During assembly and installation, I was concerned about several key components that were provided with the antenna. My first concern, the locking nuts on the turnbuckles. The way the turnbuckles are supposed to be installed on the antenna for the elements, the standard thread locking nut is not on the side of the turnbuckle that attaches to the metal center support. Rather, the locking nut is on the side of the turnbuckle that holds the support rope or Phillystran. I did not like that arrangement at all. I thought it would be better to have a locking nut on the side of the antenna that could not rotate due to vibration or wind. Therefore, I added left hand threaded nuts to the other end of the each turnbuckle as well, thus locking both sides.
The antenna comes with just enough cable clamps to use two per end on the Phillystran support guys. Another amateur I know, that has previous experience with a M2 full size 40 meter beam, indicated that with two cable clamps, the Phillystran support for those elements had slipped. To prevent that, I added a third clamp to each end of the Phillystran.
Another concern of mine, was the boom support. M2 provides a section of Dacron rope to support the boom. IMO, with a 42 foot boom, the rope may not last very long. At first, I contemplated using aircraft grade cable for the boom support, but I wanted to avoid any interaction from using a metal support. Therefore, I changed from rope to 2100 pound rated Phillystran.
Moreover, the last two components that really concerned me, was the rather small boom to mast plate and the 4 muffler style clamps provided to secure the antenna to the mast. They appeared inadequate to me, and my suspicions were realized during the installation, because the clamps failed.
I own a tilt-over, crank up tower. To install the antenna, I planned to install the center section of the antenna. Add the front boom section, director, and support. Rotate the antenna 180 degrees. Then install the rear boom section, reflector and support. During assembly, things went as planned, until I attempted to crank the tower back over to install the rear boom section, after I had rotated the antenna.
The unbalanced weight of the antenna literally warped the boom plate and two of the four mast clamps, causing the antenna to rotate out of control on the mast. Luckily, no permanent damage occurred, because the elements flexed, rather than bent, when they made contact with the ground. To remedy that issue, I purchased a much larger boom plate and solid cast aluminum clamps with stainless bolts from DX Engineering. In my opinion a must for this large antenna. The new plate and clamps are working excellent to support this large antenna.
Tuning and On the Air: The advantage to the M2 dual driven linear loaded design, is the increased usable bandwidth and near full size antenna performance in a smaller size footprint. Using the "Full Band" settings provided in the manual, the antenna covers the entire 40 meter band with an SWR below the advertised max SWR of 2:1. This has been confirmed on my installation. The measured SWR is 1.5 on the lower band edge at 7.000, 1.2 at the upper band edge of 7.300, and exhibits a nice smooth curve bottoming out around 1.1 on 7.180. No additional adjustments were necessary, but now it is necessary to retune a six meter beam that is four feet above this one (now resonance is 49.850), so there is some minor interaction to that antenna.
At this time, I don’t have my rotator control lines installed, so the antenna is fixed at 45 degrees East of North towards Europe. So far, the gain seem so be on par as advertised. I’ve worked a few stations and have received “Big Signal” reports from stations on the other end, when I am just running 200 watts, at 1.5 KW, I've been told, I am the loudest station heard!
I notice the bulk of U.S. stations usually given "5/9", while I am given 5-20+ over S-9 signal reports. I am copying stations easily as well. As expected, the antenna works just as well on receive too. In comparison to a ladder line fed 120 foot inverted V at 70 feet, the beam has much better receive on DX in the direction it is pointed, I’ve seen as much as 7 S units in difference.
Based on performance, I am very pleased with the antenna. I hope to be more active on 40 meters, a band that I haven't used much in the past. 73 and Good DXing.
|Failed Mast Clamps|
|Warped Boom Plate|
|TH-11DX, 40M4LLDD, + 5 Elements on 6 Meters|
|Improved Boom to Mast Plate 40M4LLDD|