Cushcraft XM240 tower installation
My father-in-law and I were working on the coax trench, PVC sections and ground rods when Dave (KI0Q) called to see if we wanted to try to put the antennas on the tower. We didn’t have a lot of daylight to work with and we were concerned about rain later in the day, but we decided to at least see how much of the prep work could be done.
This meant that Duane and I had to do some final preparations on the XM240 prior to the installation. We had an hour or so before Dave would get to my QTH and install his gear (ropes, pulleys, mast climbing steps, etc.).
My neighbor (Chris) and a buddy from my church who’s getting into the tower climbing business (Jeff) also came by to help.
My final checklist prior to installing the Cushcraft XM240 included:
- Adjusting the truss system (3 ft above the boom)
- Tightening the bolts/nuts
- Final measurements for the driven element and reflector (just below the mid point of the 40 meter ham band)
- Grounding the reflector to the boom
- Bug-proofing the boom
The last two items were not “per the Cushcraft instructions” but were XM240 tips that I’ve picked up through the internet. Some users have reported a clicking noise on 40 meters due to static build-up and arcing from the reflector to the boom. They’ve cured this by grounding the reflector (reportedly without any performance impact). Additionally, this should help with top loading when shunt feeding the tower on 80 meters or 160. The problem was how are folks grounding that element.
We came up with a battlefield solution… ground the U-bolt to the element by inserting a wire between the element and U-Bolt (in the bushing)… best explained through this photo:
If you look closely you can see a small aluminum wire that’s been bent up and wedged between the U-bolt and the element (in the bushing gap). That should keep the element grounded (via the u-bolt) to the boom).
What’s this about bug-proofing the XM240 boom? Well, from what I’ve gathered, the issue is that Cushcraft supplies plastic caps for the ends of the boom. I’ve read where hams have taken down their XM240s to find a lot of water in the boom - essentially stored in there, trapped by these caps. Not wanting to just leave the ends fully exposed to bugs, birds and anything else, I went to the ham radio antenna building aisle of my local grocery store to find “antenna boom bug filters” - which I then trimmed to size. These should let the water pass through and keep the critters out.
Once Dave was ready, we got the antenna in position and began the lift. We used a pulley at the top of the mast, a pulley at the bottom of the tower and two tag lines. Having the extra helpers really made things go well. Due to a sticky pulley, it took a bit longer than we had hoped (so some of the pics get a bit dark).
By the end of the day the XM240 was proudly mounted ~12 ft above the ANwireless HD-70. Best comment of the day was from my XYL… “It doesn’t look so big up there.”
