for the elements are in the correct location. The Dimension Sheet is used as a reference to check and confirm that all measurements are correct before installing the Elements. This is also a good time to measure and carefully mark the location of the center of the Mast Clamp on the Boom.
The eye bolts that attach the Boom truss cable are also installed at this time.
Element Installation
Element Installation Details
Next came the installation of the elements. We began with the Horizontal reflector and worked towards the front of the antenna. The elements are held in place with insulated buttons and stainless locks. The elements are first installed in the correct location and carefully centered using a steel ruler. Vise-grip pliers are then used to hold the element in its centered position while the M2 supplied tool is used to push the lock on the opposite side of the element. The center is next checked again and if all looks good, the second lock is installed. This process is continued until all of the elements are in place. We pay careful attention to the markings on each element as part of the installation procedure to ensure that all of the elements are in the correct location on the boom.
H-Element Installation Complete – Ready for V-Element Installation
Once all of the elements are in place, the antenna is rotated 90 degrees to enable boom adjustments to align the elements. It is common for the boom sections to be misaligned a bit after the initial assembly. A combination of clocking each boom section either a bit one way or the other or sometimes removing the bolts holding two sections together and turning them 180 degrees relative to each other will create a perfect alignment of the elements. Once this is done, all of the bolts that hold the Boom sections together are fully tightened taking care not to distort or crush the Boom tubes.
The same installation process is repeated for all of the vertical elements.
Driven Element Assembly
Feedpoint Assembly
The Driven Element feed point blocks are installed next. The mounting screw and the Allen screws in the Shorting Bars all receive a light coat of Blue Locktite thread locker prior to installation.
Next, we loosely install the blocks in their correct location on the Boom and then install the Shorting Bars loosely on the Feed Point Block and Driven Element. Once these parts are in place, the screen that holds the Block to the Boom can be tightened fully, guaranteeing a perfect alignment of all of the parts.
The next step was to accurately set the spacing between the Feed Point Block and each shorting bar. I used a dial caliper to do this accurately but it can also be done with the careful use of a metal machinist’s or similar ruler.
The final step for each feed point was to install the 1/2 wave Coax Balun to the Feed Point Block. Be careful not to overtighten the coax connectors. Just make them snug and you are set. The supplied cable ties are used to secure the Balun to the boom.
The same steps are repeated for the Vertical feed point. It’s a good idea to install connector dust caps on the feed point Block connectors to keep them clean and dry prior to installation.
Vertical and Horizontal Feedpoint Orientation
It is critical that the relative orientation between the Horizontal and Vertical Feedpoint Blocks be the same on all four of the antennas in the array. If this is not the case, the pattern of the array will be upset which will have a major negative effect on the array’s performance.
Mast Clamp and Boom Truss
Mast Clamp Installation
The Mast Clamp assembly is installed next using the center mark placed on the Boom earlier. I also marked the backside of the Mast Clamp plate to show its center to make lining things up easy. The clamps should be oriented according to the H-frame mounting diagram (show at the front of this article).
Boom Truss Assembly
The final step in the assembly process is the assembly of the Boom Truss. The 2MXP28 Yagi is supplied with a Phillystran cable. The height of the Boom Truss will be set later when the antennas are attached to the H-frame so we just installed both ends of the Phillystran cable to the Eye Hooks installed in the Boom. The connections are made using the supplied Strain Relief Loops and small cable clamps. A drop of oil on each nut helps things go together smoothly. We had some Phillstran cable end caps so I installed them on the Phillystran cable ends to protect against water ingress. The turnbuckles, remaining clamps/strain reliefs, end caps, and truss clamp assembly were stored in a plastic Ziploc bag and cable-tied to the Boom to be installed later when the antennas are attached to the H-frame.
Final Details…
Completed 2MXP28 Antenna
It’s a good idea to give everything one last go-over now that the antenna is complete. All bolts and screws are checked for tightness, the Elements are all confirmed to be in the right locations, and the feed point assemblies are given a final check.
Four 2MXP28 Antennas Ready for Installation
Our EME project involves the assembly of four of these antennas with a total of 112 elements! It took me about 3 days to assemble each antenna (working about 3-4 hours each day). We stored the antennas on our deck to make space in our shop as we went. The antennas are well supported using low saw horses and woodblocks so as not the bend the Booms or the Elements.
The next step in our project will be to assemble and test the Elevation Rotator system. You can read more about our EME station project via the links that follow:
If you’d like to learn more about How To Get Started in EME, check out the Nashua Area Radio Society Teach Night on this topic. You can find the EME Tech Night here.
Sometimes we learn from problems and mistakes. We all go through this from time to time. It is part of the learning aspect of Amateur Radio. My most recent experience came while integrating our new tower-based satellite antenna system. After the antennas were up, initial testing revealed the following problems:
After an initial attempt to correct these problems with the antennas on the tower, we decided to take them down again to resolve the problems. The removal was enabled, in part, via rental of a 50 ft boom lift.
The lift made it relatively easy to remove the Satellite Antenna Assembly from the tower. We placed it on the Glen Martin Roof Tower stand that was built for the Portable Satellite Station 3.0. Once down, the Satellite Antenna System was completely disassembled and a replacement Alfa-Spid Az/El rotator was installed.
Cross Boom Truss System
The photo above shows the reassembled cross boom and associated truss supports. Note the tilt in the truss tube on the left side. This allows the antennas to be flipped over 180 degrees without the truss contacting the mast.
Reinforcement Bushing
As mentioned in the previous article, polycarbonate reinforcement bushings are installed in the fiberglass parts to prevent the clamps from crushing the tubes. The photo above shows one of the bushings installed at the end of one of the truss tubes.
Bushing Pin
The bushings are held in place with small machine screws. This ensures that they remain in the correct locations inside the fiberglass tubes.
Thorough Ground Test
With the Satellite Antenna Array back together and aligned, we took a few days to operate the system on the ground. This allowed me to adequately test everything to ensure that the system was working correctly.
Tower Integration Using A 50 ft Boom Lift
With the testing complete, the antennas went back up on the tower, and the integration and testing work resumed. Having the boom lift available made the remaining integration work much easier.
Control Cable Interconnect Boxes On The Tower
There are quite a few control cables associated with the equipment on our new tower including:
The M2 Orion Rotator which turns the mast that holds the 6 m Yagi and the Satellite Antenna Array
A combination of junction boxes near the top of the tower and at the base make connecting and testing of the control circuits easier and more reliable. Tower mounted junction boxes were used to terminate the control cables near the rotators and antennas.
The junction box at the base creates a single interconnect and testing point for all of the control cables. We’ve used this approach on both of our towers, and it makes things very easy when troubleshooting problems or making upgrades. Control cables for all of the tower systems were run to the temporary station set up in our house and terminated with connectors that are compatible with our Portable Satellite Station 3.0 system.
The Preamp System was mounted near the top of the new tower and the feedlines from the 2m and 70 cm Satellite Antennas were connected to it. LMR-400uF coax is run from the Preamp System as well as from the Directive Systems DSE2324LYRM 23 cm Satellite Yagi and the M2 6M7JHVHD 6 m Yagi on our new tower to the station in our house to complete the feedlines. These LMR-400uF feedlines will be replaced with 7/8″ hardline coax to our shack in the spring when warmer weather makes working with the hardlines easier.
Temporary Station Setup
With all of the tower integration work done, we set up the station in our house for testing. This is the same station that is our Portable Satellite Station 3.0 with two additions:
An iMac Computer which replaces the MacBook laptop used in the portable configuration
Both of these additions will become part of the final Satellite Station 4.0 when it is moved to a permanent home in our shack.
Rotator Controls
The rotator set up on the new tower provides two separate azimuth rotators. The lower one above turns both the 6 m Yagi and the Satellite Antenna Array together. The upper box controls the Alfa-Spid Az/El rotator for the satellite antennas. Using two separate rotators and controllers will allow us to integrate the 6m Yagi into the microHam system in our station and will allow the MacDoopler Satellite Tracking Software running on the iMac to control the Satellite Antennas separately. When we are using the 6 m Yagi, the Satellite Antennas will be parked pointing up to minimize any coupling with the 6 m Yagi. When we are using the Satellite Antennas, the rotator that turns the mast will be set to 0 degrees to ensure accurate azimuth pointing of the Satellite Antennas by the Alfa-Spid Az/El rotator.
PSK Reporter View using the M2 6M7JHVHD 6 m Yagi
So how does it all perform? With WSJT-X setup on our iMac, I was able to do some testing with the new 6 m Yagi using FT8. The IC-9100 Transceiver that we are using can produce 100W with WSJT-X. The 6m band is usually not very open here in New England in January so I was quite pleased with the results. As you can see from the PSKReporter snapshot above, the new antenna got out quite well on 6 m using 100W. I made several contacts during this opening including one with W5LDA in Oklahoma – a 1,400 mi contact. The 6M7JHVHD is a much quieter antenna on the receive side which helps to make more difficult contacts on 6 m.
MacDoppler Tracking AO-91
We’ve made a little over 100 satellite contacts using the new system so far. With the satellite antennas at 45 feet, it’s much easier to make low-angle contacts and we can often continue QSOs down to elevation angles of 5 degrees or less. I have not had much of a chance to test 23 cm operation with AO-92 but I have heard my signal solidly in AO-92’s downlink using the L-band uplink on the new tower. This is a good sign as our IC-9100 has only 10W out on 23 cm and we are using almost 100 ft of LMR-400uF coax to feed our 23 cm antenna.
Satellite Grids Worked and Confirmed
I’ve managed to work 10 new grid squares via satellites using the new antenna system including DX contacts with satellite operators in France, Germany, the United Kingdom, Italy, Spain, and Northern Ireland using AO-07 and FO-29. These were all low-angle passes.
So what did we learn from all of this? Due to concern over possible snow here in New England, I did not take the time to fully ground test the satellite antennas and new rotator before it went up on the tower the first time. My thinking was that the setup was the same as that used on Portable Satellite Station 3.0 for over a year. The problem was the replacement parts and new control cables were not tested previously and both of these created problems that were not discovered until the antennas were at 45 feet. While it would have made increased the risk that the antennas would not have gotten up before the first winter snowstorm here, it would have been much better to run the antennas on the ground for a few days as I did the second time. Had I done this, both problems would have appeared and have been easily corrected.
The next step in our project will be to add transverters to our FlexRadio-6700 SDR and integrate the new antennas into our shack. You can find other articles about our Satellite Station 4.0 project here:
Our club, the Nashua Area Radio Club, has quite a few members who are interested in space communications. We built a simple portable satellite station last year for our 2016 Field Day operation to learn about satellite communications and create something new for folks to work with during 2016 Field Day.
Simple Portable Satellite Station
Our 1.0 Portable Satellite Station was a relatively simple setup built around an HT, an Elk 2m/70cm satellite antenna, and some gear to improve the receive performance and transmit power output of the HT. All of the gear was mounted on a board to make it easy to transport and it is powered by a LIPO rechargeable battery. The gear in our 1.0 station is made up of the following:
Our first contacts with our 1.0 station were made using the Elk Antenna hand-held. Later, we created a “plumber’s special” setup with a camera tripod to make pointing the antenna easier. Note the angle meter from a local hardware store which measures the elevation angle of the antenna.
AO-85 (Fox-1A) U/V Mode FM Cube Satellite
This setup worked great for making FM contacts through AO-85 (Fox-1A), a U/V mode FM EasySat. We used the 1.0 station on multiple occasions including Field Day 2016 and several of our club members used it to make their first satellite contacts. The Full-Duplex HT allowed us to hear our own signal coming back from the satellite which was an important tool to help with aiming the antenna properly. The ELK Dual-Band antenna is also a good choice because it uses a single feed point and a single polarization for both the 2m and 70cm bands.
1.0 Station Team Operating Approach
We used the team operating approach outlined above. This worked especially well for new folks who had not made a satellite contact before as it enabled each of the three team members involved in making the contact to focus on a specific part of the contact. We used orange plastic tent stakes to make AOS, Time of Closest Approach, and EOS to mark headings for each satellite pass. Small flashlights used at the stakes made them glow for night-time passes.
These goals have become the basis for building our Portable Satellite Station 2.0. More on the new station in Part 2 of this series. Other articles in the series include:
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.
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
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
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 that 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
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 coax 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
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 the 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. 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
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)
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
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.
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 that 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.
Updated microHam Antenna System Diagram
With all of the coax and control connections complete, I was able to update the microHam system design information for our station and add the new receive antenna system to our setup. You can find more about the programming of our microHam system here.
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-nulling configuration, and the Phase control is adjusted to maximize the nulling 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
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 (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 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)
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
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
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.
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
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
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
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
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 backyard when they are both off the tower.
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
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
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
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
The assembly of all the new element sweep tubes (shown above) was done next. Each antenna has six sweeps.
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
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
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
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
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, it 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
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
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
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
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.
This post is about the assembly of the second of our four Yagi Antennas – the M2 Antenna Systems 2M18XXX. This antenna uses 18 elements on 2m to provide approximate 17 dBi gain in a very tight pattern. It is designed for weak-signal and EME work on the 2M band. The specifications for the 2M18XXX are as follows (Courtesy M2 Antenna Systems, Inc.):
Model
2M18XXX
Freq. Range
144-146 MHz
Gain (single antenna)
17.14 dBi
Front/Back
26 dB Typical
Beam Width
E=26° by H=28°
Feed Type
“T” Match
Feed Imped.
50 Ohms Unbalanced
Max VSWR
1.2:1
Connector
“N” Female
Boom Length
36.5′
Max Element Length
41″
Turning Radius
19′ 6″
Stacking Dist.
14′ H, 14.5′ W
Mast Size
2″ Nom.
Wind area / Survival
2.9 SqFt. / 100 MPH
Weight
14 Lbs.
# of Elements
18
I began by doing a careful inventory of all of the parts for the antenna and gathering the necessary tools for assembly. Due to its size, I opted to assemble the 2M18XXX outdoors near the tower.
2m Yagi Parts
The first step was the assembly of the boom. I used the 2 foot high sawbucks that I made for the purposes of building our yagi antennas. A set of carpenter’s clamps were used to hold the boom in place on the bucks during assembly. The installation of the elements was next.
2m Yagi Boom and Elements
This step takes some time as each element has a different length and must be carefully centered on the boom. To make this easier, I marked the boom with a felt tip pen to indicate the location of each element for easy cross-reference with the dimension sheet from M2 Antenna Systems.
2m Yagi Element Layout (Courtesy M2 Antenna Systems, Inc.)
Next came the assembly of the driven element and associated balun. The location of the shorting bars on the Driven Element Assembly is important in order to get a proper match between the feedline and the antenna.
2m Yagi Driven Element
The 2M18XXX has a long boom (36 1/2 ft.) and requires a Truss Support. The picture below shows the boom truss support system after it is assembled. The standard mast plate and hardware supplied with this antenna by M2 Antenna Systems will accommodate up to a 2″ mast. We will be using a 3″ mast so M2 supplied a custom mast plate and a Truss Support that clamps directly to our 3″ mast. To make the antenna easier to test, I first assembled it with the 2″ hardware so that I could test it without attaching it to the mast.
2m Yagi Boom Support Truss
Here is a picture of the completed 2M18XXX. It is a very well-built antenna and it should perform well once it is installed at the 110 ft + level on our tower.
Completed 2m Yagi
I am going to move onto the construction of the first of our SteppIR DB36 antennas next. I will provide a post covering this step of our project next.
You can read more about our tower project via the articles which follow:
