After a year’s worth of planning and 10 months of construction, we have our new 2m EME Antenna System installed on our EME Tower and working! This stage of our project took about a week and included a lot of help from Matt and Andrew at XX Towers.
The first step was to arrange the four 2MXP28 Yagis that we built on saw horses near our EME Tower and check each antenna’s vertical and horizontal SWR. Performing SWR measurements with the antennas close to the ground like this does not produce very accurate measurements. Doing this does allow one to spot potential problems if some of the measured SWR fail to show a resonance or are wildly different than the other antennas in the group. All of our antennas checked out as expected.
We also rented a 50-ft Boom Lift and set it up near our EME Tower. A tool like this is almost essential to safely assemble and adjust a large, complex antenna system involving an H-Frame. It also speeds up the assembly and adjustment process considerably.
Elevation Rotator and H-Frame
The first step was to install the MT-3000A Elevation Rotator on the mast. We pre-installed the control cable for the elevation rotator before installing it on the tower. This enabled us to get it temporarily hooked up to the Rotator Controller in our shack so that we could adjust the elevation of the H-Frame and Antennas as we installed them.
Next, Matt and Andrew installed the H-Frame Crossboom and Truss assembly on the Elevation Rotator. The assembled Vertical Risers went on next to complete the H-frame. The time spent pre-assembling these components and marking centers to enable accurate final assembly saved a great deal of time.
With the H-Frame in place, we installed the upper 2MXP28 Yagi Antennas next. The image above shows the rigging of the boom trusses which was done on the Tower.
Next came the lower 2MXP28 Yagis. We spent considerable time leveling and aligning all of the Antennas and H-Frame components at this stage.
Feedlines, Electronics, and Balancing
The T-Brace assemblies and Antenna Phasing Lines were installed next. Each Antenna requires two LMR-400 Phasing Lines and these coax cables add considerable weight to the backs of the Antennas. The T-Braces support these cables and help to align the Antennas on the H-Frame.
We replaced the Vertical H-Frame Boom Truss Pipe with a heavy section of Mast Pipe to act as a counter-weight and balance the final H-Frame and Antenna assembly. This step is critical to ensuring a long life for the Elevation Rotator’s drive system and chain.
The photo above shows the final installation of the Power Dividers, Antenna Phasing Lines (there are 8 in total), the MAP65 Preamp Housing, and the Feed and Control Cables that run down the Tower. We took the time to carefully make SWR measurements on each Antenna and check all of the connections to the MAP65 Housing at this stage.
Antenna Integration Details
The Rotator Loop contains the following cables and Coax Feedline connections from the H-Frame/Antenna assembly:
- Vertical and Horizontal Rx Feedlines
- Tx Feedline
- Elevation Rotator Control Cable
- MAP65 Housing Control Cable
All of these cables are bundled and securely fastened to the H-Frame Cross Boom and to the Tower. Andrew is a master at this sort of rigging!
I took some time to finalize the Control Cable connections at the base of our tower. Time was spent with a voltmeter doing checks to ensure that everything was connected correctly and working. This effort resulted in the discovery and correction of some wiring errors and a faulty relay in the MAP65 housing. Had I not done these steps, we would have surely destroyed the Preamps in the MAP65 Housing when we transmitted for the first time.
Testing Our New Antenna System
A series of SWR measurements were taken before sealing the coax cable connections on the tower. SWR measurements were checked and recorded for future reference at the following points in the feedline system:
- At the ends of the phasing lines associated with each antenna
- At the output of the two Power Dividers on the tower
- At the shack entry ground block
Measurements were taken separately for both the Vertical and Horizontal elements of the final Antenna System. The image above shows a typical SWR measurement for our final Antenna System.
I did many final checks and adjustments while the Boom Lift was still here. These steps included:
- Checking the oil level in the elevation rotator
- Re-lubing the elevation rotator chain
- Adjusting the limit switch stops on the Elevation Rotator to allow enough over-travel for future adjustments and maintenance
- Checking all hardware for tightness
- Sealing all coax cable connectors with Coax Wrap and Electrical Tape
- Making some final adjustments to align the four 2MXP28 Antennas with each other and the H-Frame
The next step in our project will be the integration of our new 2m EME Antenna System into our shack. This step will include the final setup, configuration, and testing of the Rotator Controller, Interim SDR Receiver, Transmitter, Amplifier, and the MAP65 and Moon Tracking Software.
You can read more about our EME station project via the links that follow:
- EME Station 2.0 Part 1 – Goals and Station Design
- EME Station 2.0 Part 2 – Excavation, Footings, and Conduits for New Tower
- EME Station 2.0 Part 3 – Phase Tuned Receive Coax Cables
- EME Station 2.0 Part 4 – New EME Tower Is Up!
- EME Station 2.0 Part 5 – Control Cables and Rotator Controller
- EME Station 2.0 Part 6 – Tower Grounding System
- EME Station 2.0 Part 7 – Building Antennas
- EME Station 2.0 Part 8 – Elevation Rotator Assembly and Sub-System Test
- EME Station 2.0 Part 9 – H-Frame Assembly
If you’d like to learn more about How To Get Started in EME, check out the Nashua Area Radio Society Tech Night on this topic. You can find the EME Tech Night here.